Skip to main content

Full text of "USPTO Patents Application 08479810"

See other formats


REMARKS 



This paper contains corrections of inadvertent errors in Applicants' Fifth 
Supplementary Amendment submitted March 1, 2004, in response to the Office Action 
dated February 4, 2000. This is based on a review of Applicants' record copy of this 
Amendment. 

Attachment 21 of the Fifth Supplementary Amendment submitted on March 1, 
2004 did not contain all pages it was intended to contain. In attachment A hereto there 
are the missing pages that should be added to Attachment 21 of the Fifth 
Supplementary Amendment submitted on March 1,2004. 

Attachment 36 of the Fifth Supplementary Amendment submitted on March 1, 
2004 is empty. Attachment B hereto contains what was intended to be contained in 
Attachment 36 of the Fifth Supplementary Amendment. 

In line 8 of page 100 and in the second last line of page 101 of the Fifth 
Supplementary Amendment submitted on March 1 , 2004 after "See Attachment A of 
Applicants response dated May 14, 1998" there appears "[Attachment 23]." 
Attachment 23 of the Fifth Supplemental Amendment dated March 4, 2004, does not 
contain Applicants 1 response dated May 14, 1998 but only Attachment A thereto. 

In line 9 of page 100 and in the last line of page 101 of the Fifth Supplementary 
Amendment submitted on March 1, 2004 after "See Attachment H of Applicant's 
response dated November 28, 1997" there appears "[Attachment 24]." Attachment 24 
of the Firth Supplemental Amendment dated March 4, 2004 does not contain 
Applicants 1 response dated November 28, 1997 but only Attachment H thereto. 

At page 118, four lines from the bottom, after "Poole article [Attachment 21]", it 
should correctly read "Poole article [Attachment 22]." 



Serial No.: 08/479,810 



Page 2 of 3 



Docket: YO987-074BZ 



At page 172, 9 lines up from the bottom, "Poole Book [Attachment 21]" should 
correctly read "Poole Book [Attachment 31]." 



At page 166, at the end of the last line there should be "[Attachment 44]." 

At page 131, last two lines "[Attachment 42]" should correctly read "[Attachment 

44]." 

At page 173, second line of the last paragraph refers to "Attachment A of their 
response of December 1 1 , 1998." This is Attachment 29 of the Sixth Supplemental 
Amendment dated March 1 , 2004. 

At page 173, fourth line from the last paragraph states "in Attachment 43 of this 
response there are listed 4 United States Patents with the term "rare earth like" or 
similar terms in the claims." Attachment 43 does not contain this information. This 
information is in as Attachment B of the Amendment submitted on November 28, 1997. 

Please charge any fee necessary to enter this paper and any previous paper to 
deposit account 09-0468. 




Reg. No. 32,053 
(914) 945-3217 



IBM CORPORATION 



Intellectual Property Law Dept. 
P.O. Box 218 

Yorktown Heights, New York 10598 



Serial No.: 08/479,810 



Page 3 of 3 



Docket: YO987-074BZ 




ATTACHMENT A 



COPPER OXIDE 
SUPERCONDUCTORS 



Charles P. Poole, Jr. 
Timir Datta 
Horacio A. Farach 

with help from 

M. M. Rigney 
C. R. Sanders 

Department of Physics and Astronomy 
University of South Carolina 
Columbia. South Carolina 



WILEY 

A Wiley-Interscience Publication 
JOHN WILEY & SONS 

New York • Chichester • Brisbane • Toronto • Singapore 



] 



Copyright © 1988 by John Wiley & Sons, Inc. 

All rights reserved. Published simultaneously in Canada. 

Reproduction or translation of any pan of this work 
beyond that permitted by Section 107 or 108 of the 
1976 United States Copyright Act without the permission 
of the copyright owner is unlawful. Requests for 
permission or further information should be addressed to 
the Permissions Department, John Wiley & Sons, Inc. 

Library of Congress Cataloging in Publication Data: 

Poole. Charles P. 
Copper oxide superconductors / Charles P. Poole. Jr.. Timir Dana 
and Horacio A. Farach: with help from M. M. Rignev and C R. Sanders 
P- cm. 

"A Wilcy-Intcrscicncc publication." 
Bibliography: p. 
Includes index. 

