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In re Patent Application of Date: May 15, 2008 

Applicants: Bednorz et al. Docket: YO987-074BZ 

Serial No.: 08/479,810 Group Art Unit: 1751 

Filed: June 7, 1995 Examiner: M. Kopec 


Commissioner for Patents 
United States Patent and Trademark Office 
P.O. Box 1450 
Alexandria, VA 22313-1450 


CFR 37 §41 .37(c) (1) (ix) 


Part 3 


Respectfully submitted, 

/Daniel P Morris/ 

Dr. Daniel P. Morris, Esq. 
Reg. No. 32,053 
(914) 945-3217 

Intellectual Property Law Dept. 
P.O. Box 218 

Yorktown Heights, New York 10598 



In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Group Art Unit: 1751 
Examiner: M. Kopec 

Date: March 1 , 2004 

Docket: YO987-074BZ 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 


© Springcr-Verhg 1986 

Possible High T c Superconductivity 
in the Ba-La-Cu-O System 

J.G. Bednorz and K.A. Muller 

IBM Zurich Research Laboratory, RQschlikon, Switzerland 
Received April 17, 1986 

Metallic, oxygen-deficient compounds in the Ba-La-Cu-O system, with the composi- 
tion Ba x La 5 -,C\i 3 0 5( 3_ r) have been prepared in polyciystalline form. Samples with 
x= 1 and 0.75, >>>0, annealed below 900 °C under reducing conditions, consist of three 
phases, one of them a perovskite-like mixed-valent copper compound. Upon cooling, 
the samples show a linear decrease in resistivity, then an approximately logarithmic 
increase, interpreted as a beginning of localization. Finally an abrupt decrease by up 
to three orders of magnitude occurs, reminiscent of the onset of percolative superconduc- 
tivity. The highest onset temperature is observed in the 30 K range. It is markedly 
reduced by high current densities. Thus, it results partially from the percolative nature, 
bute possibly also from 2D superconducting fluctuations of double perovskite layers 
of one of the phases present. 

I. Introduction 

"At the extreme forefront of research in supercon- 
ductivity is the empirical search for new materials" 
[1]. Transition-metal alloy compounds of ^415 
(NbjSn) and B 1 (NbN) structure have so far shown 
the highest superconducting transition temperatures. 
Among many A 15 compounds, careful optimization 
of Nb— Ge thin films near the stoichiometric compo- 
sition of Nb 3 Ge by Gavalev et al. and Testardi et al. 
a decade ago allowed them to reach the highest T e = 
23.3 K reported until now [2, 3]. The heavy Fermion 
systems with low Fermi energy, newly discovered, are 
not expected to reach very high T t 's [4]. 

Only a small number of oxides is known to exhibit 
superconductivity. High-temperature superconduc- 
tivity in the Li-Ti-O system with onsets as high 
as 13.7 K was reported by Johnston et al. [5]. Their 
x-ray analysis revealed the presence of three different 
crystallographic phases, one of them, with a spinel 
structure, showing the high T r [5]. Other oxides like 
perovskites exhibit superconductivity despite their 
small carrier concentrations, n. In Nb-doped SrTi0 3 , 
with n=2x 10 2O cm~\ the plasma edge is below the 
highest optical phonon. which is therefore unshielded 

[6]. This large electron-phonon coupling allows a T c 
of 0.7 K [7] with Cooper pairing. The occurrence of 
high electron-phonon coupling in another metallic 
oxide, also a perovskite, became evident with the dis- 
covery of superconductivity in the mixed-valent com- 
pound BaPb^xB^Oa by Sleight et al., also a decade 
ago (8]. The highest T c in homogeneous oxygen-defi- 
cient mixed crystals is 13 K with a comparatively low 
concentration of carries n=2-4 x 10" cm 3 [9]. Flat 
electronic bands and a strong breathing mode with 
a phonon feature near 100 cm"', whose intensity is 
proportional to T c , exist [10]. This last example indi- 
cates that within the BCS mechanism, one may find 
still higher T t 's in perovskite-type or related metallic 
oxides, if the electron-phonon interactions and the 
carrier densities at the Fermi level can be enhanced 

Strong electron-phonon interactions in oxides 
can occur owing to polaron formation as well as in 
mixed-valent systems. A superconductivity (metallic) 
to bipolaronic (insulator) transition phase diagram 
was proposed theoretically by Chakraverly [11]. A 
mechanism for polaron formation is the Jahn-TeNer 
effect, as studied by Hock el al. [12]. Isolated Fc 4 *, 
Ni 3 * and Or* in octahedral oxygen environment 

inotzmnd K.A. Mulkr: Ba-La-Cu-O 

show strong Jahn-Tellcr (J.T.) effects [13]. While 
SrFeCVIX), is distorted perovskite insulator, 
LaNi(III)C>3 is a J.T. undistorted metal in which the 
transfer energy of the J.T. e t electrons is suflidently 
large [14] to quench the J.T. distortion. In analogy 
to Chakraverty's phase diagram, a J.T.-type polaron 
formation may therefore be expected at the border- 
line of the metal-insulator transition in mixed perovs- 
kites, a subject on which we have recently carried 
out a series of investigations [15]. Here, we report 
on the synthesis and electrical measurements of com- 
pounds within the Ba— La— Cu— O system. This sys- 
tem exhibits a number of oxygen-deficient phases 
with mixed-valent copper constituents [16], i.e., with 
itinerant electronic states between the non-J.T. Cu 3 * 
and the J.T. Cu J+ ions, and thus was expected to 
have considerable electron-phonon coupling and me- 
tallic conductivity. 

/. Sample Preparation and Characterization 

Samples were prepared by a coprecipitation method 
from aqueous solutions [17] of Ba-, La- and Cu-ni- 
trate (SPECPURE JMC) in their appropriate ratios. 
When added to an aqueous solution of oxalic acid 
as the precipitant, an intimate mixture of the corre- 
sponding oxalates was formed. The decomposition 
of the precipitate and the solid-state reaction were 
performed by heating at 900 "C for 5 h. The product 
was pressed into pellets at 4 kbar, and reheated to 
900 °C for sintering. 

2. X-Ray Analysis 

X-ray powder diflractograms (System D500 SIE- 
MENS) revealed three individual crystallographic 
phases. Within a range of 10° to 80° (20), 17 lines 
could be identified to correspond to a layer-type per- 
ovskite-like phase, related to the K 2 NiF 4 structure 
(o=3.79A and c=13.21 A) [16]. The second phase 
is most probably a cubic one, whose presence depends 
on the Ba concentration, as the line intensity de- 
creases for smaller x(Ba). The amount of the third 
phase (volume fraction > 30% from the x-ray intensi- 
ties) seems to be independent of the starting composi- 
tion, and shows thermal stability up to 1 ,000 °C. For 
higher temperatures, this phase disappears progres- 
sively, giving rise to the formation of an oxygen-defi- 
cient perovskite (La,Ba 3 Cu 6 0 M ) as described bv Mi- 
chel and Raveau [16]. 

. :ndenceorraistivityinBaJj J _ J ,CujO J ,3 
for samples with jt(Ba)= 1 (upper curves, left scale) and x(Ba)= 
0.75 (lower curve, right scale). The first two cases also show the 
influence of current density 

3. Conductivity Measurements 

The dc conductivity was measured by the four-point 
method. Rectangular-shaped samples, cut from the 
sintered pellets, were provided with gold electrodes 
and contacted by In wires. Our measurements be- 
tween 300 and 4.2 K were performed in a continuous- 
flow cryostat (Leybold-Hereaus) incorporated in a 
computer-controlled (IBM-PC) fully-automatic sys- 
tem for temperature variation, data acquisition and 

For samples with Jc(Ba)<1.0, the conductivity 
measurements, involving typical current densities of 

0. 5 A/cm J , generally exhibit a high-temperature me- 
tallic behaviour with an increase in resistivity at low 
temperatures (Fig. 1). At still lower temperatures, a 
sharp drop in resistivity (>90%) occurs, which for 
higher currents becomes partially suppressed (Fig. 1 : 
upper curves, left scale). This characteristic drop has 
been studied as a function of annealing conditions, 

1. e., temperature and 0 2 partial pressure (Fig. 2). For 
samples annealed in air, the transition from itinerant 
to localized behaviour, as indicated by the minimum 
in resistivity in the 80 K range, is not very pro- 
nounced. Annealing in a slightly reducing atmo- 
sphere, however, leads to an increase in resistivity 
and a more pronounced localization effect. At the 
same time, the onset of the resistivity drop is shifted 

lowa,d s tie 30 K region. Curves © and © IO=orded 

b, " k ^ »i™»fc%c 

13 K w,th ,„ „„*, aronild 35 R « » 

on an expanded temperature scale THe V- 


IN. Discussion 

l b Ll?! StiV '7 behaVi ° Ur of our s ™Pl« Fie 1 
s qua aanvelv very similar l0 the £ 

L-T-O system, and in 

^n'^ 0 ^r iDe thiD ^ R In- 
hibit a nearly 8 ££. SSmcT" 1 ""' ^ htter «" 
a logarithmic • typHf £ r ™ ° f the ° 

density (Fig 3? X ' ( } Wth Increa «ng current 

pretation SZZ£SZZ £ " SUPP ° m ° Ur bter - 

^.SoTZ cn^' r 35 d,SCUSSCd In 
been ^ ^ 
Uon appears to he v»v? ^ 1 8 ^ 11,13 trop- 
in the thS fitas HsTJ ,n systems, i.e. 
grain bounda^e ^ZTS" 
with interpenetrat. P n P 7r! cr y sta »i"e phases 
the Li- T T!o m' ? g n ' are Present ' as fou "d in 
The onse, ca TaS be 1?,' n* " U " CU " ° SyS ' em " 

Therefore u„d~e? t he a a ; e : e eXh,bi,S ,Ws behavi ° Ur 

to be identified as the start to superconductive coop- 
erative phenomena in the isolated grains. It should 
be noted that in granular A!, Cooper pairs in coupled 
grams have been shown to exist already at a point 
where ,(7) upon cooling has decreased by only 20% 

i°J rfo Va,UC - Thi$ has P roven Qualitative- 
ly II °J and more recently also quantitatively [201 by 
the negative frequency shift occurring in a microwave 
cavity. In m J films a shouMcr « 

sbft owing to 2D fluctuations was observed aboS 
the T c of the grams. In our Ba-La-Cu-O system, 
a senes of layer-hke phases with considerable variety 
in compositions are known to exist [16, 21], and 
therefore 2 D correlations can be present 

The granularity of our system can be justified 
from the structural information, and more quantita- 
tively from the normal conductivity behaviour. From 
the former, we know that more than one phase is 
present and the question arises how large are the 
grams. This can be inferred from the logarithmic 
fingerprint m resistivity. Such logarithmic increases 
are usually associated with beginning of localization 
A most recent example is the Anderson transition' 
ui granular Sn films [22]. Common for the granular 
Sn and our samples is also the resistivity at 300 K 
tying m the range of 0.06 to 0.02 Hem, which is near 
the microscopic critical resistivity of p e = 10 Ufi/e 2 
for localization. From the latter formula, an inter- 
atomic distance L„ in the range of 100 A is computed 
thus a size of superconducting grains of this order 
of magnitude must be present. Upon cooling below 
7;, Josepnson junctions between the grains phase- 
lock progressively [23] and the bulk resistivity gradu- 
ally drops to zero by three orders of magnitude, for 
sample 2 (Fig. 1). At larger current deSties^e 
weaker Josephson junctions switch to normal resistiv- 
ity, resulting in a temperature shift of the drop as 
shown in Fig. 3. The plateau in resistivity occurring 
below the 80% drop (Fig. 1) f or the higher current 
density of 0.5 A/cm', and Fig. 2 curve ©) may be 
ascribed to switching of junctions to the normal state 
The way the samples have been prepared seems 
to be of crucial importance: Michel et al [21] ob- 
tained a smgle-phase perovskite by mixing the oxides 
of La and Cu and BaC0 3 in an appropriate ratio 
and subsequent annealing al 1 ,000 °C in air We also 
applied this annealing condition to one of our sam- 
ples, obtained by the decomposition of the corre- 
sponding oxalates, and found no superconductivity 
Inus, the preparation from the oxalates and anneal- 
ing below 950 °C are necessary to obtain a non-per- 
ovski.e-type phase with a limited temperature ranee 
of stability exhibiting this new behaviour. The forma- 
tion of this phase at comparat. vely low temperatures 
.s favoured by the intimate mixture of the compo- 

J.G. tnd K_A. M SBer: Ba-U-Co-o Syaein 

nents and the high reactivity of the oxalate 
to the evolution of large amounts of H o " rf ^ 8 
during decomposition. 3 and C °i 

IV. Conclusion 

In the concentration ranee invesii«t«i 

of the Ba-La-Cu-O «L ? & ' """Pounds 

^m^u^c^TS^ meta " iC 31 Wgh 

«£. ™hng^^^^ 

under reducing conditions show features associa^ 


1. Tiniham. M.. Bcasky. MR., Larbalestic DC Clark A P 

;^slsssssl^s^ 2firich ph ~ 

llT* ^ G - : Physics 108 »■ "35 (1981) 

^ bJ*J ftTtrJ S^crconduoivily fa rf. and /-Band Met- 

8 '^^i™™' *"**• FE - ™* Con,- 
Batlogg B : Physica 126 B, 275 (1984) 

es^st' R - : phys - RevB m - 2682 (,9s2j; 

" n^msT B K ' : J " Phys U " *°- L " (I979): J Phvs 42 - 

"'^^r^^'^^z^ Efrec ' in Moiecu,cs 

oi ox.oc and rela.ed compounds. In: Landoli-Boerns.ein Nc» 

J.G. Bednorz and K.A. Muller: Ba-La-Cu-O System 

Series. Vol III/4a: Crystal and solid state physics. Helrwege, 
K.H.. HeUwege, A.M. (eds.), p. 262, Fig. 73. Berlin, Heidelberg. 
New York: Springer- Veriag 1970 

15. Bednorz, J.G.. Muller, K.A.: (in preparation) 

16. Michel, C, Ravcau, B.: Chim. Min. 21, 407 (1984) 

17. Bednorz, J.G.. Miiller, KA, Arend, H., Granicher. H.: Mat. 
Res. Bull. 18 (2), 181 (1983) 

18. Suzuki. M.. Murakami. T., Inamura, T.: Shinku 24. 67 (1981) 
(in Japanese) 

Enomoto, Y.. Suzuki, M.. Murakami, T., Inukai. T.. Inamura, 
T.: Jpn. J. Appl. Phys. 20, L661 (1981) 

19. Muller. K.A.. Pomerantz, M„ Knoedler. CM.. Abraham, D 
Phys. Rev. Lett. 45, 832 (1980) 

20. Stocker. E., Butut. J.: Solid State Commun. 53, 915 (1985) 

21. Michel. C, Er-Rakho, L, Ravcau I 

21 (m6" aeSen<,0nCk ' C "' BrUynSeraede ' Y - : ^v. B 33. 1 
23. Deutscher, G., Entin-Wohlman. C. Fishman 
Phys. Rev. B 21, 5041 (1980) 

J.G. Bednorz 
K.A. Muller 

IBM Zurich Research Laboratory 

■ : Mat. Res. Bull. 20, 6 

i. S., Shapira, 

Nott Added in Proof 

Chemical analysis of the bulk composition of our samples revealed 
a delation from the ideal La/Ba ratios of 4 and 5.66. The actual 
ratios arc 16 and 18. respectively. This is in agreement with an 



Page 1 of 3 

Exploring Superconductivity 
Georg Bednorz 

In 1987, Georg Bednorz shared the Nobel Prize in Physics with his partner and mentor, K. Alex Muller 
"For their important breakthrough in the discovery of superconductivity in ceramic materials." Their 
breakthrough, accomplished in an IBM research lab in Switzerland, centered around the fabrication of a 
new copper-oxide compound that was superconducting at temperatures high enough to dramatically 
extend the applications of superconductors. To comprehend the significance of Bednorz's work, one • 
must first understand the history of research in superconductivity . 

Early investigations of superconductors that operate at temperatures higher then 23.2° K focused on 
metallic compounds that are good conductors of current at room temperature. In 1957 John Bardeen, 
Leon N. Cooper, and J. Robert Schrieffer (Nobel Prize in Physics, 1972) of the University of Illinois 
presented a new theory of superconductivity that changed the focus of research. In ordinary conductors 
some energy is lost to resistance because the conducting electron s scatter off impurities and vibrating 
atoms, known as phonons. According to the BCS theory (named for the initials of its originators), 
superconducting current is carried by pairs of electron s. This pairing keeps individual electron s from 
scattering off impurities, thus preventing resistance and establishing the superconducting state. 
Furthermore, it is the interaction between the electron s and the atomic structure of the superconductor 
that is responsible for the electron pairing. 

With this new theory, the search for high-temperature superconductors shifted from metals and metal 
alloys to materials that display a strong interaction between the electron pairs and the underlying atomic 
structure. Scientists turned to oxides, which are normally insulators . . 

The initial research led to modest advances. In 1973 David Johnston at the University of California at 
San Diego discovered superconductivity in lithium-titanium oxide at 13.7° K. In 1975 Arthur Sleight at 
Du Pont Research observed barium-lead-bismuth oxide superconducting at 13° K. X-ray analysis 
indicated the presence of significant interaction between electron s and the vibrations of the structural 
atoms (phonons). This fit the BCS theory and suggested that further research on metal oxides might 
prove rewarding. 

In 1983 Alex Muller, who had been conducting research on insulator s , proposed that Bednorz 
collaborate with him in a search for high-temperature superconductors in metal oxides . Bednorz agreed 
because he felt the combination of Muller's vision and his expertise in solid-state physics would lead to 

They first experimented with nickel oxides, but had disappointing results. Progress was slow and the 
amount of time and energy they could devote to this work was limited because it was not a major focus 
at the IBM research facility. The two men persevered, however, because they knew that oxide materials 
satisfied the requirements of the current BCS theory and that under the proper conditions such a material 
should prove to be superconducting at high temperatures. 

Click here V£0 To hear Georg Bednorz describe their early work. 


Page 2 of 3 

Then in the fall of 1985 Bednorz read a paper by Claude Michel, L. Er-Rakho, and Bernard Raveau 
(from the University of Caen) that described their work with copper-oxide compounds. Bednorz 
immediately realized that a mixture of copper and barium would have the properties he was seeking, and 
on that very day he fabricated the new compound, a ceramic insulator composed of lanthanum, barium, 
and copper oxide. Since he could not duplicate the exact conditions under which the French scientists 
prepared their compound, he used a different preparation scheme. As it turned out, that "chance" 
modification led to the Nobel Prize. 

Click here To hear Georg Bednorz describing the results of their modification. 

In January 1 9§6 the new material was tested and the resistance analysis indicated that it was 
superconducting. Bednorz recalls that "when it happened, I didn't trust my eyes." The fabrication 
scheme he used had a different amount of oxygen and a more moderate heating process than the original 
French one; this turned out to be a key to its superconducting character. Bednorz's corhpound-and all 
subsequent metal-oxide superconductors-contained very thin sheets of copper oxide separated by layers 
of other metal oxides . There appears to be a direct correlation between the number of copper-oxide 
layers in a superconductor and its critical temperature . In gener al, the greater the number of copper- 
oxide layers, the higher the critical temperature . By varying the barium content and heating conditions, 
Bednorz was able to produce a material that was superconducting at temperatures as high as 30° K, 
seven degrees higher than the existing record. 

When Bednorz's laboratory detected the initial data supporting the high-temperature superconductivity 
of the copper-oxide ceramic material, Bednorz and MUller had to make a difficult decision. There had 
been many unsubstantiated and overrated claims of high-temperature superconductors, and they 
wondered if they should publish their results immediately in a prominent journal or wait until they 
substantiated their results with the more rigorous magnetic tests (to detect the Meissner effect ). Delays 
at this stage would mean that others working on similar projects could publish their findings first and 
receive the credit. They decided to submit their results at once to a journal that would not have many 
specialists as readers. They also wanted a journal with a fair amount of time between submission and 
publication, which would allow them to complete the magnetic testing before the article appeared. Their 
initial results were submitted to the Swiss Journal Zeitschrift fur Physik on April 17, 1986, and were 
published in the September issue. The paper received little attention, and by mid-October they had final 
confirmation of superconductivity . 

Click here ® To hear Georg Bednorz describing their thoughts on publishing their results. 

Bednorz and Mtiller announced their discovery to the physics community, which was initially skeptical. 
Their colleagues questioned the validity of the data, and many laboratories throughout the world set out 
to verify their claims. After confirmation by the University of Tokyo, the University of Houston, and 
Bell Laboratories, the scientific community began to realize that their claim of high-temperature 
superconductivity was valid. 

Attention in the scientific community then focused on raising the temperature, and by the end of 1986 
Bednorz raised the critical temperature of the barium-lanthanum-copper oxide system to 40° K by 
replacing barium with strontium. Researchers from the University of Houston and the University of 
Alabama, led by Paul Chu, then found that they could raise the compound's critical temperature to 52° K 
by applying pressure to the present metal oxide superconductor. This connection between compression 
of a crystal and an elevated critical temperatur led Paul Chu to replace lanthanum with a smaller atom, 
yttrium. On February 16, 1987, his research group established the critical temperature of yttrium- 


Page 3 of 3 

barium-copper oxide at 92° K. This advance was particularly significant because this compound could 
be cooled with cheap and readily available liquid nitrogen. These new materials were dubbed high- 
temperature superconductors. 

The newest members of the superconductor family contain bismuth or thallium. On January 22, 1988, 
Hiroshi Maeda of Tsukuba Laboratories of the National Research Institute of Metals discovered a 
critical temperature of 105° K for a bismuth-calcium-strontium-copper oxide compound. On January 26, 
1988, Paul Chu reported a critical temperatur of 120° K for the same system. On February 22, 1988, 
Zhengzhi Sheng and Allen Hermann of the University of Arkansas announced that a compound of 
thallium-calcium-barium-copper oxide exhibited an onset critical temperature of 120° K. Many research 
groups are now working diligently to find new materials that display even higher critical temperature . 

i _ 
It is worth noting that there is no accepted theory to explain the high-temperature behavior of this type 
of compound. The BCS theory, which has proven to be a useful tool in understanding lower-temperature 
materials, does not adequately explain how the Cooper pairs in the new compounds hold together at 
such high temperatures. When Bednorz was asked how high-temperature superconductivity works, he 
replied, "If I could tell you, many of the theorists working on the problem would be very surprised." 

Back to Interactive Learning Studio 


"A Snapshot View 

High Temperature Superconductivity 

Ivan K. Schuller 1 , Aran Bansil 2 , Dimitri N. Basov 1 , Malcolm R. 
Beasley 3 , Juan C. Campuzano 4 , Jules P. Carbotte 5 , Robert J. Cava 6 , 
George Crabtree 4 , Robert C. Dynes 1 , Douglas Finnemore 7 , 
Theodore H. Geballe 3 , Kenneth Gray 4 , Laura H. Greene 8 , Bruce N. 
Harmon 7 , David C. Larbalestier 9 , Donald Liebenberg 10 , M. Brian 
Maple 1 , William T. Oosterhuis 10 , Douglas J. Scalapino 11 , Sunil K. 
Sinha 1 , Zhixun Shen 3 , James L. Smith 12 , Jerry Smith 10 , John 
Tranquada 13 , Dale J. van Harlingen 8 , David Welch 13 

University of California, San Diego, 2 Northeastern University, 
3 Stanford University, 4 Argonne National Laboratory, 5 McMaster 
University, 6 Princeton University, 7 Ames Laboratory, 8 University 
of Illinois, 9 University of Wisconsin, 10 U.S. Department of Energy, 
"University of California, Santa Barbara, 12 Los Alamos National 
Laboratory, 13 Brookhaven National Laboratory 


Table of Contents 

I. Summary 

II. Structure, Bonding and New Systems 

1. Synthesis and Fabrication 

a) Bulk 

b) Thinfilms 

c) Doping in the Cuprate Superconductors 

2. Other Topics of Interest: 

a) Applied pressure 

b) , Spin, lattice, and.charge correlations 

3. Conclusion 

III. Electronic structure and quasiparticle dynamics 

1 . Techniques 

a) Electron Tunneling 

b) Angular Resolved Photoemission Spectroscopy (ARPES) 

c) Infrared Spectroscopy 

2. Magnetism, Competing Order, and Phonons 

a) Magnetism and Spin Fluctuations 

b) Competing Orders 

c) Phonons and Electron-Phonon Interactions 

rV. Vortices 

1 . Single Vortex Physics 

a) Confinement 

b) Pseudovortices and Vortex Core States 

c) Hybrid Materials 

2. Multivortex Physics 

a) Disordered Glassy and Liquid States 

b) Dynamic Phases 

c) Josephson Vortices and Crossing Lattices 

3. Instrumentation 

V. Proximity and Interface Effects 

VI. Nonequilibrium Effects 

VII. Theory 

1. Preamble 

2. Phenomenological Approach 

a) Status 

b) Key issues and opportunities 

3 . Numerical Studies of Hubbard and t- J Models 

a) Status 

b) Key issues and opportunities 

4. Electronic Structure 

a) Status 

b) Key issues and opportunities 

VIII. Defects and Microstructure with an Eye to Applications 


I. Summary 

This report outlines the conclusions of a workshop on High Temperature 
Superconductivity held April 5-8, 2002 in San Diego. The purpose of tins report is to 
outline and highlight some outstanding and interesting issues in the field of High 
Temperature Superconductivity. The range of activities and new ideas that arose within 
the context of High Temperature Superconductors is so vast and extensive that it is 
impossible to summarize it in a brief document. Thus this report does not pretend to be 
all-inclusive and cover all areas of activity. It is a .restricted snapshot and it only presents 
a few viewpoints. The complexity and difficulties with 'high temperature 
superconductivity is well illustrated by the Buddhist parable of the blind men trying to 
describe "experimentally" an elephant. These very same facts clearly illustrate that this is 
an extremely active field, with many unanswered questions, and with a great future 
potential for discoveries and progress in many (sometimes unpredictable) directions. 

It is very important to stress that independently of any current or future 
applications, this is a very important area of basic research. 

High T c S upercond uctivity 

Fig. 1 Status of High Temperature Superconductivity.[l] 


Basic research in high temperature superconductivity, because the complexity of 
the materials, brings together expertise from materials scientists, physicists and chemists, 
experimentalists and theorists. Much of the research in High T c superconductivity has 
spilled over to other areas of research where complex materials play an important role 
such as magnetism in the manganites, complex oxides, two and one dimensional 
magnets, etc. Applications could greatly benefit from the discovery of new 
superconductors which are more robust and allow easier manufacturing. Perhaps this is 
not possible since a naive inspection of superconductors seems to indicate that the higher 
the T c the more complex the material. An excellent review where many target needs for 
applications have been - outlined is an NSF report years ago. Many of the comments 
made there regarding applied needs, are still valid [2]. 

It is important to realize that this field is based on complex materials and because 
of this materials science issues are crucial. Microstructures, crystallinity, phase 
variations, nonequilibrium phases, and overall structural issues play a crucial role and can 
strongly affect the physical properties of the materials. Moreover, it seems that to date 
there are no clear-cut directions for searches for new superconducting phases, as shown 
by the serendipitous discovery of superconductivity in MgB 2 . Thus studies in which the 
nature of chemical bonding and how this arises in existing superconductors may prove to 
be fruitful. Of course, "enlightened" empirical searches either guided by chemical and 
materials intuition or systematic searches using well-defined strategies may prove to be 
fruitful. It is interesting to note that while empirical searches in the oxides, gave rise to 
many superconducting systems, similar (probable?) searches after the discovery of 
superconductivity in MgB 2 have not uncovered any new superconductors. Anyhow, this 
illustrates that superconductivity is pervasive in many systems and thus future work 
should not be restricted to a particular type of materials systems. See Chapter II. 

Research in the electronic properties of High T c superconductors has proven to be 
particularly fruitful. This has lead to improvements in electronic structure techniques 
which unquestionably have an effect on other fields. The improvement on real and 
reciprocal space resolution uncovered many interesting properties. However, it is not 
clear at the present time whether many of these properties are related in some essential 
way to superconductivity or they are just accidentally present. It seems that the presence 
of competing phenomena is present in most high temperature superconductors. Thus it is 
natural to investigate systems which are close to some form of instability such as the 
metal-insulator transition, magnetic phases, electronic instabilities such as stripe phases, 
etc. Comparisons of classical infrared spectroscopy, and photoemission measurements 
with tunneling may prove to be fruitful. In particular, mapping with high resolution (in 
real and reciprocal space) the electronic structure may prove to hold some of the keys to 
the mechanism of superconductivity. To make these useful, issues such as surface 
contamination, surface segregation, and in general heterogeneity of the materials close to 
surfaces or interfaces must be addressed, and are particularly important in these very 
short coherence length superconductors. This is particularly important for surface 
sensitive probes such as photoemission. Several techniques such as Raman scattering, 
NMR and muon spin depolarization are not addressed in this snapshot, although they give 


valuable information and are heavily researched. Complementary measurements are 
particularly useful if a whole battery of tests, in the same sample, which are structurally 
characterized in detail, are performed. The "quality" of samples on the other hand, must 
be well established by structural criteria which are well defined "a-priori" and not based 
on circular or theoretical arguments. See Chapter III. 

The properties of High Temperature Superconductors in a magnetic field have 
proven to be particularly interesting. A myriad of new phases have been uncovered in the 
vortex system and have lead to the establishment of a very complex phase diagram the 
details of which are still being established. The presence of many phases and the 
interactioii/competitiorifcloseness to magnetic phases allows for much new research using 
artificially structured pinning. New lithography and preparation techniques allow 
modifications and confinement of these materials in length scales approaching the 
superconducting coherence length and certainly the penetration depth. Moreover, novel 
imaging techniques are arising which can give detailed microscopic images of the vortex 
system. This of course can provide the microscopic picture of the magnetic state of high 
temperature superconductors and will probably also help improvements on their use. See 
Chapter IV. 

Many basic research studies and a large number of applications require the High 
Temperature Superconductors to be in proximity with other materials. Thus issues of 
proximity effects, spatial variations close to an interface or surface, structural and 
materials variations are particularly important in thin film and/or nanoscopic structures. 
For this purpose it is important to investigate the mutual interaction between 
superconductors and other materials. This requires careful preparation and detailed 
characterization of inhomogeneous materials, together with superconducting 
measurements as a function of well-defined structural parameters. This may also allow 
addressing issues such as the importance of the proximity to other ordered phases such as 
magnetic and electronic inhomogeneities which are naturally existent or are artificially 
engineered. It is not even clear in the various models of high temperature 
superconductivity or even experimentally how the proximity effect occurs. What is the 
dependence of the order parameter in an ordinary or magnetic metal, or a low 
temperature superconductor when in proximity with a d-wave superconductor? See 
Chapter V 

Contrary to low temperature superconductors, high T c ones have received very 
little attention under nonequilibrium (time dependent, strongly driven, exposed to varying 
radiations, etc.) conditions. This may prove to be a very interesting and novel direction 
for ceramic oxides. These types of studies may hold important clues to the mechanism of 
superconductivity, may unravel new physics and are important in many applications. For 
instance, simple issues such as the microscopic nature or even existence of critical 
slowing down close to the superconducting phase transition has not been firmly 
established. See Chapter VI. 

The theory of high temperature superconductivity has proven to be elusive to 
date. This is probably as much caused by the fact that in these complex materials it is 


very hard to establish uniquely even the experimental phenomenology, as well as by the 
evolution of many competing models, which seem to address only particular aspects of 
the problem. The Indian story[l] of the blind men trying to characterize the main 
properties of an elephant by touching various parts of its body seems to be particularly 
relevant. It is not even clear whether there is a single theory of superconductivity or 
whether various mechanisms are possible. Thus it is impossible to summarize, or even 
give a complete general overview of all theories of superconductivity and because of this, 
this report will be very limited in its theoretical scope. The general view point 
(determined by "majority vote") seems to be that low temperature superconductors are 
phonon mediated whereas high T c ones are somehow "unconventional" and anisotropic, 
although the origin of the anisotropy remains "controversial. Because of this, numerical 
studies in well-defined theoretical models may prove to be particularly illuminating and 
may help uncover the essence of superconductivity. Particularly, understanding and 
further developing the t-J model looks like a promising numerical direction. Electronic 
structure calculations combined with well developed methodologies seem to explain 
quantitatively many aspects of superconductors with moderate T c s. How far can these 
type of approaches be pushed? Could they in fact explain ab-initio superconductivity in 
some of the cuprates? Moreover, first principle electronic calculations may be very useful 
in providing parameters for model hamiltonians. Another approach which at least allows 
parametrizing in some useful way the properties of superconductors has also been used. 
How far can these type of models go and how universally can they explain the 
(superconducting or normal) properties is not clear at this stage. There are several 
important issues which must be kept in mind. It may be that there is a theoretical model 
which has the essence of the problem in it and it either has not yet been developed or has 
not yet percolated to the conscience of the community. Moreover, it seems that to date no 
theory has been developed which has predictive power as far as materials system are 
concerned. Since purely theoretical approaches have difficulties so far in identifying a 
clear avenue for search, empirical studies in which materials parameters and properties 
are correlated with superconducting properties may prove useful[3]. This may serve at a 
later stage as a test ground for theories. Comparisons of theoretical ideas which rely only 
on the layered material of high T c ceramics, with artificially engineered layered 
superlattices should not be neglected and may prove to be useful. See Chapter VII. 

Finally, there seems to be still much work needed to understand in detail the 
connections, control and effect of defects on high temperature superconductivity. This of 
course is very important for applications, particularly those which require high critical 
currents such as power applications. Moreover, the intrinsic brittleness highlights that 
understanding and controlling the mechanical properties while not directly related to 
superconductivity, is a very important and promising new area of research, especially in 
connections with large scale applications. See Chapter VIII. 

In the rest of this paper we will expand on these issues and attempt to outline 
some well defined promising directions of research. The focus is mostly on basic research 
challenges and opportunities, which hold back progress. 


II. Structure, Bonding and New Systems 

The discovery of new superconducting materials has played an important role in 
the advancement of the field of superconductivity research since its inception[4-7]. This 
was perhaps most dramatically displayed by the discovery of the high T c cuprates in 
1986. The influence of new superconducting systems continues to this day, for example 
through the discovery in 2001 [8] of MgEfe. Thus far, the existence of a totally new 
superconductor has proven impossible to predict from first principles. Therefore their 
discovery has been based' largely on empirical approaches,' intuition, and even 
serendipity. This unpredictability is at the root of the excitement that the condensed 
matter community displays at the discovery of a new material that is superconducting at 
high temperature. New systems can be found by either bulk methods or thin film 
methods, each of which has its own advantages, disadvantages, challenges and 
opportunities. The search for new materials has always been[9], and remains an important 
area of research in the field of superconductivity . 

Fig. 2 The crystal structure of MgB 2 . The graphite-like array of boron (shown in black) 
is critical to the occurrence of high temperature superconductivity in this compound. 

Also important for the development of potentially practical materials and the 
understanding of the complex physical phenomena which occur in superconducting 
materials has been the use of chemical doping or manipulation to influence the electronic 
and magnetic properties of the superconducting systems. An example of the former 
chemical doping is the introduction of small flux pinning chemical precipitates in 
conventional intermetallic superconductors and 123-type superconductors. Examples of 
the latter are found in the "lightly doped" cuprates and other perovskite structure 
transition metal oxides where the concepts of charge and orbital ordering have recently 
emerged as important considerations in attempts to understand magnetic and electronic 
properties. These cooperative states join other such states such as charge density waves 
and spin density waves as critically influential in determining the ultimate electronic 


ground state of complex materials. Chemical doping has played an essential role in these 
areas. Importantly, it allows for the systematic variation of electronic properties as a 
function of variables such as lattice size, carrier concentration, and magnetic or non- 
magnetic disorder, providing a basis for the development of theoretical models. This area 
of research is highly active in the field of superconductivity, and will continue to be of 
great importance in the future. 

1. Synthesis and Fabrication 

a) Bulk 

In the high density of states conventional intermetallic superconductors, the BCS 
coupling through the lattice may be viewed as a general lattice phenomenon. In more 
recently discovered superconductors, such as MgB2, it has been found that one particular 
phonon mode - an in-plane boron mode that modulates bond lengths and angles within 
the flat B honeycomb lattice in the case of MgB 2 - is responsible for coupling to the 
conduction electrons and is the driving force for superconductivity [10, 1 1]. Conclusions 
about the nature of the phonons and electrons that are responsible for the 
superconductivity in a particular material can be arrived at nowadays by sophisticated 
experimental study and theoretical analysis. In particular the band-structure experts can 
calculate the effect that a particular phonon has on the electrons at the Fermi energy in a 
particular superconductor by doing "frozen phonon calculations". Such calculations are 
highly instructive for superconducting materials like MgB 2 . 

This analysis is after the fact, unfortunately, for people whose interest is in 
finding the new superconductors in the first place. So given the fact that undirected 
combinatorial chemistry will never get through all the possible element/treatment 
combinations in a search for superconducting materials, one important issue to be 
resolved in future research is to translate the physics of superconductivity into a set of 
chemical hypotheses to guide the search for new ones. The era of finding new high 
temperature superconductors in intermetallic compounds like Nb 3 Ge appears to be long 
gone. The new breed of high T c superconductors is quite different - even beyond the 
cuprates, which are their own special case. The difference lies in the type of chemical 
bonding these superconductors display, even in what look like classic intermetallic 
compounds such as MgB 2 and LuNi2B2C[12]. Thus one important issue for future 
research is to explore how the nature of the chemical bonding present influences the 
superconductivity in "conventional" intermetallic compounds. 

Initially promising reports of electronic doping through charge injection into a 
variety of organic and inorganic compounds in FET device structures have recently been 
called into question[13]. Nonetheless, conceptually they point out that another area of 
future research in new superconducting systems should be that non-thermodynamic 
synthetic methods should be actively pursued. Modulation doping, the chemical analogue 
of charge injection, for transferring charge between layers in fine scaled multilayerd 
films, has potential which is yet to be exploited. Other methods for non-thermodynamic 
synthesis with high potential for success include quenching from high pressure or from 

the vapor, epitaxial thin film layer by layer or block-by-block growth, photodoping, 
electrochemical synthesis at low temperatures, ion exchange, framework stabilization of 
structures, and electrochemical intercalation. 

b) Thin Films. 

There are many examples of stabilization of non thermodynamic compounds in 
thin films in both the cuprate superconductors and in dielectric or ferroelectric materials 
by. using epitaxy with substrate or buffer layers. In the most extreme examples of this 
type of metastable material it may be a single atomic layer or even an interface that has 
the desired- properties. On such short length scales, chemical bonding is the predominant 
influencing factor. Different physical and chemical methods of growth influence the 
behavior of surfaces and very thin layers. Great progress has been made in 
characterization after growth - such as Transmission Electron Microscopy (TEM) and X- 
ray probes, but a great deal more may be gained in the future by incorporating techniques 
that can be used in situ to characterize surfaces during growth. 

Of particular interest in the search for new materials is the "phase spread method" 
used with success by some materials physicists. In this method, thin films are made by 
intentionally introducing composition gradients, for example by having three atomic 
sources in a triangular geometry, such mat their deposition areas only partially overlap. 
The film thus fabricated contains mixtures of the source atoms in systematically varying 
ratios depending on proximity of substrate to one or another of the source. Annealing of 
such composition spreads under different conditions can be employed to search 
significant areas of phase space. 

Photoexcitation provides another non-thermodynamic method to perform doping 
studies on thin films in a reproducible way without changing material, thus avoiding the 
inherent difficulties with controlling stoichiometry, uniformity, and homogeneity of the 
samples[14, 15]. Persistent photoexcitation has been performed in many cuprate 
superconductors and on the magnetic manganites at low temperatures below 100K. Large 
changes in conductivity, Hall effect, mobility, and superconducting transition 
temperatures have been observed. In the best model for this process, light generates an 
electron hole pair and the electron is trapped in a defect thus changing the hole doping in 
the electronically active layer providing a potentially useful way to trim device properties 
and "write" artificial nanostructures without need for lithography. 

c) Doping in the Cuprate Superconductors. 

The properties of the cation-substituted and oxygen-doped high-temperature 
superconductors have been studied in detail since 1987. In general, the physical 
properties (temperature-dependent resistivity, superconducting transition temperature, 
Hall effect, etc.) and the structural properties of the HTS cuprates behave quite 
differently as a function of substitutions in comparison to conventional superconductors. 
Doping and ion-induced disorder have shown that a small change in physical structure 
can induce a dramatic change in the electronic structure in these materials. This was one 


of the first indications that they were unconventional superconductors. The details of the 
effects of atomic substitutions or doping are not yet fully understood in the cuprate 
superconductors, and this represents an active area of current research. Concentrating on 
YBa2Cu307-6 (YBCO) for example, some of these issues are: 

i) Doping on the Y-site. 