I. Copper oxide superconductors. I. Dana. Timir. II. Farach 
Horacio A. III. Title. 

QC611.98.C64P66 1988 
539.6 '23-dc 19 88-18569 CIP 
ISBN 0-471-62342-3 

Printed in the United States of America 

10 98765432 1 



2_ 



PREPARATION AND 

CHARACTERIZATION OF SAMPLES 



A. INTRODUCTION 

Copper oxide superconductors with a purity sufficient to exhibit zero resistivity 
or to demonstrate levitation (Early) are not difficult to synthesize. We believe 
that this is at least partially responsible for the explosive worldwide growth in 
these materials. Nevertheless, it should be emphasized that the preparation of 
these samples does involve some risks since the procedures are carried out at 
quite high temperatures, often in oxygen atmospheres. In addition, some of the 
chemicals are toxic, and in the case of thallium compounds the degree of toxicity 
is extremely high so ingestion, inhalation, and contact with the skin must be 
prevented. 

The superconducting properties of the copper oxide compounds are quite 
sensitive to the method of preparation and annealing. Multiphase samples con- 
taining fractions with T c above liquid nitrogen temperature (Monec) can be syn- 
thesized using rather crude techniques, but really high-grade single-phase speci- 
mens require careful attention to such factors as temperature control, oxygen 
content of the surrounding gas, annealing cycles, grain sizes, and pelletizing 
procedures. The ratio of cations in the final sample is important, but even more 
critical and more difficult to control is the oxygen content. However, in the case 
of the Bi- and Tl-based compounds, the superconducting properties are less sen- 
sitive to the oxygen content. 

Figure V-l illustrates how preparation conditions can influence supercon- 
ducting properties. It shows how the calcination temperature, the annealing 
time, and the quenching conditions affect the resistivity drop at T c of a BiSrCa- 
CuO pellet, a related copper-enriched specimen, and an aluminum-doped coun- 

59 



60 



PREPARATION AND CHARACTERIZATION OF SAMPLES 

300, _ 



1 200- 



o 

a 

05 



100 




100 



T(K) 



200 



300 



Fig. V-l. Effects of heat treatments on the resistivity transition of BiSrCaCuO? 6 (a) 
calcined at 860°C, (b) calcined at 885°C, (c) calcined at 901°C, (d) aluminum-doped 
sample calcined at 875°C, prolonged annealing, (e) copper-rich sample calcined at 
860°C, (/) aluminum-doped sample calcined at 885°C, slow quenching and (g) calcined 
at 885°C, prolonged annealing, and slow quenching (Chuz5). 



terpart (ChuzS). These samples were all calcined and annealed in the same tem- 
perature range and air-quenched to room temperature. 

Polycrystalline samples are the easiest to prepare, and much of the early work 
was carried out with them. Of greater significance is work carried out with thin 
films and single crystals, and these require more specialized preparation tech- 
niques. More and more of the recent work has been done with such samples. 

Many authors have provided sample preparation information, and others 
have detailed heat treatments and oxygen control. Some representative tech- 
niques will be discussed. 

The beginning of this chapter will treat methods of preparing bulk supercon- 
ducting samples in general, and then samples of special types such as thin films 
and single crystals. The remainder of the chapter will discuss ways of checking 
the composition and quality of the samples. The thermodynamic or subsolidus 
phase diagram of the ternary Y-Ba-Cu oxide system illustrated in Fig. V-2 con- 
tains several stable stoichiometric compounds such as the end-point oxides 
Y 2 0 3 , BaO, and CuO at the apices, the binary oxides stable at 950°, (Ba 3 Cu0 4 ) 
Ba 2 Cu0 3 , BaCu0 2 , Y 2 Cu 2 0 5 , Y 4 Ba 3 0 9 , Y 2 Ba0 4 , and (Y 2 Ba 4 O v ), along the 
edges, and ternary oxides such as ( YBa 3 Cu 2 0 7 ), the semiconducting green phase 
Y 2 BaCuO s , and the superconducting black solid YBa 2 Cu 3 0 7 - 5 in the interior 
(Beye2, Bour3, Capol, EagU, Frase, Hosoy, Jonel, Kaise, Kurth, Kuzzz, 
Leez3, Lianl, Malil, Schni, Schnl, Schul, Takay, Torra, Wagne). Compounds 
in parentheses are not on the figure, but are reported by other workers. The 
existence of a narrow range of solid solution was reported (Panso), and then 
argued against (Wagne) by the same group. 



Fig. V-2. Terna 
phase [Y 2 BaCuC 
other compound: 



B. METHODS 

In this section t 
state, the copre 
solid-state techi 
superconductoi 
cal processes in 
superconductoi 
atomic scale an 
and some famil 
more competen 
In the solid-: 
of the desired o 
Sr, Tl, Y, or ot 
oxides in nitric 



METHODS OF PREPARATION 61 



CuO 



iSrCaCu0 7 - 6 {a) 
luminum-doped 
iple calcined at 
and (g) calcined 



the same tern- 

the early work 
1 out with thin 
paration tech- 
ich samples, 
n, and others 
entative tech- 

>ulk supercon- 
h as thin films 
ys of checking 
or subsolidus 
Fig. V-2 con- 
1-point oxides 
0 ,(Ba 3 Cu04), 
) 7 ), along the 
tg green phase 
n the interior 
urth, Kuzzz, 
). Compounds 
workers. The 
so), and then 



BaO 




2 Cu 2 O s 



Ba 3 Y 4 0 9 BaY 2 0 4 



Compound 


Slowly cooled 
to room temperature 


123- 


YBa 2 Cu 3 0 6 5 + i 


o 7 


143 


YBa4Cu 3 0 8 5 + 6 


o 9 


385 


- Y 3 BaeCu 5 Oi7.5+6 


o 18 


152 


- YBa 5 Cu 2 0 85+ 6 


o 9 


211- 


Y 2 BaCuO s 






Ba 2 Cu0 3+i 


o 33 



Fig. V-2. Ternary phase diagram of the Y 2 0 3 -BaO-CuO system at 950°C. The green 
phase [Y 2 BaCuO s , (211)] the superconducting phase [YBa 2 Cuj0 7 .6, (123)], and three 
other compounds are shown in the interior of the diagram (DeLee). 



B. METHODS OF PREPARATION 

In this section three methods of preparation will be described, namely, the solid 
state, the coprecipitation, and the sol-gel techniques (Hatfi). The widely used 
solid-state technique permits off-the-shelf chemicals to be directly calcined tnto 
superconductors, and it requires little familiarity with the subtle physicochemi- 
cal processes involved in the transformation of a mixture of compounds into a 
superconductor. The coprecipitation technique mixes the constituents on an 
atomic scale and forms fine powders, but it requires careful control of the pH 
and some familiarity with analytical chemistry. The sol-gel procedure requires 
more competence in analytical procedures. 

In the solid-state reaction technique one starts with oxygen-rich compounds 
of the desired components such as oxides, nitrates, or carbonates of Ba, Bi, La, 
Sr, Tl, Y, or other elements. Sometimes nitrates are formed first by dissolving 
oxides in nitric acid and decomposing the solution at 500°C before calcination 



62 PREPARATION AND CHARACTERIZATION OF SAMPLES 

(e.g., Davis, Holla, Kelle). These compounds are mixed in the desired atomic 
ratios and ground to a fine powder to facilitate the calcination process. Then 
these room-temperature-stable salts are reacted by calcining for an extended pe- 
riod ( * 20 hr) at elevated temperatures ( * 900°C). This process may be repeated 
several times, with pulverizing and mixing of the partially calcined material at 
each step. As the reaction proceeds, the color of the charge changes. The process 
usually ends with a final oxygen anneal followed by a slow cool down to room 
temperature of the powder, or pellets made from the powder, by sintering in a 
cold or hot press. Sintering is not essential for the chemical process, but for 
transport and other measurements it is convenient to have the material pellet- 
ized. A number of researchers have provided information on this solid-state re- 
action approach (e.g., Allge, Finez, Galla, Garla, Gopal, Gubse, Hajkl, Hatan, 
Herrm, Hikal, Hirab, Jayar, Maenl, Moodl, Mood2, Neume, Poepp, Polle' 
Qadri, Rhyne, Ruzic, Saito, Saitl, Sawal, Shamo, Takit, Tothz, Wuzz3). 

Some of the earlier works on foils, thick films, wires, or coatings employed a 
suspension of the calcined powder in a suitable organic binder, and the desired 
product was obtained by conventional industrial processes such as extruding, 
spraying, or coating. 

In the second or coprecipitation process the starting materials for calcination 
are produced by precipitating them together from solution (e.g., Asela, Bedno, 
Leez7, Wang2). This has the advantage of mixing the constituents on an atomic 
scale. In addition the precipitates may form fine powders whose uniformity can 
be controlled, which can eliminate some of the labor. Once the precipitate has 
been dried, calcining can begin as in the solid-state reaction procedure. A disad- 
vantage of this method, at least as far as the average physicist or materials scien- 
tist is concerned, is that it requires considerable skill in chemical procedures. 

Another procedure for obtaining the start-up powder is the sol-gel technique 
in which an aqueous solution containing the proper ratios of Ba, Cu, and Y 
nitrates is emulsified in an organic phase and the resulting droplets are gelled by 
the addition of a high-molecular-weight primary amine which extracts the nitric 
acid. This process was initially applied to the La materials, but has been per- 
fected for YBaCuO as well (Cimaz, Hatfi). 