Doping with the heavy Rare Earth (RE) ions on the Y-site, even with Gd, does not 
affect T c , except for substitutions of the Y with Pr. The effects of Pr-doping remain 

* I 

ii) Doping on the CuO chains. 

Substitutions of 3+ ions (e.g., Al, Co, Fe) primarily replace Cu in the CuO chains. 
Extra oxygen is simultaneously incorporated into the chain layer, the c-axis lattice 
constant increases, and an orthorhombic to tetragonal transition occurs. Since the extra 
oxygen compensates for the valence of the substituted cation, it remains an open question 
as to whether the resulting doped materials are underdoped or overdoped. Also, it has 
long been known that not only is the T c of YBCO dependent on the oxygen 
concentration, but also on how the oxygen is ordered. Open issues remain, such as why 
do the chain oxygens need to be ordered to maximize the T c ? 

Hi) Doping in the Cu0 2 planes. 

Both Ni and Zn predominately replace copper in the Cu0 2 planes without 
significant structural change. However, T c falls faster in these cases than it does with 
increased 3+-cation doping on the chains or oxygen doping on the chains. That is an 
indication that the loss of structural continuity of the Cu02 plane is more detrimental to 
the superconducting transition temperature than the lattice changes that occur due to 
doping on the CuO chains. There are interesting data comparing the Ni and Zn-doping: 
Tc falls faster with increasing the Zn doping than with increasing the Ni doping. 
Conversely, the room temperature resistivity increases faster and the Relative Resistance 
Ratio (RRR) [R(300) / R(0)-extrapolated] reduces faster with increasing Ni doping than 
increasing Zn doping. Therefore, Zn destroys the superconducting phase faster and the Ni 
destroys the normal metal phase faster. Remaining issues are: Why do Ni and Zn 
substitution reduce T c so dramatically? and Why does Zn suppress the superconducting 
state faster than Ni, while Ni suppresses the normal state faster than Zn? 

iv) The Role of the Charge Reservoir Layers. 

The cuprates containing Hg, Tl and Bi ions in their charge reservoir layers have 
unusually high T c s. These ions are known to charge disproportionate, which makes them 
negative U-centers. Under some circumstances it is known that negative U-centers can 
be superconducting pairing centers. It is of great interest to determine whether 
superconducting pairing on the charge reservoir layers is responsible for the enhanced T c s 


of the Hg, Bi and Tl cuprates, and if so whether the negative U approach can be turned 
into a general method for finding and enhancing superconductivity. 

2. Other Topics of Interest 

a) Applied Pressure. 

The investigation of high temperature superconductors under high pressure has 
the advantage that the basic interactions responsible for superconductivity can be 
changed without introducing disorder into the system as encountered in alloying 
experiments. The drawback is that one has to deal with massive high pressure cells, small 
sample sizes, and technical difficulties that increase with the higher the pressure range of 
interest. Measurements of the pressure dependence of T c are the most straightforward 
since this can be accomplished through measurements of the electrical resistivity and the 
ac magnetic susceptibility under pressure. The electrical resistivity in the normal state, 
which can be accessed even below T c by suppressing superconductivity with a magnetic 
field, yields complimentary information about phonons and magnetic excitations that are 
responsible for the superconductivity. Other types of measurements such as NMR and 
specific heat have been made under pressure. It would be useful to develop techniques for 
making other types of measurements under pressure and extending the range of pressures 
currently accessible. 

b) Spin, Lattice, and Charge Correlations. 

"Doping" generally refers to the introduction of charge carriers into the 
conduction or valence bands of a material. However, because of the large coupling 
between charge, spin and lattice in the cuprate superconductors and other transition metal 
oxides, doping of these materials with charge carriers can also be accompanied by the 
formation of static and dynamic spin and/or charge ordered phases on a microscopic 
scale. These "stripe phases," have recently been observed in many perovskite based 
transition metal oxides, including several cuprates, and may be a general feature of 
transition metal oxides[16, 17]. The role these microscopic inhomogeneous spin or 
charge phases play in high temperature superconductivity, magnetism, and other effects 
that have been attributed to them, is, however, unclear at this time. 

The comprehensive understanding of spin/charge self-organization in oxides is a 
challenging task. This is a new viewpoint in the survey of strongly correlated phenomena 
in solids - a field that until recently has been primarily focused on the properties of 
nominally homogeneous systems. Intrinsically inhomogeneous spin and charge systems 
in transition metal oxides call for both original theoretical approaches and for the 
development of novel experimental tools suitable to deliver important information. 
Existing experimental information on the electronic and lattice properties of stripes 
systems is incomplete and therefore many fundamental problems related to spin/charge 
ordered regime in solids remain unresolved. 


3. Conclusion 

We believe that the opportunities for new materials to greatly influence the future 
of superconductivity research remain large, both from the point of view of fundamental 
science and the development of practical superconducting materials. We believe that 
chemical doping, non-thermodynamic synthesis, the discovery of totally new materials, 
the investigation of strongly correlated charge and electronic systems, and the use of 
chemical principles to help answer questions about the nature of superconductivity are 
exciting areas for future research. • 

III. Electronic Structure and Quasiparticle Dynamics 

High-T c superconductivity is achieved when a moderate density of electrons or 
holes is introduced in antiferromagnetic (AF) Mott-Hubbard insulator hosts by chemical 
or field-effect doping. Gross features of the evolution of the electronic structure as doping 
progresses from Mott insulator to d-wave superconductor are known from the systematic 
transport, photoemission and optical studies[18-21]. The doping-driven phase diagram of 
high-T c systems is exceptionally rich owing at least in part to the fact that at the verge of 
the metal-insulator transition boundary magnetic, electronic, lattice and orbital degrees of 
freedom are all characterized by similar energy scales. Optimally doped cuprates (having 
highest T c for a given series) reveal a well-defined Fermi surface in close agreement with 
the results of the band structure calculations[22]. Nevertheless, the dynamics of charge 
carriers appears to be highly anomalous defying the grounding principles of the Fermi 
liquid theory. Numerous attempts to describe the electronic properties using strong 
coupling Eliashberg theory have been only partially successful[23-25]. Using this 
approach it became possible to find a consistent description of many of the features 
established through a combination of tunneling, photoemission, optical and neutron 
scattering measurements for YBCO and the Bi2212 families of materials. However, 
many other systems of cuprates fail to follow the same patterns[26, 27]. Moreover, 
because of the extremely strong inelastic scattering established for most high T c 
superconductors the concept of strongly interacting quasiparticles underlying the 
Eliashberg formalism is in question. 

Early on it became established that superconducting currents in cuprates are 
carried by pairs of holes or electrons similar to that of conventional BCS 
superconductors. However, a viable description of the pairing interaction is yet to be 
found. Numerous experimental results indicate that the process of the condensate 
formation in cuprates is much more complex than the BCS picture of a pairing instability 
of the Fermi gas. One example of a radical departure from the BCS scenario is that the 
opening of the superconducting gap in cuprates is preceded by the formation of a partial 
gap (pseudogap)[28]. There is still a debate as to whether this pseudogap is related to the 
superconductivity. The pseudogap appears to be strongly anisotropic around the Fermi 
surface mirroring the anisotropy of the superconducting gap. These observations 
prompted the "precursor to superconductivity" scenarios for the pseudogap. Within this 


view, the formation of pairs precedes the development of global phase coherence 
between paired states [29]. Observations of vortex-like excitations [30] as well as of finite 
superfluid stiffness[31] at T>T C are in accord with the preformed pairs hypothesis. The 
process of the superconducting condensate formation in high-T c cuprates also appears to 
be notably different from the BCS scenario. In particular, the energy scales involved in 
the formation of the superconducting condensate are anomalously broad and exceeds the 
magnitude of the superconducting energy gap by more than one order of magnitude[32, 
33]. These latter results inferred from optical spectroscopy are consistent with the view 
that the kinetic energy is lowered in the superconducting state. Similar conclusions also 
emerged from the detailed analysis of the photoemission spectra[34]. The electronic 
properties of»the highJ'T e superconductors have been probed by several complementary 
techniques. These techniques have shown substantial technological improvements in part 
driven by the need for higher energy and k resolution. In addition there is a growing 
belief that these materials may have real space inhomogeneities and so that a high 
resolution real space probe is desirable. Among the techniques that have revealed 
substantial insight because of technical improvements, we discuss electron tunneling, 
angular resolved photoemission spectroscopy, and infrared spectroscopy. 

1. Techniques 

a) Electron Tunneling. 

Electron tunneling (both quasiparticle and Josephson tunneling) has been a 
powerful technique to probe the excitation spectrum, the superfluid density and the pair 
wave function phase of conventional superconductors. With high T c cuprates, the 
technique has been no less informative. Currently, much of our understanding of the 
order parameter symmetry has come from Josephson effect studies[35] and the non-BCS 
nature of the excitation spectrum that comes about from the symmetry has been clearly 
observed[36]. C-axis and a-b plane quasiparticle tunneling have illustrated the extreme 
anisotropy of these superconductors and shown that surfaces are very different with 
possible bound states due to the broken symmetry at Ihe a-b interface[37]. Intrinsic c-axis 
tunneling[38] has attempted to address the relationship between the superconducting gap 
and the pseudo gap. The debate over whether the pseudogap and the gap are intrinsically 
coupled continues. 

STM studies offer an important additional feature that has already yielded some 
surprises. STM quasiparticle tunneling has allowed both microscopy and spectroscopy 
with good energy resolution and the spatial resolution to study the gap parameter on a 
length scale smaller than the superconducting coherence length[39]. Some of the current 
thinking on the high T c superconductors concludes that there are intrinsic 
inhomogenieties (especially in the underdoped limits) in the superconducting properties. 
Coupling the high energy resolution with the high spatial resolution, along with the 
recently developed superconducting STM[40] will allow direct spatial studies of the 
energy gap, bound states and the superfluid density. Recent investigations have 
illustrated the local effects of non-magnetic and magnetic impurities[41] in the high T c 
materials and a background periodicity in the electronic density[42] (charge density wave 


or spin density wave?) which requires further investigation. It is not clear whether this 
periodicity in the electronic density is associated with the superconductivity in these 
materials. Finally, the combination of high resolution quasiparticle spectroscopy and 
Josephson probe will allow quantitative investigation of spatial variations of the order 
parameter and superfluid density around impurities, at interfaces and proximity junctions. 
In conventional superconductors these two quantities are related but with spatial 
inhomogeneities, it is no longer required. For the high T c materials, some theoretical 
models require inhomogeneities that would result in the superfluid density having 
different behavior than the energy gap. This will allow us to address both fundamental 
issues and applications. For example, current studies show that a magnetic impurity does 
not suppress the energy gap[31]. It has been ; concluded that superconductivity is not 
affected but the superfluid density has not yet been investigated. In addition, much is still 
to be learned about the proximity effect at the interface between the high T c materials and 
other metals. Tunneling will allow us to probe this interface. 

b) Angular Resolved Photoemission Spectroscopy (ARPES). 

ARPES experiments have contributed to our understanding of the electronic 
structure and superconducting properties by revealing the Fermi surface information,[43] 
and a large superconducting gap anisotropy that is consistent with d-wave pairing 
state. [44] 

Recent improved resolution, both in energy and in k have resulted in 
unprecedented data which allow us to map the electronic dispersion curves (E vs. k) for 
bands below the Fermi level E F [45, 46]. Angle resolved photoemission studies are now 
mapping the dispersion curves for several cuprates (and other perovskite oxides). As a 
result of the enhanced energy and k resolution, it has been demonstrated that in addition 
to E and k, the linewidths AE (related to scattering rate j/) and Afc (related to the 

inverse mean free path I) can also be determined. While mapping these quantities over 


an extensive phase space of E and k is still to be done, these measurements have revealed 
some very important insight already. Close to Ef an electron mass enhancement[47-49] 
(E vs. k measures the velocity and hence the effective mass m*) is observed in the 
dispersion curves which is both energy and temperature dependent. These measurements 
can be thought of as directly probing the self-energy of the carriers with all their 
dressings as a result of the interactions the carriers experience. In conventional 
superconductors, these interactions and mass enhancements are a result of the electron- 
phonon interaction; the mechanism responsible for superconductivity in the simple 
materials. Indeed, for many in the field it was the measurement of the strength of the 
electron-phonon interaction (via tunneling for example) which confirmed the phonon 
mechanism of superconductivity. The measurements of ARPES are being carried out in 
several laboratories in the U.S. and elsewhere and the mass renormalization effects are 
observed at several facilities and in several materials. 

There is still disagreement as to some of the details of these measurements and to 
their interpretation^, 50, 51]. Electron-phonon interactions, electron-spin interactions 
and electron-electron interactions have all been suggested and all result in enhanced mass 


due to the interactions. Temperature dependent studies also illustrate that these 
interactions are at low energy and result from strong interactions. 

It is clear that mapping of these dispersion curves over a wider volume of the E-k 
phase space is important. It is especially critical with the high T c cuprates because of the 
large electronic anisotropy of the materials. Furthermore, because of the symmetry of the 
order parameter, mapping of the self energy effects as a function of k around the Fermi 
surface is especially critical. If these observed renormalizations are the signature of the 
mechanism responsible for superconductivity in the high T c materials, an extensive map 
of the electronic renormalized map will be valuable if the analogy with low T c 
superconductors is'relevant/ In the case of low T e materials the renormalized mass 
m = nil + A) where X =electron-phonon interaction averaged over the Fermi surface. 

Current ARPES measurements could be determining quantitatively the strength of 
the interaction and the mechanism of superconductivity. As a final caveat, it must be 
remembered that both APRES and tunneling are surface probes. 

In this connection, inelastic X-ray scattering (IXS), which is not sensitive to 
surfaces or defects, is a valuable probe of bulk states. For high momentum and energy 
transfers IXS directly measures the ground state momentum density of electrons, while 
spin density is measured in magnetic IXS scattering, with improved resolution that has 
been achieved with synchrotron light sources, IXS has revealed surprising electron 
correlation effects with simple metals and has been extended to study the electronic 
excitations of the present compound of high T c superconductors. Its application to 
ceramic superconductors would be most worthwhile. [52, 53] 

c) Infrared Spectroscopy. 

Infrared (IR) and optical spectroscopy is ideally suited for the studies of 
superconductivity because of the ability of these techniques to probe such fundamental 
parameters as the energy gap and the super fluid density[54]. Notably, IR spectroscopy 
allows one to investigate the anisotropy in these parameters through measurements 
performed with the polarized light[55]. Because IR/optical information is representative 
of the bulk and measurements can be performed on the micro-crystals, these studies allow 
one to examine common patterns of a large variety of materials which may not be 
suitable for examination with other techniques. Optical techniques offer means to probe 
strong coupling effects in the response of quasiparticles. In this context IR, tunneling and 
ARPES results are complimentary to each other. It is therefore desirable to "map" 
renormalization effects using a combination of several spectroscopic methods. Charge- 
and spin-ordered states in solids can be conveniently examined through the analysis of 
the IR-active phonon modes. The latter circumstance is important for the investigation of 
self-organization effects which dominate the dynamics of charge carriers at least in 
under-doped cuprates. 

IR measurements can be performed in high magnetic field. Present work in the 
use of IR in high field experiments is restricted to a few experiments but several groups 


are actively involved into adapting IR instrumentation for these challenging 
measurements. These studies promise to yield detailed information on dynamics of both 
pancake and Josephson vortices. More importantly, DC fields currently available in 
optical cryostats (up to 33 T) are sufficient to destroy superconductivity thus giving 
spectroscopic access to the normal state properties at T«T C . Transport measurements in 
strong magnetic field highlighted anomalies of the normal state in LaSrCuO (LSCO) 
series of cuprates[56]. Spectroscopic measurements will be instrumental in distinguishing 
between (conflicting) interpretations of these results and will also help to unravel generic 
trends of the normal state behavior at T<<Tc between several classes of superconductors. 

2. Magnetism, Competing Order, arid Phonons 

a) Magnetism and Spin Fluctuations. 

As discussed earlier, superconductivity in the cuprates is achieved by doping 
holes or electrons into an antiferromagnetic-insulator state. The magnetism is essentially 
an electronic effect, as it results from strong Coulomb repulsion between pairs of 
conduction electrons on the same Cu atom, together with the Pauli exclusion principle. 
Considerable knowledge of antiferromagnetism (AF) and spin fluctuations in the 
cuprates[57, 58]. has been obtained experimentally using neutron scattering, nuclear 
magnetic resonance (NMR), and muon spin rotation (n.SR) spectroscopy. The general 
significance of antiferromagnetic correlations and spin fluctuations in theoretical 
mechanisms of high-temperature superconductivity is motivated by this experimental 

In hole-doped cuprates, 2% holes doped into the CuC>2 planes are generally 
sufficient to destroy AF long-range order, but a minimum of 5-6% are necessary to 
induce superconductivity. Considerable attention has been devoted to characterizing the 
evolution of the AF spin fluctuations with doping. The bandwidth of the magnetic 
excitations, -300 meV in the ordered AF, appears to change relatively little with doping. 
In LSCO, the low-energy spin fluctuations become incommensurate as doping increases, 
with a characteristic wave vector displaced from that of the AF by an amount 5. Similar 
incommensurability has been observed in YBCO, but additional features are the presence 
of a gap in the low-energy fluctuation spectrum followed by a commensurate "resonance" 
peak. The gap and peak energies both increase with hole concentration up to optimum 
doping, at which the resonance-peak energy is ~ 40 meV. Recent results on other 
families of superconducting cuprates indicate that the resonance peak is a common, 
although not universal, feature[59]. 

Electron doping has a weaker effect on the AF state, with a transition directly 
from AF order to superconductivity occurring at an electron concentration near 12%. 
Initial neutron measurements indicate that the AF spin fluctuations remain commensurate 
in the superconducting phase. Studies over a broad energy range are made challenging 
by the presence of crystal-field excitations from the rare-earth ions. 


Progress in the characterization of spin fluctuations has been enabled by the 
development and improvement of techniques for growing large single crystals and by 
forming large-volume mosaics of small crystals. Neutron scattering studies of hole- 
doped cuprate systems other than LSCO and YBCO are in early stages, and considerable 
progress is likely in the next few years. Improvement in the homogeneity of large 
underdoped YBCO crystals would be helpful for some of the issues discussed below. 
The availability of sufficient access to appropriate neutron scattering facilities may also 
be a limiting factor. 

b) Competing Orders. 

A phenomenon known as "stripe" order has been observed by neutron and X-ray 
diffraction in several variants of the LSCO family [60, 61]. Spin-stripe order is indicated 
by the appearance of elastic magnetic superlattice peaks at the same incommensurate 
wave vectors at which the low-energy spin fluctuations occur. These are usually 
accompanied by the observation of another set of superlattice peaks split about 
fundamental Bragg points, indicative of charge-stripe order. The presence of stripe order 
is generally (although not always, as in the case of La 2 Cu04 +y ) associated with a 
reduction in the superconducting transition temperature. However, there is also a linear 
correlation between T c and the incommensurability of the spin fluctuations in the absence 
of stripe order. 

There is also some evidence of stripe correlations in YBa2Cu306+x O chains. The 
temperature dependence of the associated superlattice intensities suggests a coupling to 
electronic correlations, and possibly to charge stripes[62]. Certain spin fluctuations have 
been found to have an incommensurability similar to mat found in LSCO; however, the 
cause of the incommensurability is controversial. 

The recent scanning tunneling microscope (STM) observations of spatial 
modulations of the electronic density of states (DOS) in the CuCb planes of BSCCO has 
stimulated considerable speculation. The observed period of 4a (a, the in-plane lattice 
constant) suggests a connection with the charge and spin stripes found in LSCO. Clearly, 
a combination of tunneling and scattering studies is needed to clarify the nature of the 

There are many unresolved issues associated with the problem of stripes. Is stripe 
order a type of electronic instability, like conventional charge-density-wave order, that 
only competes with and limits superconductivity? Is it possible for a stripe-liquid phase 
to exist? Are stripe correlations common to all superconducting cuprate families, or do 
they only occur in special cases? Are spin stripes always associated with charge stripes, 
or are these distinct types of order? Do stripes (or possibly another type of 
inhomogeneity) exist in electron-doped cuprates? Studies with a wide range of 
techniques will be needed to answer these questions. Stripes are but one kind of order that 
has been proposed to have a connection with the various "pseudogap" phenomena that are 
observed in underdoped cuprates[63]. A number of theories have put forward the 
hypothesis that a new order parameter appears in the pseudogap regime. Two particular 


examples are quadrupolar orbital currents , and the staggered flux phase or d-density- 
wave (DDW) state. In both cases, orbital currents result in local magnetic moments that 
should be, in principle, detectable by neutron scattering. So far, neutron scattering 
experiments have been unable to find evidence for such phases, which predict no 
breaking of translational symmetry; however, the presence of quadrupolar currents 
provides a possible explanation for the recent observation of time-reversal-symmetry 
breaking by photoemission[64]. The possible existence of orbital moments remains an 
open issue. 

c) Phonons and Electron-Phonon Interactions. 

The role of electron-phonon interactions in the cuprates has been the subject of 
renewed interest, motivated in part by a recent interpretation of ARPES data [28] An 
important technique for characterizing phonon dispersions and densities of states is 
inelastic neutron scattering. (Note that neutron measurements of the phonon DOS in 
MgB 2 provided an important validation of the theoretical evaluations of electron-phonon 
coupling in that system.) Dispersion anomalies in the Cu-0 bond-stretching modes, 
clearly associated with some kind of electron-phonon coupling, have been the subject of 
controversy for several years. The experiments are constrained by weak scattering cross 
sections and limited crystal size. Further experimental studies, together with serious 
theoretical analysis, are necessary in order to make real progress in this area Inelastic X- 
ray scattering has also been used recently to study optical phonons in a cuprate. 

Figure 3. Schematic 
representation of excitations 
and collective modes in high- 
T c superconductors. A 
remarkable variety of effects 
in these materials have typical 
energy scales of about 50-70 
meV, including: phonons, 
magnetic resonance, 
superconducting gap and 
pseudogap as well as "kinks" 
in the ARPES spectra. 
Competition, interplay and 
interdependence between 
these effects are responsible 
for complexity of the strongly 
correlated state in these 



IV. Vortices 

Most of the electromagnetic properties of Type II superconductors are determined 
by vortices in static and dynamic configurations. Rapid progress in manipulating and 
measuring vortices in recent years has greatly expanded the limits of known and 
imaginable vortex phenomena This chapter outlines several research directions that are 
now within reach and that will develop new concepts and strategies for fundamental 
science and applications. 

1. Single Vortex Physics. ' 

a) Confinement. 

Advances in micro- and nano-scale patterning and in high sensitivity 
measurements now enable studies of single vortices, allowing a wide range of new 
physics to be explored. Vortices enter mesoscopic samples[65-68] one-at-a-time at field 
intervals determined by flux quantization, AH ~ Oq/L 2 where <3> 0 is the flux quantum and 
L the sample dimension. The entry of each vortex produces a step change in the 
magnetization, corresponding to a first order phase transition. In circular disks, vortices 
are predicted to configure in shell pattems[69] reminiscent of electrons in atoms and 
leading to magic numbers of high stability. At certain fields a collection of discrete 
Abrikosov vortices transforms to a single giant vortex containing the same number of 
flux quanta and a circulating current at the outer edge of the sample. This phase 
transition is reminiscent of Wigner localization in electronic systems. In lower symmetry 
disks such as squares, vortices and antivortices coexist to simultaneously satisfy flux 
quantization and rotational symmetry[67]. 

Studies of confined vortices can be extended to layered superconductors such as 
NbSej and the cuprates, where the superconducting coherence length £ and the magnetic 
penetration depth Xare quite different, and to other experimental probes like STM that 
directly image the superconducting order parameter. Confinement need not be limited to 
a single disk. Arrays of disks, each containing confined vortices, can interact through a 
superconducting substrate. Confinement in a line geometry[65] allows motion of 
confined vortices to be studied[70]. Confined disks connected by lines offer many 
analogies to single electron behavior including the Coulomb blockade and single electron 

Individual vortices in an array can be manipulated by imposing an artificial 
mesoscopic template. One approach is to lithographically pattern a superconducting film 
with an array of holes, or antidots, each of which traps one or more vortices[71-74]. 
Trapping vortices one-by-one has practical implications: it can dramatically enhance the 
pinning effectiveness and critical current, and it can lead to extremely sharp switching 
effects at matching fields. These switching features offer the potential for three terminal 
devices, where the supercurrent across the antidot array is modulated by a control 
magnetic field operating near the matching field. Antidots are predicted to trap vortices 



with multiple flux quanta if the hole size is large compared to the coherence length. The 
properties of these multiquanta vortices are largely unexplored. Such antidots, for 
example, could enable the construction of information storage devices operating with 
integer rather than conventional binary bits. 

Mesoscopic templating can be extended in several exciting directions. The 
technique can be applied to cuprate high temperature superconductors[75], where the 
nanoscale coherence length enables many tens of flux quanta to be trapped in a single 
mesoscopic hole. Unlike low T c superconductors, the cuprates have clearly defined 
lattice, liquid, and glassy phases that will react quite differently to the imposed order of 
the templates First order vortex lattice melting, for example, is expected to be 
fundamentally modified by commensurate or incommensurate templates. Aperiodic 
templates provide another new direction. The vortices trapped in the holes create 
aperiodic scattering centers for free interstitial vortices whose dynamics will be quite 
different from those in ordered or random pinning arrays. Templates created to date have 
been limited by lithography to lattice spacings slightly less than one micron, putting the 
first matching field at about 20 Gauss. Electron beam and self-assembly techniques, for 
example based on diblock copolymers [76] anodic aluminum oxide[77] or inverse 
micelles[78], can be used to make templates with nanometer lattice constants. This much 
smaller spacing puts the commensurate vortex lattice in the strong interaction limit where 
collective effects dramatically alter its behavior. The one study on dense templates 
reported so far[79] shows that strong pinning persists well below T c . High density 
templates bring the first matching field up to the kG range, much more interesting for 
applications than the tens of Gauss range accessible to lithographic templates. High 
density templates offer an intriguing new strategy for pinning the vortex liquid, where 
eliminating shear motion requires one pin site per vortex. In BSCCO and YBCO this 
opens large areas of the H-T phase diagram to practical use. 

b) Pseudovortices and Vortex Core States. 

The observation of unusual thermomagnetic effects in the underdoped region of 
LSCO above the superconducting transition temperature and below the pseudogap 
temperature[80] suggests that vortex-like excitations may be associated with the 
pseudogap state. The properties of these pseudovortices are still under examination and 
may hold important insights into the underdoped state. Pseudovortices may be 
observable as fluctuations using experiments with short time scales and local resolution, 
such as magnetic resonance or muon spin rotation. 

The suppression of the superconducting energy gap in the vortex core creates a 
natural potential well that captures observable bound states in cuprate 
superconductors[81, 82]. These bound states provide a window on the nature of pairing, 
because they are sensitive to the presence of nodes in the gap that distort the core 
potential. STM sees not only the bound state, but also the anisotropy of the energy gap 
around the core, providing direct information on the nodal structure. These experiments 
would be particularly valuable if performed systematically for under and over doped 
regimes, where the nature of the normal and superconducting states changes 


continuously. In other organic and heavy fermion superconductors where the order 
parameter is a complex vector, the core states will display subtle details reflecting the 
exotic pairing. These core states are within reach experimentally but remain unexplored. 

In the vortex core the superconducting order parameter is suppressed, providing a 
fascinating opportunity to search for competing types of order without physically altering 
the material. Indications of spin density waves[42] and pseudogaps[83] in the cores of 
BSCCO suggest a strong interplay of these types of order with superconductivity. The 
same approach could be employed to search for competition with antiferromagnetism[84] 
charge stripes, and other proposed ordered states. 

The existence of two superconducting gaps[85] in MgB 2 raises fundamental 
questions about their effect on the core states. Strong variations in the core potential and 
the bound states are expected as the relative strength of the two gaps varies with 
temperature and field. This fascinating area is now within reach and is virtually 

c) Hybrid Materials. 

We are now entering a new era of materials sophistication allowing studies of 
superconductors exposed to internal magnetic fields. Such internal fields arise in 
magnetic/superconducting hybrid structures[86], including naturally occurring 
RuS^GdCUjOg [87] and the magnetic borocarbides[88, 89], and artificial hybrid 
structures containing patterned magnetic and superconducting layers[90]. There are 
fundamental questions regarding how superconductors respond to internal magnetic 
fields: the conventional mechanisms of Meissner shielding and vortex penetration for 
external fields are not necessarily adequate. 

Fig 4. Superconductor/magnet bilayer. The vortex field polarizes the magnet locally, 
producing a radial magnetic texture. 

In bilayer hybrids, the field of an individual vortex in the superconducting layer 
locally polarizes the adjacent magnetic layer creating a tiny magnetic texture.[9\] Fig 4 
shows a radial magnetic texture, where the vertical arrows represent the vortex magnetic 




field and the horizontal arrows the induced polarization of the magnetic layer. The 
coupled vortex-magnetic texture pair is a new compound object whose static and 
dynamic properties are virtually unexplored. One important element is the interaction 
between pairs, which is mediated by dipole and exchange interactions in the magnetic 
layer, Lorentz forces in the superconducting layer, and magnetostatic interactions 
between the layers. The resultant interaction potential is distinctively more complex than 
the simple repulsive potential of bare vortices. Dynamics brings in yet another element, 
the de-polarization and re-polarization of the magnetic layer that is required if a vortex in 
the superconducting layer is to move. Beyond the new physics of vortex-texture pairs, 
there is an additional attractive feature. The properties of the hybrid can be tuned by 
selecting the materials (e.g., the easy direction and the anisfttropy urthe magnetic layer), 
the relative thickness of the two layers, and the magnetic field direction. In multilayer 
hybrids with parallel applied field, an array of n-Josephson vortices can be formed, while 
tipping the field away from the layers induces Abrikosov-texture pairs. 

There are equally fascinating possibilities in hybrids composed of magnetic dots 
deposited on a superconducting layer. Here the magnetic dot is a pin site that is isolated 
from the superconductor, avoiding deleterious effects of the pinning defect on current 
flow. Recent work on superconducting/magnetic dot hybrids [92-94] has defined several 
important issues, such as (i) the spontaneous creation of vortices and anti vortices in zero 
applied field, (ii) the annihilation of antivortices by external field-generated vortices, (iii) 
the nature of matching field effects, (iv) the effect of magnetic dot repolarization at high 
field, and (v) the dynamics of dot-generated vortices under a driving Lorentz force. 
These basic unexplored issues become even more fascinating when the scale of the 
magnetic dot array is reduced from present day lithographic dimensions to much smaller 
self-assembled dimensions. The interaction of flexible and compressible vortex lattices 
with rigid pinning geometries has many analogies in epitaxial growth, absorption of 
noble gases on surfaces and even plasma physics in confined geometries. Thus progress 
in this area has broad relevance well beyond the field of superconductivity. 

2. Multivortex Physics 

a) Disordered Glassy and Liquid States. 

The collective behavior of vortices is much like that of atoms: their mutual 
interaction energy creates lattices, quenched disorder by random pinning produces 
glasses, and thermal disorder melts the lattice or glass to a novel liquid state. The liquid 
and glassy states of vortex matter offer major challenges for understanding the magnetic 
properties of superconductors. Two kinds of glassy state have been proposed, the vortex 
glass[95] for disorder by point defects, and the Bose glass[96] for disorder by line 
defects. While experiments confirm the second order Bose glass melting transition, the 
tilt modulus and the resistive behavior of these disordered systems are at odds with each 
other and with theory [97]. For point disorder, even the voltage-current scaling behavior 
expected at melting is not observed[98] . Experimentally, lattice and glassy melting 
coexist in the same phase diagram[99-101], sometimes accompanied by novel "inverse 
melting" regions. Quasi crystals are another disordered phase of vortex matter, triggered 


by pentagonal or decagonal boundaries. The thermodynamics of melting in this phase 
intermediate between lattice and glass will be fascinating. 

The vortex liquid shows equally fascinating behavior arising from thermal 
disorder rather than quenched disorder. Recent specific heat measurements! 102] reveal 
two liquid phases separated by a second order phase transition. Understanding the nature 
of these two phases and the transition between them is a challenge not only for vortex 
matter but also other line liquids like polymers and liquid crystals. The vortex liquid 
offers another promising opportunity, to study the interplay of thermal and quenched 
disorder. The addition of quenched disorder to the liquid shifts the freezing transition up 
for columnardefects, iown for point defects. The effect of the two kindff of quenched 
disorder on liquid state thermodynamics and on its driven dynamics is ripe for incisive 
experiments. Disordered vortices offer a rich complexity that is easily accessible 
experimentally yet so far defies theoretical descriptioa Their behavior is fundamental to 
applications of superconductivity, and to the basic science of condensed matter systems 

b) Dynamic Phases. 

The rich equilibrium phase diagram of vortices is matched by its driven dynamic 
behavior. The onset of motion at the critical current is a complex dynamic process 
governed by the distribution of pinning strengths, the vortex-vortex interactions, the 
temperature, and the driving Lorentz force. The plastic motion that normally 
accompanies depinning can now be directly observed through Lorentz microscopy [103] 
and magneto-optical imaging[104]. This emerging spatio-temporal resolution opens 
possibilities for systematic experimental studies to characterize the depinning process as 
a function of the basic variables. Such previously hidden onset phenomena as vortex 
channeling, vortex hopping from pin site to pin site, and the distinction between 
avalanche and continuous onset are becoming observable. This wealth of experimental 
information drives new theoretical descriptions of the depinning process. The plastic 
motion inherent in depinning makes its description in terms of partial differential 
equations of hydrodynamics challenging. However, statistical descriptions in terms of 
time dependent position and velocity correlation functions can be created that break new 
ground for describing the onset of plastic motion. Beyond depinning, there are a host of 
dynamic phenomena that are now amenable to observation, including vortex creep, 
thermally assisted flux flow, hysteresis in I-V curves, and memory effects. The concept 
of vortex focusing and rectification through the ratchet effect is especially 
interesung[105]. A fundamental microscopic understanding of these phenomena would 
lead to better engineered superconducting devices where stability and high depinning 
forces are crucial [106]. 

c) Josephson Vortices and Crossing Lattices. 

Highly layered cuprates such as BSCCO support naturally occurring Josephson 
vortices, where the absence of a core and the large lateral penetration depth 
fundamentally alter the behavior typical of Abrikosov vortices. The two kinds of vortices 
co-exist and interact in the presence of a tilted applied field, where the perpendicular field 


induces a pancake vortex lattice and the parallel field induces a Josephson vortex lattice. 
The two crossing lattices interact to produce a complex phase diagram[107], containing 
spontaneous vortex stripes and intricate melting behavior for fields very close to the ab 
plane[108]. Advances in scanning Hall probe technology [109] and magneto-optical 
imaging[ 1 10] now allow these crossing lattice states to be imaged, directly illuminating 
these phase transitions in real space. The dynamic properties of Josephson lattices are 
also fascinating. Because they have no core and no conventional pinning, Josephson 
vortices can be driven at very high speeds. They are predicted to undergo a dynamic 
phase transition, from a highly distorted hexagonal structure at low speed to a stacked 
configuration at high speed[l 11]. The most remarkable prediction is that the high speed 
Josephson lattice emits Terahertz radiation with a frequency inversely proportional to the 
transit time for one lattice constant[l 12]. This offers the appealing possibility to create a 
new class of Terahertz radiation sources from dc components, with an adjustable 
frequency determined by the driving current and applied magnetic field. 

3. Instrumentation. 

Advances in STM, scanning Hall probes, magneto-optical imaging, Lorentz 
microscopy, high sensitivity specific heat and magnetization have driven recent and rapid 
progress in vortex physics. Further advances in instrumentation are on the horizon. 
Lorentz microscopy of vortex systems has recently been achieved at 1 MeV, showing 
unexpected changes in vortex orientation in BSCCO films[113] and dynamic structure in 
apparently static crossing lattices[114] Magneto-optical imaging can now see single 
vortices[104], opening a new window on real space dynamics. Higher resolution can be 
achieved with development of near field magneto-optical imaging, an advance that is 
within reach using available techniques. Specific heat experiments are ripe for much 
higher sensitivity using MEMS (micromachines) to eliminate addenda corrections and 
innovative temperature sensing. This new instrumentation will drive not only vortex 
physics but also will advance many other areas of condensed matter physics. 

V. Proximity and Interface Effects 

The superconducting proximity effect involves the mutual influence of 
neighboring superconducting and non-superconducting materials across an 
interface! 115]. Such mutual influences can be profound. They can affect greatly the 
physical properties of bom materials and are important in any application or scientific 
measurement that involves interfaces. Related effects occur at vacuum interfaces at the 
surface of a superconductor. The proximity effect is central to the physics of the 
coupling of superconductivity across non-superconducting barriers that make possible the 
Josephson junctions used in high-T c superconducting electronics[116] and the grain 
boundary interfaces that are presently the primary factor limiting current flow in high- 
current superconducting tapes[117]. The proximity effect is also central to the broader 
application of the extremely powerful but surface sensitive techniques of photoemission 
spectroscopy and the growing arsenal of scanning local probes to these materials. The 
importance of grain boundaries as current liming factors in HTS tapes is also discussed in 


Chapter VII of this report. And the importance of surface effects in the application of 
ARPES and scanning probes is discussed in Chapter III. 

To all of this must be added the possibility of surface doping through the use of charge 
transfer from deposited over-layers or the electrostatic field effect. The recent 
determination of scientific misconduct in some reported results using field-effect doping 
to induce high-temperatures superconductivity does not undermine the basic scientific 
rationale for such work. Indeed, field effect doping (both capacitive[118] and 
ferrolectric[l 19]) has a long history that continues up to today. The situation has been 
reviewed recently [120]. Clearly, charge transfer and field-effect doping remain 
potentially elegant approaches to creating new superconductors and developing model 

systems for studying two-dimensional superconductivity. 

For all these reasons mastery of the proximity and interface effects in the high 
temperature superconductors is essential to progress in the field. 

In conventional, low-T c superconductors the understanding of the proximity effect 
is relatively well developed for interfaces with normal metals[121]. The reasons are the 
power of BCS theory along with the simplification provided by the generally long 
superconducting coherence lengths typical of low-T c materials (and conventional normal 
metals). These long coherence lengths tend to average out and temper interface effects 
and thereby permit the use of simple, phenomenological boundary conditions for most 
purposes. The proximity effect with a ferromagnet is qualitatively different, however, and 
its understanding remains under developed. The new twist here is that the pair wave 
function has an oscillatory decay in the ferromagnetic (FM) material[122], in contrast to 
the simple exponential decay found in the normal-metal case. 

High-T c superconductors are very different. The very short coherence lengths 
characteristic of these materials make them much more susceptible to the influence of 
neighboring materials and internal defects virtually at the atomic level. Hence, the use of 
phenomenological boundary conditions is problematic, and microscopic theory will have 
to play a larger role. Of course, there is no well developed microscopic theory of the 
high-Tc superconductors. In addition, the strong doping dependence of the cuprate 
superconductors makes them sensitive to charge transfer at interfaces, where there is a 
tendency to form npn-like junctions[123], introducing further new complexity. The d- 
wave nature of the pairing also leads to new features in the proximity effect (and the 
related Andreev scattering process at interfaces) that have not been fully explored. One 
now well-accepted example is the reduction of the pair wave function to zero at surfaces 
whose normal points along the direction of the nodes in the energy gap[124]. 

There are also intriguing experimental results that suggest new physics is 
operating in the proximity effect with the high-T c superconductors. The anomalous 
normal state properties of the cuprates, particularly in the pseudo-gap regime at low 
doping, seems incompatible with the use of the conventional theory (based on low-T c 


superconductors and normal metallic behavior) to describe the proximity effect with 
these phases. In addition, various systematic studies of the proximity Josephson coupling 
of the ab-planes of the cuprate superconductors across these normal phases imply 
characteristic lengths of the proximity coupling that are larger than can be readily 
explained with conventional ideas[125]. The alternative possibility that longer coherence 
lengths are possible in the normal planes and/or that the range of the proximity effect 
with conventional normal metals on the c-axis of BSCCO is shorter than can be readily 
explained with conventional ideas[126] is intriguing. 

From the theoretical perspective, understanding of the proximity effect with a 
material near a quantum phase transition (sucn as the superconductor/ insulator or 
metal/insulator transitions) with their associated quantum fluctuations is lacking even in 
the case of conventional superconductivity. It is presumably even more challenging in 
the case of the cuprates, which exhibit several such transitions as a function of doping, 
due to their highly correlated nature. In addition, there are speculations that negative U 
centers in the blocking layers are playing a role in the high-T c of some cuprates in a kind 
of internal proximity effect[127]. 

Finally, the ability to exploit widely the powerful but inherently surface sensitive 
electronic probes of the high-T c superconductors such as ARPES and the various 
emerging scanning probes will depend on dealing somehow with their complicated 
surface chemistry and altered doping of the CuCh planes near the surface due to the lack 
in general of a charge neutral cleavage plane in the unit cell of the cuprates, with the 
notable exception of Bi 2 Sr 2 CaCii20x (2212 BSCCO). 

Key to understanding proximity and interface effects is the controlled preparation 
and characterization at the atomic level of the various interfaces of interest. Only by 
creating and understanding such model interfaces can the necessary phenomenology be 
developed that can guide applications (with their real, more complicated interfaces) and 
permit unambiguous scientific study of these materials with surface sensitive techniques. 

Fortunately, recent advances in the controlled thin film deposition of highly 
refined interfaces of various kinds have been developed for the high-T c superconductors 
and complex oxides more generally! 128]. Atomic layer (or block by block) epitaxial 
growth has been achieved in some cases. Grading of individual layers as a film is built 
up may be necessary and likely is possible. The same techniques may also be useful in 
preparing the surfaces of bulk single crystals for study by ARPES and/or scanning 

The techniques capable of such refined interface preparation involve the 
combination of very well controlled deposition techniques with various in-situ means of 
monitoring the growth. These include Molecular Beam Epitaxy (MBE), Pulsed Laser 
Deposition (PLD) and sputtering. The need for an oxidizing atmosphere presents 
technical problems, but these are increasingly under control. In-situ Reflection High 
Energy Electron Diffraction (RHEED) is now commonly available for structural 
characterization and techniques to measure in-situ and in real time the temperature and 


composition of a growing film are likely to become available. Such instrumentation will 
greatly facilitate progress. Ex-situ, post-deposition characterization is necessary, 
however, in order to confirm the structure away from the growth conditions. 

At the same time, techniques for preparing well-defined grain boundaries of 
various types for physical study in both crystals and thin films have been developed. 
Advances in electron microscopy have also been developed that permit not only the 
structural characterization of the grain boundaries but also determination of the spatial 
dependence of the electric potential (and therefore the distribution of charge) across the 
boundary, at least on average. Such information will greatly facilitate progress in 
understanding the electrical properties of these grain boundaries. Still needing 
development are probes capable of characterizing the lateral dependence of the structure 
and properties of these interfaces (particularly electrical transport). Presumably local 
scanning probes can be brought to bear usefully on these questions. Similarly, techniques 
need to be developed that can reveal the point defects present near the boundaries that are 
not visible in TEM and may be playing a significant role in achieving charge neutrality 
near the boundary. 

In concert with better sample preparation and more thorough physical study will 
need to be the systematic development of phenomenological theories that incorporate 
appropriately the known physics of the high-T c superconductors and the realities of the 
materials themselves. First principle predictive value is probably not possible nor is it 
necessary from the point of view of furthering the science. Phenomenological models 
may provide useful models of interfaces for applications and guide the empirical process 
of materials optimization. 

In summary, study of the proximity effect is a critical element in the evolving 
study of the high temperature superconductors. The key issues are: developing the model 
materials systems that will enable understanding at the required atomic level; developing 
tools to make and measure such interfaces, in particular scanning probes; surface doping 
and charge transfer studies, developing a unified theory of Ihe proximity effect that deals 
with the material realities and the novel physics of the high-T c superconductors; and 
applying all this knowledge in surface sensitive studies of these materials. 

VI. Nonequilibrium Effects 

A very general case of nonequilibrium dynamics in an electronic system starts by 
creating a high-energy electron (e.g., by optical absorption) followed by a cascade of 
excited states with smaller and smaller energies until the excess energy can escape the 
system, generally by phonons. In superconductors, nonequilibrium effects also occur 
with a transport current, for example, at interfaces exhibiting proximity effects, including 
grain boundaries (see Chapters V and VIII). The nonequilibrium effects of currents are 
especially important when magnetic vortices appear either from applied fields or the self- 
field of the current. The excitation energies are not too large (<ksT c ) in these cases, 
which are discussed in the dynamic phases of vortices part of Chapter IV and under 
pinning in Chapter VIII. 


Returning to the cascade processes mentioned at the start, these are indicated 
schematically in Fig. 5. They include electron-phonon and electron-electron scattering 
and are relatively fast, being -10" 12 sec to achieve thermal energies! 129]. The eventual 
loss of excess energy results from the escape of phonons from a finite sized sample and it 
is much slower, being generally -10" 6 sec, due to the small velocity of sound and 
significant phonon-electron scattering. In the case of a superconductor, this strongly 
affects the final relaxation step, the recombination into Cooper pairs and escape of the 
excess energy by phonons. In superconductors, scattering between electron-like and 
hole-like branches (see Fig. 5) only occurs after 'theimalization' to energy scales of order 
of the energy gap. in high-temperature superconductors (HTS), the d-wave energy gap 
depends on the momentum direction, exhibiting nodes along the (n, ir) wave vectors. 
Thus a new element of nonequilibrium processes in HTS is the relaxation of momentum 
around the Fermi surface. 

Fig. 5. Energy, E, versus momentum, k, for quasiparticle excitations in a 
superconductor with energy gap, A, showing electron-like (k>kF> and hole-like 
(k<k F ) excitation branches. Also shown schematically are possible relaxation 
cascade processes for an initial electron-like excitation of energy, E»A. Energy 
relaxation occurs by emission of a phonon, scattering off another quasiparticle or 
breaking a Cooper pair. Relaxation between the electron-like and hole-like 
branches occurs preferentially when E~A. The final step (not shown) is the 
relaxation of the excess quasiparticle density back to Cooper pairs and the 
concomitant escape of a phonon with energy ~2A. 

Progress has been made to understand the fast scattering rates in HTS using thermal 
Hall conductivity [130], microwave absorption[131] and optical pump-probe 
experiments[132-136], but crucial pieces are missing. These include systematic studies 


that cover a wide spectrum of pump and probe frequencies, other complementary 
experiments and connections to theoretical predictions. Less attention has been paid to 
the traditional nonequilibrium studies[137, 138] in LTS that have addressed a wide range 
of effects of excess quasiparticle densities and/or branch imbalances between electron- 
like and hole-like quasiparticles. The opportunities in the latter case are exotic, numerous 
and largely untapped. 

It is quite interesting that the scattering times derived from thermal 
conductivity[130], microwave absorption[ 131] and optical pump-probe experiments [132] 
exhibit a very similar magnitude and temperature dependence. While the first two probe 
nodal quasiparticles at the (it, n) points of the k-d* pendent d-wave density of states at an 
energy scale of -kgT, most pump-probe experiments excite the HTS with 1.5 eV photons 
whose energy is -200 kBT c and the cascade can include all k states. In addition, the 
probe response, which measures the reflectivity changes after optical pumping, varies 
dramatically with probe frequency (even changing sign) so the specific property of the 
nonequilibrium distribution being addressed is less clear. One expects that these probe- 
frequency dependencies will reflect features of the electronic system such as the plasma 
frequency as well as the changes due to these nonequilibrium states. For example, the 
temperature dependence of the amplitude of the 90 meV probe energy response to a 1.5 
eV pump energy[133], shows a strong correlation with the amplitude of the neutron 
resonant spin excitation[139]. The resolutions of these fascinating mysteries promise a 
rich new field of research that can bring considerable insight into non-thermal processes 
in electronic oxides and possibly into the mechanism of HTS. For these experiments, it 
seems that much could be answered if another probe, like tunneling, could be done on 
such fast time scales (-10 psec) to complement the optical data. 

The eventual recombination and energy transfer to phonons has been addressed in 
mm-wave absorption measurements that probe the reflectivity at a frequency of -0.3 
meV. The authors find relaxation times in the 1 0" 6 sec range and intuit a more significant 
bottleneck than LTS due to the unique properties of the 'nodal quasiparticles. They also 
suggest an analogy to the T relaxation process[140] found for He. The long relaxation 
time means that the traditional nonequilibrium effects found in LTS, which have 
addressed the effects of excess quasiparticle densities and/or branch imbalances between 
electron-like and hole-like quasiparticles, should be observable in HTS. Such 
nonequilibrium effects in high-temperature superconductors (HTS) comprise a research 
area that is ready for exploitation. 

Numerous effects of perturbations by tunnel-junction injection of quasiparticles 
(unpaired electrons), microwave or optical illumination, etc. are readily observed in low 
T c superconductors (LTS) and these have been understood in terms of electron-phonon 
scattering[137, 138]. This is consistent with the electron-phonon coupling mechanism 
for these superconductors. Occasionally the effects of direct electron-electron (Coulomb) 
scattering must also be considered. In HTS the situation is potentially much more 
interesting for at least two reasons. The d-wave symmetry of the order parameter admits 
a momentum-dependence to the quasiparticle energy spectrum and there are additional 
spin and charge excitations that have been suggested as potential candidate bosons for the 


attractive interaction. The latter excitations are seen by neutron scattering and would be 
expected to interact with quasiparticles. By studying the relaxation processes in 
nonequilibrium it may be possible to address the importance of these excitations if their 
effects on the relaxation of nonequilibrium quasiparticle distributions can be identified. 

Nonequilibrium states are here classified as those states for which the quasiparticle 
(or, e.g., phonon) distribution exhibits an energy profile different from thermal 
equilibrium No matter how high the energy of the fundamental excitation process, in a 
fairly short time the excess energy of the perturbation relaxes,, predominantly, into a state 
for s-wave superconductors in which it resonates between phonons of energy 2A and 
quasiparticles* of energy ~A. This is due to the high density of quasiparticle' states near A 
in the BCS density of states and it results in a bottleneck for the escape of the 2A 
recombination phonons into the thermal bath since they are resonantly reabsorbed by the 
high density of Cooper pairs. This increases the effective recombination time above the 
bare value (typically by one to two orders-of-magnitude). 

The observations of many diverse nonequilibrium effects observed in low T c 
superconductors (LTS) benefit from the long time constants for the ultimate 
recombination into Cooper pairs. This is due to the 2A-phonon bottleneck and the small 
energy scale of A in LTS also contributes to a long bare recombination time due to the 
small phase space available in the decay channel via phonons (density of phonon states 
-co 2 ). Nonequilibrium studies in LTS have discovered new effects, like energy gap 
enhancement by microwave or tunnel-junction injection, branch or charge imbalance and 
new applications, like weak-link Josephson devices, superconducting three-terminal 
devices and particle detectors. See Ref. 9 for more complete reviews of these topics. 
The greater richness of the interactions in HTS, together with the nonconventional order 
parameter, large energy gap and the naturally layered structure can be anticipated to 
provide additional phenomena and applications. Examples include the coupling of ac 
Josephson oscillations to phonons or the possibility of terahertz oscillators enabled by the 
coupling of coherent Josephson vortex flow in BSCCO to Josephson plasmons to produce 
electromagnetic radiation. For instance, in the latter case, one can test predictions of the 
occurrence of dynamically stabilized vortex configurations and the interaction with 
Josephson vortices with Josephson plasmons. In addition, the large energy gap in HTS 
cuprates make them attractive candidates to extend the frequency range of tunnel- 
junction mixers beyond that of LTS junctions. Although energy gap enhancement, by 
microwave illumination[141, 142] or tunnel junction injection[143], is well established in 
LTS, the discovery of photoinduced superconductivity in underdoped cuprates is unique 
and unexpected — it produces substantial increases in T c that are persistent[14]. 

The large A 0 in HTS, compared to LTS, may be expected to lead to shorter bare 
recombination times, but under many circumstances nonequilibrium effects can still 
occur. For example, the longer effective relaxation time due to resonant 2A-phonon 
adsorption mentioned above is largely a geometrical escape factor that may be quite 
similar[134] to that found in LTS. This resonant adsorption is usually referred to as 
phonon trapping since the nonequilibrium perturbation energy must be converted into, 


and carried away by, phonons. Phonons can be expected to play that same role in HTS, 
since, e.g., spin and charge excitations cannot leave the electronic system. But also, an 
additional trapping mechanism may occur due to the nodes of the d-wave order 
parameter. This proposed effect is the momentum-space analogy of the real-space 
quasiparticle traps devised for LTS superconductive detectors [144]. In such detectors, 
Cooper pairs in a large volume of superconductor (with a relatively large gap, A,) interact 
strongly with incident irradiation to produce excess quasiparticles. The detector is 
arranged so that the quasiparticles have a high probability of diffusing into an attached 
superconductor with a smaller gap, A s , before the energy escapes the system via phonons. 
The smaller A s results in a longer bare recombination time due to the smaller phase space 
of phonons of energy co=2A s . In addition, the excess energy of quasiparticles, ~Ai, 
converts into a greater number of quasiparticles with E~A S . 

In a proposed relaxation mechanism, quasiparticles produced in the high-A regions 
away from the nodes at the (re, re) points would diffuse to traps in momentum space at the 
lower energy states near the nodes. Several mechanisms can be envisioned, e.g., direct 
scattering of quasiparticles by phonons or spin excitations and pair breaking into near- 
nodal quasiparticle states by nonequilibrium phonons or spin excitations. The 
interpretation of nonequilibrium data in these regimes could be connected to models for 
the mechanism of HTS (see Chapter VII). It will be interesting to explore the relation of 
the specific momenta of spin excitations with relaxation processes across the d-wave 
Fermi surface. The multiplying factor upon energy degradation implies mat a single 1.5 
eV photon could create up to 4000 quasiparticles trapped at the nodal points with an 
energy scale of ~4 K. As pointed out above, measurable recombination times in excess 
of 10" 6 sec have been reported in HTS. 

The ease of fabrication of thin-film superconductor-insulator-superconductor tunnel 
junctions was also a vital component of previous studies of LTS materials. Making 
junctions with two HTS electrodes has proved much more difficult and most tunneling 
studies have relied on point-contact or STM tunnel junctions. However significant 
progress has been made using MBE growth of multilayers of HTS with lattice-matched 
insulators as well as the internal junctions of BSCCO crystals offer another opportunity 
that is unique to the HTS cuprates. In the latter case, it seems necessary to intercalate 
molecules (e.g., iodine or mercury bromide) between the Bi-0 bilayers to reduce the 
current for injection near the energy gap, 2A, and avoid a significant weakening of the 
superconducting state[145]. 

VII. Theory 

1. Preamble 

Since the discovery of high T c superconducting materials, there have been many ideas 
put forth to explain their unusual and often perplexing physical properties. Here, rather 
than attempting to survey the field, we offer three individual perspectives. 

2. Phenomenological Approach 

a) Status. 

The cuprates are highly correlated systems close to the Hubbard-Mott 
antiferromagnetic insulating state. In the underdoped regime, pseudogap signatures[28] 
gd well beyond ordinary metallic behavior. Here we will limit die discussion to the 
optimally doped case where Hubbard-Mott modifications may not be so severe. In this 
case generalizations of techniques developed for ordinary superconductors may be 
applicable with appropriate modifications and give valuable insight. For conventional 
superconductors phonon structures in current-voltage characteristics of planar tunneling 
were exploited to derive a complete picture of the electron-phonon spectral density 
a 2 F(co) [146]. This function defines the kernels that enter the Eliashberg equations. The 
theory accurately predicts (at the 10% level) the many deviations from universal BCS 
laws which have been seen in a broad range of experiments [146]. Similar equations 
suitably generalized to include d-wave symmetry[23, 147, 148] can lead to an equally 
good understanding of the observed superconducting properties of optimally doped 
YBCO. In this approach the general framework of a boson exchange mechanism is 
retained with a boson exchange spectral density (denoted by I^co)), to be determined 
from experimental data. In the high temperature oxides, rather than tunneling, including 
STM, the technique of choice has so far been the infrared conductivity, from which one 
can construct a model of I 2 x(w)- [23, 147, 148] When applied to the conventional s-wave 
case the method reproduces the tunneling derived model for a 2 F(co)[149, 150]. In the 
oxides the optical scattering is dominated by a fluctuation spectrum which is largely 
featureless and which extends over a large energy scale of order several hundred meV 
(the order of J in the t-J model). Such a spectrum is expected in spin fluctuation theories 
such as the nearly antiferromagnetic Fermi liquid (NAFL)[151, 152] or in the marginal 
Fermi liquid (MFL)[153]. 

In the superconducting state a new phenomenon has been identified. One finds 
increased scattering at some definite finite value of co associated with the growth of a new 
optical resonance in the charge carrier boson spectral density, the energy of which (coj 
corresponds exactly to the energy of the spin resonance measured by inelastic neutron 
scattering (when available). This correspondence does not prove, but provides support 
for a spin fluctuation mechanism (rather than the MFL). Moreover the spectral density 
derived from the infrared data, (at T c in optimally doped YBCO) shows a form 
characterized by a spin fluctuation energy cOsf [152]. This form is progressively modified 
by the growth of the resonance at co n and attendant reduction of spectral weight at smaller 
energies as the temperature is lowered below T c . The spectrum obtained depends on 
temperature (through feedback effects due to the onset of superconductivity)[154, 155], 
and leads to good agreement with observed properties of the superconducting state. 
While the generalized (for d-wave) Eliashberg equations are not as firmly grounded in 


the basic microscopic theory as in the phonon case, they do offer a phenomenology 
within which superconducting properties can be understood. These include the 
condensation energy per copper atom, the fraction of total spectral weight which 
condenses into Cooper pairs at T=0, the temperature dependence of the superfluid 
density, the peak observed in microwave data as a function of temperature and its shift in 
position with microwave frequency, the similar peak in the thermal conductivity, and the 
frequency dependence of the infrared conductivity 

b) Key Issues and Opportunities. 

An important issuli for the future is to extend the calculations to the underdoped 
regime. There is as yet no systematic quantification of pseudogap effects and 
contradictory views exist as to their origin. In the preformed pair model[29] the 
pseudogap and superconducting gap have a common origin with die superconducting 
transition related to the onset of phase coherence. In the d-density wave model[156] 
(DDW) a new order parameter competes with superconductivity. Another problem that 
needs resolution is understanding the new ARPES data which have been interpreted as 
giving strong signatures of phonon effects[157-159]. The dressed quasiparticle energies 
must also contain important renormalization due to the spin fluctuations. Certainly a pure 
phonon model is incompatible with the infrared optical data. However, it is well known 
that transport and quasiparticle scattering rates are different. In transport, backward 
collisions assume additional importance in the depletion of current, as compared with 
quasiparticle scattering. The quasiparticle electron-boson spectral density may have 
important contributions from both phonons and spin fluctuations, while the transport 
spectral density may be dominated by spin fluctuations. An important aim for the future 
should be to achieve a common understanding of ARPES, optical and tunneling data 

3. Numerical Studies of Hubbard and t-J Models 

a) Status. 

Numerical studies of the high T c cuprate problem have been used to determine what 
types of correlations are significant in specific models. They have shown that the 2D 
Hubbard and t-J models exhibit anuferromagnetic[160, 161], striped domain wall[162], 
and d x , 2 pairing correlations[162-165]. The similarity of this behavior to the 
phenomena observed in the cuprate materials support the notion that the Hubbard and t-J 
models contain much of the essential physics of the cuprate problem. 

This is really quite remarkable when one considers that these are basically two 
parameter models involving U/t or J/t and the doping x = 1-n. Furthermore, boundary 
conditions or added next-nearest-neighbor hopping terms can shift the nature of the 
dominant correlations showing that the antiferromagnetic, stripe, and pairing correlations 
are delicately balanced in these models, reminding us of the behavior of the materials 


b) Key Issues and Opportunities. 

While we have seen that many of the basic cuprate phenomena appear as properties of 
these models, the interplay of the various correlations and the nature of the underlying 
pairing mechanism remain open. Thus a key issue is to determine whether the underlying 
physics is to be understood in terms of spin-charge separation[166, 167], SO(5) 
symmetry[130], stripes[168], spin-fluctuation exchange[169], or whether additional 
phonon mediated interactions may play a supporting role[46, 170]. With the 
understanding which has been gained and with further development of computational 
techniques, we have the opportunity of addressing these issues. Here it is important to 
realize that the search for th'e appropriate theoretical framework for understanding the 
cuprates also includes seeking to determine what type of models (and ultimately 
materials) are described by various scenarios. For example, we would like to understand 
what types of strongly correlated models exhibit spin-charge separation or more generally 
some type of fractionalization. Is there a sufficient temperature range for strongly 
correlated 2-leg ladders to renormalize so that an SO(5) description is appropriate? Do 
stripes suppress or enhance pairing? What role do phonons play and how is the electron- 
phonon interaction affected by strong Coulomb interactions? What is the structure of the 
phase diagram for these models? What new materials or material modifications will the 
answers to these questions suggest? 

It should also be noted that theoretical progress in first-principles band theory 
simulations of ARPES intensities in the high-T c 's has been made and the inclusion of the 
electron-phonon and strong correlation effects in these simulations can advance the 
interpretation of the data[171]. 

We are in a position to address these issues and we also have the opportunity to take 
advantage of more than a decade and a half of advances driven by the cuprate discovery. 
As part of this effort we need to continue the development of numerical techniques. We 
should also work to establish closer connections to the electronic structure and quantum 
chemistry communities for key information on the basic orbitals and effective parameters 
that enter model descriptions of real materials. 

4. Electronic Structure 

a) Status. 

The discovery of superconductivity in MgB 2 and the subsequent response by the 
computational community demonstrated the remarkable progress that has been achieved 
in first principles calculations for the electronic properties of conventional (phonon 
mediated) superconductors. Indeed, o?F((0) can now be calculated accurately for fairly 
complex materials using density functional methods. For example, first principles 
evaluation of the electron-phonon interaction was used to calculate the superconducting 
transition temperature of the simple hexagonal phase of Si under high pressure[172]. Not 
only can the electron-phonon coupling be obtained, but also complete phonon dispersion 
curves for the whole Brillouin Zone (BZ) are being calculated using perturbation theory 


(harmonic approximation). If anharmonic terms are important, frozen phonon 
calculations yield total energies as a function of the relevant lattice distortions. Indeed, 
structural phase transitions involving soft phonon modes are frequently analyzed via such 
total energy calculations. While phonon frequencies and eigenvectors are needed to 

evaluate a 2 F(u>), it is difficult to draw conclusions about superconductivity from phonon 
dispersion curves. It is interesting however, that first principles calculations of phonons 
in the cuprates have in general yielded good agreement with neutron scattering 
experiments (see for example [173]and references therein). 

When Local Density Approximation (LDA) calculations were unable to produce the 
insulating antiferromagnetic state in the cuprate phase diagram[174], it became clear that 
new approaches for dealing with correlation and moving beyond standard band structure 
techniques were needed. The first of these new "band structure" approaches, the 
LDA+U method, introduces a Hubbard U term into the LDA equations, affecting the 
orbitals for which the correlations are strong[175]. The more recent LDA++, and 
Dynamical Mean Field Theory (DMFT) methods make a more direct attack at calculating 
the electron self-energy, 2(k,o>) [176-179]. The computational resources for evaluating 
the dynamics are demanding, and while good progress is being made, results have only 
been obtained for prototype systems. Although there is not yet a satisfactory band 
structure based technique for treating spin fluctuations when going from the Mott- 
Hubbard insulating state to optimally doped high T c materials, straight forward band 
structure calculations of the doped cuprates yield Fermi surface geometries in remarkably 
good agreement with precise angle resolved photoemission experiments. Band structure 
calculations have also been valuable in identifying the relevant orbitals and in estimating 
values of the parameters that enter more phenomenological models. 

b) Key Issues and Opportunities. 

A key ingredient in solving the Eliashberg equation for phonon mediated 
superconductivity is the simplification made possible by Migdal's theorem. In exploring 
other boson mechanisms with higher frequency spectra the role of the retarded Coulomb 
interaction, u*, needs to be revisited[180]. It has been suggested that for vanadium the 
effective u,* is larger than expected because of the pair-breaking influence of spin 
fluctuations[181]. In the one band Hubbard model it has also been argued that strong 
correlations suppress the electron phonon coupling in a 2 F and transport quantities [182]. 
The recent angle resolved photoemission measurements which show mass 
renormalization for bands passing through the Fermi energy may provide a quantitative 
measure of the electron-phonon interaction for specific states[159]. A comparison with 
first principles calculated values would be most interesting. 

There are many other questions, many identified in this document, which are now 
being approached with model Hamiltonians. While electronic structure practitioners are 
eager to participate in and learn from such studies, and to provide parameters and insights 
where possible, there is a strong desire to develop the apparatus required for a real first 
principles treatment of the phenomena There are many insights and ideas that need to be 


developed first. Perhaps the situation today is not so different than in the early 1960s 
when the Fermi surface was considered exotic. The dividends from the investment in 
physics of that period are the basis for what is now considered "routine" materials 
science, with applications ranging from Stockpile Stewardship to material processing to 
drug design. Solving the "high T c problem" will likewise result in valuable tools and 
insights leading to future applications. 

VIII. Defects and Microstructure with an Eye to Applications 

Crystal lattice defects and their organization on the scale of nanometers to 
micrometers' ("microstructure" for short) play a vWy significant role in the science and 
technology of superconducting materials: [183-188] For one thing, defects are 
unavoidable in the world of "real materials," and it is vital to characterize their nature and 
distribution so as to understand their effects on superconductivity. It is also vital to 
control the defect distribution in the polycrystalline, large-scale microstructure of 
conductors since appropriate nanoscale defects are responsible for developing high 
critical current densities, J c , within grains. But planar defects, especially grain 
boundaries, block grain-to-grain transmission of the current, dictating the geometry of 
conductors because of the sensitivity of J c to strain defects, etc. Defects can also provide 
insights into fundamental questions, e.g., the use of grain-boundary junctions in the 
investigation of order-parameter symmetry in cuprate superconductors. HTS conductors 
are available from several companies worldwide and have been used to demonstrate large 
components of the electric power grid such as power cables, motors, transformers and 
fault current limiters. Josephson-junction devices and other electronic devices based on 
HTS technology are in an advancing state of commercial development. However, we are 
still far from understanding or being able to optimize HTS material properties in the way 
that we have learned to do for the workhorse conductor of LTS (Nb-Ti). The main point 
is that our ability to adequately control defects and microstructures is still rudimentary. 
Some of the remaining key issues derive from the anisotropic nature of the cuprates and 
their low carrier density. These characteristics result in inadequate magnetic flux 
pinning, percolative current flow past many interfacial barriers, inability to control the 
phase state, and a general lack of materials control. 

Extensive investigation of the cuprates has developed a firm understanding of 
some of their microstructure-sensitive properties. First of all, it is painfully clear that 
crystallographic texture and phase purity must be tightly controlled for high J c in 
cuprates. It also seems unavoidable that magnetic flux pinning at temperatures, above 
about 30K, is inadequate in the present conductor material, Bi-2223. It is just too 
anisotropic for magnetic field applications, though adequate for self-field use in power 
cables at 77K_ YBCO has much greater potential for applications in fields at 77K than 
Bi-2223, because its mass anisotropy is about 7, rather than the -100 of Bi-2223, even 
though it's T c is 92 K rather than the 1 10 K of Bi-2223. By contrast it has been quickly 
established that MgB 2 has only a small anisotropy (values vary from about 2 to 7, though 
with a greater weight on lower numbers) and that grain boundaries are not serious 
obstacles to current flow. ;Flux pinning also appears to be strong, leading to high critical 
current densities in prototype wires. In many respects MgB 2 appears to be exactly what 


its 39 K T c suggests, intermediate in properties between LTS and HTS, benefiting in 
particular from lower anisotropy and relatively insensitive to planar defects. 

It is not surprising at all that understanding of defects in cuprate superconductors 
is such a hard-won commodity, because these are very complex materials (the most 
practically important material, Bi-2223 (Bi,Pb>2Sr2Ca2Cu30io.x) forms a 7-component 
system when embedded in Ag). The continued attention to grain boundaries and to the 
search to understand flux-pinning defects has enhanced and will continue to increase our 
knowledge of defects in complex oxides in a much wider context, e.g., the understanding 
of defects in manganites, ferroelectric perovskites, etc. Continued investment in the 
materials physics of defects in HTS materials is attractive, not just because of the 
implications for superconductivity technology 

What, then, are some of the outstanding issues in this field and how can we solve 
them? We need a new phenomenology, which combines the new physics of HTS with a 
realistic description of defects and microstructure in these complex materials. At present, 
almost all of the phenomenological discussion of the effects of defects and microstructure 
on the superconducting properties of HTS materials is based on theoretical concepts 
appropriate to s wave LTS. How do defects in HTS materials really interact with 
correlated-electron phenomena, stripe-phases, and electronic phase separation? We will 
not understand the answers to such questions without a basic theory of defects in complex 
oxides that takes account of their complex electronic state and proximity to the metal 
insulator transition. 

Knowledge of lattice defects and microstructure in HTS materials is mostly 
confined to YBCO (and other 123-structure cuprates) and to the 2212 and 2223 phases of 
BSCCO. Why stick to these "old favorites?" To a very large degree, this reflects a 
"tyranny of practicality and materials complexity," which inhibits the development of a 
wider knowledge needed to understand broader aspects of the materials physics of HTS 
materials. Many HTS materials are much more complex to make and appropriate recipes 
for "good sample" manufacture are lacking. It is believed that much might be learned 
from infinite layer materials. For example, their structures are not neatly divisible into 
charge reservoir and superconducting blocks. Since grain boundaries in HTS are 
believed to be disruptive to current precisely because charge transfer to the conducting 
cuprate planes is perturbed, their study in infinite layers might be particularly valuable. 

Many issues involving magnetic flux pinning in HTS materials remain to be 
clarified. Although much is known about the thermodynamics and phase-diagrams of 
vortex matter in HTS materials, (see Chapter IV), much remains to be learned about the 
elementary interactions between vortices and defects, e.g., the physics of the elementary 
pinning forces, f p , for various types of defects and their systematic variation among 
various cuprates. Furthermore, the knowledge of the behavior of defects, such as 
dislocations and plastic flow in vortex lattices themselves, is mostly extrapolated from 
the LTS case and almost certainly needs revision in such strongly anisotropic cases as Bi- 
2223, where line vortices in LTS materials break up into largely, but not completely 
disconnected pancake vortices. Experiments need to be designed specifically to 


illuminate the fundamental nature of defect-vortex interactions in HTS materials. These 
would be particularly valuable when combined with parallel conductor development 
activities. The intermediate nature of MgB 2 makes the nature of elementary pinning 
forces, vortex-lattice elasticity and plasticity very interesting. Are these properties 
fundamentally different or similar to those of NbsSn and other LTS intermetallic 
compounds? Does the complex electronic band structure and anisotropy of MgB2 make 
it's flux-pinning fundamentally different from that in the A15 compounds? 

What is learned about the interactions between defects and correlated-electron 
phenomena in HTS materials will pay dividends in a wider range of materials, e.g., 
rrianganites', and phenomena, e.g., magnetism and- metal-insulator transitions. In fact, the 
interactions between defects and transport properties in the normal state of cuprates are 
very poorly understood, too. A better understanding here would greatly improve the 
ability to characterize the nature and concentration of defects in cuprates in a quantitative 

There are many needs and opportunities in the science of defects and 
microstructure of cuprates, in addition to the direct connection to superconductivity (e.g., 
flux-pinning and weak links). The latter provides the motivation for microstructural 
control, but understanding of the basic materials science of defects and microstructure is 
needed to exercise such control efficiently. Here, too, experiments and theory designed 
to gain basic understanding that can couple to the activity driven by practical 
considerations would be very valuable. For example, there is a considerable lack of 
serious theory and modeling, as well as of basic experimental studies, of the 
thermodynamics, kinetics, and mechanisms of nucleation and growth of epitaxial oxides 
of relevance to coated conductors (including buffer layers, etc.), despite there being a 
large amount of process development in this area. Understanding of the fundamentals of 
phase formation in cuprate systems is sparse. There is also a serious need for quantitative 
understanding of the elementary defects, such as point defects, dislocations, twin 
boundaries, stacking faults, etc., which are the "elementary particles" of microstructure in 
HTS phases. This, together with quantitative descriptions of microstructure and defect 
chemistry, is needed to develop an adequate phenomenology of current transport and flux 
pinning in HTS systems. 

Another area of fundamental materials physics that is relatively unexplored for 
HTS materials is that of mechanical properties, especially elasticity, anelasticity, and 
fracture. There is a paucity of basic experimental data, and these complex materials 
require theoretical methods more advanced than those needed for simpler materials, 
including ferroelasticity, non-linear and microcontinuum elasticity, and, models of non- 
linear lattice statics and dynamics. Furthermore, an understanding of the coupling of 
elastic strain fields to the superconductivity of HTS materials is needed to understand 
interactions between defects and superconductivity, as well as to predict the behavior of 
conductors in devices such as high field magnets where large stresses arise during device 


The quantitative description of HTS-based conductors also requires improved 
methods of modeling the physical properties of composites, including mechanical, 
thermal and electromagnetic properties. The latter is particularly challenging, involving 
current and magnetic induction distributions in polycrystalline, defect-containing, 
multiphase composites. 

The discussion above indicates the great complexity of the defect physics and 
microstructural science of HTS superconductors, which are both of fundamental interest 
and of enormous relevance to practical applications. However, powerful instrumental 
tools are available to help meet this challenge, especially modern transmission electron 
microscopy and local scanning probe microscopies and spectroscopies. These tools now 
permit the characterization of atomic and electronic structure, as well as elastic strain 
fields, over length scales ranging from atomic resolution to micrometers. This affords an 
unprecedented ability to obtain images and spectroscopy of atomic, charge, and strain 
distributions, which will revolutionize our quantitative understanding of defects and 
microstructure. The use of such instrumental tools, together with microscale 
electromagnetic characterization, coupled with the development of HTS-appropriate 
theoretical phenomenology, has the potential to yield, important new insights into this 
complex problem, with wider implications for many complex new materials of the future. 


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Applicants: Bednorz et al. / *\ Docket: YO987-074BZ 

Serial No.: 08/479,810 ( MAR 0 3 2004 |j q ^ ^ ^ ^ 

Rled: June 7, 1995 ^^g^ Examiner: M. Kopec 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 


Page 1 of 187 


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In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Group Art Unit: 1751 
Examiner: M. Kopec 

Date: March 1 , 2004 
Docket: YO987-074BZ 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 


h^P- iperature superconductor^ 

C.N.R. Rao and A. K. Raychaudhuri 

The following tables give properties of a number of high temperature superconductors. Table I lists the crystal structure (space group and lattice 
constants) and the critical transition temperature 7* c for the more important high temperature supercooductors so far studied. Table 2 gives energy gap. 
cooed current density, and penetration depth in the superconducting state. Table 3 gives electrical and thermal properties of some of these materials 
■ die normal state. The tables were prepared in November 1992 and updated in November 1994. 


1. Ginsburg. D.M, Ed, Physical Properties of High-Temperature Superconductors. Vols. I — III, World Scientific, Singapore, 1989—1992. 

2. Rao, C.N.R.. Ed., Chemistry of High-Temperature Superconductors, World Scientific, Singapore, 1991 . 

1 Shackelford, J F., The CRC Materials Science and Engineering Handbook, CRC Press, Boca Raton, 1992. 98—99 and 122—123. 

4. Kaldis, E,Ed„ Materials and CrystaUographic Aspects ofHT c -Superconductivity, Kluwcr Academic PubL. Dordrecht, The Netherlands, 1992. 

5. Malik, S.K. and Shah. S.S., Ed, Physical and Material Properties of High Temperature Superconductors, Nova Science PubL, Coramack, 
N.Y., 1994. 

6. aunaissem, O. et al, Physica, C230, 231—238, 1994. 

7. Antipov, E.V. eL aL, Physica, C215. 1—10. 1993. 

Table 1 

Structural Parameters and Approximate T c Values of High-Temperature Superconductors 
Material Structure TJK (maximum value) 

* * l-a/JJO+ti 

Bmab; a ~ 5.355 b — 5 401 c=1315A 


14/mmm; a = 3.779, c = 1323 A 


14/mmm; a = 3.825, c = 19.42 A 

w YRa.C^n.O-. 

Pmmm; a = 3.821, fc = 3.88S, c = 1 1.676 A 



Ammm; a = 3.84. b = 3.87. c = 2724 A 


f Y^a,Cu/J I5 

Annum; a = 3.851, b = 3.869. c = 5029 A 


KY Bi 2 Sr J C U 0 6 

Amaa; a = 5 362, * = 5374, c = 24.622 A 


4 9 BijCaSrjCuPg 

a = 5.409. * = 5.420, c = 3053 A 


* * Bi^rjCuAo 

A,aa; a = 539. b = 5.40. c = 37 A 


jC/o Bi^r^,, 1 Ce,) 2 Cu 2 O I 0 

P4/mmra; a = 3.888, c = 1728 A 


*r 11 Tl I Ba 2 Cu0 6 

Ajaa; a = 5.468. * = 5.472, c = 23238 A; 

14/mmm; a = 3.866, c = 23239 A 


* tk TljCaBaiCup, 

14/mmm; a = 3.855, c = 29318 A 


* O TljCajBajCujOio 

14/mmm; a = 3.85, c = 35.9 A 


*f TKBaUXiiOj 

P4/mmra; o = 3.83, c = 9 .55 A 


- If TKSrL*)Cu0 3 

P4/mmm;o = 3.7.c = 9A 


jt>f (TloiPt^SrjCuOj 

P4/mmm; o = 3.738, c = 9.01 A 


K.f7 TrCaBajCUjO, 

P4/mmm; a = 3.856, c = 12.754 A 


* •* (TlajPbftjJCaSrjCup, 

P4/mmm; a = 3.80, c = 12.05 A 



P4/mmm; a = 3.80. c = 12.10 A 



P4/mmm; a = 3.853, c = 15.913 A 


t-H (no L 5Pb aj )Sr J Ca J CU30 J 

P4/mram; a = 3.81, c= 1523 A 


JO.TIBa J (La 1 ,Ce Jt )jCuA 

14/mmm; a = 3.8. c = 29.5 A 


rV^lAljCaoLjC" A 

Cmmm; a = 5.435. fc = 5.463. c = 15.817 A 


P22.2; a = 5333. b = 5.421. c = 12.609 A 


>5 , (Pb.Cu)Sr J (La,Ca)Cu 2 0 7 

P4/mmm; a = 3.820, c = 1 1 .826 A 


4 (Pb.CuXSr^uXEu,Ce)CuA 

14/mmm; a = 3.837. c = 29.01 A 


p *7 Nd 2 .,Ce J Cu0 4 

14/mmm; a = 3.95, c = 12.07 A 



P4/mmra; a = 3.902, c = 3.35 A 


2 7 Sr^d^CuOj 

P4/mmm; a = 3.942, c = 3.393 A 


* 10 Baj^BiOj . 

Pm3m;a = 4287A 


* »| R^CsQo 

0=14.493 A 


*l NdBajCujOj 

Pmmm; a = 3.878. b = 3.913. c = 1 1.753 




Structural Parameters and Approximate T t Values of High-Temperatun 


*3 SraBaSrCujO, 
&i EuBaSiCujO, 
*(. DyBaSrCujO, 
\b ErBaSrCujO, (multiphase) 
t>$ TmBaSrOijO, (multiphase) 
tO YBaStCujO, 

M"it HgBajOlO, 

4- Hi. HeBajCaCujOj (annealed in O,) 

*Vi HgBa^CajCujO, 

"fVy HgBa 2 Ca 3 Cu 4 O 10 


14/mmm; a = 3.854, c = II .62 
14/mram; a = 3.845. c = 1 1 .59 
MAnmm; a = 3.849, c = 1 1 .53 
Pramra: o = 3.802, fc = 3.850, c = 1 1 .56 
Pmmm; a = 3.794. fc = 3.849, c = 11.55 
Pmmm; a = 3.787, * = 3.846," c = 1 1 .54 
Pmmra; a = 3.784, = 3.849, c = 1 1 S5 
Pnunm; 0 = 3.803, A = 3.842, c = 11.54 
I4/ramra; a = 3.878, c = 9 .507 
I4/mmra; a = 3.862, c = 1 2.705 
Pmrara; a = 3.85. c = 15.85 
Pmmm; « = 3.854, c = 19.008 


7",/K (maximum rahie) 

Table 2 
Superconducting Properties 

Je (0): Critical cuirent density extrapolated to OK 

Penetration depth in a-b plane 
k$: Boltzmann constant 





Nd il Ce JI Cu0 4 

Single Crystal 
Single Crystal 


Obtained from peak to peak value. 
* Obtained from fit to BCS-type relation. 

Energy gap (A) 

10-*xy c (0VAcm-J 

30 (film) 

10 (film. 80 K) 
0.2 (film) 




In re Patent Application of Dat e : March 1 , 2004 

Applicants: Bednorz et al. Docket: YO987-074BZ 

Serial No.: 08/479,810 Group Art Unjt: 1751 

Filed: June 7, 1995 Examiner: M. Kopec 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 





t Temperature 



kshop on Towards th 



Donald M. Ginsberg 

Professor of Physics 

University of Illinois at Urbana-Cbampaign 

jpics — 1st Asia-Pacifc 

i Superconductivity 

Worid Scientific Publishing Co. Pte. Ltd. 
P O Box 128. Fairer Road, Singapore 9128 

USA office: World Scientific Publishing Co., Inc. 
687 Hartwen Street, Teaneck, NI 07666, USA 

UK office: World Scientific Publishing Co. Pte. Ltd. 