When using commercial chemical supplies to facilitate the calcination pro- 
cess a dry or wet (acetone) pregrinding with an agate mortar and pestle or a ball 
mill is recommended. Gravimetric amounts of the powdered precursor materials 
are thoroughly mixed and placed in a platinum or ceramic crucible. Care must 
be taken to ensure the compatibility of the ceramic crucible with the chemicals to 
obviate reaction and corrosion problems. 

Complete recipes for the YBa* material have been described (e.g., Gran2). 
Typically, the mixture of unreacted oxides is calcined in air or oxygen around 
900°C for 15 hr. During this time the YBaCuO mixture changes color from the 
green Y 2 BaCuO s phase to the dark gray YBa 2 Cu 3 0 7 . 5 compound. Then the 
charge is taken out, crushed, and scanned with X rays to determine its purity If 
warranted by the powder pattern X-ray scan, the calcination process is repeated. 
Often, at this stage the material is very oxygen poor, and electrically it is semi- 



is 

I 

H 

3? 



conducting o 
sintered for s 
at «3°C/mii 
perature is ir 
conductor ph 
quenching. 1 
sand blasting 
another oxyg 
serve the sup 
An examf 
metric amou: 
ing them in 3 
dures several 
same tempei 
shows the el 
curve. 

WARNING: 

precautions i 
the high-qua 
ides in air a\ 
powdered, a. 
utes in flow, 
perature (Sh 
Allen He) 
motion on t 
Pharmacol 
antidote fer, 
cusses cases 



C. ADDITl 

This sectior 
the prepara 

In one e: 
were calcin* 
compressio 
(Graha). T 
1100°C. Sh 
for YBa* a 
distinct fro 

Anothei 
or Yb, Ba : 
tained sub 



ADDITIONAL COMMENTS ON PREPARATION 



;ired atomic 
>cess. Then 
xtended pe- 
be repeated 
material at 
The process 
wn to room 
ntering in a 
ess, but for 
erial pellet- 
lid-state re- 
jkl, Hatan, 
>epp, Polle, 
Vuzz3). 
employed a 
the desired 
; extruding, 

calcination 
.ela, Bedno, 
n an atomic 
formity can 
cipitate has 
re. A disad- 
erials scien- 
rocedures. 
-1 technique 
Cu, and Y 
ire gelled by 
:ts the nitric 
is been per- 

ination pro- 
stle or a ball 
or materials 
: . Care must 
chemicals to 

.g., Gran2). 
,rgen around 

lor from the 
d. Then the 

its purity. If 
. is repeated. 

ly it is semi- 



conducting or even nonconducting. After peptizing at > 10* ps. the Pdtetw 
sintered for several hours at =900°C in flowing oxygen and then slowly cooled 
at -rcLn down to room temperature. Slow cooling from the elevated tem- 
perature is important for producing the low-temperature orthorhombic super- 
conductor phase. The tetragonal nonsuperconducting phase may be obtained by 
q uenching P The pellet may be used as is or it may be cut into su.tab.e sizes by 
^d blasLg, with a diamond saw, or with an arc. After vigorous machimng 
another oxygen anneal (450°C, 1 hr, slow cool down) is often required to pre- 
serve the superconducting properties. _ 

In example of preparing a Bi-based superconductor involves mixing grav,- 
JSc amounts of higS-purity Bi 2 0 3 , SrC0 3 , CaC0 3 , and CuO powders, calcin- 
ing hem in air at 750-890°C, regrinding them, and then repeating these proce . 
dures several times. Then pellets of the calcined prod uct were 
same temperature and quenched to room temperature (ChuzS). Figure V 1 
sh^sTe effect of sample treatment on the resistance versus temperature 



curve. 



WARNING: As was mentioned above, thallium is a toxic material and proper 
precautions must be taken when working with it. It is useful to start by preparing 
Z hlh-auality precursor compound BaCu 3 0< or Wjj 
ides in air at 925°C for 24 hr. Then appropriate amounts ofTlfij are added, 
powdered, and pelleLd. The pellet is then heated to 880-910°C for a few mm- 
7es in flowing oxygen, and at the onset of melting it is auenched to room tern- 

^HerZL has suggested consulting the following references „ 
motion on thallium poisoning and antidotes thereto: H Heydlanf. Euro , J. 

Pharmacol. , 340 (l 969, which _ ^^77^^- 
antidote ferric cyanoferrate, and Int. J. Pharmacol, iu. if y 
cusses cases of thallium intoxication treated with Prussian Blue. 



C. ADDITIONAL COMMENTS ON PREPARATION 

This section will treat some additional methods which have been employed for 

were calcined for 2 hr at 825°C, pressed into pellets and then subjected to shock 
compression of =20 GPa at an estimated peak temperature of -1000 C 
GXT The best superconductivity was observed after 1 hr of air ^expo^re 
1100°C. Shock compression fabrication has also been reported (Murrz Mur 1) 
for YBa* and other rare-earth derivatives. This process produced monoliths, 
distinct from the usual composites. 