73 LyntonMead, Totteridge, London N20 SDH, England 

Copyright © 1989 by Worid Scientific Publishing Co. Pte. Ltd. 
Att rights reserved. This book, or parts thereof, may not be reproduced 
in any form or by any means, electronic or mechanical, including photo- 
copying, recording or any information storage and retrieval system now 
known or to be invented, without written permission from the Publisher. 

5"3~7. G23> 

Thl) book u d( 
risen to the. big 


ISBN 9971-50-683-1 

9971-50-894-X (pbk) 

Printed in Singapore by Utopia Press. 



Chapter 1: Introduction, History, and Overview of High 
Temperature Superconductivity 
D:M. Ginsberg 

Chapter 2: Thermodynamic Properties, Fluctuations, and 

Anisotropy of High Temperature Superconductors 
M.B. Salamon 

Chapter 3: Macroscopic Magnetic Properties of High Temperature 
A.P. Malozemoff 

Chapter 4: Neutron Scattering Studies of Structural and Magnetic 
Excitations in Lamellar Copper Oxides — A Review 
JR. J. Birgeneav and G. Skirant 
Chapter 5: Normal State Transport and Elastic Properties of 
High T c Materials and Related Compounds 
P.B. Allen, Z. Fisk, and A. Migliori 
Chapter 6: Rare Earth and Other Substitutions in High 
Temperature Oxide Superconductors 
J.T. Markcrtj Y. Dalichaoueh, and M.B. Maple 
Chapter 7: Infrared Properties of High T c Superconductors 

T. Timusk and D.B. Tanner 
Chapter 8: Raman Scattering in High-T c Superconductors 
G. Thomsen and M. Car dona 

Subject Index 



Donald M. Ginsberg 

Department of Physics 

University of Illinois at Urbana - Champaign 

World Scientific 

Singapore • New Jersey • London • Hong Kong 

Published by 

World Scientific PubKihing Co. Pie. Ltd. 

P O Box 128, F«ner Road, Singapore 9128 

USA office: 687 Hartwell Street, Teanedc, NJ 07666 

UK office: 73 Lynton Mead, Totteridge, London N20 8 OH 


Copyright © 1990 by World Scientific Publishing Co. Pte. Ltd. 
All rights reserved. This book, or parts thereof, may not be reproduced 
in any form or by any means, electronic or mechanical, including photo- 
copying, recording or any information storage and retrieval system now 
known or to be invented, without written permission from the Publisher. 

ISBN 981-02-0124-9 

981-02-0190-7 (pbk) 

Printed in Singapore by JBW Printers & Binders Pte. Ltd. 



Chapter 1. Introduction: A Description of Some New Materials and 
An Overview of This Book 
DM. Ginsberg 

Chapter 2. Specific Heat of High Temperature Super conductors: 
A Review 
A. Junod 

Chapter 3. Crystal Structures of High-Temperature Superconductors 
R.M. Hazen 

Chapter 4. The Microstructure of High-Temperature Oxide 
G.H. Chen 

Chapter 5. Nuclear Resonance Studies of YBa 2 Cu 3 07_4 

G. H. Pennington and G.P. SlichUr 

Chapter 6. Electronic Structure, Surface Properties, and Interface 
Chemistry of High Temperature Superconductors 

H. M. Meyer III and J. H. Weaver 

Chapter 7. The Hall Effect and its Relation to other Transport 

Phenomena in the Normal State of the High-Temperature 
Superconduct ore 
N.P. Ong 

Chapter 8. Oxygen Stoichiometric Effects and Related Atomic 
Substitutions in the High-T c Cuprates 
L.H. Greene and B.G. Bagley 

Chapter 9. The Pairing State of YBa 2 Cu307_« 

J.F. Annett, N. Goldenfeld and S.R. Renn 

Subject Index 
Appendix A 

Appendix B 



In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Group Art Unit: 1751 
Examiner: M. Kopec 

Docket: YO987-074BZ 

Date: March 1 , 2004 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 



Edited by 
C N. R. RAO, F.R.S. 

CSIRCentre oJExceBmce in Chemistry and 
Indkm Institute of Science, Bangalore. India 

World Scientific 

Singapore - New Jersey • London • Hong Kong 

s 1 


! I i 

■A— '<•* O o K i-M £ 2? «> "Jj ° -2 ~5 >j " 

a S 5 I 1 1 iM S I -5 ? U 1 1 « * I ; i f s I 

I** J 8 S3 I i 

jfiJljjfmf J3l££j|| 

0 i * 5 

f Jll 


° o S v 
? «, a a 



Crystal Chemistry and Superconductivity in the Copper Oxides i 
/. B. Goodenough and A. Manihirum 

Defects and Microstructures in Layered Copper Oxides S7 
M. Eervieu, B. Domengis, C. Michel, and B. Ravtau ' 

Between the Electronic Structure and Superconductivity fi7 
C. N.R.Rao 3 8/ 

Design of New Cuprate Superconductors and Prediction of Their 


Takakisa Arima and Yoshinori Tokura 104 

Structure and Superconductivity in Y-123 and Related Compounds 126 
G. V. Svbba Rao and U. V. Varadarajv ' 

^ffir" Bismuth ' ThaUium ~* ^ 156 

The Modulation in Bismuth Cuprates and Related Materials 18fi 
W. Tarascon, W. R. McKinnon, and Y. LePage ' 

Electron-Doped High T c Cuprate Superconductors m 

Carmen C. Almasan and M. Brian Maple 

Application of High-Pressure and High Oxygen Pressure to Cu-Oxides 243 
M. Takano, Z. Hiroi, M. Azvma, and Y. Takeda 

Copper-Less Oxide Superconductors . ... 
A. M. Umarji 267 

Synthesis, Structure and Properties of La 2 Ni0 4+ , . 28 o 
Douglas J. Butirey and Jurgen M. Eonig 

Thermodynamics of Y-Ba-Cu-0 System and Related Aspects . . 306 
a. t. Pashtn and Yu. D. Tntyakov ' 

Investigation of the Electronic Structure of the Cuprate 
Superconductors Using High-Energy Spectroscopies 

D. D. Sarma M ° 

Field Modulated Microwave Absorption in High-Temperature 

Superconducting Oxides 

Micky Puri and Larry Kevan 379 

fitt C^7nn d i? EffeCt ° n Critical Current of 

Bi2Sr 2 C ai Cu 2 O r /Ag Superconducting Tape , 0Q 
K. Togano, H. Kumakura, H. Matda, and J. Kasc ' ' ' ' 

^rop S erti e el COndUCting ^ ^ ~ Pr ° Cessin « Methods 
S. Mohan ' - - - . 411 

AbUtS i mPeratUre SupeiCOnductor Thin ™™ by Pulsed Laser 

S. B. Ogalt 454 



In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: March 1 , 2004 

Docket: YO987-074BZ 

Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 


The CRC 
Materials Science and Engineering 

James F. Shackelford 

Professor of Materials Science and Engineering 
Division of Materials Science and Engineering 

Associate Dean of the College of Engineering 
University of California, Davis 

Associate Editor 

William Alexander 

Research Engineer 
Division of Materials Science and Engineering 
University of California, Davis 

CRC Press 

Library of Congress Cataloging-in-Publkation Data 
Catalog record is available from the Library of Congress 

ISBN 0-8493-4276-7 


Direct all inquiries to CRC Press, Inc.. 2000 Corporate Blvd., N. W.. Boca Raton, Florida. 33431. 

© 1992 by CRC Press, Inc. 
International Standard Book Number 0-8493^276-7 

Printed in the United States 0123456789 

CRC Materials Science and Engineering Handbook 


The Elements \ 

Elements for Engineering Materials 2 

j Elements in the Earth's Crust 4 

"i The Periodic Table of The Elements 6 

<• The Metallic Elements 7 

The Elements in Ceramic Materials 8 

ji The Elements in Polymeric Materials 9 

I The Elements in Semiconducting Materials 10 

: Available Stable Isotopes of the Elements 12 

I Properties of Selected Elements , 20 

I Melting Points of Selected Elements 26 

I Densities of Selected Elements 28 

¥ Crystal Structure of the Elements 30 

t Atomic and Ionic Radii of the Elements 34 

, Atomic Radii of the Elements '. 39 

I Ionic Radii of the Elements 41 

; Selected Properties of Superconductive Elements 43 

T c for Thin Films of Superconductive Elements 44 

Engineering Compounds 47 

Engineering Ceramics 48 

Refractories, Ceramics, and Salts 53 

Type II Superconducting Compounds: 

Critical Temperature and Crystal Structure Data 65 

High Temperature Superconducting Compounds: 

Critical Temperature and Crystal Structure Data 98 

Crystal Structure Types 101 

Critical Temperature Data for 

|£J^2 Type 11 Superconducting Compounds 104 

e validity of all Selected Superconductive Compounds And Alloys: 

Critical Field Data 121 

n consent from T c Data for High Temperature Superconducting Compounds 1 22 

* ~ "Bonding, Thermodynamic, and Kinetic Data : 1 25 

Bond Strengths in Diatomic Molecules 

(Listed by Molecule) 126 

(Listed by Bond Strength) 135 

Bond Strengths of Polyatomic Molecules 

(Listed by Molecule) 144 

(Listed by Bond Strength) 147 

CRC Materials Science and Engineering Handbook 

Table of Contents (Continued) 

Carbon Bond Lengths (Periodic Table Presentation) i 50 

Carbon Bond Lengths """ J5 j 

Bond Length Values Between Elements 

(Listed by Bond) 154 

(Listed by Bond Length) ZZZZZ 156 

Bond Angle Values Between Elements 

(Listed by Bond) 15g 

(Listed by Bond Angle) ZZZZ 159 

Heat of Formation of Selected Inorganic Oxides 160 

Heats of Sublimation (at 25°C) of Selected Metals 

and their Oxides 173 

Melting Points of Selected Elements and Inorganic Compounds 

(Listed by Element or Compound) j 74 

(Listed by Melting Point) ZZZZ 186 

Melting Points of Ceramics 

(Listed by Compound) 19g 

(Listed by Melting Point) ZZZZZZ 202 

Heat of Fusion For Selected Elements and 

Inorganic Compounds 206 

Surface Tension of Liquid Elements 21 8 

Vapor Pressure of the Elements 

(V ery Low Pressures) 235 

(Moderate Pressures) ; 237 

(High Pressures) 240 

Specific Heat of Selected Elements at 25 °C 

(Listed by Element) 243 

(Listed by Specific Heat) 1.....Z.ZZ. 248 

Heat Capacity of Selected Ceramics "ZZ" 253 

Specific Heat of Selected Polymers ..".Z 255 

Phase Change Thermodynamic Properties 

for Selected Elements ; 2 60 

for Selected Oxides 269 

Thermodynamic Coefficients 

Description 2gj 

for Selected Elements 283 

for Selected Oxides 292 

Thermal Conductivity of Metals 

at Cryogenic Temperatures 395 

at 100 to 3000 K " " 321 

CRC Materials Science and Engineering Handbook 

Table of Contents (Continued) 

Thermal Conductivity of Selected Ceramics 334 

Thermal Conductivity of Special Concretes 345 

Thermal Conductivity of Cryogenic 

Insulation and Supports 346 

Thermal Conductivity of 

Selected Polymers 348 

Thermal Expansion of Selected Tool Steels 355 

Thermal Expansion and Thermal Conductivity 

of Selected Alloy Cast Irons 356 

Thermal Expansion of Selected Ceramics 357 

Thermal Expansion Coefficients for Materials 

used in Integrated Circuits 374 

Thermal Expansion of Selected Polymers 376 

Values of The Error Function 384 

Diffusion in Selected Metallic Systems 385 

Diffusivity Values of Metals into Metals : 406 

Diffusion in some Non-Metallic Systems 416 

Diffusion in Semiconductors 417 

Temper Designation System for Aluminum Alloys 424 

Structure, Compositions, and Phase Diagram Sources 425 

The Seven Crystal Systems 426 

The Fourteen Bravais Lattices 427 

Structure of Selected Ceramics 428 

Density of Selected Tool Steels 434 

Density of Selected Alloy Cast Irons : 435 

Density of Selected Ceramics 436 

Specific Gravity of Selected Polymers • 439 

Composition Limits of Selected Tool Steels 450 

Composition Limits of Selected Gray Cast Irons 459 

Composition Limits of Selected Ductile Irons 464 

Composition Ranges for Selected Malleable Irons 468 

Composition Ranges for Selected Carbon Steels 470 

Composition Ranges for Selected Resulfurized Carbon Steels 475 

Composition Ranges for Selected Alloy Steels 478 

Composition Ranges for Selected Cast Aluminum Alloys 498 

Composition Ranges for Selected Wrought Aiiminum Alloys 502 

Typical Composition of Selected Glass-Ceramics 506 

Phase Diagram Sources t 510 

CRC Materials Science and Engineering Handbook 

Table of Contents (Continued) 
Mechanical Properties 

T °°l Steel Softening After 100 Hours , 512 

for Various Temperatures 
Mechanical Properties of Selected Gra^Cas't fron's mo 

Mechanical Properties of Selected Duck Irons ™ 
Average Mechanical Properties of Treated Ductile'w %l 
Mechanical Properties of Selected Malleable Iron G^T 1% 

Young's Modulus of Selected Ceramics 8 525 

Modulus of Elasticity in Tension for Scfc^ " ' S 

Poisson's Ratio for Selected Ceramics 534 
Y.eld Strength of Selected Cast AluminumTlloys' - 538 

(Listed by Alloy) J 

(Listed by Yield Strength ) 541 

Y tr^cr w ^^™^' 544 

(Listed by Yield Strength ) 547 
Yield Strength of Selected Polymers' 555 


(Listed by Tensile Strength ) 567 

(Listed by Tensile Strength ) ■ 573 

Tensile Strength of Selected Ceramics ?!1 

Tensile Strength of Selected Polymers 9 
Total Elongation of Selected Cast Aluminum^ 593 

(Listed by Alloy) 

(Listed by Total Elongation ') 601 
Total Elongation of Selected Polymere 604 
Elongation at Yield of Selected Polymers' 5?? 
Shear S^ength of Selected Wrought Aluminum' AlIoy S 615 

(Listed by Alloy) 7 

(Listed by Shear Strength) 617 
Hardness of Selected Wrought Aluminum' 'aiIo^s 624 

(Listed by Alloy) J 

(Listed by Hardness) .' 631 

Hardness of Selected Ceramics 636 

Hardness of Selected Polymers 641 


^CHaterialsSclenceandE^ineerin, Handbook 

Table of Contents (Continued) 


'&sssssi&==E- - 

(Listed by AUoy) •••• 695 

^R^cfSe.eCedPo.ymers • 

Wecuical, Magnetic,^ 706 

S^TsTS^ _ ::= zZ 

t , ^Resistivity of Selected Polymer. 722 

^'^cS^SofSelectedPolymers m 

SeSc~ofSelectedPolyn,e K — 7 40 

D^XnFactorforSelec^Polyn^ -» 751 

Sesistanceof Selected Poymers..^ 75 7 

^SonofOpticalMaterialsatZKK 166 

SSonl4geofGUssCeram.cs ■•■ 770 

^^XKencyofSelectedPolymers 776 

IXc^eixofSelec.edPo.yn.ers ^ 

rST-5=!s: :::::z::::^ 

nalaWU-Tof Selected Po.ymc re 



In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: March 1 , 2004 
Docket: YO987-074BZ 
Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 


NATO Science Committee, 
chnological knowledge, 

s in conjunction with the 

ng Corporation 

ic Publishers 
on and London 

Materials and 
Crystallographic Aspects 
of HT c -Superconductivity 

edited by 


Laboratorium fur Festkorperphysik, 

Bdgenossische Technische Hochschule Honggerberg, 

Zurich, Switzerland 

rg. New York, London, 

liographical references 
tfons from international 



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Dordrecht / Boston / London 

Published in cooperation with NATO Scientific Affairs Division 

Proceedings of the NATO Advanced Study Institute on 
Materials and Crystaflographic Aspects of HT c -Siipercondudrvity 
Erice, Sicily, Italy 
May 17-30, 1993 

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Part I: Structure and Structure-Properties Rdatiooship 

M. Marezio and C. Chaillout 

A.W. Hewat 

£S£ •» *.*r »d Hi* T, 

T. Egami 

Local sfructund distortion: implication to the mechanism of high 
temperature superconductivity g 

D. Hohhvein 

Superstructures in 123 compounds X-ray and neutron diffraction 
VJ. Simonov 

materials ^* ra ^ stnic * ura l investigations of single aystals of high-T, 
C. Chaillout andM. Marezio 

Structural and physical properties of superconducting La.CuO^ 

John B. Goodenough 
1 Electron energies in oxides 

uced or . 

I photo- " ,0 ' w Goodenough 

t written system La^Sr.Q^ 

ft Goodenough 
The n-type copper oxide superconductors 


Shin-ichi Uchida 

Chaise dynamics in high T c copper oxides 
Y. Mae no 

Lattice instabilities and superconductivity in La-214 compounds 
Part II: Physics of HTSC 
D. Brinkmann 

Probing crystaUographic and materials properties of Y-Ba-Cu-O 
superconductors by NMR and NQR 

n S w?JZ' */• C0lUnS ' Rotter ' F - Holt *«S- C Feild 
U.Welp, G.W. Crabtree, JZ. Liu and Y. Fang 

Infrared properties of selected high T e superconductors 
H. Keller 

Probing high-temperature superconductivity with positive muons 
T. Schneider 

Extreme type II superconductors: Universal properties and trends 
G. Ruani 

IR-excited Raman spectroscopy on HT e superconductors 

I.Morgenstern, JM. Singer. Th. Hufilein andH.-G. Matuttis 
Numencal summation of high temperature supercorriuctoT 


l^cf^f™ 8 for m 3X131 oxygen caiteKd Iattice ****** 

AM. Hermann, M. Paranthaman and HM. Duan 

Single crystal growth and characterization of thallium cuprate 

superconductors - A review 

Part HI: Flux Pinning, Pinning Centers, Applications 


Hux pinning in high-temperature superconductors 
M. Murakami 

Hux pinning of high temperature superconductors and their applications 











/. Mannhart, / 
High-T c thin fi] 

/. Alarco, Yu. £ 
Z. Ivanov, VJC. 
J. Ramos, E. Su 
Engineered gran 

Part IV: Organ 

/. Fink, P. Adeln 
M. Knupfer, M. I 
High-energy spec 

G. van Tendeloo i 
Electron microsco 
materials and fuHe 

JackM. Williams, 
Eugene U Venturii 
Structure-property ; 
and annion-based ( 
use in the design o 

Part V: Phase Dis 

/. Karpinsfd, K. Cc 
and B. Kaldis 
Phase diagram, syn 
oxygen pressure Pc 

GJF. Voronin 
Thermodynamic sfc 

/. Mannhart, J.G. Bednorz, A. Catana, Ch. Gerbcr and D.G. Schlom 

Higji-T c thin films. Growth modes - structure - applications 453 

/. Alarco, Til Boikov, G. Brorsson, T. Ciaeson, G. Daalmans, J. Edstam, 
Z. Ivanov, VX. Kaplunenko, P.-A. NUsson, E. Olsson, HJC. Olsson, 
J. Ramos, E. Stepantsov, A. Tzalenchuk, D. Winkler and Y. -U. Zhang 
Engineered grain boundary junctions - characteristics, structure, 

Part IV: Organic Superconductors 

/. Fink, P. Adelmann, M. Alexander, K.-P. Bohnen, MS. Golden, 

M. Knupfer, M. Merkel, N. NUcker, E. Pellegrin, H. Romberg, M. Roth 

and E. Sohmen 

High-energy spectroscopic studies of fullerene and cuprate 

G. van Tendeloo and S. Amelinckx 

Electron microscopy and the structural studies of superconducting 
materials and fullerites 

JackM. Williams, K. Douglas Carlson, AravindaM. Kim, H. Hau Wang, 
Urs Geiser, John A. Schlueter, Arthur J. Schultz, James E. Schirber, 
Eugene L. Venturini, Donald L. Overmyer and Myung-Hwan Whangbo 
Structure-property relationships in radical-cation (electron-donor molecule) 
and armion-based (including fullerides) organic superconductors and their 
use in the design of new materials 

Part V: Phase Diagrams of HTSC 

/. Karpinski, K. Conder, Ch. KrUger, H. Schwerl. Mangelschots, E. Jilek 
and E. Kaldis 

Phase diagram, synthesis and crystal growth of YBaCuO phases at high 
oxygen pressure Po 2 <3000 bar. 

GJ. Voronin 

Thermodynamic stability of superconductors in the Y-Ba-Cu-0 system 585 



In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Group Art Unit: 1751 
Examiner: M. Kopec 

Date: March 1 , 2004 
Docket: YO987-074BZ 


Commissioner for Patents 
P.O. Box 1450 
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In response to the Office Action dated February 4, 2000: 


Physical and Material 
Properties of 
High Temperature 

Edited by 
S.K. Malik and S.S. Shah 


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ISBN 1-56072-114-6 : $145.00 

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Critical State Model for Samples with Non-Zero 
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P. Ckaddah and K.V. Bhagwat 

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3, Structural, Morphological and Superconducting Properties of the Thin 
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Preparation and Characterization of YBaaCujOr-S Thick Films 
D.K. Aswal, MX Gupta, A.K. Debnath, 
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In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Group Art Unit: 1751 
Examiner: M. Kopec 

Date: March 1 , 2004 
Docket: YO987-074BZ 


Commissioner for Patents 
P.O. Box 1450 
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In response to the Office Action dated February 4, 2000: 


Physica C230 (1994) 231-238 


Synthesis and characterization of HgBa,Ca C» o 

(«=l,2,and3) - ,Ul " 0 *'«« 

O. Chmaissem, L. Wessels, Z.Z. Sheng 

Department of Phwn J u;~l * .- . e 

Rec«ved 17May 1994; re vis e dma n u^p lreceived20June , 994 

120. a,300'Cfor 18 h rcsuhs in „ eLu^of* fS3t22. ° W " ^ of ^—P^ 

•.very. X-ray diffraction Iin« of Hg-1223 can be indexed in ? a=3 " 8624 ( 1 > •2-7045(2) A, respec- 



Following the discoveiy of superconductivity with 
r.=94 K in the one-layer HgBa 2 Cu0 4+ , compound 
|1 J, a variety of new mercury cuprates have been 
synthesized [2-10]. HgBa 2 Cu0 4+ , (Hg-1201 ) is the 
first memSer of the homologous series Hg- 

and third members are 94 K, 127 K and 134 K, re- 
spectively.HgBa J Ca fl _ I C U)l 0 2n+2+rf areisostructura] 
to the Tl based superconductors Tl- 
Ba 2 Ca„- ,Cu n 0 2 „ + , {11,12] but unlike the thallium 
compounds the mercury layers are heavily oxygen 
deficient. The structure of the Hg based supercon- 
ductors HgBa 2 Ca„_ , Cu„0*, + J+< can be described as 
a sequence of layers: 

[(Ba0) c (HgO a ) o (BaO) c (CuO 2 ) o - 
' Corresponding author. 

{{n- 1 )(Ca) c (Cu0 2 ) o }] (BaO) c .„ 

in which blocks (BaO) c (HgO,) 0 (BaO) c having the 
rock-salt structure and a thickness of about 5 5 A al- 
ternate with blocks (Cu0 2 ) c { (/, _ i ) (Ca ) c (Cu0 2 ) 0 } 
havmg a perovskite-like structure and an approxi- 
mate thickness [4.00+( n -i) x3 .i6] A. The sub- 
scripts o and c indicate if the cation is at the origin or 

m ?f^ Cr ?l ^ mCSh in cach ,avcr AU Hg-1201 
[13,14] Hg-1212 [3] and Hg-1223 [15] are found 
to crystallize with symmetry of space group P4/ 
mmm. An orthorhombic symmetry was also pro- 
posed by Meng et al. [16] for Hg-1223. 

The research conducted on the thallium-based 
compounds showed that these materials offer a wide 
variety of possible substitutions on the different sites 
of their structures. Many compounds were prepared 
having their T c above 1 00 K. As we mentioned above 
many new mercury-related compounds were already 
successfully synthesized with T c around 100 K Fur- 

1223 becomes superconducting at is3 X f" 
no pxBctical value bt^^^^^ve 

ducting compounds of hijh P^yl^T™"' 
ous challenge until this date One oJ^T 

(2 ) the sealed quartz tube methods 

sealed quartz tube together 
thesis of the mercury compounds has proved 
ferent preparauon procedures such as start;*..! ' 

2. Experimental 

Several methods were tried 
aeded in synthesize* J"^ ^ f ° re we finaMv « 

Prer^resupercondSn^lT WCre first nude « 
method (mixing the S * ^ ^^e-ste 

heating b^"g^^ 
Preparation were all b2ed (oTL f " ™ C 0the 
•n which we n ° ° nthetw °- st epmethoc 

B^a^.CuX^ebest^r^ 01 

*>™ula fl9]. ^hiometric 

crucible and introduced in, ' . an aJuraina 

«»'C for 1-2 htte^mrlnf/ 6316(1 ^ at 
to 750T * / "- ^e temperature is then increased 
'o 750 Cand maintained for 1-2 h beW thT?^ 
Perature is increased , 0 800-930-0 ^ e « 
heated a, this temperature for llf* Itf £ " 

3.5°C/min.) to 20-*nn°n n. <• ^_ 
turned off. C ™ C fuXnacc Was 

inp 1 ?l a , S " PrePared Samp,es wcre sub J' e «ed to a heat- 
3 flo ^Sasof oxygen: thesampt 
zZT ^?* m ° 3 preheated fu ™ace at 300 "C 

T a dry t x qUCnChCd * ^ tCmperatUre 

the samples were characterized using the X-ray 

Sh S^S? ° D 3 PMipS ,83 °" diff ™°<neter 
Wto Cu Ka radiation and showed that the supercon- 
ducting phases were the majority phases in^IHhe 

eld. ffhyaca C 230 (1994) 2TT-238 

g the X-ray 
he supcrcon- 
es in all the 

samples prepared under the conditions described 
above together with some impurity phases which may 
be estimated to be in the order of 5-20%. These im- 
purity phases are mainly CaHg0 2 and CaO. The AC 
magnetic susceptibility measurements showed that 
the samples prepared at temperatures above 900°C 
and the samples heated for more than 1 0 h were not 
superconducting. These experiments also showed 
sharp transitions from the normal state to the super- 
conducting state with A7" c in the order or 5 K. 

3.1. Hg-1201 

As the first member of the homologous series 
HgBa 2 Ca„_iCu n 0 2a+2+ ,, Hg-1201 does not contain 
calcium; its synthesis can be done very easily using 
our procedures with very good quality and a sharp 
superconducting transition. The precursor was first 
heated at 750°C (1-2 h) and after the total decom- 
position of the barium nitrate the temperature was 
raised to 900°C for 20 h before being pulled out and 
quenched to room temperature in the dry box. Slow 
cooling in the furnace gave the same good quality of 
precursors. The resulting precursor was partially 
melted and very well crystallized. An appropriate 
amount of HgO was added to the precursor and pel- 
letized. Pellets of both precursor (P) and non-re- 
acted mixture of HgO+precursor (HBCCO) were 
sealed together at a weight ratio (P /HBCCO) of 0.48 
and slowly heated (3°C/min) to 810 o C maintained 
for 6 h, and then slowly cooled (3.5°C/min) to 
575°C. The power was then shut off and the furnace 
was naturally cooled to room temperature. 

X-ray diffraction pattern of a Hg- 1 20 1 sample pre- 
pared under these conditions is presented in Fig. 1 
and shows that Hg-1201 is the majority phase 
(>95%) and that the compound is nearly single 
phased. The structure is tetragonal with the space 
group P4/mmm, and there is no evidence of any kind 
of special extinction. The refined cell parameters of 
the as-synthesized sample are: a=3.8831 ( 1 ) A and 
c=9.5357(2) A. 

AC magnetic susceptibility and resistivity mea- 
surements (Fig. 2) performed on Hg-1201 samples 
show a sharp superconducting transition and a zero 

Fig. 1. X-ray diffraction pattern of an as-prcparcd Hg-1201 sam- 
ple. The lines are indexed in a tetragonal cell with lattice con- 
stants a = 3.883 1 ( 1 ) A and c= 9.5357 (2 ) A. 

0 50 100 150 200 250 300 

Temperature (K) 

Fig. 2. Resistivity measurements carried out on a Hg-1201 sam- 
ple. A sharp drop of the resistivity is observed at 94 K in the as- 
synthesized sample, it increases up to 97 K in the oxygen-an- 
nealed sample (300*C, 18 h). AC magnetic measurements (real 
and imaginary parts) are shown in the inset. 

resistance at 94 K. Annealing the sample in 0 2 at 
300 °C for 18 h results in an increase of its critical 
temperature up to 97 K. The curves presented in Fig. 
2 show the resistivity measurements of the as-pre- 
pared and the oxygen-annealed sample. The oxygen- 
annealed samples were checked by X-ray diffraction 
and found to be remaining intact with no sign of any 
apparent change in the structure. 

With the introduction of the calcium into the 
structure, the synthesis procedures become more del- 


O. Chmaissem et al. /Physica C 230 (1994) 231-238 

icatc and special care should be taken in the different 
stages of the preparation. 

Some groups have reported the successful synthe- 
sis of Hg-1212 and Hg-1223 using the single-step 
method [20-24J. However, their procedures in- 
cluded the preparation of fresh oxides of BaO and 
CaO and the isolation of the sample from the quartz 
walls by wrapping the materials with a gold or silver 
foil f21-23] or even by using alumina tubes to be 
inserted in the quartz tubes [24]. Our experiments 
using this method were not successful probably be- 
cause the samples were introduced in the quartz tubes 
without wrapping. Unlike the preparations based on 
the two-step method, the samples are rudely reacted 
with the quartz even at temperature as low as 750°C 
and the resulting materials were multi-colored pow- 
ders with no sign of any homogeneity and particu- 
larly no superconductivity. 

Our Hg-1212 samples were prepared by repeating 
the same procedures employed for the synthesis of 
Hg- 1 20 1 . The purity of the samples was estimated by 
both the X-ray diffraction patterns and the AC mag- 
netic-susceptibility measurements. We found that 
samples prepared at temperatures between 825 °C and 
860°C contain not more than 65% of the supercon- 
ducting phase Hg-1212. Table 1 shows the depen- 
dence of the Hg-1212 volume percentage on the 
preparation conditions. The best samples were ob- 
tained by heating at relatively low temperature 790°C 
for 1 0 h. X-ray diffraction pattern and the supercon- 
ducting properties are shown in Figs. 3 and 4, respec- 
tively. Hg-1212 is also tetragonal with lattice param- 

eters a=3.8624(l) A and c=l2.7045(2) A The 
T c ^ .of the as-prepared samples is between 1 10 K 
and 120 K. Samples annealed in 0 2 at 300°C for 18 
h have their T ctmK increased up to 1 27 K. 

3.3. Hg-1223 

Ba 2 Ca 2 Cu 3 0 7 precursors were prepared by heating 
the starting materials at 935°Cfor 7 h. Details are in 
the experimental section. The first preparations based 
on these precursors were partially successful as we 
were able to obtain a superconducting volume in the 
order of 60%. However, the superconducting phase 
was Hg-1212 rather than Hg-1223 (according to the 
X-ray diffraction patterns). Table 2 shows two sets 
of experiments with detailed synthesis conditions of 
Hg-1212 from nominal 1223 composition. The up- 
per part of the table concerns the preparations in 
which the weight ratio P/HBCCO=0. The intro- 
duced pellets were only those with the nominal com- 
position HgJBajCajCujO, assuming that the pre- 
pared precursors had their initial composition. The 
mercury oxide was added in excess to the stoichio- 
metric formula in order to compensate the loss re- 
sulting from its reaction with the quartz tube. In the 
lower part of the table are presented the experiments 
of the Hg controlled vapor by using the method de- 
scribed in the experimental section with the weight 
ratio P/HBCCO>0. In these preparations the esti- 
mated superconducting volume (Hg-1212) is rang- 
ing between 0 and 60%. These estimations are based 
on the X-ray diffraction patterns which also showed 























Heating rate 

Cooling rate 

rc) P 


vol. (%) 









































O. Chmaissem et al /Physica C 230 (1994) 2\ 

2) A. The 
vecn 110K 

i by heating 
ctails are in 
itions based 
ssful as we 
•lume in the 
cling phase 
rding to the 
ws two sets 
raditions of 
on. The up- 
jarations in 
The intro- 
iroinal com- 
iat the pre- 
Dsition. The 
he stoichio- 
the loss re- 
tube. In the 
method de- 
i the weight 
>ns the esti- 
12) is rang- 
ns are based 
also showed 


2-Theta (deg.) 
Fig. 3. X-ray diffraction pattern of an as-prepared Hg-1212 sam- 
ple. The diffraction lines are indexed in a tetragonal cell with the 
lattice parameters <i=3.8624( 1 ) A and c=12.704S(2) A. 


100 150 200 250 300 

Temperature (K) 

Fig. 4. Resistivity measurements of a sample Hg-1212. The fig- 
ure shows clearly the increase of the 7" coo «, from 117 K (as-syn- 
thesized sample) to 127 K (oxygen-annealed sample). The inset 
shows the AC magnetic measurements (real and imaginary parts) 
performed on an oxygen-annealed sample. 

that the impurity phases are CaHg0 2 and CaO, with 
traces of a weak unknown phase. It is clear from the 
table that the formation of the superconducting phase 
is favored by the presence of the precursor pellets. The 
highest superconducting volume is obtained when 
heating to temperatures close to 850°C. At 870 e C the 
sample (chl 1 ) is still superconducting but with a de- 
creased volume down to 40% and the sample is par- 
tially melted, indicating that preparations above this 
temperature could not be carried out successfully. 

This work was carried out simultaneously with at- 
tempts to synthesize the fourth member of the mer- 
cury-based series, namely Hg-1234. The first results 
showed that the superconducting phase obtained with 
precursors assumed to be BajCa 3 Cu„0 9 (234) was 

Hg-1223. By consequence, we started a new series of 
experiments based on the 234 precursors for the syn- 
thesis of Hg-1223. 

Nominal Hg x Ba 2 Ca J Cu 4 O y pellets and 
Ba 2 Ca 3 Cu40, pellets were sealed together and treated 
as described in Table 3. Very good Hg-1223 samples 
with a volume «90% were obtained with tempera- 
tures between 870 e C and 885 °C. The samples pre- 
pared at 900°C were partially melted and presented 
only 30 to 40% superconducting volume (samples ch2 
and ch5 ), a longer reaction time at this temperature 
results in the destruction of the superconducting phase 
(sample chl9). The reproducibility of the Hg-1223 
phase using these procedures is 100%. Using precur- 
sors obtained from different batches and following the 
same conditions given in Table 3 gave 90% Hg-1223 
at each time. Together with the superconducting pel- 
lets were found drops of mercury inside the closed 
quartz tube. 

X-ray diffraction pattern is given in Fig. 5 which 
shows the good quality of our Hg- 1223 sample. Based 
on the tetragonal symmetry [ 4, 1 5 ] of space group P4 / 
mmm, the refined lattice parameters were found to 
be a= 3.8564 ( 1 ) A and c= 1 5.8564(9) A. During in- 
dexing the diffraction pattern we found that many 
peaks were doubled and cannot all be indexed in the 
tetragonal symmetry, indicating that the symmetry 
might be orthorhombic. Refinements in an ortho- 
rhombic cell were equally successful and the doubled 
strong lines were all indexed in a unit cell of lattice 
parameters a=5.4537(l) A, 6=5.4247(1) A and 
c= 15.8505(7) A. 

The AC magnetic susceptibility an the resistivity 
measurements for a Hg-1 223 phasic sample are given 
in Fig. 6. The r c0OJtt is around 105 K for the as-pre- 
pared samples. A T eoostt of 1 35 K can be easily ob- 
tained by following the same annealing treatment 
performed on Hg-1 201 and Hg-1212 (0 2 , 300°C, 18 
h). The resistivity measurement shows a sharp tran- 
sition at 135 K and a zero resistance is achieved 
around 1 34 K. 

As we stated above, the preparation of Hg-1 201, 
Hg-1212, and Hg-1223 was carried out using the 
sealed quartz tube method. The insertion of 


O. Chmaissemeial. I Physica C 230 (1994) 231-236 

the preparation marked with an asterisk and x=l.5 feral! the cth^n^Z.^ rat '° ^^/Hg^^/^O, where 1 f 0 




Heating rate 






preheated furnace 

















Cooling rate 

t.5 -room temp, 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 

Table 3 

istTcl CuTT ? Ca i ed 0,M l° r pn >™ ti ™ of Hg-1223. The nominal wml 

of the precursors used in these experiments 
x= 1 .5 for the preparations marked with an asterisk 



Heating rate 









































Cooling rate 


1.0- room temp. 




1.5- 550*C 


2.5 temp. 

1.0— room temp, 
power shut off 
power shut off 
power shut off 
power shut off 
power shut off 

vol. (*,) 

Ba^a^.C^O, pellets (P) together with Hg- 
- •Ba a a n _,Cu„O y . pellets (HBCCO) in the sealed 
quartz tubes suggests that the total amount of the ma- 
terial inside the tube is mercury deficient. Surpris- 
ingly, drops of mercury were observed in almost all 
the experiments. The formation of Hg-1212 instead 
of Hg-1223 from nominal 1223 composition and the 
formation of Hg-1223 instead of Hg-1234 from nom- 
inal 1 234 composition mean that there are some cal- 
cium and copper left. CaHg0 2 was observed as the 
major impurity phase and there are negligible traces 

of CuO and its related compounds. One may specu- 
late that the copper and the mercury cations are 
mixed. The substitution of Cu for 8% Hg was ob- 
served by Wagner et al. [13J in their Hg-1201 sam- 
ple. As a consequence, they found additional extra 
oxygen atoms on the edges of the mercury layer (J, 
0, z) together with the already existing extra oxygen 
atoms at ( J, { , 0). In the first, second, third and fifth 
member of the mercury-based series the mercury at- 
oms are found to have an unusually high temperature 
factor [ 14, 1 5,25-27 ] . This can be reduced to a more 

CujO, where jr=l for 


O. ChmaissemetaL /Physica C 230 (1994) 231-238 


One may specu- 
cury cations are 

8% Hg was ob- 
:irHg-1201 sam- 

additional extra 
nercury layer (|, 
ing extra oxygen 
d, third and fifth 
s the mercury at- 
high temperature 
jduced to a more 

2-Theta (deg.) 

Fig. 5. X-ray diffraction pattern of an as-prepared Hg-t223 sam- 
ple. The diffraction lines are indexed in both tetragonal cell with 
lattice constants «=3.8S64( 1 ) A and c= 1 5.8565(9) A and or- 
thorhombic cell (in parentheses) with lattice constants 
a= 5.4537 ( 1 ) A, b= S.4247( 1 ) A and c= 1 5.8505(7) A. The in- 
set shows the splitting of the line ( 1 1 0) (tetragonal symmetry) 
into two lines, 2 0 0 and 0 2 0 (orthorhombic symmetry). 

100 150 200 250 300 

Temperature (K) 

Fig. 6. Resistivity measurements carried out on both as-synthe- 
sized and oxygen-annealed Hg-1223 samples. The T toM (origi- 
nally 105 K.) is increased up to 135 K. The curve shows a sharp 
transition around 135 K with a zero resistance at about 134 K. 
The real and imaginary parts of the AC magnetic-susceptibility 
measurements carried out on an oxygen-annealed sample are 
shown in the inset 

reasonable value by mixing the mercury cations with 
atoms like copper for example. This possibility was 
investigated but not proved. The successful prepara- 
tion of nearly "100%" pure Hg-1201 samples using 
our method where the mercury cations enclosed in 
the quartz tube present only 0.57 mole to 1 mole of 
the precursor Ba 2 CuO J+x confirms that the mixing of 
Cu and Hg is very possible. The increase of T coiaa 
(97 K) might be due to this mixing. However, this 
conclusion must be interpreted with some caution. A 

molar ratio Hg/Cu of 0.57 seems to be rather small 
compared to 0.85 found by Wagner et al.. Even though 
our sample looks pure using the X-ray diffraction 
technique, it might not really be the case. An unde- 
tectable (by X-rays) amorphous Ba-Cu-O sub- 
stance could exist in the powder as well. Such obser- 
vation was reported by Dolhert et al. [28] who 
studied the low delectability of excess yttrium and 
barium in YBa 2 Cu 3 0 7 by X-ray diffraction. Thus the 
X-ray "pure" sample may not be actually very pure. 
However, the formation of (Hg, 
Cu ) Ba 2 Ca„ _ i Cu„0 2n+ 2 +f is possible and seems to be 
dependent on the preparation conditions. More de- 
tails need to be studied. As the X-rays are not too sen- 
sitive to the oxygen anions, neutron experiments are 
needed to determine the value of the extra oxygen at- 
oms and their location and to confirm the occupancy 
of the mercury sites and also to investigate the possi- 
bility of any change in the structure. 

Our Hg-1223 phase is very likely to be orthorhom- 
bic. The orthorhombicity of our samples is observed 
by the splitting of some of the X-ray diffraction lines. 
The possibility of the coexistence of two phases with 
very high rate of overlapped lines would suggest that 
these two phases are both members of the mercury- 
based series and by consequence we must be able to 
observe at least two well-defined superconducting 
transitions in our measurements. As this was not the 
case and as the lines (00/) are singles and not split 
we may conclude that our Hg-1223 phase is ortho- 
rhombic. The refined cell parameters are in good 
agreement with those reported by Meng et al. [16] 
and Huang et al. [29] for their orthorhombic samples. 


We thank John Shultz for his assistance in powder 
X-ray diffraction. This work was supported by the 
Advanced Research Projects Agency and the Arkan- 
sas Energy Office, USA. 

[ 1 ] S.N. Putilin, E.V. Antipov, O. Chmaissem and M. Marerio, 
Nature (London) 362 (1993) 226. 

O. Chmaissem a al. /Physica C 230(1994) 231-23S 

[2] A. Shilling. M . Cantoni. J.D. Guo and M.R. On. Nature 

(London) 363 (1993) 56. 
{ 3 J S.N. Putilin, EV. Antipov and M. Mareao, Physica C 2 1 2 


f 4) E.V. Antipov, S.M. Loureiro. C ChaiUout, JJ. Capponi. P 
Bordet, J J. Tholence, S.N. Putilin and M. Mareao, Physica 

[5] C Martin, M. Huve, G. Van Tendeloo, A. Maignan. C 
MKteL M. Hervieu and B. Raveau, Physica C212 (1993) 

[6] A. Maignan. C. Michel, G. Van Tenddoo. M. Hervieu and 

B. Raveau, Physica C 216 (1993) I. 
[7 J R^. Liu, D.S. Shy. S.F. Hu and D.A. Jefferson, Physica C 

[8] F. Goutenoire, P. Daniel, M. Hervieu. G. Van Tendeloo, C. 

Michel, A. Maignan and B. Raveau, Physica C216 ( 1 993) 

[9] D. Pelloquin. M. Hervieu, C. Michel, G. Van Tendeloo. A 
Maignan and B. Raveau, Physica C 2 1 6 ( 1 993) 257 

1 10) M. Hervieu, G. Van Tendeloo, A. Maignan, C Michel F 
Goutenoire and B. Raveau, Physica C 2 1 6 ( 1 993 ) 264 

[IlJZi Sheng and A.M. Hermann, Nature (London) 332 
(1988) 55. 

II2JZ.2. Sheng and A.M. Hermann, Nature (London) 332 
(1988) 138. 

[ 1 3 ] JI_ Wagner. P.G. Radaelli, D.G. Hinks, JX>. Jorgensen, J F 
Mitchell, B. Dabrowski, G.S. Knapp and MA Beno, Physica 
C210 (1993) 447. ^ 

1 14 J O. Chmaissem, Q. Huang. S.N. Putilin, M. Mareao and A 
Santoro, Physica C 212 (1993) 259. 

[15JO. Chmaissem. Q. Huang, E.V. Antipov, S.N. Putilin, M 
Mareao. S.M. Loureiro, J J. Capponi, J.L. Tholence and A 
Santoro, Physica C 2 1 7 ( 1 993 ) 265. 

{ 16) R.L Meng. L Beauvais, X.N. Zhang, ZJ. Huang. Y.Y. Sun, 
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[17JC.W Xhu. L Gao F. Chen, ZJ. Huang, R.L. Meng and 
f.8,w Y - Xue - N " ure (Lo"<K>n) 365 (1993) 323. . 
£ Nunez-Regueiro. J.L. Tholence. E.V. Antipov. Jj 
Cvp^.^Marezio. Science 262 (1993) 97 

' 'SSsif ■ u Kc - °™> Mod - ^- *~ b. 

I20JP.G. RadaeBi JJ_ Wagner. B_A. Hunter, B.A. Beno. OS. 

(W3)» ***** DG ' HinkS ' PhySia C 2,6 
(21 J M. Itoch a. Tokiwa-Yamamoto. S. Adachi and H 

Yamauchi, Physica C212 (1993)271 
[22 J A. Tokiwa-Yamamoto. K. Isawa. M. Itoch. S. Adachi and 

H. Yamauchi. Physica C 2 1 6 ( 1 993) 250 
[23 J WJ. Zhu. YZ Huang. LQ. Chen, C Dong, B. Yin and Z.X. 

[ 24 J M. Paranthaman, Physica C 222 ( 1 994 ) 7 
[25JS.»1 Loureiro, E.V. Antipov. J.L. Tholence, JJ. Capponi, 

ufm^ Q ' Huang " nd M Marczio - Physica C 17 

[26JE.V. Antipov, J J. Capponi, C. ChaiUout, O. Chmaissem. 

S M. Loureu-o. M. Mareao, S.N. Putilin, A. Santoro and 

J.L. Tholence, Physica C218 (1993) 348 
[27] Q. Huang. O. Chmaissem. JJ. Capponi. C ChaiUout, M. 

(199T)°i Th ° knCe aild San,0r0, Phy5iCa C 227 

III I D ° IhCn and N D - S »* ncer > Mater. Lett. 9 (1990) 537 
[29] ZJ. Huang, R.L. Meng. X.D. Qiu. Y.Y. Sun, J. Kulik, Y Y 
Xue and CW.Chu, Physica C 21 7 (1993) I 

is given 
rmitted by 
tide to the 
mot given 
81 may be 
per page.) 
Jrposes, or 

PnysicaC215 (1993) 1-10 


The synthesis and characterization of the HgBa 2 C2L 2 Cu 3 O g+s and 
HgBa 2 Ca3Cu40,o +< j phases 

E.V. Antipov **, S.M. Lourciro b , C. Chaillout b , J J. Capponi b , P. Bordet b , J.L. Tholence c 
S.N. Putilin » and M. Marezio bd 

• Department of Chemistry: Moscow State University. 119899 Moscow. Russian Federation 
" Laboratoirede CrisiallographieCNRS-UJF. BP 166. 38042 Grenoble Cedex 09. France 
' CRTBT. CNRS-UJF. BP 166. 38042 Grenoble Cedex 09. France 
' AT&T Bell Laboratories. Murray Hill. NJ 07974. USA 

Received 28 June 1993 

Revised manuscript received 9 July 1 993 

The third (Hg-1223) and the fourth (Hg-I234) members of the recently-discovered homologous series Hg- 
Ba 1 Ca._,Cu«Oj. + 3 4 . < have been synthesized by solid state reaction, carried out at 950°C under 50 kbar at different annealing 
times. These phases have a tetragonal cell with lattice parameters: a=3.8532(6) A, c= 15.818(2) A and a=3.8540(3) A, 
c= 19.006(3) A. respectively. The c parameters are in agreement with the formula c=9.5 + 3.2(n— I). Electron microscopy study 
showed similar lattice parameters as well as the occurrence of different intergrowths and stacking faults. A periodicity of 22 A has 
also been detected, which may be attributed to the existence of the Hg-1 245 phase. EDS analysis data of several grains of Hg-1 223 
and Hg-1 234 are in agreement with the proposed chemical formulae. AC susceptibility measurements show that an increase of 
the superconducting transition temperature with n in the HgBajCa.- iCu.Oj. +l+< series occurs till the third member, after which 
is to be achieved. 

1. Introduction 

Superconductivity at about 94 K and well above 
120 K has been recently reported for HgBa 2 Cu0 4+ , 
(Hg-1201) [1] and HgBa 2 CaCu 2 0 6+ , (Hg-1212) 
[2], respectively. These phases are the first and the 
second members of the Hg-based homologous series 
of layered Cu mixed oxides. Their structures contain 
rock-salt-like slabs, such as (BaO) (HgO<) (BaO) al- 
ternating with either one (Cu0 2 ) layer in the former 
or an anion-deficient perovskite-like slab, such as 
(Cu0. 2 }(CaE])(Cu0 2 ), in the latter. A supercon- 
ducting transition temperature as high as 133 K has 
been reported for a multiphasic sample in the Hg- 
Ba-Ca-Cu-O system by Schilling et al. [4]. These 
authors could not identify by X-ray diffraction the 
phases responsible for the superconductivity at this 
temperature, but proved by high resolution electron 
microscopy that the sample contained the Hg-1212 
and Hg-1223 phases as well as different inter- 
growths. Putilin et al. [2] showed that in the sample 

containing Hg-1212 as the majority phase, a small 
drop on the AC susceptibility curve versus T oc- 
curred at about 1 32 K which could be attributed to 
the third member of the Hg-bearing series. 

Putilin et al. also showed [2] that it was possible 
to synthesize the Hg-1212 phase, practically in pure 
form, under high pressure (40-60 kbar) and at 
800°C for about 1 h. The high pressure synthesis al- 
lows one to lower the mercury oxide decomposition. 
This decomposition occurs at ambient pressure at a 
temperature at which the reactivity of the other com- 
ponents is very low. It was suggested that the same 
technique could be used for obtaining the higher 
members of the series. We found that the reactions 
have to be carried out at higher temperatures 
(950°C) and for longer annealing times. The same 
occurs for the higher members of the Bi- or Tl-based 
Cu oxide series, which are formed by the formation, 
at the initial stages of the reaction, of the lower mem- 
bers of the corresponding families. We report herein 
the synthesis and characterization of the Hg- 

092 l-4534/93/$O6.0O© 1993 Elsevier Science Publishers B.V. All rights reserved. 

fw C f^ i0,+i MS-*™) and HgBa 2 Ca 3 Cu<0 
u c ,or 3 and 3.5 h, respectively. 

Ba P rr d r r n SamP ' eS COnlainin « Hg- 
oblamed by h lg h-pressure and high-temperature re- 
acnons usmg the belt-type apparatus oHhe Ubo' 
atcre de Cnstallographie. A precursor wi* , he 
nommal composition Ba 2 Ca 2 C U3 O x was preyed by hjgh-purity nitrates: BaCNO^ ^dlh 
>99%), Ca(N0 3 ) 2 4H.O (Normapu L L^T"' 

alytical reagent) and Cu(NO,), 3H n ,c. 

Chemical Inc 99 5%> tk" V " 2 ° (Strem 
v«i int., yjo%). 7"h e mixture thus obtain^ 

was mmally heated at 600'C in air foM2 h Z 

regrinded and annealed at 925«C for 72 h in M ox 

ygenflowwith three intermediate regrindmgs it 

SsstJSSi" ,, rr of yel,ow Hgo 5«5 

lund^ thC mixtUre was thorough^ 

grounded in an agate mortar and sealed in a Pt can 
ule specie for high pressure synthesis. Var£u S ~ 
emperatures and annealing times at a pressure o 50 
kbar were tned in order to obtain the Hg-1223 and 
Hg-1234 phases. In these experiments"V P Ss Ur e 
was first mcreased to 50 kbar, subsequently the tern 
penuun .was raised to the desireTa, U e d^ ng h" 
then the temperature and the pressure were kin,' 
constants 1-4 h. After this, JfuTaSpZr^ 


and SCANPI programs w ere used for processing the 

The phase HgBa 2 Ca 2 Cu 3 0 8+ , was present in the 
samp, e syn.hestzed a, 950'C for 3 h (sample I) to- 
gether wuh a smaller amount of Hg-1212, CaO and 
CuO. and traces of CaHgO, [6] and of an unknown 
Phase whose intensities were less than 4%. Z X ^ 

diffraction pattern of sarrmle I afi<»r k. l. 
straction is shown in r^^^"*- 


c~ li. 618(2) A. The characteristic 001 n-fw V* 
shown in the insert. No systematic abseil ° D * 
served, leading to space gro^p ^mm 
Tormula per unit cel.. TheVea'sur^ vie of V 
parameter of Hg- 1 223 corr«nn a * of the c 

with/i=3[lj. t -2'-3+J.2(/j-l) 

A scanning electron microscope JEOL 84<u 

(EDS) attachment was used for the analysis of Z 
canon composition of the two prepared Z^Ka 

I«oed formula of ihe Hg-1223 phase. 

The lattice paramelers of He-1212 refined fi™ 
ten reflections (.=3.859(4) A, c= 12 ^ A ^ 
h a ^ Cm ^ thc data of Pu «*n e. al [2 1 
£££ ST J 31 thCre " ^riappSbi- 

Sh, S re H m T of thc Hg - 1212 and > 

of Si m , 3 ^ M ° re0Ver ' ^ *« Sections f 

line a^ T aPPmgS n ° l us » 

of ,h S,t,CS ° f lhC ,W ° Phases - How <™. > 

s"ow c he H K n ?2 I ?? ,22 K ° 03and ,04) 
Phase in " ^ Pred ° minan ' 

mI h J wT,hT ^ 53011)16 1 ° f the ,ower member «°- 
gethe w,«h the ,n ltl al oxides, CuO and CaO, ob- 

not C o m md r ,e / tha ' ,hC f0rmation of "8- 1 223 was 

thes' ^ 3 3 " annCa,in8 period " ^ e s ^ 

thes is earned out at 900°C for 2 h led to the for- 
mats of Hg-1212 which was found fobe the main 

™Z< n ?L e " n ? e l0Bether with the startin * ««■ 

pounds. These data show that the formation of 
Hg-1223 occurs through the synthesis of the lower 
members of the series. The increase of the annealing 

and sub- 
ons cor- 
(6) A, 
ection is 
and one 
of the c 

£ V. Aiaipov etal./ HgBa£ajCufl,+, and HgBa^Vi jCu<O l0 +, 

U h a if 


Fig. 1 . X-ray powder pattern for sample 1. Indexed XRD intensities correspond to Hg- 1223 and Hg-12 1 2 (underline). Impurities of CaO. 
CuO. CaHg0 2 and an unknown phase are marked by ( ' ). The inset displays the characteristic intensity of 001 for Hg-1 223. 

time up to 3.5 and 4 h at 950°C and the same pres- 
sure led to the expected disappearence of Hg-1 21 2 as 
well as of CaO. In these samples the formation of a 
new phase was detected. Its amount was relatively 
high (more than 50%) in samples annealed for 3.5 
h (sample II). A total of 17 reflections of this phase 
were indexed on a tetragonal cell with lattice param- 
eters a=3.8540(3) A, c= 19.006(3) A. As for Hg- 
1223 no systematic absences were observed, leading 
to space group P4/mmm. Similar parameters were 
found by electron diffraction (sec below). The c pa- 
rameters ofthis phase corresponded to the value cal- 
culated from the formula cs9.5 + 3.2(n- 1 ) for 
n=4. This strongly suggested that the new phase was 
the fourth member of the .Hg-based series: Hg- 
Ba 2 Ca 3 Cu4O|0 + <. The approximate cations ratio de- 
termined by EDS analysis of five well-crystallized and 
flat grains was Hg:Ba:Ca:Cu= 
9(1): 18(1 ):29(2):44(2). These data are in good 
agreement with the proposed formula for the new 

Besides Hg-1 234 as the main phase, a smaller 
amount of Hg-1 223 was present in sample II to- 
gether with small amounts of CuO and of an un- 
known phase. This unknown phase was predomi- 
nant in a sample treated for 5 h in the same 
conditions which did not contain any member of the 
Hg-based series and did not exhibit any supercon- 
ductivity. The presence of the latter oxides can be 
explained as a result of the decomposition of Hg- 1 223 
and the formation of Hg-1234. Hg-1212 was absent 
in this sample as well as in that annealed for 4 h. The 
X-ray diffraction pattern of sample Ii after back- 
ground subtraction is shown in fig. 2. The ratio of 
the main intensities for both Hg-based layered cu- 
prates, 104forHg-1223 and 105 for Hg-1234, shows 
that the latter was the main phase in this sample. As 
for sample I the overlapping of hkO reflections for 
both phases occurs because of the similarity of the 
two a parameters. Moreover, the hk6 reflections of 
Hg-1234 are overlapped with the hkS ones of Hg- 



£ V.Antipovetal. fHgBa£a£u&,+ t aniHgBa/:a£:ujO„+, 


Jl- , % li ji 

Fig. 2. X-ray powder pattern for sample II. 1 
and an unknown phase are marked by ( * ). 

3. Electron microscopy 

The I and II samples were studied by electron mi- 
croscopy. A suspension of crystals in acetone was 
grounded in an agate mortar. The crystallites were 
recovered from the suspension on a porous carbon 
film. A Philips EM 400T operating at 120 kV was 

Figure 3 (a) and (b) shows two diffraction pal- 
terns obtained for sample I corresponding to the 
[001] and the <110> zone axes of the Hg- 
BajCa 2 Cu,Og +<5 (Hg-1223) phase, respectively. In 
both cases, the diffraction spots are sharp, which in- 
dicates that the crystal is well ordered. In fig. 3(b), 
one can notice a modulation of the intensity of the 
diffraction spots along the c*-axis, with maxima for 
AW reflections with l=5n (n=6, 1,2, ...). On the mi- 
crograph (fig. 3(c)) corresponding to the diffrac- 
tion pattern shown in fig. 3(b ), one can see the very 

60 70 80 2 Thcta 

correspond to Hg-1234 (bold) and Hg-1223. Impurities ofCuO 

regular periodicity of the fringes separated by 15.8 
A. During the observation under the electron beam, 
dark spots appeared near the edge of the crystal, 
probably due to the decomposition of the crystal. 

Some diffraction patterns obtained for other crys- 
tals present diffuse lines parallel to the c*-axis and 
passing through the Bragg spots (fig. 4 (a)). They 
are due to the presence of intergrowths as given evi- 
dence for by fig. 4(b). On this micrograph, two dif- 
ferent spacings of 1 5.8 A and 12.7 A can be mea- 
sured, attributed to Hg-1223 and Hg-1212, 

In the case of sample II, almost all the observed 
crystallites have diffraction patterns corresponding 
to the Hg-1234 phase (HgBa 2 Ca,Cu 4 O, 0+ <) with cell 
parameters a=6=3.85 A and c= 19 A. Figure 5(a) 
and (b) give examples of the [001 ] and < 100) zone 
axes, respectively. As for Hg-1223, also for Hg-1234 
the intensity of the Bragg spots varies according to 

E. V. Anlipor el at. /HgBa/Ta^CujO,^ and HgBajOj/Ttt^ 

by 15.8 
>n beam, 
■ crystal, 
axis and 
)). They 
iven evi- 
. two dif- 
bc mea- 

with cell 
ure 5(a) 
)0> zone 
jrding to 

Fig. 3. Electron diffraction patterns of Hg-1 223 taken along (001 ] 
(a)and <110) (b) rone axes, (c) Micrograph corresponding to 
the diffraction pattern (b). The interfringe spacing is IS.8 A. 

the value ofthe / index, the maxima of intensity being 
obtained for l=6n (n=0, 1, 2, ...). This intensity 
pattern might be explained by the fact that c/6 is 
equal to 3.17 A, which corresponds to the distance 
between two neighboring (Cu0 2 ) layers. The in- 
crease of the layer number n in the structure leads to 
the increase of the intensity of the hkl reflections with 

Fig. 4. Electron diffraction pattern of sample 1 along < 100> and 
corresponding micrograph showing the intergrowths of Hg-1 223 

l=n+2. These periodicities of the (Cu0 2 ) layers ex- 
plain the overlapping of such reflections on the X- 
ray powder pattern (see above). Most of the images 
taken along the < 100) zone axis show very regular 
fringes separated by 1 9 A (fig. 5(c) ). However, some 
crystals present intergrowths between the Hg-1 223 
and Hg-1234, as revealed in fig. 6. In this case, the 
following sequence is observed over about 500 A: 
-19 A-19 A-19 A-19 A-19 A-22 A-. On the corre- 
sponding diffraction pattern, besides the diffraction 
spots of the Hg-1234 phase, additional spots related 
to the 22 A periodicity are present. Such a period- 
icity may be attributed to a 1245 phase (Hg- 
Ba 2 Ca4Cu s O,2 + ,). The fact that the extra diffraction 
spots are sharp indicates that this phase is well or- 
dered at least over a certain number of cells in these 

4. AC susceptibility measurements 
The critical temperature T C) and the apparent su- 

Fig. 5. Electron diffraction patterns of Hg- 12 J4 taken along [001 1 
(a) M d <100> (b) zone axes, (c) Miut>graph corresponding to 
the diffraction pattern of (b). The interfringe spacing is 19 A. 

perconducting volume of samples I and II have h~« 

fine powder samples. This avoids overestimate Z 
the superconducting volume due to the larger screed 
•ngs m sintered samples. The AC suscepL.^ 
measured wtth an alternating maximum field of 0^ 
Oe and a frequency of 119 Hz. The temperature was 

The as-synthesized sample I undergoes a transi- 
tion from the paramagnetic to the diamagnetic state 
with an onset above 133 K (fig. 7). Several mea- 
surements were made with the same sample and the 
reproducibility of T c is K (mainly due to the 

thermal contact between the sample and the ther- 
mometer). The estimated magnetic susceptibility at 
4 K corresponds to a large volume of ideal dia- 
magnetism indicating the bulk nature of supercon- 
ductivity. We can suggest that the sharp and large 
drop on the AC susceptibility curve above 133 K 
should correspond to the Hg-1223 phase because Hg- 
1212, which is present in this sample as the minority 
Phase, has a T c not higher than 126 K [3]. 

The as-synthesized sample II undergoes a transi- 
tion from the paramagnetic to the diamagnetic state 
with an onset as high as 1 32 K. Actually, two onsets 
at two different temperatures are visible, the smaller 
one at 1 32 K and the larger one at about 1 26 K. There 
are two Hg-based layered cuprates in this sample: Hg- 
1 234 as the main phase and Hg-1223 as the minority 
one. Taking into consideration the results of sample 
I, we might suggest that the first onset (132 K) cor- 
responds to Hg-1223 and the larger one at the lower 
temperature (126 K) to Hg-1234. In any case, it is 
obvious that T c for Hg-1234 is not higher than that 
for Hg-1223. 

5. Discussion 

The synthesized HgBa 2 Ca 2 Cuj0 8+<f (Hg-1223) 
and HgBa 2 Ca 3 Cu 4 O 10+ , (Hg-1234) phases are the 
third and the fourth members of the Hg- 
Ba 2 Ca„_ 1 Cu n 0 2n+J+< , series, in analogy with those 
of Hg-1201 [1,7,8] and Hg-1212 [2] their struc- 
tures can be schematized as containing rock-salt-like 
slabs, (BaO)(HgO,)(BaO), alternating with per- 
ovskite-like slabs, consisting in three (Hg-1223) or 

SAMPLE 1> as synthesized 

1*7. AC susceptibility v, Tfora^^ 

ng as the main phase and of Hg- 1223 as the 

1212 The appropriate treatment for He- 1234 ran 

occurs for the TlBa,Ca n. n i. 

„ • f . . . "r 2V - a "-i Cu «y2n+3 +( f homologous 

~at(9? ,nCTeaSeSUPt ° th - 

iD^JSr ^ ,aWe 1 ,h3t H « the 

increase of r c ,s accompanied by a decrease of the a 

Tabic I 

Lattice parameters i 

£ V. Antipovetal. , HgBa&fiufl.^and HgBa^u^ 
'direction temperature for Hg-based Cu oxide 

HgBa 2 CuO <w 

HgBa,Ca,Cn,O 10+< 









~) ~ 

[4), this work 
this work 

the system leads to intergrowths due to different 

1 r/f m p "\ tCI * rowths already reported 
n ref. [4]. Possibly, the occurrence of different in- 
tergrowths may explain why the variation versus 
temperature of the AC susceptibility does not pres- 
ent d,slinct and abrupt transitions which could be 
attributed to pure Hg-1212, 1223 and 1234 phases 
The synthesis of the higher members of the Hg- 
based homologous series as bulk samples has been 
performed at higher temperatures than that used for 
Hg-1212 and w,th longer treatment times. We sug- 
gest that the synthesis of such phases occurs through 
the formation at an initial state and subsequent de- 
composition of the lower members of the series. This 
feature is similar to that existing for the Tl- 
r Z' , ° J " +3 -< homologous series [91. The 
use of high pressure, possibly, lowers the mercury 
oxide decomposition. It also leads to a decrease of 
subility of CaHgO a , whose synthesis at the first stage 
of the reaction inhibits the formation of Hg-based 


Toe-authors would like to thank M.F. Gorius, M. 

Pcrroux and R. Argoud for their technical assistance 

the French M.mstry of Foreign Affairs. EVA and SNP 
would like to thank the support of the Russian s£ 
SS-rS? ° n nd ^vity (PrS 

dSfp k T SUpP ° ned by lhe Era «™ Stu- 
dents Exchange Program. 


Nature (London) 362 ( 1 993) 226 

m EV - M Manzio - c ™ 

14] Sculling, M. Cantoni, j. D . Guo Md H R ^ 

(London) 363 (1993 ) 56. 
1 5 ] KJE. Johansson, T. Palm and P.-E. Werner. ). Phys. E: Sci 

lustrum. 13 (1980) 1289 J»-«^aa. 
' 6J f'M ^ D. Kashporov, E.V. Amipov artd 

(mRuS , * aniCheSk0iKhimiii36 (,99,) IMJ 

(7 J O. ^ Q. Huang. S.N. Puulin. M. Marezio and A. 

Santoro. Physics C212 (1993) 259 

191 S Naka^ma. M. Kilcuchi. Y. Syono. T. Oku. D. Shindo. K. 

[ 10 J I. Bryntse and S.N. Putilin, Physics C 2 1 2 ( 1 993) 223. 




In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: March 1, 2004 
Docket: YO987-074BZ 
Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 



In response to the Office Action dated February 4, 2000: 


Physic* C 215 (l?93) 1-10 


or by any 
r, Elsevier 

The synthesis and characterization of the HgBa 2 Ca 2 Cu 3 08 +< $ and 
HgBa 2 Ca 3 Cu 4 0,o + & phases 

E.V. Antipov • b , S.M. Lourciro b , C. Chaillout b , J.J. Capponi b , P. Bordet \ J.L. Tholencc c , 
S.N. Putilin • and M. Marezio M 

* Department of Chemistry. Moscow State University. 1 19899 Moscow. Russian Federation 
" Laboratoire de Cristallographie CNRS-UJF. BP 166. 38042 Grenoble Cedex 09. France 

' CRTBT. CNRS- UJF. BP 166. 38042 Grenoble Cedex 09. France 

* AT&T Bell Laboratories. Murray Hill. NJ07974. USA 

Received 28 June 1993 

Revised manuscript received 9 July 1 993 

The third (Hg-1223) and the fourth (Hg-1234) members of the recently-discovered homologous series Hg- 
Ba,Ca..,Cu.O I . + j +4 have been synthesized by solid state reaction, carried out at 950'C under 50 kbar at different annealing 
limes. These phases have a tetragonal cell with lattice parameters: 0=3.8332(6) A. r= 1 5.8 18(2) A and a =3.8540(3) A, 
c= 19.006(3) A, respectively. The c parameters are in agreement with the formula ce9.5+3.2(«- I ). Electron microscopy study 
showed similar lattice parameters as well as the occurrence ofdiflcrcnt intergrowths and sucking faults. A periodicity of 22 A has 
also been detected, which may be attributed to the existence of the Hg-1 245 phase. EDS analysis data of several grains of Hg-1 223 
and Hg-1 234 are in agreement with the proposed chemical formulae. AC susceptibility measurements show thai an increase of 
the superconducting transition temperature with ji in the HgBa,Ca„_ iCu„0,« + ,* , series occurs till the third member, after which 
a saturation seems to be achieved. 

1. Introduction 

Superconductivity at about 94 K and well above 
120 K has been recently reported for HgBa 2 Cu0 4+< 
(Hg-1201) [1J and HgBa 2 CaC Uj 0 6+<l (Hg-1212) 
[2 J, respectively. These phases are the first and the 
second members of the Hg-based homologous series 
of layered Cu mixed oxides. Their structures contain 
rock-salt-like slabs, such as (BaO)(HgO,)(BaO) al- 
ternating with either one (Cu0 2 ) layer in the former 
or an anion-deficieni perovskite-like slab, such as 
(CuO^(CaD)(Cu0 2 ). in the latter. A supercon- 
ducting transition temperature as high as 133 K has 
been reported for a multiphasic sample in the Hg- 
Ba-Ca-Cu-0 system by Schilling et al. |4J. These 
authors could not identify by X-ray diffraction the 
phases responsible for the superconductivity at this 
lemperature, but proved by high resolution electron 
microscopy that the sample contained the Hg-1212 
and Hg-1223 phases as well as different inter- 
growths. Putilin et al. [2] showed that in the sample 

containing Hg-1212 as the majority phase, a small 
drop on the AC susceptibility curve versus T oc- 
curred at about 1 32 K which could be attributed to 
the third member of the Hg-bearing series. 

Putilin et al. also showed (2] that it was possible 
to synthesize the Hg-1212 phase, practically in pure 
form, under high pressure (40-60 kbar) and at 
800°C for about I h. The high pressure synthesis al- 
lows one to lower the mercury oxide decomposition. 
This decomposition occurs at ambient pressure at a 
temperature at which the reactivity of the other com- 
ponents is very low. It was suggested that the same 
technique could be used for obtaining the higher 
members of the series. We found that the reactions 
have to be carried out at higher temperatures 
(950°C) and for longer annealing times. The same 
occurs for the higher members of the Bi- or Tl-based 
Cu oxide series, which are formed by the formation, 
at the initial stages of the reaction, of the lower mem- 
bers of the corresponding families. We report herein 
the synthesis and characterization of the Hg- 

092M534/93/JO6.OO© 1 993 Elsevier Science Publishers B.V. All rights reserved. 

(Hg_ 1234) phases. The reactions were carried ouUn 

at ^oTf" P ; ara f, ,lndCr h,Bh pre " u 'e(50 kbar) 
at 950 C for 3 and 3.5 h, respectively. 

E - * AmiP ° Ve ' a ' /H ^^^H g Bo Mut O la . 

2. %nlhesis and characterization by X-ray and 
fc-DS analysis 

Powder samples containing the He 

obtained by and high-temperature re- 
asons the belt-type apparatus of the UhQ l 
atcre de Cnsta.lographie. A precursor with The 
nominal compos.tion B^Ca^Q, was prepared by 

>99%),Ca(N0 3 ) J 4H J 0 (Normapur Prolabo an- 
alytical reagent) and CufNO,), 3H 2 0 (S rem 
Chemical Inc., 99.5%). The mixture thus obtained 
was .nitially heated at 60b°C in air for 12 h. then 
regrinded and annealed at 925 'C for 72 h in an ,„ 
ygen flow with three intermediate regrindings. Then," 
the sto,ch.ometr.c amount of yellow HgO (Aldrich, 

.J > J?** d ,he mixture was thoroughly 
grounded ,n an agate mortar and sealed in a P, cap^ 

temneT h, ' 8h PrCSSUre Synthesis - ^us 

temperatures and annealing times at a pressure of 50 

Hg-1234 phases. In these experiments the pressure 
was first mcreased to 50 kbar. subsequently the tern! 
perature was ra.sed to the desired value during 1 h 
then the temperature and the pressure were kept 

shut off and the pressure decreased to normal con- 
ditions in 30 min. 

f r J! 1 ' Samf i eS WCrC StUdicd b * X " rav Powder dif- 
fraction performed with a Guinier focusing camera 
and Fe Ka radiation ( 1 .93730 A). Finely powdered 
■Leon (a = 5.43088 A a, 25»C) was used Z an n 

a^^D."" au,omalfc fllm ^nner. The SCAN3 
and SCANPI programs were used for processing the 

sZnJ hiS l HgBa * Ca > Cu > 0 "' ^ £ present in the 
sample synthesized a, 950«C for 3 h (sample I) to- 
gether with a smaller amount of Hg-1212. CaO and 
CuO a„ d traces of CaHgO, [6] and of an unknown 
phase whose intensities were less than 4%. The X-ray 

difTraciion P a, «<™ ^sample I afler background suh. 
fraction is shown in fig. | The 20 ref£T 
responding to Hg-,223 were indexed ^ 

bli the n t ^^ hara ^,ic001renectiont 

formula per unit celf. TheTea^T," ^ 
parameter of Hg-1223 corresponded ,o Z ex^L 
value calculated by the formula ^9 5+3 2^ 
with n=3 [I]. -"•Ji-J^(n-I) 
A scanning electron microscope JEOL 840a 

TEDsfattaT " ^o^py 
(EDS) attachment was used for the analysis of the 
canon composition of the twoprepared samp es Ka 

K>ns .and U- hnes for the Ba and H g ones. EDS anal- 
ysis of several well crystallized and flat grains showed 
*at bes,des Hg, Ba, Ca, Cu and O no ££££ 

rnr ent 7o , r hCSam tr ThCaVerag€mC,a,ra: ° 

HgBa:Ca:Cu = ,3 ( 2)^^ ):26( nC,) Z 
standard deviations between parentnesei 
^n sto.chiome.ry is in good agreement with the ex- 
pected formula of the Hg-1223 phase 
,^ n laUlCe Parame,crs of Hg-1212 refined from 
ten reflections (,,=3.859(4) A, c= 12.68(2) A) are 

ISTE*" 1 thC d3,a ° f Pu,i,in « * 12 J- «t 
w° ^ ,ha ' ,hcrC is overlapp „g be- 
if ^ n i hC *f rCfleCtionS 0f the »H2'2 and th£ i 

" g l? 12 ° verla P W1,h «»e hkS refiections of Hg- j 
min?'^.!* ° VCr,appin * s did allow us to deter- ' 
mine all , hc ,„, C ns,t,es of the two phases. However. > 

H, m , ,°, n, * m,CnSi,ieS ° f ,hc s,ron 8«« «"es for > 
V ? u" d ,03 > and "H223 ( ,03a„d 104, , 
show^ clearly ,ha, the Hg-1223 is the predominant ' 
Phase in sample I (fig. | ). 

P„I hC PrC t enCC in Sample 1 of ,hc ,owcr member to- * 

inhia ' ° xides ' Cu0 and CaO. ob- , 

v-ously ,nd.cates that the formation of Hg-1223 was * 

noi ^complet e after a 3 h annealing period. The syn- , 

If $ ° Ut at 900 ° C f <" 2 h led to the for- * 

ma, IO n of Hg-1212 which was found to be the main _ 

Phase ,n the sample together with the starting com- * 

pounds. These data; show that the formation of , 
Hg-1 223 occurs through the synthesis of the lower 
members of the series. The increase of the annealing 

E. V. Aniipav rt al. / HgBa/:a£ufl,+ t vaA HgBa,CVi.rC«,<?« + , 

2000 " 



il j lu,.. j .,4 

* A , l .t}k . \\ (.1 

Fig I X-ray powder pattern for sample 1. Indexed XRD intensities correspond to Hg- 1 223 and Hg- 1 2 1 2 (underline). Impurities of CaO. 
CuO. CaHgO, and an unknown phase are marked by ( • ). The inset displays the chararteristic intensity of 001 for Hg-1 223. 

lime up lo 3.5 and 4 h at 950°C and the same pres- 
sure led to the expected disappearence of Hg- 1 2 1 2 as 
well as of CaO. In these samples the formation of a 
new phase was detected. Its amount was relatively 
high (more than 50%) in samples annealed for 3.5 
h (sample II). A total of 17 reflections of this phase 
were indexed on a tetragonal cell with lattice param- 
eters a=3.8540(3) A, c= 19.006(3) A. As for Hg- 
1223 no systematic absences were observed, leading 
to space group P4/mmm. Similar parameters were 
found by electron diffraction (see below). The c pa- 
rameters of this phase corresponded to the value cal- 
culated from the formula c=9.5+ 3.2(n- 1 ) for 
n=4. This strongly suggested that the new phase was 
the fourth member of the Hg-based series: Hg- 
BajCa 3 Cu,,O,0+j. The approximate cations ratio de- 
termined by EDS analysis of five well-crystallized and 
flat grains was Hg:Ba:Ca:Cu= 
9(1): 18(1 ):29(2):44(2). These data are in good 
agreement with the proposed formula for the new 

Besides Hg-1234 as the main phase, a smaller 
amount of Hg-1 223 was present in sample II to- 
gether with small amounts of CuO and of an un- 
known phase. This unknown phase was predomi- 
nant in a sample treated for 5 h in the same 
conditions which did not contain any member of the 
Hg-based series and did not exhibit any supercon- 
ductivity. The presence of the latter oxides can be 
explained as a result of the decomposition of Hg-1223 
and the formation of Hg-1234. Hg-1 212 was absent 
in this sample as well as in that annealed for 4 h. The 
X-ray diffraction pattern of sample Ii after back- 
ground subtraction is shown in fig. 2. The ratio of 
the main intensities for both Hg-based layered cu- 
prates, 104 for Hg-1223 and 105 for Hg-1234, shows 
that the latter was the main phase in this sample. As 
for sample 1 the overlapping of hkO reflections for 
both phases occurs because of the similarity of the 
two a parameters. Moreover, the hk6 reflections of 
Hg-1234 are overlapped with the hkS ones of Hg- 

E. V. Antipov el at. /HgBa/:a J Cu J O ttt aadHgBa I Ca J Cu 4 0,^ 



Aa. .1.1 „.|f 

Fig. 2. X-ray powder pattern for sample II. Indexed XRD intensities correspond to Hg-1234 (bold) and Hg-1223. Impurities orCuO 
and an unknown phase are marked by ( * ). 

3. Electron microscopy 

The I and II samples were studied by electron mi- 
croscopy. A suspension of crystals in acetone was 
grounded in an agate mortar. The crystallites were 
recovered from the suspension on a porous carbon 
film. A Philips EM 400T operating at 120 kV was 

Figure 3 (a) and (b) shows two diffraction pat- 
terns obtained for sample I corresponding to the 
[001] and the <110> zone axes of the Hg- 
B&iCajCujOt+i (Hg-1223) phase, respectively. In 
both cases, the diffraction spots are sharp, which in- 
dicates that the crystals well ordered. In fig. 3(b), 
one can notice a modulation of the intensity of the 
diffraction spots along the c*-axis, with maxima for 
hkl reflections with l=Sn (n=0, 1,2, ...). On the mi- 
crograph (fig. 3(c)) corresponding to the diffrac- 
tion pattern shown in fig. 3(b), one can see the very 

regular periodicity of the fringes separated by 15.8 
A. During the observation under the electron beam, 
dark spots appeared near the edge of the crystal, 
probably due to the decomposition of the crystal. 

Some diffraction patterns obtained for other crys- 
tals present diffuse lines parallel to the c*-axis and 
passing through the Bragg spots (fig. 4 (a)). They 
are due to the presence of intergrowths as given evi- 
dence for by fig. 4(b). On this micrograph, two dif- 
ferent spacings of 15.8 A and 12.7 A can be mea- 
sured, attributed to Hg-1223 and Hg-I212, 

In the case of sample II, almost all the observed 
crystallites have diffraction patterns corresponding 
to the Hg-1234 phase (HgBa 2 Ca 3 Cu 4 0,o + <) with cell 
parameters o=6=3.85 A and c= 19 A. Figure 5(a) 
and (b) give examples of the [001] and <100> zone 
axes, respectively. As for Hg-1223, also for Hg-1234 
the intensity of the Bragg spots varies according to 

i. . . Antipor et at. / HgBaJTojCutO,*, and HgBajCojCH^ 

Fig. 3. Electron diffraction patterns of Hg-1 223 taken along (001 ) 
(a) and < 1 10> (b) zone axes, (c) Micrograph corresponding to 
the diffraction pattern (b). The interfringe spacing is 1 5.8 A. 

the vahie of -the / index, the maxima of intensity being 
obtained for l=6n («=0, I, 2, ...). This intensity 
pattern might be explained by the fact that c/6 is 
equal to 3.17 A, which corresponds to the distance 
between two neighboring (Cu0 2 ) layers. The in- 
crease of the layer number n in the structure leads to 
the increase of the intensity of the hkl reflections with 

Fig. 4. Electron diffraction pattern of sample I along < I00> and 
corresponding micrograph showing the intergrowths of Hg-1 223 
and Hg<1212. 