Another technique involved the formation of a precursor alloy of Eu, Ba Ui 
or Yb Ba Cu by rapid solidification, with the superconducting materials ob- 
tained subsequently by oxidation (Halda). A novel method involved preparing 



64 PREPARATION AND CHARACTERIZATION OF SAMPLES 

the superconductors from molten Ba-Cu oxides and solid rare-earth-containing 
materials. In principle this process may be better controlled and complicated 
shapes can be molded or cast (Herma). 

Pulsed current densities of 300-400 A /cm 2 with rise times of 0.6 ^sec at room 
temperature were used to convert the weakly semiconducting phase of YBaCuO 
to the stable metallic phase (Djure, Djurl). 

A claim was made that thermal cycling from cryogenic temperatures to 240 K 
raised the T c of YBa* and YBaCuO-F (with some F substituting for O) to 159 K. 
Cycling above 140 K lowered T c . This cycling process could possibly change the 
density of twins and thereby enhance J c . 

A freeze-drying technique was reported as producing sintered materials ho- 
mogeneous in composition and small in porosity (Stras). The low-temperature 
firing of oxalates (T < 780°C) has also been reported as producing a homogene- 
ous material of small grain size (Manth). 

Both Bi and Pb act as fluxes during the sintering process (Kilco). Bismuth 
substitution appears to reduce the normal state resistivity by about an order of 
magnitude without affecting the superconducting properties. 

A convenient method of separating the superconducting particles from a pow- 
dered mixture using magnetic levitation has been reported (Barso). This may be 
used to select the superconducting fraction after each calcination process. 

D. FILMS 

The new ceramic oxide superconductors presently lack mechanical properties 
such as ductility which are needed for high-current applications like magnet wire 
fabrication (Jinzz-Jinz3) and power transmission. To circumvent some of these 
deficiencies for microelectronic applications one can prepare thin films on suit- 
able substrates. Some devices such as Josephson junctions require thin super- 
conducting films. Many workers have discussed the preparation and properties 
of LaSrCuO- (e.g., Adach, Delim, Kawas, Koinu, Matsu, Nagat, Naito, Teral) 
and YBaCuO- (e.g., Burbi, Charz, Evett, Gurvi, Hause, Hongz, Inamz, Kwozz, 
Kwozl, Manki, Scheu, Somek, Wuzz4) type films. 

Almost every conceivable thin-film deposition technique such as electron 
beam evaporation, molecular beam epitaxy, sputtering, magnetron, laser abla- 
tion, screening, and spraying has been tried with the copper oxide system. Some 
of these techniques require expensive, elaborate apparatus, although descrip- 
tions of simple thin-film deposition systems are also available (e.g., see Koinl). 
Some representative examples of deposition procedures will be discussed. 

Epitaxial films of YBa 2 Cu 3 0 7 . 6 on (100) SrTi0 3 were produced using three 
separate electron beam sources (e.g., Chaud, Chaul, Laibo). The deposition 
was done in lO^-lO" 3 torr 0 2 with a substrate temperature of 400°C. The de- 
posited films were atomically amorphous with a broad X-ray peak. The epitaxial 
ordering was achieved upon annealing in 0 2 at 900°C with the orthorhombic c 
axis essentially perpendicular to the plane. 



FILMS 65 



rth-containing 
d complicated 

,6/isecatroom 
tse of YBaCuO 

atures to 240 K 
or 0)tol59K. 
ibly change the 

i materials ho- 
w-temperature 
ig a homogene- 

:ilco). Bismuth 
out an order of 

rles from a pow- 
o). This may be 
>n process. 



nical properties 
ike magnet wire 
it some of these 
in films on suit- 
uire thin super- 
i and properties 
t, Naito, Teral) 
Inamz, Kwozz, 

uch as electron 
tron, laser abla- 
ie system. Some 
though descrip- 
; .g., see Koinl). 

discussed, 
iced using three 

The deposition 

400° C. The de- 
ik. The epitaxial 

orthorhombic c 



i 



High-quality superconducting films were obtained using a multiple electron 
beam to evaporate metallic sources in a flow of molecular oxygen at 4-5 X 10 
torr (Hammo, Ohzzz). The deposition .ate ^ was 10 "^"^J^ 
ited film in oxygen it was heated for 3-6 hr m a flow of oxygen at 650 C, raised to 
7S0-C for 1 hr then to 850°C for 1 hr, and finally slowly cooled down in the 

^'superconducting films were prepared using a double ion beam sputtering ar- 
ranged nt (Madak). The target beam was Ar at 40 m A and the substrate beam 
was Ar or an Ar-0 2 mixture at 10-500 eV and 2 m A. The base pressure was 5 X 
To-' torr and, with the gas, 4 X 10- torr. The best substrate materials such as 
ZrO,-9% Y 2 0 3 did not appreciably interact, diffuse, or change the deposited 
fi m The films were - 1 M m thick and were rendered superconducting by oxy- 
gen annealing. Zero resistance was attained at 88 K. The »P^ ndw ^«^- 
erties depended upon the ion beam energy, substrate temperature annealing 
conditions, composition, and the extent of poisoning froir -thesubstr ate 

Films of dysprosium barium copper oxide were grown (Webbz) by molecu ar 
beam epitaxy (MBE) using a Varian 360 MBE system and the nucleate pro- 
cess was monitored by reflection high-energy electron diffraction (RHEED). The 
copper was incompletely oxidized in metallic microcrystals growing in a sea of 
amorphous Ba and Dy. After deposition superconducting films were obtained by 
hieh-temperature oxygen annealing. . , . „u 

Films of Y, ,Ba, 5 Cu 3 0 6 4 approximately 3300 A thick with a surface rough- 
n!s IT 00 A were prepared (Dijkk, Inamz, Wuzz4). These films were depo, 
ited on SrTi0 3 , sapphire, and vitron carbon by evaporation fron, J* ȣǪ k 
pellet of YBaCuO 1 cm diameter and 0.2 cm thick at a pressure of 5 X 10 torr. 
The evaporation was produced by several thousand pulses of laser irradiation (3- 
Thz ~ 30 nsec width, 1 J/pulse, 2 W). For best results the substrate was 
hea^To^C. As deposited thin films were we,, bonded to the ^stra^and 
they appeared shiny dark brown and were electrically insulating. The films were 
oxygen annealed at 900°C for 1 hr and then slowly cooled over a period of several 
hours. Standard four-probe resistivity measurements indicated the onset of su- 
perconductivity around 95 K and, for a (100) SrTi0 3 substrate with zero resis- 
tivity achieved near 85 K. The laser ablation technique was also employed for 
LaSr* (Moorj) and YBa* (Naral). _ 

Films were obtained from sandwiched multilayers by depositing Y 2 0 3 , BaO 
and Cu in layers (Nasta, Tsaur) on Zr0 2 , MgO, and sapphire substrates ; at 
200°C and 10" 5 torr. Oxygen treatment for 1-2 hr at ~850°C permitted the 
layers to diffuse, homogenize, and oxygenate, and thereby form the supercon- 
ducting compound (Baozz). Films on Ni have also been reported ,n which super- 
conductivity was obtained by a diffusion process involving the Cu substrate, 
Y 2 0 3 , and BaC0 3 composite (Tachi). 

Some 5000- A thick films of YBaCuO have been deposited using an ultrahigh 
vacuum dc-magnetron getter-sputter deposition system. The deposition rate 
was 0.2 A/sec, the substrate temperature was 1050°C, and the target-to-sub- 
strate distance was 12 cm. The scattering was done in an Ar-O z atmosphere. 



PREPARATION AND CHARACTERIZATION OF SAMPLES 



The X-ray and electron microscope examinations indicated some variation 
among the substrates arranged on the heater. Inhomogeneities were observed 
even within the film made on a single substrate. As deposited the films were 
oxygen deficient, and annealing produced suitable compositions. The reversible 
oxygen incorporation was monitored by the systematic splitting of the strongest 
X-ray peaks. The oxygen diffusion coefficient at 600°C was lO" 15 rnVsec and the 
activation energies for desorption and absorption were 1.1 and 1.7 eV, respec- 
tively. The highest onset temperature was 99 K with complete superconduction 
at 40 K. Exposure to water inhibited the superconductor (Barns, Kishi Yanzz) 
A device structure with a Y 2 0 3 barrier has also been studied (Blami) ' 

Another work showed that films produced by dc magnetron sputtering are 
copper deficient if the substrate-to-target distance is large or if the substrate is at 
an elevated temperature (Leez5). 

Superconducting YBaCuO thin films with a large surface area ( = 5 cm X 
5 cm) were grown on A1 2 0 3 , sapphire, and MgO up to a 500°C substrate temper- 
ature by magnetron and diode techniques. Rutherford back scattering (RBS) 
indicated a uniform composition across magnetron-deposited film areas with di- 
ameters up to 5 cm, and the diode film composition homogeneity was even bet- 
ter, but over a smaller area (~2.5 cm diameter). The as-deposited films were 
annealed m oxygen at different temperatures and exposure times. Prolonged 
high-temperature annealing (>850°C) increased the impurity phase. The high- 
est T e films had a wide range of composition, with the maximum T c film copper 
rich. On the basis of an in-situ resistivity study of YBa* thin films a rapid heat- 
ing to about 900°C in flowing helium followed by slow cool down in flowing oxy- 
gen was recommended (David). 