/=«+2. These periodicities of the (Cu0 2 ) layers ex- 
plain the overlapping of such reflections on the X- 
ray powder pattern (see above). Most of the images 
taken along the < 100 > zone axis show very regular 
fringes separated by 19 A (fig. 5(c)). However.some 
crystals present intergrowths between the Hg-1 22 3 
and Hg-1 234, as revealed in fig. 6. In this case, the 
following sequence is observed over about 500 A: 
-19 A-19 A-19 A- 19 A- 19 A-22 A-. On the corre- 
sponding diffraction pattern, besides the diffraction 
spots of the Hg-1234 phase, additional spots related 
to the 22 A periodicity are present. Such a period- 
icity may be attributed to a 1245 phase (Hg- 
Ba 2 Ca4Cu,0 12+< ). The fact that the extra diffraction 
spots are sharp indicates that this phase is well or- 
dered at least over a certain number of cells in these 

4. AC susceptibility measurements 
The critical temperature T c , and the apparent su- 


E. V. Antipov et al. /HgBa£a£ufl M and HgBa£a£u<O to + t 

Fig. 5. Electron diffraction patterns of Hg-1234 taken along (001 ] 
(») and < I00> (b) zone axes, (c) Micrograph corresponding to 
the diffraction paitem of (b). The imerfringe spacing is 19 A. 

perconducting volume of samples I and II have been 
determined from AC susceptibility measurements on 
fine powder samples. This avoids overestimates of 
the superconducting volume due to the larger screen- 
ings in sintered samples. The AC susceptibility was 
measured with an alternating maximum field of 0.01 
Oe and a frequency of 1 19 Hz. The temperature was 
measured by a calibrated 100 fi platinum 

The as-synthesized sample I undergoes a transi- 
tion from the paramagnetic to the diamagnetic state 
with an onset above 133 K (fig. 7). Several mea- 
surements were made with the same sample and the 
reproducibility of T c is +/-I K (mainly due to the 
thermal contact between the sample and the ther- 
mometer). The estimated magnetic susceptibility at 
4 K corresponds to a large volume of ideal dia- 
magnetism indicating the bulk nature of supercon- 
ductivity. We can suggest that the sharp and large 
drop on the AC susceptibility curve above 133 K 
should correspond to the Hg-1223 phase because Hg- 
1212, which is present in this sample as the minority 
phase, has a 7" c not higher than 126 K [3]. 

The as-synthesized sample II undergoes a transi- 
tion from the paramagnetic to the diamagnetic state 
with an onset as high as 132 K. Actually, two onsets 
at two different temperatures are visible, the smaller 
one at 1 32 K and the larger one at about 1 26 K. There 
are two Hg-based layered cuprates in this sample: Hg- 
1 234 as the main phase and Hg- 1 223 as the minority 
one. Taking into consideration the results of sample 
I, we might suggest that the first onset ( 1 32 K) cor- 
responds to Hg-1 223 and the larger one at the lower 
temperature (126 K) to Hg-1234. In any case, it is 
obvious that T c for Hg-1234 is not higher than that 
for Hg-1223. 

5. Discussion 

The synthesized HgBa,Ca 2 Cu,0 8+< , (Hg-1223) 
and HgBa 2 Ca,Cu 4 O 10+ , (Hg-1234) phases are the 
third and the fourth members of the Hg- 
Ba 2 Ca n _,Cu,,0 J „ +2+< series, in analogy with those 
of Hg-1201 [1,7,8] and Hg-1212 [2J their struc- 
tures can be schematized as containing rock-salt-like 
slabs, (BaO)(HgO.,)(BaO), alternating with pcr- 
ovskite-like slabs, consisting in three (Hg-1223) or 



1212. The appropriate treatment for Hg-1234 can 
possibly change 7; for this phase, therefore, we can 
only conclude that for the as-prepared samples a sat- 
uration of 7" c seems to occur in the Hg-Ba-Ca-Cu- 
O system at the third member. A similar behavior 

occurs for the TIBa 2 Ca ( ,_,Cu.O J<1+ , + , homologous 
series, for which T c increases up to the third member 
(120 K) also [9J. 

One can see in table 1 that for the Hg series, the 
increase of T c is accompanied by a decrease of the a 

Table I 

Lattice parameters and transition temperatures for Hg-based Cu oxides 


Short form 

a Ik) 




HgBa,CuO« + , 
HgBa,CaCu,O t+/ 






HgBa,CajCu«0, 0 w 






|4). this work 
this work 

the system leads to intergrowths due to different 
numbers of (Cu0 2 ) and Ca layers in the perovskite- 
Jike slabs. Such intergrowths were already reported 
in ref. [4 J. Possibly, the occurrence of different in- 
tergrowths may explain why the variation versus 
temperature of the AC susceptibility does not pres- 
ent distinct and abrupt transitions which could be 
attributed to pure Hg-1212, 1223 and 1234 phases. 

The synthesis of the higher members of the Hg- 
based homologous series as bulk samples has been 
performed at higher temperatures than that used for 
Hg-1212 and with longer treatment times. We sug- 
gest that the synthesis of such phases occurs through 
the formation at an initial state and subsequent de- 
composition of the lower members of the series. This 
feature is similar to that existing for the Tl- 
Ba 2 Ca„_ l Cu„0 2 , +3 _ < homologous series [9]. The 
use of high pressure, possibly, lowers the mercury 
oxide decomposition. It also leads to a decrease of 
stability of CaHgOj, whose synthesis at the first stage 
of the reaction inhibits the formation of Hg-based 


Tbe- authors would like to thank M.F. Gorius, M. 

Perroux and R. Argoud for their technical assistance 
The visit of EVA has been supported by the fund from 
the French Ministry of Foreign Affairs. EVA and SNP 
would like to thank the support of the Russian Sci- 
entific Council on Superconductivity (Project 
"Poisk"). SML was supported by the Erasmus Stu- 
dents Exchange Program. 


[ 1 S.N. Putilin, E.V. Antipov, O. Chmaissem and M. Marwio 

Nature (London) 362 ( 1 993 ) 226. 
|2]S.N. Putilin, E.V. Antipov and M. Marezio. Physica C2I2 


13] S.M. Loureiro and JJ. Cappoui, private communication. 
(4J A. Schilling, M. Cantoni. J.D. Guo and H.R. Oil. Nature 

(London) 363 (1993) 56. 
1 5) K.E. Johansson. T. Palm and P.-E. Werner. J. Phys. E.: Sci 

Instrum. 13 (1980) 1289. 
f 6 J S.N. Putilin. M.G. Rozova, D. Kashporov. E.V. Anlipov and 

UM. Kovba. Zh. Neorganicheskoi Khimiii 36(1991) 1645 

(in Russian). 

[7] O. Chmaissem. Q. Huang. S.N. Putilin. M. Marezio and A. 

Santoro, Physica C 212 (1993) 259. 
1 8 1 J.L Wagner. P.G. Radaelli, D.G. Hinks, JD. Jorgensen, J.F. 

Mitchell. B. Dabrowski. G.S. Knapp and M.A. Beno, Physica 

C2I0 (1993) 447. 
19J S. Nakajima, M. Kikuchi. Y. Syono. T. Oku. D. Shindo, K. 

Hiraga. N. Kobayashi, H. Iwasaki and Y. Muto. Physica C 

1 10 J 1. Bryntse and S.N. Putilin. Physica C 212 ( 1993) 223. 



In re application of: 

Date: November 6, 2006 

Applicants: Bednorz, et al. 

Docket: YO987-074BZ 

Serial No.: 08/479,810 

Group Art Unit: 1751 


June 7, 1995 

Examiner: M. Kopec 


Commissioner for Patents 
P.O. Box 1450 
Alexandria, VA 22313-1450 

I hereby certify that this Ninth Response After Final Rejection (_4_ pages) 
is being facsimile transmitted to the U.S. Patent and Trademark Office to (571) 

In response to Office Action dated October 20, 2005, please consider the 


Dr. Daniel P. Morris, Esq. 
Reg. No. 32,053 



Serial No. 08/479, 810 

1 Docket No. YOR919870074US5 


In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: January 30, 2008 

Docket: YO987-074BZ 

Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
Box AF 

P.O. Box 1450 
Alexandria, VA 22313-1450 

Submitted at the Suggestion of the Examiner in response to the 

In response to the Advisory Action dated November 15, 2007 please consider the 

Advisory Action dated November 15, 2007 










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In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Group Art Unit: 1751 
Examiner: M. Kopec 

Docket: YO987-074BZ 

Date: November 25, 2006 


Commissioner for Patents 
Box AF 
P.O. Box 1450 
Alexandria, VA 22313-1450 


I hereby certify that this Supplementary Response, (_3_ Pages Plus 
Attachment A and Attachment B) is being transmitted by first class mail to the 
U.S. Paieilfarty Trademark OfficeonNovember 25, 2006. 

In response to the Office Action dated October 20, 2005 please consider the 





In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: March 20, 2008 

Docket: YO987-074BZ 

Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
Box AF 

P.O. Box 1450 
Alexandria, VA 22313-1450 

Submitted at the Suggestion of the Examiner in response to the 
Advisory Action dated November 15, 2007 

In response to the Advisory Action dated November 15, 2007 please consider the 

Respectfully submitted, 

/Daniel P. Morris/ 

Intellectual Property Law Dept. 
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Reg. No. 32,053 
(914) 945-3217 





Edited by 



Cryogenic Engineering 

Edited by 

B. A. Hands 

Department of Engineering Science, University of Owx a 
and St. Hilda's College, Oxford, England 


Academic Press 

Harcourt Brace Jovanovich, Publishers 
Orlando New York San Diego Austin 
Boston Tokyo Sydney Toronto 

24/28 Oval Road, London NW1 7DX 

United States Edition published by 
Orlando, Florida 32887 

Copyright © 1986 by 
Academic Press Inc. (London) Ltd. 

All rights reserved. No part of this book may be reproduced 
or transmuted m any form or by any means, electronic or 
mechanical, including photocopy, recording, or any 
information storage and retrieval system without permission 
in writing from the publishers 

British Library Cataloguing in Publication Data 

Cryogenic engineering. 
1. Low temperature engineering 
I. Hands, B.A. 
621 .5'9 TP482 

ISBN 0-12-322990-1 
ISBN 0-12-322991-X (Pbk) 

Computer typeset and printed by 
Page Bros (Norwich) Ltd 

C. A. Baili 
eering S 
and Fell 

R. A. Byrn 

D. Dew-Hi 
versity o 
versity C 

D. Evans 
OQX, Er 

E. J. Grego 

B. A. Hand 
eering S< 
and G.E 

G. Krafft 

J. T. Morj 
OX11 oc 

N. Nambud 

B. W. Rid 

J. M. Robei 

H. Sixsmitl 

W. L. Swii 


Science, 1 
R. M. Thoi 

T. J. Websl 



C. A. Bailey University Lecturer, Cryogenics Laboratory, Department of Engin- 
eering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, England 
and Fellow of Keble College, Oxford 

R. A. Byrns Consultant, 2457 Marin Avenue, Berkeley, California 94708, U.S.A. 
Formerly Staff Senior Scientist, Lawrence Berkeley Laboratory, University of 
California, Berkeley, California 94720, U.S.A. 

D. Dew-Hughes University Lecturer, Department of Engineering Science, Uni- 
versity of Oxford, Parks Road, Oxford OX1 3PJ, England and Fellow of Uni- 
versity College, Oxford 

D. Evans Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 
OQX, England 

E. J. Gregory Chief Process Engineer, Marston-Palmer Limited, Wobaston Road, 
Fordhouses, Wolverhampton WV10 6QJ, England 

B. A. Hands Research Associate, Cryogenics Laboratory, Department of Engin- 
eering Science, University of Oxford, Parks Road, Oxford OX1 3PJ, England 
and G.E.C. Lecturer in Engineering, St. Hilda's College, Oxford 

G. Krafft Koordinationstelle Technologietransfer, Kernforschungszentrum 
Karlsruhe GmbH, Postfach 3640, D-7500 Karlsruhe 1, West Germany 

J. T. Morgan Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire 
OX11 OQX, England 

N. Nambudripad Tata Institute of Fundamental Research, Homi Bhabha Road, 
Bombay 400 005, India. Formerly of the Cryogenics Laboratory, Department of 
Engineering Science, University of Oxford 

B. W. Ricketson Cryogenic Calibrations Limited, Pitchcott, Aylesbury, Buck- 
inghamshire HP22 4HT, England 

J. M. Robertson Heat Transfer and Fluid Flow Service, Atomic Energy Research 
Establishment, Harwell, Oxfordshire OX11 OR A, England 

H. Sixsmith Creare Inc., PO Box 71, Great Hollow Road, Hanover New 
Hampshire 03755, U.S.A. 

W. L. Swift Creare Inc., PO Box 71, Great Hollow Road, Hanover New 

Hampshire 03755, U.S.A. 
W. J. Tallis Design Engineer, Cryogenics Laboratory, Department of Engineering 

Science, University of Oxford, Parks Road, Oxford OX1 3PJ, England 
R. M. Thorogood Director, Cryogenic Research Programs, Air Products and 

Chemicals Inc., PO Box 538, Allentown, Pennsylvania 18105, U.S.A. 
T. J. Webster Consultant, 38 Parkland Grove, Ashford, Middlesex TW15 2JR 

England. Formerly Safety Manager, British Oxygen Company Ltd., England ' 


The 1960s saw great activity in the field of cryogenic engineering, stimulated 
particularly by the American space effort and by developments in superconductivity. 
As a result, a number of books on cryogenic engineering in general were published. 
Since then, most volumes have concentrated on a particular aspect of the subject, 
rather than attempting a comprehensive review. In view of the steady, if unspec- 
tacular, advances made since that time, it seems opportune to attempt a new 
account of the basic science and of the engineering methods employed. 

Cryogenic engineering covers a wide spectrum of disciplines, in traditional terms 
embracing much of electrical, mechanical and chemical engineering, its dis- 
tinguishing feature being the use of temperatures well below ambient. In order to 
produce a volume of reasonable length, it was decided to assume that the reader 
should have knowledge appropriate to that of a final-year or graduate engineer or 
physicist. Further, since much of the body of knowledge of engineering at room- 
temperature can be applied directly to cryogenic problems, reference in such 
cases is made to standard textbooks, although since this book is biased towards 
engineering, the physicist may need to consult rather more of them than the 

It was also decided, again on the grounds of overall length, to restrict the account 
of superconductivity. The design of superconducting magnets is very largely an 
electrical engineering problem, the cryogenic design, apart from training problems 
and stabilisation, being relatively straightforward. Further, the monograph 
"Superconducting Magnets" by M. N. Wilson (Oxford University Press, 1985) 
treats the subject comprehensively, and is required reading for anyone with other 
than a superficial interest in magnet design. Thus, the coverage of this topic is 
deliberately brief. 

There are some other deliberate omissions, also. In particular, an account of 
refrigeration using hydrogen and neon is omitted , on the grounds that the techniques 
involved are broadly the same as those used for helium. Similarly, the particular 
problems involved with cryogenics in space are given only passing mention, since 
most of the design principles involved are also applicable to earth-based equipment. 
There is no attempt to provide complete property data; general trends are indicated, 
and, it is hoped, enough references for the reader to locate detailed data as 
necessary. However, since the book is intended for potential (and practising) 
cryogenic engineers, details of practical methods and current practices have been 


The production of this book has been a co-operative effort, and I thank the 
authors for their tolerance of the editor's quirks. I should like to acknowldge those 
who have read parts of my own contributions and assisted with the provision of 
information, photographs and diagrams, particularly Dr A. Acton Dr V D Arp 
Mr R. J. Allam, Dr C. A. Bailey, Dr M. L. Christie, Dr. G. Davey Prof G B 
Donaldson, Mr R. Harper, Dr D. B. R. Kenning, Dr R. D. McCarty Dr W 
Obert, Dr. C. Ruiz, Dr L. Solymar and Dr. R. M. Thorogood. Acknowledgements 
and sources for diagrams and photographs are given as appropriate in the text- I 
am most grateful to the organisations which supplied these and gave permission for 
their use. I am indebted to Johanne Beaulieu for preparing much of the text to 
Mrs Judith Takacs for drawing the diagrams with her usual patience and skill and 
to Mrs Stella Seddon for preparing the index. Finally, gratitude is due to my family 
for their tolerance, and for foregoing the use of the dining table for many months 

In the tables of data, a dash indicates that information was not available. 

1.1 Introd 

1.2 The C 

1.3 Featui 

1.5 AirS< 

1.6 Liquic 

1.8 Supen 

1.9 Cryog 

1.10 Cryog 

1.11 Medic 

1.12 Cryop 

1.13 Instrui 


2.1 Introdu 

2.2 Propert 

2.3 Hydrog 

2.4 Helium 

2.5 Equatic 


id I thank the 
aiowldge those 
ie provision of 
Dr V. D. Arp, 
iy, Prof G. B. 
Carry, Dr W. 
: in the text; I 
permission for 
of the text, to 
and skill, and 
e to my family 
many months. 

A. Hands 



1. A Survey of Cryogenic Engineering 
B. A. Hands 

1.1 Introduction 

1.2 The Cryogenic Temperature Range 

1.3 Features of Cryogenic Engineering 

1.4 Liquefied Natural Gas (LNG) 

1.5 Air Separation 

1.6 Liquid Hydrogen 

1.7 Liquid Helium 

1.8 Superconducting Magnets and Machinery 

1.9 Cryogenic Electronics 

1.10 Cryogenics in Space 

1.11 Medical and Biological Applications 

1.12 Cryopumping 

1.13 Instrumentation 

General Bibliography 
Bibliography of Specific Topics 
Non-specialist Reading 

2. Properties of the Cryogenic Fluids 
B. A. Hands 

2.1 Introduction 

2.2 Property Data 

2.3 Hydrogen 

2.4 Helium 

2.5 Equations of State 

5.9 Density Wave Oscillations 

5.10 The Ledinegg Instability and Pressure-drop Oscillations 

5.11 Geysering 

5.12 Thermoacoustic Oscillations 

5.13 Stratification, Thermal Overfill and Rollover 

5.14 Sloshing 

6. Heat Transfer to Fluids 
J. M. Robertson 

6.1 Introduction 

6.2 Heat Transfer to Single-phas* 

6.3 Heat Transfer Rates 

6.4 Pool Boiling 

6.5 Boiling in Channels 

6.6 In-tube Condensing 

7. Heat Transfer Below 10 K 
G. Krafft 

7.1 Introduction 

7.2 Basic Considerations 

7.3 Heat Transfer to Supercritical Helium 

7.4 Heat Transfer to Two-phase Helium 

8. Heat Exchangers 
E. J. Gregory 

8.1 Introduction 

8.2 Regenerators 

8.3 Coiled Tube Heat Exchangers 

8.4 Plate and Fin Heat Exchangers 

9. Electrical Conductors at Low Temperatures 
D. Dew-Hughes 

9.1 Introduction 

9.2 Simple Theory of Electrical Resistivity 

9.3 Real Conductors at Low Temperatures 

9.4 Magnetoresistance 

9.5 Superconductivity 

9.6 Theories of Superconductivity 

9.7 Flux-pinning and Critical Current Density 

9.8 Conductor Stability 

9.9 Stress Effects 

9.10 Commercial Superconductors 

10. Mechanical Design with Metals 

10.1 Introduction 

10.2 Elastic Moduli 

10.3 Plastic Behaviour 

10.4 Fracture Behaviour 

10.5 Fatigue Behaviour 

10.6 Aluminium Alloys 

10.7 Stainless Steels 

10.8 Nickel-Iron Alloys 

10.9 Titanium Alloys 

10.10 Copper Alloys 

10.11 General Discussion 

11. Design with Non-metallic Materials 
D. Evans and J. T. Morgan 

11.1 Introduction 

11.2 Mechanical Properties of Polymer 

11.3 Thermal Contraction 

11.4 Thermal Conductivity 

and their Relation to Structure 

12. Construction and Assembly Methods 
W. J. Tallis 

12.1 General Design Considerations 
. 12.2 Permanent Joints 

12.3 Demountable Joints 

12.4 General Comments 



13. Principles of Refrigeration, Liquefaction and Gas Separation 
C. A. Bailey and B. A. Hands 

13.1 Refrigeration 

13.2 Liquefaction 

13.3 Cooling Methods 

13.4 Simple Cycles 

13.5 Irreversibility 

13.6 Second Law Violations 

13.7 Compound Cycles - 

13.8 The Separation of Gases \ 

13.9 Principles of Distillation '■. 

13.10 The Single Column Linde System '-. 

13.11 The Double Column i 
References , 

14. Cryogenic Turbines and Pumps 
H. Sixsmith and W. L. Swift 

14.1 Introduction 

14.2 Turboexpander Design 

14.3 Gas Bearings 

14.4 Protective Devices 

14.5 Turbine Performance 

14.6 Pumps 

14.7 Conclusions 

15. Large Helium Refrigeration and Liquefaction Systems 
R. A. Byrns 

15.1 Specification of Heat Load and Capacity 


15.2 Design of J-T Stage 


15.3 The Claude Cycle 


15.4 Design and Optimisation 


15.5 Compressors 


15.6 Heat Exchangers 


15.7 Expanders 


15.8 Control, Instrumentation, Purity and Gas Management 


15.9 Distribution and Cooling Methods 


15.10 Large Helium Plants 


15.11 Large Purification Liquefiers 


15.12 The 1500 W Refrigerator 


15.13 Lawrence Liyermore National Laboratory (3000 W) System 


15.14 Fermi National Accelerator Laboratory (23 kW) System 



15.15 Brookhaven 24.8 kW Refrigerator 388 

15.16 Refrigeration Equipment Cost 389 
References 389 

16. Large Gas Separation and Liquefaction Plants 
R. M. Thorogood 

16.1 Introduction 

16.2 Cryogenic Air Separation Processes 

16.3 Natural Gas Processes 

16.4 Natural Gas Liquefaction Processes 

16.5 Equipment for Large Air Separation ] 

16.6 Equipment for Natural Gas Plants 

16.7 Operation and Safety 

17. Small Refrigerators 
N. Nambudripad 

17.1 Introduction 

17.2 The Stirling Refrigerator 

17.3 The Gifford-McMahon Refrigerator 

17.4 The Pulse-tube Refrigerator 

17.5 The Vuilleumier Refrigerator 

17.6 Losses in Regenerative Mechanical Coolers 

17.7 Regenerators 

17.8 Magnetic Refrigeration 

18. Thermometry 
B. W. Ricketson 

18.1 Introduction 

18.2 Temperature and Accuracy 

18.3 Criteria for Choosing a Sensor 

18.4 Sensors 

18.5 Thermal Anchorage for Electrical Leads 

18.6 Measurement 

18.7 Temperature from the Measurement 

18.8 Conclusion 



Symbols Used 


:ompressor Aftercooler 



Turbine Expander 
with Electric 

Turbine Turbine 
Expander Compressor 

-txi- -w- 

Valve Check Valve 

Absorber Vessel 



A Survey of Cryogenic Engineering 


1.1 Introduction 

1.2 The Cryogenic Temperature Range 

1.3 Features of Cryogenic Engineering 

1.4 Liquefied Natural Gas (LNG) 

1.5 Air Separation 

1.6 Liquid Hydrogen 

1.7 Liquid Helium 

1.8 Superconducting Magnets and Machinery 

1.9 Cryogenic Electronics 

1.10 Cryogenics in Space 

1.11 Medical and Biological Applications 

1.12 Cryopumping 

1.13 Instrumentation 

General Bibliography 
Bibliography of Specific Topics 
Non-specialist Reading 

1.1 Introduction 

Most of this book is concerned with an outline of the theory and practice 
of cryogenic engineering. It has not been possible within a volume of 
reasonable size to explore every aspect in detail, nor has it been possible 
to give a detailed account of all the applications of cryogenics. This chapter 
is intended to give an impression of the wide range of cryogenic engineering. 
After a discussion of the meaning of cryogenics, the chapter covers the 
uses of the commoner cryogenic liquids (natural gas, oxygen, nitrogen, 
hydrogen and helium), and then deals with superconductivity and cryo- 

c. (London) Limiud 

pumping. The chapter concludes with a brief outline of cryogenic 

1.2 The Cryogenic Temperature Range 

The 1960s were a decade which saw a rapid expansion both in low- 
temperature physics and in the commercial exploitation of low-temperature 
techniques. Towards the end of this period, a need was felt for the stand- 
ardisation of low-temperature terminology, and, on the initiative of Pro- 
fessor Nicholas Kurti, the Comite d'etude des termes techniques francais 
organised a meeting in 1969, at which was formed a small international 
committee to consider the terminology of low temperatures, remembering 
the necessity of unambiguous translation between English and French, and 
paying due regard to current practice in the United States. As an example 
of the confusion which then existed, temperature levels in Britain were, by 
some people, referred to as 'low' (below 0°C), 'very low' (around 100 K), 
'deep low' (around 4 K) and 'ultra low' (less than 0.3 K), although the 
French had only two terms 'basse' and 'tres basse'. It was never clear how 
the British users of this terminology would refer to temperatures in the 
microkelvin region! 

The working group, with members from six countries, made its re- 
commendations in 1971 [1.1], and these have largely been accepted by the 
scientific community. 'Cryogenics' and the corresponding prefix 'cryo' were 
to refer to 'all phenomena, processes, techniques or apparatus occurring 
or used at temperatures below 120 K' approximately, that is, around or 
below the normal boiling point of liquefied natural gas. It was recognised, 
however, that some inconsistencies were unavoidable, in particular the use, 
on historical grounds, of the terms cryohydrate, cryoscopy, cryochemistry 
and the French cryodessication, all of which refer to temperatures well 
above 120 K; and, because they use cryogenic fluids and techniques, cryo- 
surgery, cryomedicine and cryobiology. Otherwise, the temperature range 
between 120 K and 0°C is covered by 'refrigeration' technology. 

The scientific community has, on the whole, adhered to these proposals, 
but they have not been rigidly adopted by industry, where the technology 
of handling liquid ethylene (at around 150 K) is, with some justification on 
the grounds of the equipment used, included in the cryogenic domain, and 
'cryogenic' is also used, with less justification, to describe equipment 
designed for use at still higher temperatures. However, since all fluids 
and materials used in cryogenics must at some time be brought to room 
temperature, properties and processes in the temperature range up to room 
temperature cannot be ignored. 


In this book, we 
engineering' to refe 
most widely used liq 
liquefied natural gas 
liquid hydrogen (LI 
importance of hydro 
range, the product) 
regarded as 'physics 1 
at present to experii 
demagnetisation anc 
be covered in this vc 

1.3 Features of Cryo 

It is worth considerii 
'ordinary' (or room 1 
that the properties o 
a particular mystiqu 
accepted that, in fac 
behave similarly to c 
ability to recognise an 
the use of low temp 
different from that re 
ment of design criter 
with identification c 
methods to achieve 
should, therefore, be 
in its own right. 

There are, howevt 
eering temperature n 
fluidity — the ability o 
The superfluid state b 
etical physicists for m 
has been achieved. 1 
because of the very h 

The other phenomt 
of electrical resistan< 
different for each met; 

* According to [1.1], the 
wide acceptance. 


i in low- 
the stand- 
ee of Pro- 
« francais 
ench, and 
1 example 
i were, by 
id 100 K), 
lough the 
clear how 
res in the 

de its re- 
ted by the 
;ryo' were 
around or 
ar the use, 
tures well 
ues, cryo- 
ture range 

ication on 
main, and 
all fluids 
t to room 
ip to room 


In this book, we follow the 1971 recommendation and take 'cryogenic 
engineering' to refer to the temperature range below about 120 K. The 
most widely used liquids, in order of descending normal boiling point, are 
liquefied natural gas (LNG), liquid oxygen (LOX), liquid nitrogen (LIN), 
liquid hydrogen (LH 2 ) and liquid helium (LHe), although at present the 
importance of hydrogen has declined. At the lower end of the temperature 
range, the production of temperatures less than about 1.5 K may be 
regarded as 'physics' rather than 'engineering', since their use is restricted 
at present to experimental work. Therefore, techniques such as adiabatic 
demagnetisation and the use of the light isotope of helium (He 3 ) will not 
be covered in this volume. 

1.3 Features of Cryogenic Engineering 

It is worth considering at this stage the differences between cryogenic and 
'ordinary' (or room temperature) engineering. For a long time, it was felt 
that the properties of cryogenic fluids were in some way peculiar, so that 
a particular mystique arose around this area of engineering. It is now 
accepted that, in fact, cryogens (with the exception of superfluid helium) 
behave similarly to other fluids, and that the art of cryogenics lies in the 
ability to recognise and cater for the particular problems which arise through 
the use of low temperatures per se. This requirement is, of course, no 
different from that required in any other branch of engineering: an assess- 
ment of design criteria and possible causes of equipment failure, together 
with identification of the best techniques, materials and construction 
methods to achieve safe, efficient and reliable operation. Cryogenics 
should, therefore, be regarded more as a special art rather than as a subject 
in its own right. 

There are, however, two phenomena peculiar to the cryogenic engin- 
eering temperature range which merit special consideration. One is super- 
fluidity — the ability of liquid helium to behave as if it has zero viscosity. 
The superfluid state has been investigated by both experimental and theor- 
etical physicists for many years, and a deep understanding of its behaviour 
has been achieved. From the engineer's point of view, it is of interest 
because of the very high rates of heat transfer which can be attained. 

The other phenomenon is that of superconductivity,* the complete loss 
of electrical resistance below some well-defined temperature which is 
different for each metal. Superconductivity is of increasing technical import - 

* According to [1.1], the proper term is superconduction, but this word has never achieved 
wide acceptance. 

, B - A. HANDS 

1962, the discovery of the J^^^^T^ ^ 
of superconducting electronic devices P °° r 4 ° 3 neW ran 8 e 

the second ,aw of tterZZ^** ^EfT™ faan 
roughly in inverse promrtion toTh?™ t f ? 3t the Work wiU incr ease 
For instance, to ext7a« 1 F o h ^t agmt "f ofthe ab ^I"te temperature, 
of work, while to ex act I J^VTkT * ? ^ ab ° Ut 37 > 

practice, of course, reversLiliUannoL 681 ° f work " *» 

required is somewhat larger byaT^J ^ the WOrk actuallv 
temperatures, to a At ^lK^^W 
economic grounds there is every iZ^Tt^T ^ ^ on 
wherever possible avoid the use of cryogenics 

^^^^S^^ b - bom towards the end of 
in Geneva, Switzerland nd bj SKi?,"^* by Ra ° Ul Pictet 
France.* Each used a different tec^nl p ? Chatl "on-sur-Seine in 
470 bars to about 140 S techm ^ e - P*tefs was to cool oxygen at 

through a valve, and saw , t ^ th& ° Xygen to esca Pe 

jet. Cailletet, on the X\^d ^oo/edT ^ " the resulti ^ 
liquid sulphur dioxide, JJt^eT^ T * ^ ~ 29 ° C Usin S 
a mist of droplets in hi gl^SdSST CXpansi0n to fo ™ 

Pictet's method of 'cascade' coo nl'fni P ^?! PS T ° f lnt5reSt t0 observe th *t 
is still used in many d5 g L of e^ 

m association with exteLJolkZchZ ^ 

paved the way for the liquefaction S l« ^ f ° r l0Dg periods and 

invention, the liquids wen suS " °£ h y dro g en and helium. Until Dewar's 

vacuum insulated, gl as ? fl a k™ ^ '"If, T ° f hlgher ^rature. The 
'Thermos'; in the sciZmc C l^ 7 OWn t0 the general P ubl * ™ a 
is also used for .mE^^^^S* T' iS P referred a " d 
Developments during the next two 1 ? ° r P ol y meric construction . 
in France and Un^^^J^^^^^ Claude 
- fractal d.sttliat.on of ^T^^^^^Z 

* Which scientist was first is of no concern to us here , 
has been discussed recently by Kurti [1.2], 

'r is the ensuing controversy, which 


ilds, and its forming companies which are still in the forefront of cryogenic engineering 

y studied. In today to market their inventions. Finally, in 1908, helium, the last of 

a new range the 'permanent' gases, was liquefied by Kamerlingh Onnes, who shortly 

afterwards produced superfluid helium by reducing the vapour pressure 

is that work above the liquid using a vacuum pump. It is worth noting, in these days of 

juired; from plentiful supplies, that Onnes's helium was painstakingly extracted at 

will increase Leiden from large quantities of monazite sand imported from India 

emperature. especially for the purpose. 

; about 3.7 J Between the two World Wars, there was a steady development in the 

of work. In production of oxygen and nitrogen by the distillation of liquid air (the 

'ork actually process of 'air separation'), and during the 1930s plants producing around 

er cryogenic 100 m 3 (100 1) of liquid oxygen per day were in operation. Liquid helium 

2. Thus, on was still a comparatively rare and expensive commodity, the rate of pro- 

f cryogenics duction being limited to a litre or two per hour, often only on an intermittent 

basis , and the liquid being available in only very few laboratories throughout 
the end of the world. 

Raoul Pictet Immediately after the Second World War, Professor Sam Collins, at the 

sur-Seine in Massachussetts Institute of Technology, developed a new design of helium 

)1 oxygen at liquefier using reciprocating expansion engines, which was capable of 

de and solid making liquid on a continuous basis at a rate of several litres per hour. At 

n to escape the same time, the extraction of helium from natural gas wells, begun 

he resulting during the 1920s, had greatly increased, so that helium gas, although still 

-29°C using comparatively expensive, was no longer a rare commodity, 

sion to form As a result, when, during the 1960s, Type II superconducting wire was 

Dbservethat produced in quantity on a commercial basis, enabling high-field super- 

n expansion conducting magnets to be constructed for the first time, liquid helium 

>ugh usually was readily available for cooling . This development was quickly exploited by 

those research establishments concerned with high-energy nuclear physics, 
since the saving in energy costs compared with those of an equivalent 
water-cooled system quickly outweighed the much higher capital cost. 
As confidence was gained, magnets of increasingly complex design were 
constructed, so that each of the major laboratories now contain several 
tens of superconducting magnets. In parallel with these developments, 
refrigerators incorporating expansion turbines rather than reciprocating 
engines were developed; a number of refrigerators capable of extracting 
several kilowatts at 4 K have now been built. 

As to the future, it is clear that the production of oxygen, nitrogen and 
argon by the fractional distillation of liquid air will remain a major industrial 
process for many years. The transport of liquefied natural gas by sea at 
present forms a vital link in the world's fuel supply system , but will decrease 
in importance as supplies of natural gas diminish and other energy sources 
are developed. Hydrogen may well be one of these fuels, but at present in 

energy terms it is expensive to produce, requiring large amounts of primary 
energy, and the liquefaction process also consumes much energy. Liquid 
hydrogen, therefore, may never be economically viable as a fuel other than 
for a few specialised applications. 

Superconducting magnet technology has assumed great importance, and 
since it is economically attractive compared with the use of conventional 
magnets and can also produce more uniform and time-invariant fields, 
applications are expanding. For a number of years, superconducting mag- 
nets have been routinely manufactured for experimental work in physics 
and chemistry, notably for nuclear magnetic resonance (NMR) and electron 
spin resonance (ESR). These methods have recently been extended to 
biological applications and now to medical diagnosis. This latter provides 
the first truly large-scale, commercial application of superconductivity. 

Although superconducting motors, generators, transmission lines, and 
so on have been under active development in a number of countries, the 
scenario so far has been that each advance in superconducting electrical 
engineering has been matched by an advance in the corresponding room- 
temperature technology. Since the latter is usually less complex, it has been 
more attractive on the grounds of both cost and reliability. 

In electronic engineering, the Josephson effect opened new prospects in 
the precise determination of voltage, in the measurement of very small 
magnetic fields and in rf applications. Devices based on the Josephson 
effect are now used on a routine basis. 

Thus, although cryogenics is a field of relative antiquity, there has been 
an unusually long time between the discovery of some phenomena and 
their commercial exploitation. This was particularly so in the case of 
superconductivity, which was discovered in 1911 but only ceased to be a 
laboratory curiosity some 50 years later. On the other hand, devices using 
the Josephson effect were marketed within a few years of its prediction and 

1.4 Liquefied Natural Gas (LNG) 

Natural gas is typically composed of 85-95% methane, the remainder 
being mainly nitrogen, ethane, propane and butane, although quantities of 
heavier hydrocarbons, carbon dioxide, water, sulphur compounds and, 
occasionally, mercury, may also be present, the precise composition 
depending upon the reservoir from which it is extracted. Certain sources, 
notably in Kansas, are comparatively rich (about 0.4%) in helium and are 
the major sources of this element. Natural gas is extracted by drilling in a 
way similar to that used for oil production and is somewhat refined before 




amounts of primary 
uch energy. Liquid 
as a fuel other than 

at importance, and 
lse of conventional 
ne-invariant fields, 
>erconducting mag- 
tal work in physics 
NMR) and electron 
been extended to 
rhis latter provides 
smission lines, and 
zr of countries, the 
inducting electrical 
^responding room- 
omplex, it has been 

;d new prospects in 
ment of very small 
I on the Josephson 

lity, there has been 
ne phenomena and 
so in the case of 
Dnly ceased to be a 
hand, devices using 
of its prediction and 

ine, the remainder 
though quantities of 
lr compounds and, 
irecise composition 
id. Certain sources, 
>) in helium and are 
cted by drilling in a 
what refined before 

use: the heavier hydrocarbons are separated as natural gas liquid (NGL) 
or as liquefied petroleum gas (LPG), and the nitrogen content may be 

Natural gas was used on a local basis in the United States during the 19th 
century for both fuel and heating; by the 1940s it was being distributed by 
pipeline throughout much of the country and now provides about a quarter 
of America's energy requirements. Since about 1975, Great Britain has 
relied entirely on natural gas for its gas supplies; it forms a significant part 
of Japan's energy consumption; and its use is widespread throughout 
Europe and the USSR (Table 1.1). 

Table 1.1 

Past and Projected Consumption of LNG (10 6 t/year)° 


United States 

Western Europe 






















Sources of natural gas (10 6 t/year)° 

Americas USSR Middle East Far East Africa Total 

1980 1 - 3 15 22 41 

1990 6-30 9-35 13-17 35-39 67-78 130-199 

■ From Thorogood [1.3]. 

Sources of natural gas are scattered relatively evenly around the globe, 
with the result that a trade has developed in transferring the gas to areas 
of large demand. Thus there are, for instance, major pipelines from Alaska 
southwards, and from the USSR to Western Europe. However, much gas 
is liquefied for both transport and storage to take advantage of the large 
decrease in specific volume which is achieved without the necessity for 

The first shipments of LNG by sea were made on an experimental basis 
from Lake Charles, United States, to Canvey Island, England, during 1959, 
and as a result of the success of these voyages a regular service from Algeria 
to Canvey Island was instituted in 1961, carrying about 700,000 t/year. 
Twenty years later, routes had been established from Algeria and Libya to 
Europe, from Algeria to the United States, and from Alaska, Abu Dhabi, 


Fig. 1.1 The LNG tanker 'LNG Aquarius', launched in 1977, L.O.A. 285 m. The LNG 
is carried in 5 spherical aluminium tanks, each of 25,260 m 3 capacity. (Courtesy of British 
Gas Corporation.) 

Indonesia and Brunei to Japan, and another ten or so routes were under 
active development [1.4]. The shipping terminals are supplied by large 
liquefiers with up to 5000t/day capacity in a single train (Fig. 16.22). 

Apart from storage at liquefaction plants and trading terminals, natural 
gas is stored as liquid for 'peak shaving' operations, that is, to provide an 
additional source of gas during periods of peak demand when the normal 
supply system is inadequate (usually in winter). Liquefaction, using small 
(200 t/day) plants takes place during periods of low demand in the summer. 
Storage tanks may be as big as 100 m in diameter and 30 m in height, 
containing tena of thousands -of tonnes of liquid (Fig. 1.2). In the past, they 
were usually constructed of either aluminium or 9% nickel steel; now, 
prestressed concrete (with a suitable thin metal liner to eliminate porosity 
problems) is being increasingly used. During the 1960s, a number of tanks 
were formed by excavating a hole in the ground and installing a thin 
steel liner,, but this design has proved to be unsatisfactory due to large 
evaporation rates and to an ever-increasing area of frozen ground around 
the tank, although new designs are now being developed in Japan. 



Besides these large-scale facilities, in some areas it has proved economic 
to distribute LNG by truck and to keep it in small storage vessels close to 
the point of use. The technology adopted is similar to the well-established 
methods used for oxygen and nitrogen. 