The post-deposition anneal cycle was avoided by producing the films in a 
high-pressure reactive evaporation process involving rapid thermal annealing 
(Latnr). Smooth films were obtained on zirconia and SrTi0 3 substrates. Screen 
printing of oxide superconducting films is also possible (Budha, Fuzzl) and 
simple spray deposition has been reported (Gupta). Films have also been made 
by coating and spinning off the solutions. Aqueous and aqueous-alcoholic 
mixed solutions of the metal nitrates (Coop2), metal acetates in dilute acetic acid 
(Ricel), and sol-gels (Kraml) have all been reported. These processes are poten- 
tially important for commercial superconducting coatings on silicon (Kraml) 
on yttrium-stabilized zirconia (YSZ), on SrTi0 3 (Coop2, Gupta), and on MgO 
(Gupta, Ricel). 6 



E. SINGLE CRYSTALS 

The bulk properties of oxide superconductors are averages over components 
parallel and perpendicular to the Cu-O planes. In addition, for orthorhombic 
samples there is an averaging over properties that differ for the a and b direc- 
tions in this plane. This in-plane anisotropy is especially pronounced for the 
123 struc t"re in which the Cu-O-Cu-O chains lie along the b axis The 



best way to ui 
crystals. Unf. 
anisotropy ca 
twinning prol 
gle crystals. 

A number 
X-ray diffrac 
(e.g., Crabt, 
and micro- R; 
scribe how si 
Crystal Grow 
Millimetei 
oxide flux (1 
Taka4, Zhou 
contaminatic 
a hot press o 
(Satoz). 

Small sing 
der which wi 
sphere and t! 
ture also pro> 
melting a st< 
followed by 1 
A gold en 
(1 X 2 X 0.1 
was heated ii 
400°Cat25° 
on the surf a< 
the crucible 
A detailec 
crystal by th< 
1:3 and 2:5 
multistep tei 
found at the 
crucibles. P 
crucibles we 
ported. A si 
DyBa* as la 



F. ALIGN1 

Clearly higl 
of supercon 



ALIGNED GRAINS 67 



some variation 
; were observed 

the films were 
. The reversible 
of the strongest 

mVsec and the 
1.7 eV, respec- 
iiperconduction 

Kishi, Yanzz). 
lami). 

i sputtering are 
e substrate is at 

rea ( — 5 cm X 
bstrate temper- 
rattering (RBS) 
m areas with di- 
:y was even bet- 
uted films were 
mes. Prolonged 
hase. The high- 
i T c film copper 
as a rapid heat- 
i in flowing oxy- 

; the films in a 
rmal annealing 
:>strates. Screen 
la, Fuzzl), and 
also been made 
ieous-alcoholic 
ilute acetic acid 
esses are poten- 
ilicon (Kraml), 
0, and on MgO 



best way to understand these materials is through experiments on perfect single 
crystals. Unfortunately, untwinned YBa* crystals are not available so the a, b 
anisotropy cannot be resolved. Tetragonal superconductors should not have this 
twinning problem. In this work twinned monocrystals will be referred to as sin- 
gle crystals. 

A number of experiments have been carried out on monocrystals such as 
X-ray diffraction (e.g., Borde, Hazen, Lepag, Siegr, Onoda), magnetic studies 
(e.g., Crabt, Schnl, Worth), mechanical measurements (e.g., Cookz, Dinge), 
and micro-Raman spectroscopy (e.g., Hemle). In this section we will briefly de- 
scribe how such crystals are made. The December 1987 issue of the Journal of 
Crystal Growth was devoted to superconductors. 

Millimeter-size (La 1 . x Sr JC ) 2 Cu0 4 single crystals were grown in a molten copper 
oxide flux (Kawal). Another basic technique employs other fluxes (Haned, 
Taka4, Zhoul), namely, PbF 2 , B 2 0 3 , PbO, Pb0 2 , with the risk of possible Pb 
contamination. LaSr* crystals were also grown by the solid phase reaction using 
a hot press of pellets (Iwazu) and rapid quenching of a nonstoichiometric melt 
(Satoz). 