Purification ('upgrading') of natural gas is achieved by cryogenic 
methods. Many natural gas sources contain significant quantities of nitrogen 
and carbon dioxide, which reduce the calorific value and render the gas 
incompatible with other supplies to the pipeline distribution network 
Upgrading plants are based on successive liquefaction and separation of 
the various components of natural gas and are frequently installed at the 
well-head. In these plants, solid impurities (sand, etc.) are filtered, and 
then water, sulphur compounds and carbon dioxide are removed using 
either molecular sieves or chemical absorption, for example, using glycol 
to absorb water or monoethanol amine to absorb carbon dioxide Liquefac- 
tion can then take place without blocking the low-temperature heat 
exchangers with frozen components of the gas. Currently, natural gas 
companies are projecting a significant increase in the number and size of 
such plants. This increase is associated with the use of nitrogen injection 
into the gas wells to enhance gas recovery, thus creating a double use of 
cryogenics for both injection and rejection, since the nitrogen will be 
produced on-site by the fractional distillation of liquid air 

1.5 Air Separation 

The production of oxygen, nitrogen and argon by the fractional distillation 
of air, or 'air separation' as it is known, forms a vital part of the infra- 
structure of the industrialised world. The major developments have 
occurred since the Second World War: in 1948, a system to produce 140 
t/day of liquid oxygen was built in the United States; in the 1970s plants 
with ten times that capacity were under construction in various parts of the 
world. The daily world production of oxygen is now about 5 x 10 5 t (Fig 
1.3), a purity of around 99.5% being easily achievable even on this scale 
By far the greatest amount of oxygen is consumed by the chemical and 
steel industries (Table 1.2). Since the daily consumption of a chemical or 
steel works may amount to several hundred tonnes per day it has become 
common practice to build an air separation plant on an adjacent site and 
deliver the oxygen by pipeline. Because a continuous supply is essential 
stringent conditions may be imposed by the user, and emergency electrical 
generators and back-up storage vessels may have to be provided to guaran- 
tee a supply until faults can be rectified or oxygen brought in by road 


lose to 

he gas 
tion of 

at the 
d, and 
1 using 

e heat 
ral gas 
size of 

use of 
will be 

; infra- 
5 have 
ice 140 

5 of the 

t (Fig. 
5 scale, 
cal and 
lical or 
ite and 


i ol 1 1 1 i I 

I960 1965 1970 1975 1980 1985 
Fig. 1.3 Worldwide annual production rate of oxygen. (Courtesy of R. M. Thorogood.) 

A considerable quantity of oxygen is produced in gaseous form and 
compressed into cylinders to be used, for instance, for welding, in diving and 
hospitals. Other important and growing uses for oxygen are in the partial 
oxidation of coal and heavy hydrocarbons to synthesise gas mixtures for 
methanol production and to produce hydrogen for ammonia production, 
and in the treatment of waste water by activated sludge processes. The use 

Table 1.2 

Industrial Consumption of Oxygen in the United States in 1979° 

Steel making 

Basic oxygen process 

Open hearth process 

Electric furnace 

Cutting, welding, blast 
furnace air enrichment 
Non-ferrous metals 
Fabricated metal products 

Ethylene oxide 

Titanium dioxide 
Propylene oxide 
Vinyl acetate 


Pollution control 

* From Thorogood [1.3]. 

Percent of total consumption 




of oxygen in the production of fuels from coal is expected to increase as 
oil reserves diminish, an important aspect of this being the very large 
consumption which will be required at an individual site, perhaps 20,000-. 
30,000 t/day: the SASOL II complex which is operational in South Africa 
uses 15,000 1 of oxygen per day. 

Liquid oxygen is also produced in quantity for use in aerospace activities, 
both as a fuel oxidiser and for life support systems. The amounts required 
can be large: for instance, each Apollo flight to the moon consumed about 
2000 1 (Fig. 1.4), and the annual consumption of the American space 
programme at its peak was about 400,000 1 [1.5]: 

At the same time as oxygen is separated from air, nitrogen is also, of 

course, produc 
oxygen. In th 
by-product an 
developed am 

Liquid nitro 
cations, such s 

(1) for coc 
tamination mu 

(2) for free 
uses up to TOO 

(3) in the i 
either side of 1 
whole system; 

(4) in recla 
of many metal 
cold motor ve 
constituents se 
can be shatter© 
which does no 
treated. In Belj 
being fragment 
consumption o 
from the non-f 

(5) in defla 
deflashing can 
each item indi\ 

(6) in the h 
resistance of ce 

(7) for the 
the cattle indus 

(8) in astroi 

(9) ingroui 
to be performe 

(10) in bon 
porarily harmle 

However, th 
for various che 
dependent upor 
for such applies 
and chemical t 

course produced, the current world-wide consumption being about that of 
oxygen In the early years of the industry, nitrogen was considered a 
by-product and sold relatively cheaply. However, new uses have been 
developed and some plants are now biassed more towards nitrogen 
production. ,. 

Liquid nitrogen is a useful source of cold and finds a diversity of appli- 
cations, such as: 

(1) for cooling cold traps in vacuum systems, especially where con- 
tamination must be avoided, as in semi-conductor device manufacture; 

(2) for freezing food: one major fast-food franchise in the United States 
uses up to 700 t/day for freezing hamburgers; 

(3) in the repair of pipelines: by freezing the liquid in the pipeline on 
either side of the fracture, a repair can be effected without emptying the 

Wh (4) C Ynred'amation processes, where use is made of the embrittlement 
of many metals and polymers, at low temperatures, when, for instance, 
cold motor vehicle tyres can be pulverised, and the steel and polymer 
constituents separated and re-used; the polymer coating of electric cables, 
can be shattered into small pieces while the copper or aluminium conductor, 
which does not become brittle, remains intact. Large items can also be 
treated. In Belgium, for example, complete automobiles are cooled before 
being fragmented; it is claimed that the process reduces the overall energy 
consumption of the process and makes it easier to separate the ferrous 
from the non-ferrous (non-embrittled) scrap; 

(5) in deflashing of moulded polymer products: in the embrittled state, 
deflashing can be achieved by a tumbling process rather than by treating 
each item individually ; 

(6) in the heat treatment of metals: for instance, to improve the wear 
resistance of certain tool steels; 

(7) for the storage of biological specimens, especially bull semen tor 
the cattle industry; 

(8) in astronautics, for pre-coolingfuel tankspriorto filhngwith oxygen; 

(9) in ground freezing, to enable tunnelling and excavation operations 
to be performed in wet and unstable soils; 

(10) in bomb disposal, for freezing explosives to render them tem- 
porarily harmless. 

However the widest use for nitrogen is as an inert blanketing gas. 
for various 'chemical and metallurgical processes. The purity required is 
dependent upon use, with medium purities (1-3% oxygen) being acceptable 
for such applications as blast furnace feed systems, coal handling systems 
and chemical tank purging. High purity (less than lOppm oxygen) is 

14 B. A. HANDS 

essential for many purposes, of which steel annealing, float glass manu- 
facture and fabrication of semi-conducting devices are important examples. 
Gaseous nitrogen is also used as a feedstock for the production of some 
chemicals, particularly ammonia. For large-scale uses, the nitrogen is sup- 
plied by an on-site plant or by pipeline. In other cases, it is often convenient 
to store the nitrogen as liquid rather than as gas in cylinders and vaporise 
it as required. 

As already mentioned, a relatively recent and growing use of nitrogen is 
as a displacing medium in the recovery of oil and gas. By forcing oil or 
natural gas out of the well under pressure, a significant increase in the 
percentage extracted can be achieved. Such applications are of large volume 
and require delivery pressures between 130 and 700 bars. 

The other major constituent of air is argon, which is in great demand for 
inert blanketing when nitrogen is too reactive, and for inert gas-shielded 
welding (TIG, MIG, etc.), although helium tends to be preferred in the 
United States. Because a very high purity (>99.9%) is required for most 
purposes, the impure product from several air-separation plants may be 
sent to a central point for purification. The air-separation industry is, in 
fact, so competitive that the recovery of argon may be necessary to prevent 
a plant running at a loss. The demand for argon is increasing rapidly, and 
it is possible that in the future some air-separation plants will be operated 
for the production of argon only, the nitrogen and oxygen being discarded. 
Although much argon is supplied as compressed gas, it is more economical 
for even moderate users to receive and store argon as liquid. 

Of the minor constituents of air (Table 1.3), neon, krypton and xenon are 
extracted mainly for use in the lamp industry and laboratory instruments. It 
is not at present economic to recover helium due to its availability from 
LNG wells. 

Potential Yield of Atmospheric Rare Gases from a 1000 t/day Oxygen Plant" 

Total in air passing 

through plant 

Typical yield 

(m 3 /hr at NTP) 


Cylinders per day 











. 2 








" From Thorogood [1.3]. 

1. A SURV 

1.6 Liquid 

explosive < 
(0.02 mJat 
no unusua 
1970s, whe 
Its importE 
for exampl 
gas or fuel 
scale, elecl 
due mainlj 
burning hy 
hydrogen. ' 
since it cle* 
the resultin 
tigation of 
(Chapters 1 
higher. A cc 
and para (C 
conversion i 
being usual 
Care must a 
oxygen whi< 
believed, ca 
perature pai 
Liquid hy 
nuclear phys 
a target for l 
from the enj 
to measure 
interactions ; 
volume of lie 
of a charged 
a piston in oi 




e of nitrogen is 
' forcing oil or 
ncrease in the 
)f large volume 

1.6 Liquid Hydrogen 

Hydrogen gas is a somewhat hazardous substance to handle due to its wide 
explosive concentration range with air (4-72%) and its low ignition energy 
(0.02 mJ at 30% concentration), although the liquid itself appears to present 
no unusual problems and was in wide use for cooling purposes until the 
1970s, when liquid helium became more easily available in large quantities 
Its importance as a cryogen has declined considerably since then, so that 
for example, in Great Britain it is no longer commercially available 

Hydrogen gas is produced on a large scale by the reaction of steam with 
hydrocarbons, particularly natural gas, or by the partial oxidation of natural 
gas or fuel oil. The gasification of coal may also be used. On a smaller 
scale, electrolysis of water is used, in spite of its higher cost, which is 
due mainly to the higher binding energy of hydrogen in water than in 
hydrocarbons, to the high cost of electricity (itself often produced by 
burning hydrocarbons), and to the low efficiency of electrolytic cells 
Electrolytic hydrogen may cost twice as much as the cheapest 'chemical 1 
hydrogen There is currently interest in developing hydrogen as a fuel, but 
since it clearly does not make sense to produce it from other fuels (with 
the resulting overall loss in available energy), there is widespread inves- 
tigation of methods for producing hydrogen from water using various 
tnermocnemical methods. 

Hydrogen may be liquefied using cycles similar to those in use for helium 
(Chapters 13 and 15), except that the cycle pressures are about five times 
higher. A complication is that, because hydrogen exists in two forms, ortho 
and para (Chapter 2), the inclusion of catalysts to promote ortho-to-para 
conversion must be considered. Great care must be taken with safety it 
being usual to provide a blast wall between the liquefier and its operators 
Care must also be taken to free the hydrogen from impurities, especially 
oxygen which can promote unwanted ortho-para conversion and it is 
believed, cause an explosion if accumulated as solid in the lower' tem- 
perature parts of the plant. 

Liquid hydrogen still finds two particular applications. In high-energy 
nuclear physics experiments, liquid hydrogen or deuterium may be used as 
a target for the particles produced from the accelerator. More interesting 
from the engineering point of view is the bubble chamber, which is used 
to measure the properties of charged particles and to elucidate their 
interactions and decays. A bubble chamber consists essentially of a closed 
volume of liquid held at a pressure well above saturation. On the passage 
of a charged particle, the pressure is rapidly reduced, usually by means of 
a piston in one wall of the chamber, so that the liquid is in the superheated 


is taken, and he liquid is recompressed before bulk boiling occurs Te 
whole cycle taking a few tens of miUiseconds. A large magnet surrounds 

The other application for which liquid hydrogen is still nroducfH in 
quantity is as a fuel for space vehicles" When use'd with o L^n it^as^ 
high propulsive energy per unit mass, and on this basis waTfo -in stanT 
chosen for the fuel of the second and third stages of th docket St?' 

^l^^ofT 1 ^^ each of which 

ArZT ( } hqUld hvdro g en (Kg- 1.4): in the late 1960s the 

American space programme was using about 40 OOOt/year [1 5] In he 

three Les^h^H l""* b T hydr ° gen has a ca,orific value about 
three tunes higher than kerosene which was used for the first stage of 


as ^Zu^T W L d£SP f 3d disCUSsionofthe POssibilityofusinghydrogen 
a Irtdv men one/ M 0iI SU PP UeS diminish although 

hydrogen is however, a major problem. Storage as metal hybrid LlSses 
a large w eig ht and cost penalty because of the metals used and K 
absorption capacity. Storage as liquid is clearly convenient but reTu Z 
t^^VZST earUer ' akhOU8h S ° me » -Turn 

nvHroLn' 1 uf ^ ^ US, " g 3 miXtUfe ° f S0,id ™ d liquid-'slush 

Xn ?Z 5,derable p C \ re would nave to be taken in the'disposaTof 
~' « safe W ay. p er h a ps a more serious drawback is the energy 
required for liquefaction, which may amount to as much as a third of he 


o photograph 
g occurs, the 
let surrounds 
leduced from 
ocarbons and 
J particularly 
lore straight- 
rogen bubble 
lining several 
led by other 
ler chambers 

produced in 
gen, it has a 
for instance, 
>cket for the 
>umed about 
e 1960s, the 
[1.5]. In the 
120 tonnes 
value about 
irst stage of 
lower. Thus 
fuelled with 

Qg hydrogen 
h, although 
f producing 
:he question 
isily ignited 
:e hydrogen 
that overall 
; storage of 
des imposes 
id their low 
>ut requires 
in volume 
uid — 'slush 
disposal of 
the energy 
hird of the 

18 B. A. HANDS 

calorific value of the fuel liquefied. This, together with the present high 
cost of production from non-hydrocarbon sources, makes hydrogen econ- 
omically unattractive, although several experimental automobiles have 
been successfully run with liquid hydrogen as fuel for a number of years 

1.7 Liquid Helium 

The importance of helium to the physicist and cryogenic engineer is that it 
is the only route to temperatures below about 10 K, apart from magnetic 
cooling methods which are unlikely to become practical on anything but a 
very small scale. The provision of helium refrigeration is, therefore, a 
necessary adjunct to the use of superconducting magnets. 

The largest sources of helium in the western world are currently the 
natural gas wells of the states of Texas and Kansas in the United States. 
Wells in Poland, Northern Germany and the USSR (at Orenburg) also 
produce large quantities. Helium is present in these wells at a concentration 
of about 0.2-0.7% and is extracted by liquefying the other constituents. 
Although at present there is plenty of helium available, there are worries 
that if the growth in both size and number of superconducting magnets 
continues at the present pace, there could be a severe shortage in a few 
decades as natural gas wells become exhausted, even though the United 
States has considerable quantities of helium stored in underground porous 
rock— a result of the so-called 'conservation' programme which has now 
been discontinued [1.6]. Outside America, 'conservation' has a rather 
different connotation— that of recycling the gas after use, rather than 
exhausting it to the atmosphere. Such recovery is usually justifiable on 
economic grounds alone, since gaseous helium is not cheap, but it is worth 
noting that large quantities are used in welding and in oxygen-helium 
atmospheres for diving, from which helium recovery is not feasible. 

A major landmark in the development of helium technology came in 
1946 with the design by Professor Sam Collins of a liquefier which did not 
require the feed helium to be pre-cooled and which could be operated 
continuously for long periods. Previous to this, small-scale experiments 
were done by liquefying helium in situ, for example, by precooling with 
liquid hydrogen (sometimes itself produced in situ) and then adiabatically 
expanding. Continuous liquefaction was achieved using cascade cooling 
with liquid air (or nitrogen) and hydrogen followed by Joule-Thomson 
expansion. The latter method could produce a few litres of helium per 
hour, but required the simultaneous operation of both a hydrogen and a 
helium liquefier, the liquid air or nitrogen usually being available from a 
commercial source, 


The Collins : 
proved to be a 
meant that fairl 
still marketed to 
bearings were d 
liquefiers, and s> 
refrigerators. TJ 
engine, have no 
high efficiency. ' 

Another probi 
to compress the 
since all will fret 
is especially imr. 
to be run contu 
contaminations 1 
believed that w; 
blockages in one 
received general 
based, piston rin 
compressors, bei 
reciprocating cor 
require a sophisti 
for a malfunctior 
refrigerator itselJ 
more frequent m 
for more massivi 
tamination is sim 

1.8 Superconduct 

Perhaps the one : 
has been the exj 
conductivity or tl 
phenomenon was 
major part in eleci 
was destroyed , by 
presence of a maj 
remained unfulfii; 
'high-field' supero 
remain supercond 




present high 
irogen econ- 
lobiles have 
ber of years. 

leer is that it 
Dm magnetic 
lything but a 
therefore, a 

:urrently the 
nited States. 
2nburg) also 
; are worries 
ing magnets 
age in a few 
1 the United 
ound porous 
ich has now 
las a rather 

rather than 
ustifiable on 
at it is worth 
Dgy came in 
hich did not 
be operated 
:ooling with 
;ade cooling 

helium per 
rogen and a 
lable from a 

The Collins liquefier, which used a reciprocating expansion engine, 
proved to be a reliable machine, although the presence of nibbing seals 
meant that fairly frequent maintenance was required; its derivatives are 
still marketed today. During the 1950s, high-speed turbines running on gas 
bearings were developed as the external work components for hydrogen 
liquefiers, and soon afterwards this technique was incorporated in helium 
refrigerators. These turbines, although less robust than a reciprocating 
engine, have no rubbing surfaces and can achieve a large throughput at 
high efficiency. They are now usually specified for large refrigerators and 

Another problem in the design of refrigerators arises from the necessity 
to compress the gas. The helium feed must be free of oil, water and air, 
since all will freeze at some point in the system and cause blockages: this 
is especially important today, when superconducting systems may have 
to be run continuously for many months. To achieve such service, oil 
contaminations less than 1 part in 10 7 may have to be specified, and it is 
believed that water contamination of about 3 parts in 10 8 has caused 
blockages in one system [1.7]. Two types of compressor appear to have 
received general acceptance, reciprocating compressors with dry, polymer- 
based, piston rings, and oil-flooded screw compressors. Oil-flooded screw 
compressors, being rotating machines, suffer from fewer problems than 
reciprocating compressors and are more compact and vibration-free, but 
require a sophisticated oil-removal system. Furthermore, it is not unknown 
for a malfunction to occur such that much of the oil is delivered into the 
refrigerator itself. Reciprocating compressors have the disadvantage of 
more frequent maintenance intervals, more vibration and a requirement 
for more massive foundations, but the equipment for removal of con- 
tamination is simpler. 

1.8 Superconducting Magnets and Machinery 

Perhaps the one major disappointment in the development of cryogenics 
has been the exploitation of the "electrical engineers' dream" — super- 
conductivity or the complete absence of electrical resistivity. After this 
phenomenon was discovered in 1911, hopes persisted that it would play a 
major part in electrical engineering, even though the superconducting state 
was destroyed by the passage of a current of only a few amperes or the 
presence of a magnetic field of only a few tenths of a tesla, but the dream 
remained unfulfilled for some 50 years. In the late 1950s, a range of 
'high-field' superconductors were discovered, so called because they would 
remain superconducting in fields of tens of tesla. Also, their critical tem- 

it to operate* the «° ^ and ^ 

In order to optimise the perforce n ? ?, ^ COUld sustai «- 
learnt, and even today new dSn^ ' many , Subt,e techniques had to be 
Nevertheless, ^ZTZl ^u SUCCessful - 

basis, and, for larfe magnetsTle^st at aco^ I M 3 P r ° ductio °-line 
copper equivalents, to thich h ey are "!f ■ ^ ^ their ™ter-cooled 
stability of field. Y rC SUpenor on ™™g costs and in 


bore. The maximum diameter is about ^cm S lT "" 1 ' PTOdUCing 10Tin a 70 "™ 
used to absorb energy sho U .d the magnet unTxpetdW ^ °* ^ are 

me norma] state ('quench'). (Courtesy of Oxford 

Instruments Ltd"! ' 6 SUperconductin g to 

1. A SURV] 

cubic centi 
of NMR a 
use into ch 
which the 
coming int< 
nucleus (pi 
radiation, t. 
magnetic fi 
between 0.: 
the x, y ar 
correlating I 
mation may 
intensity of 
Since the wj 
body, a 3-di 
lattice and s 
acquired. Th 
(Fig. 1.7), w 
and a stabilit 
Still at a 
nuclei due to 
resonant freq 
vivo. Process 
tissue during t 
B Na nucleus, 
Because the m 
of protons, m; 

No adverse 
MRI or MRS. 
field, which ca 
necessary), an. 
ferrous objects 
For MRS am 
used, the lattei 
cryogenics for : 
conductivity, tt 
per year worldv 
Large magne 


I (niobium) were 5-10 K 
construction of a super- 
ding the wire into a coil, 
ise' the magnet and allow 
)f the wire could sustain. 
>tle techniques had to be 
ys completely successful, 
ally on a production-line 
s than their water-cooled 
on running costs and in 

d applications in research 

is a split-pair magnet, wound 
., producing 10 T in a 70 mm 
on top of the assembly are 
from the superconducting to 

laboratories. Small magnets, providing a uniform field over a few tens of 
^Z 0 ^ 1 " 1 !^^ mainly USed by P h y sicists (Kg- 1-6); the development 
of NMR and ESR techniques for analytical purposes has extended their 
use into chemistry and biology [1.8], and more recently, into medicine, in 
which the technique known as MRI (Magnetic Resonance Imaging) is 
coming into routine clinical use. In MRI, the resonance of the hydrogen 
nucleus (proton) is stimulated by applying radiofrequency electromagnetic 
radiation, the resonant frequency being directly proportional to the applied 
magnetic field. The patient is subjected to a uniform magnetic field of 
between 0.5 and 1.5 T, upon which are superimposed small gradients in 
the x, y and z directions. By changing the applied rf frequency and 
correlating the resonant frequency with the local field, 3-dimensional infor- 
mation may be obtained. The primary information is obtained from the 
intensity of the resonance, which depends upon the local proton density 
Since the water and lipid content is different in the various tissues of the 
body, a 3-dimensional image of the body structure may be produced and 
abnormalities such as tumours may be located. Measurement of the spin- 
lattice and spin-spin relaxation times enable further information to be 
acquired. The magnets for whole-body MRI require a bore of about 1 0 m 
(Fig. 1.7), with a field homogeneity as good as 0.1 ppm of the main field 
and a stability of 0.1 ppm per hour [1.8]. 

Still at a more experimental stage is MRS (Magnetic Resonance 
Spectroscopy). Slight variations in the local magnetic environment of the 
nuclei due to different chemical surroundings produce small shifts in the 
resonant frequency, and this enables chemical reactions to be followed in 
vivo. Processes which have been investigated include changes in muscle 
tissue during exercise using the 31 P nucleus, cellular biochemistry using the 
Na nucleus, and the kinetics of enzyme reactions using the 13 C nucleus 
because the magnetic moments of these nuclei are much weaker than those 
of protons, magnetic fields of about 6 T are generally required 

No adverse physiological, effects are believed to occur with the use of 
MKJ or MRS. The main safety problems are control of the stray magnetic 
held, which can be limited by the use of iron shielding (some 20 1 may be 
necessary), and the prevention of personnel from inadvertently carrying 
terrous objects into the region of the stray field. 

For MRS and MRI, both conventional and superconducting magnets are 
used, the latter giving superior resolution but requiring some expertise in 
cryogenics for its operation which may not be available in some hospital 
environments. This is the first large-scale, non-research use of super- 
conductivity, the current production rate being several hundred magnets 
per year worldwide. 
Large magnets have been used since the mid-1960s by high-energy 



Fig. 1.7 A superconducting magnet, designed for whole-body scanning, during assembly. 
A field in the range 0.5-1.5T is produced in a bore of 1 m. (Courtesy of Oxford Magnet 
Technology Ltd.) 

nuclear physics establishments, at first for the focusing of ionised particle 
beams between the accelerator and the experiment, and lately in the 
accelerator itself. Such magnets are often one or two metres long with a 
bore of around 10 cm; besides simple solenoids, quadrupole and other 
configurations have been constructed. A great variety of superconducting 
magnets for other uses has now been made, for example, simple solenoids 
of several metres bore for use with bubble chambers; toroidal magnets for 
plasma physics experiments; and a 'yin-yang' configuration, weighing 341 1, 
for a nuclear fusion experiment (Fig. 1.8). Fields in the region of 10 T are 
commonplace, and some magnets are pulsed on a routine basis. High- 
energy nuclear physics and nuclear fusion, have both given great stimulus 
to the development of magnet technology. 

Applications in the generation and transmission of electric power have 
not been as successful, the enthusiasm of the manufacturers being counter- 


uring assembly. 
Dxford Magnet 

ised particle 
ately in the 
long with a 
e and other 
>le solenoids 
magnets for 
ighing 341 1, 
1 of 10 T are 
basis. High- 
eat stimulus 

power have 
ing counter- 


balanced by the caution (realism?) of the utility companies [1.9]. In general, 
the story has been that advances in 'conventional' technology have remained 
ahead of the possibilities of using superconductors. Superconducting trans- 
mission lines are a good example. In 1973, it seemed that a superconducting 
system would be economically viable for powers greater than about 1 GVA 
[1.10]. Ten years later, due to advances in insulation technology of room 
temperature systems, the figure had risen to 5 or 10 GVA, and experimental 
studies had been largely abandoned, even though in 1984 the prototype ac 
transmission line at the Brookhaven National Laboratory [1.11] was run 
continuously for 4 weeks at 1 GW, and its stability demonstrated at 100% 

Similarly, in the 1970s there was considerable activity in the design and 
construction of models and prototypes of superconducting alternators for 
power generation aimed at eventual machines in the capacity range of 
1000-3000 MW. Superconducting alternators have two major advantages 
over conventional designs: a greater efficiency, and a size and weight 
smaller by a factor of about two. However, the increase in efficiency is 1% 
at the most, and this is easily negated if the alternators prove to be less 
reliable than the machines currently in use. The generating authorities are, 
therefore, proceeding with extreme caution, and again by 1985, activity in 
the western world in this field had considerably diminished, with only small 
programmes remaining in the USA, Japan and Germany. However, it was 
reported in 1985 [1.12] that in the USSR, an experimental alternator was 
switched into the Leningrad supply in the summer of 1984, and that 
construction of 300 MVA alternators is proceeding. 

At present, only one superconducting device is believed to be in use by 
an electricity supply authority in the western world. A superconducting 
magnet capable of storing 38 MJ of energy has been installed at the Tacoma 
substation of the Bonneville Power Administration in the United States. 
Energy is transferred between the magnet and the transmission line in a 
controlled way to damp out subsynchronous oscillations in the ac electricity 
supply [1.13]. An advantage of the system is the relatively fast response 
time of 10 ms. Much larger magnets have also been proposed as 'peak 
shaving' energy storage devices, which would be used in much the same 
way as pumped water storage is now. 

There has been considerable interest in superconducting motors. The 
most promising application appears to be for ship propulsion, where, for a 
given power, a superconducting motor combined with a superconducting 
generator is much smaller than a conventional system. The motors are 
generally of the dc homopolar type. The small rotating mass facilitates 
rapid speed changes, and the motor will operate efficiently at low speed, 
thus removing the need for a gear box. However, on economic grounds a 



conventional system is still superior, and the main use for a superconducting 
unit may be in naval vessels, for which flexibility and small size are important 
advantages, and in icebreakers, because of the frequent reversals of direc- 
tion at low speed. 

A different form of power unit is the linear motor, which, when combined 
with magnetic levitation, forms a suitable system for driving high-speed 
trains. Japanese National Railways has pursued such a development [1.14], 
intended for the commuter line between Kobe and Tokyo, which was 
predicted to reach full capacity soon after 1980. Work started in the 1960s, 
and the first prototype was successfully tested in 1975. Since then, the 
design has been considerably refined, and in 1979 the version known as 
ML-500 ran at 517 km/hr, a world record. Propulsion is by linear synchron- 
ous motor, the high-frequency ac power being provided by coils mounted 
on the track. Guidance and support are both achieved using a repulsive 
electromagnetic inductive method, which requires the train itself to be 
equipped with powerful magnets. In the Japanese system, each vehicle 
(28.8 m long and weighing about 10 1) is provided with eight super- 
conducting magnets of 700 kA-turns each and on-board refrigeration (Fig. 
1.9). Although the project is well advanced, there are no plans yet to 
introduce the train into commercial service, since passenger density on the 
line has increased slower than originally predicted. 

Finally, one other use of superconducting magnets is showing commercial 
promise. In the 1960s, it was established that kaolin, which is used in paper- 

Fig. 1.8 'Yin-yang' magnet for the Mirror Fusion Test Facility in Berkeley, California, 
(a) Opposite: Coil-box assembly (courtesy of University of California Lawrence Berkeley 
Laboratory), (b) Magnet during installation in the vacuum vessel, which is about 20 m in 
diameter. The (rectangular) end views of six cryopump modules for maintaining a high vacuum 
can also be seen, arranged radially around the top two-thirds of the vacuum vessel. This 
photograph indicates the complexity of a modern large cryogenic installation. (Courtesy of 
University of California Lawrence Lrvermore National Laboratory and U.S. Department of 


Fig. 1.9 A magnet-refrigerator assembly for the Japanese magnetically levitated train. 
The magnet coil is within the vacuum vessel. (Courtesy of Japanese National Railways.) 

making, could be whitened by removing the discolourants, which are 
principally due to traces of iron, by passing the clay through a magnetic 
field gradient. Since then, applications have been found in the separation 
of ores, in the purification of chemicals, in the desulphunsation of coal and 
in the cleaning of flue gases and liquid effluents. The separation of red 
blood cells from plasma is also possible. Although many of these processes 
require only comparatively low magnetic fields, the use of superconducting 
magnets may be advantageous for certain applications [1.15]. 

1.9 Cryogenic Electronics 

Many active electronic devices can be operated in a cryogenic environment 
[1.16]. They are generally of the field-effect transistor (FET) type and are 
based on silicon or gallium arsenide. For instrumentation purposes, there 
are clear advantages in placing at least some of the electronic circuitry close 
to the sensing head. However, there may also be inherent advantages in 
operating transistors at low temperatures, such as increased switching speed 
or lower noise. A serious problem is the effect on device reliability of the 
stresses induced by thermal cycling. 


two phenon 
flux, which : 
more compl' 
extremely s: 
amount of I 
Josephson el 
lead or niob 
oxide film al 
such a layei 
function of t 
Josephson jt 
uncertainty i 

The super 
from a supe 
If the loop ei 
because it is 
wave functic 
there is a ph; 
hence of the 

The rf SC 
loop, which : 
drive a curn 
measure of 
Josephson ji 
through the ] 
current is th 
nologies sin: 
methods ma 1 
dc SQUID i 
be approach' 
a known dist 
be measured 

Among a 
local anoma 
and archaeol 
routinely us< 
satellite tran; 

nd are 
i close 
ges in 
of the 


Superconducting electronic devices are in a different Hoc n, 
two phenomena-the Josephson effect an \ *t I ^relyon 
flux, which are described tT^^U STT™ °f 
more complete account is given in fl 181 Th. I' exam P le > a 
extremelysmall: 2.07 X 10-^ ( Vh h^ann" ^ ^ * 

amount of the earth's field enclosed bv a J™ ° Hmate, y Cqual to the 

superconductivity is attributed so thai S / ^ PaiFS) t0 which 
The superconducting quantum interference device (SQUID) is fnrmf-H 

28 B. A. HANDS j A SUR , 

associated with bodily activity, the fluctuations ranging from 1CT 11 T faster th; 

(from the heart) down to 10~ 15 T (from the brain) [1.19]. Gradiometer construct 

arrangements are often used in an attempt to reduce to an acceptably low there ha^ 

level the effects of local field fluctuations due to electrical equipment and architect) 
ionospheric phenomena. Advantages over the use of ECG and EEG are 
that electrodes do not have to be attached to the patient, and that the 

measurements are localised rather than averaged over some distance. By 1.10 Cry 
spatial scanning, a 3-dimensional image of, for example, brain activity can 

be constructed and the position of a malfunction pin-pointed. With a single The larg< 
detector, such an image may take several days to produce, but attempts eering ha 
are being made to develop multiple arrays using several tens of SQUIDs and hydr 
to reduce the scanning time. It may be observed that whereas MRI (Section precoolir 
1.8) gives information about the structure of tissue, these magnetic field carried f< 
measurements give information about the functional behaviour of the tanks. Tl 
tissue. SQUIDs have also been used to detect accumulations of ferro- isatapn 
magnetic material in various parts of the body. insulatioi 
Josephson junctions may be arranged in a variety of ways for other problems 
purposes. For instance, a sampling oscilloscope has been made with a time currents 
resolution of 2 psec. But perhaps the best-known application is to comput- these pre 
ers. Combinations of Josephson junctions can be designed to act as a very small act 
fast switch with low power dissipation or as a memory element. The fuel tank 
theoretical switching time is about 10 psec and the power dissipation about The sn 
1 fiW, giving a product of switching time and power consumption — the urement; 
figure of merit used for switching devices — several orders of magnitude wavelenf 
better than that of transistors. The fabrication of logic elements using such of the ci 
devices allows in principle the construction of a large capacity, compact, supercon 
high-speed computer [1.20]. Much development work was carried out on 17) is al 
this concept during the 1970s, especially by IBM. However, after '15 years utterly n 
and an estimated 100 million dollars' [1.21], IBM announced in 1983 that alternati' 
the project was abandoned, although development work in fact continues then has 
at a lower level. During that time, complete logic boards had been devel- 
oped and tested. Major problems with the technology are that large fan- 
out ratios are difficult to achieve and that superconducting circuits have a I- 11 Mw 
very low inherent impedance and so are difficult to couple with conventional 

elements at room temperature. There were also manufacturing problems, Cryogen 

since the boards could only be tested when in the superconducting state at fields. Tl 

a low temperature, and some logic gates were always destroyed due to been dis 

thermal cycling. Another factor was that, as in other branches of super- more dl 

conductivity, room-temperature devices were being developed which 'h^« i 3 

approached the advantages offered by the superconducting system; for difficult, 

instance, at the end of 1985, it was reported that miniature ceramic circuit vf 0 ]?^!! 

boards and hot electron devices were being developed by Fujitsu of Japan h i 

for use in an ambient-temperature computer which would be very much c emical 




ations ranging from 10 _11 T 
e brain) [1.19]. Gradiometer 

0 reduce to an acceptably low 
le to electrical equipment and 
he use of ECG and EEG are 
. to the patient, and that the 
raged over some distance. By 
or example, brain activity can 
:ion pin-pointed. With a single 
lays to produce, but attempts 
using several tens of SQUIDs 
-ed that whereas MRI (Section 
jf tissue, these magnetic field 

functional behaviour of the 
etect accumulations of ferro- 

1 a variety of ways for other 
>pe has been made with a time 
town application is to comput- 
in be designed to act as a very 

as a memory element. The 
id the power dissipation about 
and power consumption — the 
-several orders of magnitude 
>n of logic elements using such 
of a large capacity, compact, 
nent work was carried out on 
BM. However, after '15 years 
, IBM announced in 1983 that 
jpment work in fact continues 
; logic boards had been devel- 
technology are that large fan- 
iperconducting circuits have a 
ult to couple with conventional 
also manufacturing problems, 
n the superconducting state at 
vere always destroyed due to 
is in other branches of super- 
vere being developed which 
: superconducting system; for 
that miniature ceramic circuit 
developed by Fujitsu of Japan 
sr which would be very much 

faster than a Josephson machine. However, work continues towards the 
construction of a complete superconducting computer in Japan, where 
there have recently been striking advances in fabrication technology and 

1.10 Cryogenics in Space 

The large-scale applications of cryogenic technology to aerospace engin- 
eering have already been mentioned, in particular the use of liquid oxygen 
and hydrogen to power launch vehicles, and the use of liquid nitrogen for 
precooling purposes. In addition, liquid or cold supercritical oxygen is 
carried for life support, and helium may be carried for pressurising fuel 
tanks. The technology is similar to that used on earth, except that weight 
is at a premium, and, once in the space environment, only minimal thermal 
insulation may be needed. However, the absence of gravity poses serious 
problems, since liquid no longer separates from vapour and convection 
currents are non-existent. Special devices have to be used to overcome 
these problems. In the case of rocket motors, the vehicle may be given a 
small acceleration by an auxiliary rocket to drive the liquid towards the 
fuel tank outlet so that the engines may be started reliably. 

The small-scale applications are mainly concerned with scientific meas- 
urements, including astronomy covering the whole range of electromagnetic 
wavelengths, recording of magnetic fields and observations of the surface 
of the earth. The instruments used often include a cooled detector or a 
superconducting device. The provision of a small refrigerator (see Chapter 
17) is attractive, but the device must be of long life (several years), 
utterly reliable and low in power consumption, weight and vibration. The 
alternative is to provide a store of cryogenic liquid, but the experiment 
then has a comparatively short lifetime. Both methods are, in fact, used. 

1.11 Medical and Biological Applications 

Cryogenics has found a number of applications in the medical and biological 
fields. The use of superconducting magnets in MRS and MRI has already 
been discussed, as has the use of SQUIDs. Low temperatures are used 
more directly to enable biological materials to be frozen and stored, 
particularly thin tissues and blood. The preservation of large items is more 
difficult, since the cells suffer damage during the cooling and warming 
processes, the rapidity of which is inevitably controlled to a great extent 
by,the thermal conductivity of the material, although the injection of certain 
chemicals can minimise the damage in some cases. On the other hand, this 


damage is put to good use in the elimination of tumours by freezing. A 
major difficulty here lies in the monitoring and control of the frozen region. 
There is also insufficient understanding of the mechanisms by which cells 
are killed. Nevertheless, successful results have been obtained in the 
treatment of some conditions, and it is probable that cryosurgery will be 
more widely used in the future [1.22]. 

In agriculture, for many years cattle semen has been routinely preserved 
in liquid nitrogen for subsequent artificial insemination, and this has made 
a major contribution to the development of the industry, especially in the 
underdeveloped countries. 

1.12 Cryopumping 

Cryopumping— the removal of gas from a system by solidification onto a 
cold surface— has a number of advantages over other methods of producing 
vacua. A cryopump consists essentially of a metal plate cooled to a low 
temperature, and, therefore, can be made easily and economically in a 
large size, with considerable freedom in design configuration [1.23]. It is a 
'clean' pump, since the only working substance is the refrigerant used for 
cooling, which does not come into contact with the vacuum space. Lastly, 
all gases except helium can be pumped to extremely low partial pressures 
(Fig. 1.10). 

Although the concept of the cryopump is straightforward, the con- 
struction requires some sophisticated design, since the low-temperature 
parts must be carefully shielded from room-temperature radiation while 



1. A SURVEY 01 

allowing free access to gas molecules. This is especially so for cryopumps 
with stages at 20 K or 4 K, which must be shielded with panels at around 
80 K. Since some molecules are scattered away from the cryopumping 
surface itself by the shields, the overall capture coefficient (which is usually 
between 0.35 and 0.5 depending on the design) is much less than that of 
the bare panel and, in fact, is not much different from that of a large 
diffusion pump. 

Very large cryopumps were developed during the 1950s for use in space 
simulation chambers. Frequently, these used panels cooled to 20 K using 
a refrigerator with helium gas as the working fluid, and radiation shields 
cooled either with liquid nitrogen or with helium gas at around 100 K. 
The residual hydrogen and helium was extracted using conventional high- 
vacuum pumps. The cryopumps usually covered almost the whole of the 
interior surface of the vacuum vessel, which typically might be several 
hundred square metres in area. 

Recently, attention has turned to the provision of cryopumps for nuclear 
fusion experiments. These are required to pump hydrogen at speeds of 
10 6 -10 7 l/sec and to pressures of the order of 10~ 5 mbar or better, so that 
the coolant must be liquid helium at around 3.5 K. A number of large 
pumps of this type have now been constructed; advantage has been taken 
of the geometrical freedom mentioned earlier to produce some interesting 
configurations [1.24] such as that shown in Fig. 1.11. 

Fig. 1.12 Typical design of a small cryopump attached to a displacer refrigerator and 
intended to replace a diffusion pump. 

At the other 
cryopumps for i 
be scrupulousl; 
apertures of a i 
direct replacem 
contained refri, 
provides refrigt 
of course, pum 
temperature p; 
residual hydro£ 
and zeolites ha 
low pressures i 
restricted by a 

1.13 Instrumen 

The instrumen 
mometer, prol 
lation. The lat 
if accurate am 
procedures, as 
examined in C 

The measure 
liquids, float g 
allow the gas 
temperature of 
resistors or die 
measuring cum 
in the liquid, a 
change in hea 
unreliable beca 
heat transfer o 
and a static liqi 
of the liquid al 

In the autho: 
hydrostatic hee 
to room tempe 
temperature ei 
rising up the n 
that the liquid 


r cryopumps 
:1s at around 
ich is usually 
than that of 
it of a large 

use in space 
3 20 K using 
ition shields 
Dund 100 K. 
itional high- 
vhole of the 
t be several 

; for nuclear 
it speeds of 
tter, so that 
?er of large 
been taken 
i interesting 


At the other end of the size scale, there is an increasing interest in small 
cryopumps for industrial purposes, especially where oil contamination must 
be scrupulously avoided as in the semi-conductor industry. These have 
apertures of a few tens of centimetres and are frequently designed to be a 
direct replacement for a diffusion pump. They are cooled with a small self- 
contained refrigerator based on a displacer cycle (see Chapter 17) which 
provides refrigeration at around 100 K for the radiation shield (which also, 
of course, pumps water vapour), and cooling at around 20 K for the lower 
temperature panel, which is equipped with a sorbent material to pump 
residual hydrogen (Fig. 1.12). Sorbent materials such as activated charcoal 
and zeolites have attracted attention on account of their ability to achieve 
low pressures at comparatively high temperatures. However, their use is 
restricted by a low pumping speed and a limited absorption capacity. 

1.13 Instrumentation 

The instrument most commonly used in cryogenic engineering is the ther- 
mometer, probably on account of its cheapness and simplicity of instal- 
lation. The latter is deceptive, however, and great care must be taken 
if accurate and reliable measurements are to be obtained. Installation 
procedures, as well as the many different types of sensor available, are 
examined in Chapter 18. 

The measurement of liquid level can present problems. For the denser 
liquids, float gauges can be used, provided that the float is designed to 
allow the gas inside to contract or even condense, depending on the 
temperature of the liquid. A popular electronic device is a chain of carbon 
resistors or diodes which essentially act as resistance thermometers. The 
measuring current is adjusted so that when the sensor ceases to be immersed 
in the liquid, a large temperature change of the sensor occurs due to the 
change in heat transfer coefficient. However, the method tends to be 
unreliable because the current must be carefully adjusted and because the 
heat transfer coefficient can be similar in a fast-flowing stream of vapour 
and a static liquid. Difficulties can also arise if the saturation temperature 
of the liquid alters due to a change in pressure. 

In the author's view, the most reliable method is simply to measure the 
hydrostatic head of liquid, using pressure tappings which are brought up 
to Toom temperature to a suitable differential pressure gauge. At the low- 
temperature end, to eliminate hydrostatic head errors due to the liquid 
rising up the measuring tube, the tube must be arranged horizontally so 
that the liquid boils in the horizontal portion. Boiling can be ensured by 

34 . B. A. HANDS 

using a small heater if the natural heat leak from room temperature is not 
sufficient. Errors may occur because of unknown temperature gradients in 
the liquid and also in the vapour, whose density is often not negligible 
compared with that of the liquid, especially in helium systems. 

For liquid helium in the absence of strong magnetic fields, the super- 
conducting gauge is undoubtedly the most convenient and accurate, meas- 
uring level to within a few millimetres. The sensor consists of a length of 
Type II superconducting wire, which is heated so that it is superconducting 
below the liquid level, but normal above, so that the resistance is just 
proportional to the length of wire above the free surface. The state of the 
wire when in the vapour will again depend on the local heat transfer 
coefficient, but nevertheless a well-designed sensor appears to be unaffected 
by high velocity flows of cold gas. The heater is sometimes separate from 
the wire, sometimes the measuring current itself is sufficient. 

Many types of flowmeter have been used at cryogenic temperatures, with 
varied success, although it is usual to measure the flow at room temperature 
if possible. The low viscosity of the liquids, and their low density, means 
that turbine meters are not responsive to changes in flow rate, and also may 
be damaged by overspeeding due to the large gas flows during cooldown of 
the system; a bypass may therefore be necessary. If the liquid is near 
saturation , vapour may be formed in the throats of orifice plates and venturi 
meters unless the pressure differential is so low that it is difficult to measure. 
Again, the measuring equipment may be damaged during cooldown because 
of the large pressure differentials which may be developed. Ultrasonics and 
thermal anemometry have been used with some success, but the equipment 
is expensive and difficult to install in a cryogenic environment. Except for 
very small pipelines, the vortex-shedding meter may be the best type to 

A wide range of other instruments has been used in a cryogenic environ- 
ment. Generally, instruments used for room-temperature applications can 
be adapted, with a careful choice of materials, unless the measuring 
phenomenon itself is very sensitive to temperature or does not exist in 
the cryogenic temperature range. Many types of transistors will operate 
satisfactorily right down to liquid helium temperatures [1.16, 1.25], and this 
fact has been exploited in the design of many instruments. 


1.1 N. Kurti, 'Low Temperature Terminology', Proc. XIII Int. Congr. Refrig., Vol. I, pp. 
593-597 (Int. Inst. Refrig., 1973). 

1. A SURVEY ( 

1.2 N. Kurti, 'F 

1.3 Data kindly 

1.4 E. K. Farida 

1.5 A. O. Tisch 
. 1-10(1966). 

1.6 E. F. Hamn 
(1980); A. I- 
there a crisis 

1.7 C. H. Rode 
Cryog. Engl 

1.8 L. J. Neurit! 
pp. 32-^3, F 

1.9 B. J.Maddo 
Cryog. Eng. 
conducting a 
598, Genovi 

1.10 B. C. Belan 
in the U.S. 

1.11 E. B. Forsyi 
Cryogenics ) 

1.12 Cryogenics : 

1.13 R. I. Schen 
storage syst( 
123-132 (191 

1.14 T. Ohtsuka 
in Japan', 

1.15 J.H. P. Wai 
presented ai 

1.16 R. K. Kirsc 

1.17 H. M. Rose 

1.18 T. van Dua 
Edward Arr 

1.19 S. J. Williar 
22, 129-201 

1.20 J. Matisoo, 

1.21 The Times. 

1.22 P. Le Piver 
Engng Conj 

1.23 B. A. Hand 

1.24 B. A. Hand. 

1.25 B. Lengeler 
genics 14, 4! 




cryogenic environ- 
re applications can 
;ss the measuring 
does not exist in 
istors will operate 
.16, 1.25], and this 

igr. Refrig., Vol. I, pp.' 

1.2 N. Kurti, 'From Cailletet and Pictet to microkelvin', Cryogenics 18, 451-458 (1978). 

1.3 Data kindly supplied by R. M. Thorogood. 

1.4 E. K. Faridany, 'International trade in LNG: present projects and future outlook', Proc. 
Castech 81 LNG/LPG Conference, pp. 21-35 (Gastech Ltd., Rickmansworth, England, 

1.5 A. O. Tischler, 'The impact of the space age on cryogenics', Adv. Cryog. Engng 11, 
1-10 (1966). 

1.6 E. F. Hammel, 'Helium: its past, present and future', Adv. Cryog. Engng 25, 810-821 
(1980); A. Francis, D. Keierleber and D. Swartz, 'Helium prospects for the future: is 
there a crisis?', Adv. Cryog. Engng 29, 9-17 (1984). 

1.7 C. H. Rode, 'Cryogenic system for a 100 km superconducting collider', Proc. 10th Int. 
Cryog. Engng Conf., pp. 760-770, Helsinki, Finland (1984). 

1.8 L. J. Neuringer, 'NMR in biology and medicine', Proc. 10th Int. Cryog. Engng Conf., 
pp. 32-43, Helsinki, Finland (1984); M. F. Wood, I. L. MacDougall and P. H. Winson, 
'Superconducting magnets for NMR imaging and in-vivo spectroscopy', ibid., pp. 44- 

1.9 B.J. Maddock and W. T. Norris, 'Superconductivity in electricity supply', Proc. 7th Int. 
Cryog. Engng Conf., pp. 245-259, London, England (1978); J. G. Steel, 'Super- 
conducting a.c. generators - a utility view', Proc. 8th Int. Cryog. Engng Conf., pp. 590- 
598, Genova, Italy (1980). 

1.10 B. C. Belanger, 'Superconducting and resistive cryogenic power transmission research 
in the U.S. - an opportunity for cryogenic innovation', Adv. Cryog. Engng 20, 1-22 

1.11 E. B. Forsyth, 'Cryogenic engineering for the Brookhaven power transmission project', 
Cryogenics 17, 3-7 (1977). 

1.12 Cryogenics 25, 50 (1985). 

1.13 R. I. Schermer et al., 'Design and operation of the 30 MJ superconducting magnetic 
storage system on the Bonneville Power Administration bus', Adv. Cryog. Engng 29, 
123-132 (1984). 

1.14 T. Ohtsuka and Y. Kyotani, 'Recent progress on superconducting magnetic levitation 
in Japan', Proc. 10th Int. Cryog. Engng Conf., pp. 750-759, Helsinki, Finland 

1.15 J. H. P. Watson, 'Status report on magnetic separation using superconducting magnets', 
presented at 10th Int. Cryog. Engng Conf., Helsinki, Finland (1984). 

1.16 R. K. Kirschman, 'Cold electronics: an overview', Cryogenics 25, 115-122 (1985). 

1.17 H. M. Rosenberg, The Solid State, 2nd edn, Clarendon Press (1978). 

1.18 T. van Duzer and C. W. Turner, Principles of Superconductive Devices and Circuits, 
Edward Arnold (1981). 

1.19 S. J. Williamson and L. Kaufman, 'Biomagnetism', J. Magnetism and Magn. Materials 
22, 129-201 (1981). 

1.20 J. Matisoo, 'The superconducting computer', Scientific American 282 (5), 38-53 (May 

1.21 The Times, London, 1 December 1983, p. 19. 

1.22 P. Le Pivert, 'Cryosurgery: current issues and future trends', Proc. 10th Int. Cryog. 
Engng Conf., pp. 551-557, Helsinki, Finland (1984). 

1.23 B. A. Hands, 'Introduction to cryopump design', Vacuum 26, 11-16 (1976). 

1.24 B. A. Hands, 'Recent developments in cryapumping', Vacuum 32, 603-612 (1982). 

1.25 B. Lengeler, 'Semiconductor devices suitable for use in cryogenic environments'. Cryo- 
genics 14, 439-447 (1974). 



1. ASU 

The most useful regular cryogenic publications are: 

Cryogenics, a journal published by Butterworth Scientific Ltd., Guildford, England. 

Advances in Cryogenic Engineering, which is published by Plenum Press and is the pro- 
ceedings of the biennial Cryogenic Engineering Conference and the concurrent International 
Cryogenic Materials Conference held in the USA. It is referred to in this volume as Adv. 
Cryog. Engng. 

Proceedings of the International Cryogenic Engineering Conference series (ICEC), pub- 
lished by Butterworth Scientific Ltd., Guildford, England, and predecessors. 

Proceedings of the LNG and GasTech Conferences, which contain information on devel- 
opments in LNG technology. 

IC SQUID, proceedings of the International Conferences on SQUIDs. 

International Institute of Refrigeration (IIR) conference proceedings. 

Proceedings of the Applied Superconductivity Conference series. 

General Bibliography 

In reverse order of publication: 

R. F. Barron, Cryogenic Systems, 2nd edn, Oxford University Press (1985). 

K. D. Williamson, Jr. and F. J. Edeskuty (eds), Liquid Cryogens Vol. 1: Theory and 

Equipment; Vol. 2: Properties and Applications, CRC Press (1983). 
A. Arkharov, I. Marfenina and Ye. Mikulin, Theory and Design of Cryogenic Systems, MIR 

Publishers (1981). 

G. K. White, Experimental Techniques in Low-Temperature Physics, 3rd edn, Clarendon 
Press (1979). 

A. C. Rose-Innes, Low Temperature Laboratory Techniques. The Use of Liquid Helium in 

the Laboratory, 2nd edn, English Universities Press (1973). 
C. A. Bailey (ed.), Advanced Cryogenics, Plenum Press (1971). 

G. G. Haselden (ed.), Cryogenic Fundamentals, Academic Press (1971). 

H. Weinstock (ed.), Cryogenic Technology, Boston Tech. Publ. (1969). 

R. H. Kropschot, B. W. Birmingham and D. B. Mann (eds), Technology of Liquid Helium, 

NBS Monograph 111 (1968). 
R. B. Scott, W. H. Denton and C. M. Nicholls (eds), Technology and Uses of Liquid 

Hydrogen, Pergamon Press (1964). 
J. H. Bell, Cryogenic Engineering, Prentice Hall (1963). 
R. W. Vance (ed.), Cryogenic Technology, John Wiley (1963). 

R. W. Vance and W. M. Duke (eds), Applied Cryogenic Engineering, John Wiley (1962). 
R. B. Scott, Cryogenic Engineering, Van Nostrand (1959). 

Bibliography of Specific Topics 

In alphabetical order of author: 

A. Barone and G. Patern6, Physics and Applications of the Josephson Effect, Wiley : 

Interscience (1982). 
N. R. Braton, Cryogenic Recycling and Processing, CRC Press (1980). 

ildford, England, 
i Press and is the pro- 
incurrent International 
n this volume as Adv. 

* series (ICEC), pub- 

information on devel- 

ryogenic Systems, MIR 
j, 3rd edn, Clarendon 
se of Liquid Helium in 


logy of Liquid Helium, 
■y and Uses of Liquid 

British Cryogenics Council, Cryogenics Safety Manual -A Guide to Good Practice, 2nd edn, 

Mechanical Engineering Publications, Bury St. Edmunds (1982). 
I R Bumby Superconducting Rotating Electrical Machines, aattiidon Press (1983). 
A J Croft, Cryogenic Laboratory Equipment, Plenum Press (1970). 
B ' Deaver and J. Ruvalds (eds), Advances in Superconductivity, Plenum Press (1983). 
?.' fan Duzer and C. W. Turner , Principles of Superconductive Devices and Circuits, Edward 

R T?iZ Natural Gas by Sea, Gentry Books, London (1979); Gas Garners, Fairplay 

Press, London (1984). . 
n Fishlock (ed.), A Guide to Superconductivity, Macdonald-Elsevier (1969). 
S. Foner and B. B. Schwartz (eds), Superconducting Machines and Devices - Large Systems 

AoDlications, Plenum Press (1974). /,oci\ 
r A Haefer Kryo-Vakuumtechnik: Grundlagen und Anwendungen, Spnnger-Verlag (1981) 

(English translation to be published by Oxford University Press). 
H von Leden and W. G. Cahan, Cryogenics in Surgery, H. K. Lewis (1971). 
W L Lom Liquefied Natural Gas, Applied Science Publishers (1974). 
W R Sh, R- O. Voth, J. G. Hust, T. M. Flynn, C. F. Sindt and N. A. Ohen, Selected 

Topics on Hydrogen Fuel, NBS Special Publication 419 (1975)^ 
M Rechowicz Electric Power at Low Temperatures, Clarendon Press (WIS)- 

RTLutfSd.), Bubble and Spark Chambers, Vol. 1, Academic V^W* 1 )- 

l B. Schwab and S. Foner (eds), Superconductor Applications. SQUIDs and Machines, 

Plenum Press (1977). ■ 
F H Turner, Concrere and Cryogenics, Cement and Concrete Ass., England (1979). 
M. N. Wilson, Superconducting Magnets, Clarendon Press (1983). 

Non-specialist Reading 

K. Mendelssohn, The Quest for Absolute Zero; the Meaning of Low Temperature Physics, 

Weidenfeld & Nicholson (1966). 
D. Wilson, Superco/d, an /nrroducrion ro Low Temperature Technology, Faber & Faber 


g, John Wiley (1962). 

sephson Effect, Wiley- 




In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: November 25, 2006 

Docket: YO987-074BZ 

Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
Box AF 
P.O. Box 1450 
Alexandria, VA 22313-1450 


I hereby certify that this Supplementary Response, (_3_ Pages Plus 
Attachment A and Attachment B) is being transmitted by first class mail to the 
U.S. Palerlfarty Trademark OfficeoivNovember 25, 2006. 

In response to the Office Action dated October 20, 2005 please consider the 





In re Patent Application of 
Applicants: Bednorz et al. 
Serial No.: 08/479,810 
Filed: June 7, 1995 

Date: January 30, 2008 

Docket: YO987-074BZ 

Group Art Unit: 1751 
Examiner: M. Kopec 


Commissioner for Patents 
Box AF 

P.O. Box 1450 
Alexandria, VA 22313-1450 

Submitted at the Suggestion of the Examiner in response to the 

In response to the Advisory Action dated November 15, 2007 please consider the 

Advisory Action dated November 15, 2007 






CRC Handbook 


Chemistry and Physics 

A Ready-Reference Book of Chemical and Physical Data 



Vice President, Research, Consolidated Natural Gas Service Company, Inc. 
Formerly Professor of Chemistry at Case Institute of Technology 



Formerly Professor of Organic Chemistry at Case Institute of Technology 
Manager of Research at Glidden Durkee Division ofSCM Corporation 

In collaboration with a large number of professional chemists and physicists 
whose assistance is acknowledged in the list of general collaborators and in 
connection with the particular tables or sections involved. 

2255 Palm Beach Lakes Blvd., West Palm Beach, Florida 33409 

^ Superconductivity*^ 

B.W. Roberts 

General Electric Research Laboratory, Schenectady, New York 

The following tables on superconductivity include superconductive properties of chemical 
elements, thin films, a selected list of compounds and alloys, and high-magnetic-field superconductors 

The historically first observed and most distinctive property of a superconductive body is the 
near total loss of resistance at a critical temperature (T c ) that is characteristic of each material 
Figure 1(a) below illustrafes schematically two types of possible transitions. The sharp vertical dis- 
continuity m resistance is indicative of that found for a single crystal of a very pure element or one 
of a few well annealed alloy compositions. The broad transition, illustrated by broken lines 
suggests the transition shape seen for materials that are not homogeneous and contain unusual 
strain distributions. Careful testing of the resistivity limits for superconductors shows that it is less 
than 4x 10 ohm-cm, while the lowest resistivity observed in metals is of the order of 10" 13 
ohm-cm. If one compares the resistivity of a superconductive body to that of copper at room 
temperature, the superconductive body is at least 10 17 times less resistive 




(a) Resistivity versus temperature for a pure and perfect lattice (solid line). 
Impure and/or imperfect lattice (broken line). 

(b) Magnetic-field temperature dependence for Type-I or "soft" superconductors. 

(c) Schematic magnetization curve for "hard" or Type-II superconductors. 

The temperature interval AT C , over which the transition between the normal and superconductive 
states takes place, may be of the order of as little as 2 x 1 0 " 5 °K or several °K in width, depending on the 
material state. The narrow transition width was attained in 99.9999 percent pure gallium single crystals. 

A Type-I superconductor below T„ as exemplified by a pure metal, exhibits perfect diamagnetism 
and excludes a magnetic field up to some critical field H c , whereupon it reverts to the normal state as 
shown in the H-T diagram of Figure 1(b). 

The difference in entropy near absolute zero between the superconductive and normal states 
relates directly to the electronic specific heat, y: (S,-S,,) r _ 0 = - y J. 

The magnetization of a typical high-field superconductor is shown in Figure 1(c). The discovery 
of the large current-carrying capability of Nb 3 Sn and other similar alloys has led to an extensive 
study of the physical properties of these alloys. In brief, a high-field superconductor, or Type-II 
superconductor, passes from the perfect diamagnetic state at low magnetic fields to a mixed state and 
finally to a sheathed state before attaining the normal resistive state of the metal. The magnetic field 
values separating the four stages are given as H cl , H c2 , and H c3 . The superconductive state below 
H cl is perfectly diamagnetic, identical to the state of most pure metals of the "soft" or Type-I 

:r on Superconductive 



suDerconductor.Wween H cl and H c2 a "mixed superconductMate" is found in which fluxons (a 
Ximal un t of m agnetic f&) create lines of normal superconductor in a supe rconductive : matnx. 
The volume of the normal state is proportional to -4*M in the "mixed state" region. Thus at H 2 
the fluxrdensity has become so great as to drive the interior volume of the superconductive body 
complete* normal. Between H c2 and H c3 the superconductor has a sheath of current-carrymg 

l measurement, it is possible to determine H cl , H c2> and H c3 . Table 2-35 contain, some of the 
available data on high-field superconductive materials. 

For example, the Type-I superconductor, Hg, has entirely different magnetization behavior in h,gh 
magnetic fields wheTcontaled in the very fine sets of filamentary «^<^jr^ 
n^Sssed Vycor glass. The great majority of superconductive materials are Type II. The elements 
fn^i pure Wand a verffew precisely stoichiometric and well annealed compounds are Type-I 
with the possible exceptions of vanadium and niobium. 

Metallurgical Aspects. The sensitivity of superconductive properties to the material state is most 

centers are a 

^ow sharper tuitions than tho. that are 
s rain^r ^homogeneous. This sensitivity to mechanical state underlines a general problem m the 
Su^oC^Sic. for superconductive materials. The occasional divergent values of the critical 
Sot^^ndtf the critical fields quoted for a Type-II superconductor may he in the variation m 
Sr^eparation. Critical temperatures of materials studied early in the history of super- 
c3uctiv ty must be evaluated in light of the probable metallurgical state of the material as well as 
tiie avanlbLy of less pure starting elements. It has been noted that recent work has given extended 
consideration to the metallurgical aspects of sample preparation. 


^st-nducUve Materials and So m e of Their Properties", Process in Cryo g enics, B.W. Roberts, Vol. IV, Heywood 
408 and 482, U.S. Government Printing Office, 1966 and 1969. 



Conversion Factors 
Oe X 79.57 = A/m; katm X 1.013 X 10* = N/m 1 ; kb X 1.0 X 10' = N/m J 


T C (K) 

H 0 (oersteds) 

« D (K) 

TdiUmole" 1 deg ■ K 3 ) 







0.518, 0.52 







5.90 , 6.2 






Hg (a) 



87, 71.9 












0.14 ,0.11 




La (a) 


808, 798 


10.0, 11.3 

La (/3) 












277, 238 





































7.73 , 7.78 



4.84, 6.28 







56, 100 




2.332, 2.39 





5.43 ,5.31 

1,100, 1,400 




















Thin Films Condensed at Various Temperatures 


T C (K) 




~03, ~9.6;6.5-10.6 a ; 10.2 1 


~2 — 5,6.11,6.154, 6.173 




6.4-6.8, 7.4-8.4, 8.56 


3.43-4.5; 3.68-4.17 c 












3.6, 3.84-6.0 


< 1.7 =-4.25, 3.16-4.8 











a With KC1. 

^ith Zn etioporphyrin. 
c In glass pores. 



Data for Elements Studied Under Pressure 


T C (K) 




220-140 kb 


-140-100 kb 

Ba II 


55 kb 



85-88 kb 


>140 kb 

Bi II 


25 katm 


25.2 katm 


26.8 katm 



-37 kb 


27-28.4 katm 

Bi IV 


43, 43-62 kb 

Bi V 

8.3, 8.55 

81 kb 

Bi VI 


90, 92-101 kb 



50 kb 



>~125 kb 

Ga II 

6.24, 6.38 

>35 katm 

Ga II' 


>35 katm (P-0) 



-120 kb 


115 kb 



0--140 kb 



MOO kb 


170 kb 

Pb II 

3.55, 3.6 

160 kb 



85 kb 


93 kb 


100 kb 


-150 kb 

Se II 

6.75, 6.95 

-130 kb 



120 kb 



125 kb 


160 kb 



113 kb 



43 kb 



70 kb 



84 kb 

Tl, cub. 


35 kb 

Tl, hex. 


35 kb 



10 kb 


-1.2, -2.7 

120-170 kb 

From Roberts, 

B. W., 

Properties of Selected 

Superconductive Materials, 1974 Supplement, NBS 
Technical Note 825, U.S. Government Printing Office, 
Washington, D.C., 1974, 10. 


All compositi Aare denoted on an atomic basis, i.e., AB, A or AB 3 for compounds, unless 
noted. Solid solutions or odd compositions may be denoted as A^., or A^. A series of three or 
more alloys is indicated as A^, or by actual indication of the atomic fraction range, such as 
A 0 -o.6 B i-o.4- The critical temperature of such a series of alloys is denoted by a range of values or 
possibly the maximum value. 

The selection of the critical temperature from a transition in the effective permeability, or the 
change in resistance, or possibly the incremental changes in frequency observed by certain techniques 
is not often obvious from the literature. Most authors choose the mid-point of such curves as the 
probable critical temperature of the idealized material, while others will choose the highest temperature 
at which a deviation from the normal state property is observed. In view of the previous discussion 
concerning the variability of the superconductive properties as a function of purity and other 
metallurgical aspects, it is recommended that appropriate literature be checked to determine the most 
probable critical temperature or critical field of a given alloy. 

A very limited amount of data on critical fields, H 0 , is available for these compounds and alloys; 
these values are given at the end of the table. 

SYMBOLS: n = number of normal carriers per cubic centimeter for semiconductor super- 



T C ,°K 




Ag,BF 4 0 8 



AgBi 2 


Ag 7 F 0 . 25 N 0 . 75 O, 0 . 25 





Ag 2 F 


Ago.8-o.3Ga 0 . 2 _ 0 . 7 




Hex., c.p. 

Ago.«3,Hg 0 . 362 


D8 2 


(n= 1.40x10") 



Ago. 2 In 0 . 8 Te 

(n = 1.07 x 10") 






Ag 7 NO u 



7.2 max. 



Ag,Sn,. x 





AgTh 2 



Ago.03Tl„., 7 


Ago.94Tlo 06 








AlAu 4 


Like A13 




Al 2 CMo 3 


A13 + trace 

Al 2 CaSi 


A1 o. 1 3,Cr 0088 V 0 781 



AlGe 2 





T c , °K 



Al_ 08 Ge_ 02 Nb 3 



AlLa 3 



Al 2 La 



Al 3 Mg 2 


Cubic, f.c. 




AIMo 6 Pd 





AI 2 NNb 3 



AINb 3 






Al 0 . 27 Nb 0 . 73 _ 048 V 0 _ 025 








AI 3 Os 


AlPb (films) 


Al 2 Pt 



Al 5 Re 24 



Al 3 Th 






Alo,o8V 0 892 





AlZr 3 


Ll 2 





As 0 33 InTe 0 67 

(n = 1.24x 10") 



As 05 InTe 05 

(n = 0.97x10") 



As 0 . 5O Ni O06 Pd o 44 





AsPd 2 (low- 

temperature phase) 



AsPd 2 (high-temp, phase) 



ttSeekeyat end of table. 






T C ,'K 




T C ,°K 


— — 



Bi o5 Pbo.3.Sno..» 

C 0 .44Mo 0S6 



(weight fractions) 


C 05 Mo x Nb,_ x 





C 0 .6Mo 4 . 8 Si 3 


D8 8 

BiPd 2 


CMo 02 Ta 0 „ 



Bi 0 .« pd <>« 



CMo OJ Ta 0 . 5 
CMo 0 . 7S Ta 0 23 






CMo 0 . 8 Ta O2 



Bi 2 Pd 








10.2 max. 

Bi 2 Pd 



CMo 0 ., 3 Ti 0 I7 















C01-09N09-0 t Nb 










CNb (whiskers) 





C 0984 Nb 



Bi 2 Pt 



CNb (extrapolated) 


Bi 2 Rb 



Co.7-j.0Nbo 3 . 0 



BiRe 2 









Bi 3 Rh 






like NiB 3 

CNbo 6 -o9W 04 . OI 


Bi 4 Rh 



CNb 01 . 0 9Zr 0 ,. 01 



Bi 3 Sn 


CRb x (gold) 





CRe 00 i-oo 8 W 




CRe 00<s W 




Ll 2 


~ 1 1 (extrap- 





C 0 98 7 Ta 


Bio.2 6 Tlo.7« 





Bio.2 6 Tlo.74 


CTa (film) 




Ll 2 , ordered? 

CTa 2 







Bi 3 Zn 


CTa,_ 0 . 4 W 0 _ 0 . 6 



Bio. 3 Zr„. 7 






CTc (excess C) 






CTi 0 .5_ 07 W 05 _o 3 



C 8 K(gold) 




CGaMo 2 



CW 2 

CHf 0 ,Mo 0 j 
CHf 03 Mo 07 




CW 2 
Calr 2 

Ca I 0 3 Sr, _ ,Ti 


Cubic, f.c. 

CHf 0JJ Mo 0 75 

CHf 07 Nb O3 

CHf 06 Nb 04 



(n = 3.7-1 1.0 xlO") 




Cao.,0 3 W 





CHf 03 Nb 05 

c Hf 0 .«Nb 06 

c Hf 0 2 5 Nb 075 

C Hf 0 . 2 Nb 08 

CHf o.»-o.iTa 0 . 1 . 09 

Ck (excess K) 




CaRh 2 

Cd 03 ^o5Hgo 7 - 05 






1.77, 2.15 



Cdo 97 Pb 0 03 









Cd 0 .i 7 Tl 083 

2.3 • 

c »«o 0 Mo 
CMo" ** 
CMo 2 


Cdo.i8Tlo8 2 


6.5, 9.26 

CeCo 2 




0.46 1 


ttSee key at end of table. 






T °K 


T C ,°K 






Ge 3 Rn 5 

related to 
InNi 2 

(InSb) 0 9S _ 0 10 Sn 0 oj . 0 , 0 
(various heat treatments) 
(InSb) 0 _ 007 Sn,_ 0 „ 


Ge 2 Sc 

In 3 Sn 




(n = l.w x iv ^ 

. - .80 


In »» 2 -« Te 

(n = 0.83-1.71 x 10 22 ) 



(n = fl.j-wx iu ) 





GeV 3 

« Al 

In 3 Te 4 

Ge 2 Y 

(n = 0.47 x 10") 





H ° " . 06 ' 

7 28 

Cubic, b.c. 



Cubic, b.c. 

Ino.62Tlo. 3 g 


H 0 .05 0.95 

Cubic, b.c. 




H 0 .12 a 0.88 

2 81 

Cubic, b.c. 



Cubic, f.c. 


Cubic, b.c. 

Ir 2 La 



8 ° 96 

■x *r> 

Cubic, b.c. 

Ir 3 La 


D10 2 


Ir 3 La 7 


D10 2 



Ir 5 La 


nril' 025 

> J~\ 

Ir 2 Lu 



" 2 



Ir 3 Lu 







o.i« e ° 8 ^ h 

IrMo 3 



0.99-0.96 0.01-0.04 

IrMo 3 



urv 055 a '"°* 5 

4 4 fi S - 


IrNb 3 




s 0 o« 

Ir 04 Nb 06 



gx n l-» 

1 14-4 SS 

Ir 0 37 Nb 0 . 6J 







D8 t 



lr 0 02 Nb 3 Rh 0 9 , 



Iro.osNbjRho 95 



1 77 


,r 0.287 O 0.1«Ti 0 .57 3 


E9 3 


i*7 2 



E9 3 


Ir x Os, . x 










HfS >b ' * 

4 14 





Ir 2 Sc 



H n 
H^Tl' * 


Ir 25 Sc 



Ho La' 


IrSn 2 



l l' 6 f n . 

Ir 2 Sr 



InLa 3 

' ' ' 

Ll 2 

Ir 05 Te 03 


InLa 3 (0-35 kbar) 


IrTe 3 


B / 




InNbj" 80 ° '* 

Ir 2 Th 



4-8, 9.2 

Ir 3 Th 


' n o-o 3 Nb 3 Sn 



Ir 3 Th 7 


D10 2 

KsNbjZroj 1 " 0 ' 7 


Ir 5 Th 






In^' 5 0 85 pb° 05 " 15 

3 45 5 4°2 

IrV 2 



InPb °' 91 0 02 "°'° 9 


IrW 3 

Ir 0 28 W 0 72 





Ir 2 Y 

2.18, 1.38 


InSb (quenched from 

Ir 0 69Y 031 

1.98, 1.44 


170 kbar into liquid N 2 ) 


Like A5 

Ir 0 .7oY 0 30 






T„ °K 



T C ,°K 




NbS 2 



Os 2 Zr 








Nb 3 Sb 0 -o.7Sn,-o. 3 



PPd 30 _ 32 



NbSe 2 



P 3 Pd, (high temperature) 



NbS 2 type 

P 3 Pd, (low temp.) 



Nb,- 1.05^2 


NbS 2 type 

PRh 2 





Ll 2 

PW 3 



NbjSiSnV 3 


Pb 2 Pd 



Nb 3 Sn 



Pb 4 Pt 


Related to C16 

Nb 0 . 8 Sno.2 

18.18, 18.5 


Pb 2 Rh 







NbSn 2 



PbTe (plus 0.1 w/o Pb)f 


Nb 3 Sn 2 



PbTe (plus 0.1 w/oTOt 


NbSnTa 2 



PbTl 027 





pbT1 o.n 


Nb 2 . 5 SnTa 0 .5 



PbTl 0 . 12 


Nb 2 . 75 SnTa 0 . 25 



Pbn 0 07S 




pbT1 o.o« 





Pb l -0.16^0-0.1* 


Nb 2 SnTa 0 . 5 V 0 . 5 



PbTl 2 


NbSnV 2 



Pb 3 Zr 3 


D8 S 

Nb 2 SnV 



PbZr 3 



Nb 2 . 5 SnV„. 5 



Pd 09 Pt 0l Te 2 




NbTc 3 . 



Pdj.iS (quenched) 





PdSb 2 



Nb 0 . 6 Ti 0 .* 






1.95 max. 




Nb 0 . 88 V 0 . 12 






Nb 0 ., 5 Zr 0 . 25 





Nb 0 . 6S Zr 0 „ 


Pd 6 -,Se 


Like Pd 4 Te 

Ni 0 . 3 Th<).7 


D10 2 

Pd 2 „Se 


NiZr 2 



2.5 max. 

Ni 0 .,Zr 0 . 9 






03Rb 0 .2,-:o.29W 







PdSn 2 


(n = 1.7-12.0 x 10") 


Pd 2 Sn 




Pd 3 Sn 2 


B8 2 

(n = 10 18 -10 21 ) 



2.3, 3.85 






(«> = ~ 10 20 ) 


PdTe 2 





PdTe 2 .i 



°3 Sr 0.0sW 



PdTe 2 j 



0 3Tlo.3oW 



Pd, ,Te 



OV 3 Zr 3 


E9 3 

PdTh 2 



OW 3 (film) 

3.35, 1.1 


Pd 0 ,Zr 0 9 









Os 2 Sc 










0.37 . 




DI0 2 




Os,W,_ x 




Os 2 Y 



pt'ni 7 


Wo denotes weigh! percent. 

ttSee key at enc 

of table. 




T C ,'K 



PtTi 3 






PtV 2 . 5 



PtV 3 



PtV 3 j 



Pt 05 W 0J 



Pt x W,_. 




Pt 2 Y 

1.57, 1.70 


Pt 3 Y 7 


D10 2 




Re 0S4 Ta 036 



Re„Ti 3 



Re-Ti, _ x 

6.6 max. 

Re 0 76 V 024 



Re 0 , 2 V 00 8 



Reo' s W 0 .4 


Re 05 W O3 


D8 t 

Re 2 Y 



Re 2 Zr 



Re 6 Zr 



Rh 17 S 15 



Rh-0. 2 « Sc -0.76 

0.88, 0.92 

6.0 max. 

Rh 2 Sr 





RhTe 2 30 6 



Rh OS7 Te 033 






Rh 3 Th 7 









RhV 3 








Rh 2 Y 3 


Rh 3 Y 



Rh 5 Y 


RhZr 2 



Rh 0 005 Zr (annealed) 




Rh 0 .,Zr 0 . 9 


Hexagonal, c. 

Ru 2 Sc 



Ru 2 Th 






R"o o 5 Ti 0 95 




Ru x Ti 06 V, 

6.6 max. 

Ru 0 « 5 V 0 55 






ft See key at end of table. 



T e ,°K 


Ru 2 Y 



Ru 2 Zr 



Ru 01 Zr 09 





Bl or distorted 






Sb 2 Tl 7 





SbV 3 



Si 2 Th 


Si 2 Th 


C32, £phase 

SiV 3 



Sio. 9 V 3 AIo., 



Si 0 . 9 V 3 B 0 ., 



Si 0 ' 9 V 3 Co., 



SiV 27 Cr 03 






SiV 2 ,Mo„ 3 



SiV 2 ' 7 Nb 0 .j 



SiV 2 ' 7 Ruo.j 



SiV 2 7 Ti 0 3 



SiV 2 -Zr 03 



Si 2 W 3 

2.8, 2.84 



SnTa 3 * 


A15, highly 




A15, partially 

SnTaV 2 



SnTa 2 V 




(n = 10.5-20 xlO 20 ) 




SnV 3 



Sn o .02-O.O57 V O.98-O.9*3 

2.87 — 1.6 










Ta 0 ',_,W 0 . 2 _ 0 



TC 0 ,-0*W 0 9-0 6 





Tc 0 .«oWo.4o 


a plus a 

Tc 6 Zr 



Tho_o.5 5 Y,_ 0 ., 3 


Ti 0 70 V 0 30 





Tio.sZro.s (annealed) 


Ti 0 3 Zr 0 5 (quenched) 


V 2 Zr 



V 0 .2 6 Zr 0 . 74 


W 2 Zr 






oersteds Substmce 


Ag 2 F 




Ag 7 NO M 




Al 2 CMo 3 


•io. 8 Tlo. 2 




Mg-0 47T1-0 5J 


Bi 2 Pt 


Mo 0 16 Ti 0 84 


Bi 3 Sr 


NbSn 2 


Bi 5 Tl 3 









PbTlo 12 


Cr 0 ,Ti 0 3 V 0 6 


PbTI 0075 











Cubic, fx. 



Cubic, b.c. 



Hexagonal, close packed 



Cubic, f.c. 


White Sn 

Tetragonal, b.c. 



Tetragonal, b.c. (f.c. cell 

usually used) 










Cubic, b.c. 



"/?-W" (W0 3 ) 

Cubic fc 













B8 2 

Ni 2 In 

























Cubic, f.c. 




B / 





Tetragonal, b.c. 








CaF 2 

Cubic, f.c. 



Cubic, f.c. 


FeS 2 



Cdl 2 

. Trigonal 


MoSi 2 

Tetragonal, b.c. 


CaSi 2 



MgZn 2 



Cu 2 Mg 

Cubic, f.c. 

*See "Handbook of Lattice Spacing and Structures of Metals", W.B. 


"St k 
tur ic 



Tetragonal, b.c. 


FeS 2 








^^or om ic 


Ttra °T b 



c e .. 8 °j. na ' °' 


Na As 



Ni 3 Sn 


DO 20 



D0 22 

TiAl 3 



Ni 3 P 

Tetragonal, b.c. 

Dl 3 

Al 4 Ba 

Tetragonal, b.c. 


PtSn 4 



CaB 6 


D2 e 

MnU 6 

Tetragonal, b.c. 


CaZn 5 


D5 2 

La 2 0 3 


D5 8 

Sb 2 S 3 


D7 3 

Th 3 P 4 

Cubic, b.c. 

D7 t 

Ta 3 B 4 



Fe 3 Zn,„ 

Cubic, b.c. 

D8 2 

Cu 5 Zn 8 

Cubic, b.c. 

D8 3 

Cu 9 Al 4 


D8 S 

Mn 5 Si 3 






Mo 2 B 5 


D10 2 

Fe 3 Th 7 



CaTi0 3 


E9 3 

Fe 3 W 3 C 

Cubic, f.c. 

Ll 0 



Ll 2 

Cu 3 Au 


L' 26 

ThH 2 

Tetragonal, b.c. 

L' 3 

Fe 2 N 


n. Vol. I. Pergamon Press, 1958. p. 79. and Vol. II, Pergamon Press, 1967, p. 3. 


Ileal Temperatures, H,, , H,, , H« 3 , and the TeJRnre of FWd Observations, T.t, 


t jl1 

H tl , kg 



T ~ 2 * 




0.0039 max. 


Bi 0 5Cd 0 ,Pb 0 j 7 Sn 0 ,j 

Bi 0 .5«Pbo.4« 


0.122 max. 



Bi,. 5 «A 




Bi 0 .j3Pbo.3jSn 0 . 14 
Bi,.„.„Sn 0 . 0 .o, 

C,K (excess K) 




0.730 (H||c) 




CNb M ° 0 '" 

12.5-13 5 

0 087 

98 5 








(by weight) 
Cd„. 05 Hgo.„ 

Cr 0 ,„Ti„ 30 V.. 6 „ 




GaSb (annealed) 

GaV, „ 








GaV 45 












Hgo..o,Pb 0 .„, 
In 0 9«Pb 0 02 
K 9»Pboo4 
In, „Pb 0 o« 
Ino9i 3 Pboo«7 






In 0 316 Pb„ 6.4 
In 0 nPb 0 »3 




In, oooTe, 002 


In 0 9S T1„ 05 
In 0 90TI0 10 


In 0 .3TI0 11 
In 0 tjTIo 25 







La 3 S 4 
La 3 Se 4 


1 25 

~0 2 5 









MO-o- 5 Tc-o, 


Mo 0 . 1(i Ti„., 4 








Mo,,., 3 U 0 ,-o.t 



Moo,,Zr„, 3 


N„2.. .,.»Nb 




NNb (wires) 






No93Nb 0 , 5 Zr 0 . 15 




> 130 


Na 0 0(6 Pb„ „4 



Na 0 oi 6 Pbo9.4 

%«/o denotes weight percent. 



Compiled by Dr. Brian Randall Pamplin 

The term "semiconductor" is applied to a material in which electric current is carried by electrons or holes 
aJd wtose eleS wnductivUy when extremely pure rises exponentially with temperature and may be 
leased Tfrom ta tow "intrinsic" value by many orders of magnitude by "doping" with electncaUy active 
impurities , , ■ hv an enerKy gap m the allowed energies of electrons in the material 

"SSS^^XSd "l^Z^t^iUr kaown ^conduc^ -hil. T.bU ...