Small single crystals of YBa 2 Cu 3 0 7 _6 have been prepared from a sintered pow- 
der which was formed into a pellet and then heated, first in a reducing atmo- 
sphere and then in an oxidizing one at 925°C. Annealing a stoichiometric mix- 
ture also produced monocrystals (Liuzz). Millimeter-size crystals were grown by 
melting a stoichiometric mixture of YBa 2 Cu 3 0 7 .6 plus excess CuO at 1150°C 
followed by holding at 900°C for 4 days (Damen, see also Finel). 

A gold crucible on a gold or alumina sheet was used to obtain free-standing 
(1 X 2 X 0.1 mm) single crystals of YBa* (Kaise, Kaisl, Holtz). A charge of 2 g 
was heated in air at 200°C/hr and held at 975°C for 1.5 hr, then it was cooled to 
400°C at 25°C/hr. The molten charge creeps and forms single crystals and twins 
on the surfaces. The larger crystals formed in the space between the bottom of 
the crucible and the gold support sheet. 

A detailed account has appeared of the preparation of a 123 compound single 
crystal by the flux method (Zhoul). The flux mole ratio Ba0 2 : CuO was between 
1:3 and 2:5, and the nutrient Y 2 0 3 :Ba0 2 :CuO mole ratios were 0.5:2:3. A 
multistep temperature process was employed. Black single crystals of YBa* were 
found at the bottom and at the edge between the wall and the bottom of the 
crucibles. Platinum crucibles seemed to contaminate the samples so alumina 
crucibles were recommended. Crystals as large as 2 X 2 X 0.3 mm 3 were re- 
ported. A similar technique was used to produce single crystals of YBa* and 
DyBa* as large as 4 mm (Schnl). 



/er components 

T orthorhombic F. ALIGNED GRAINS 

; a and b direc- 

lounced for the Clearly high-quality single crystals are important for understanding the physics 

the b axis. The of superconductors. However, much useful information about anisotropics can 



68 PREPARATION AND CHARACTERIZATION OF SAMPLES 



be obtained by studying the properties of aligned grains, which are much easier 
to fabricate. 

A superconducting sample can be initially a collection of randomly oriented 
grains, but various techniques can be used to partially orient these grains so that 
the c ax.s lies preferentially in a particular direction. For example uniaxial com- 
pression tends to orient compacted grains, with compressed 90-/xm particles ex- 
hibiting more alignment than compressed 10- M m particles (Glowa). Epoxy- 
embedded grains have been aligned under the influence of an applied magnetic 
field and pressure (Arend). 

X-ray and magnetic measurements have been reported on aligned crystalline 
grains of YBa* (Farrl). Optical studies have also been made on aligned grains. 
The critical current density for samples cut parallel to the compression axis of 
such grains was nearly isotropic with respect to the direction of an applied mag- 
netic field, and it was a factor of 6 smaller than that for the samples cut perpen- 
dicular to this axis (Glowa). 



G. REACTIVITY 

The oxide superconductors are not inert materials, but rather they are sensitive 
to exposure to certain gases and to surface contact with particular materials. 
Great care must be exercised to avoid contamination from water vapor and car- 
bon d.oxide in the atmosphere. In addition these materials are catalytic to oxy- 
genation reactions, and these factors result in the occurrence of various chemical 
and other interactions, especially at elevated temperatures. The granular and 
porous nature of the materials has an accelerating effect on such reactions. 

Samples of YBaCuO may degrade in a matter of days when exposed to an 
ordinary ambient atmosphere; they react readily with liquid water, acids, and 
electrolytes, and moderately with basic solutions. The reaction with water 
(Barns, Kishi, Yanzz) produces nonsuperconducting cuprates. The effects of ac- 
etone and other organics (McAnd) have been determined, and stable carboxyl 
groups have been found in the YBaCuO lattice (Parmi). 

Hydrogen enters the YBaCuO lattice at elevated temperatures and forms a 
solid solution. Low concentrations have very little effect and high concentrations 
degrade the superconducting properties (Berni, Reill, Yang3). The effects of ex- 
posure to oxygen at elevated temperature and oxidation have been discussed sev- 
eral places m this review (e.g., Blend, Engle, Tara3). 

The foregoing evidence for the reactivity of the oxide superconductors makes 
it necessary to consider methods of passivation or protecting them from long- 
term degradation. An epoxy coating was found to provide some protection 
(Barns). Coating the surface with metals can be deleterious since metals such as 
Fe (Gaozl, Hillz, Weave) and Ti (Meyel) react with the surface of LaSrCuO or 
YBaCuO. There is evidence for the passivation of the surface of LaSr* with gold 
(Meyer). & 



H. THERM 

Thermograv 
pie during £ 
oxygen conti 
an oxidizing 
procedures < 
the method i 
John4, Leez 
ferential th( 
procedures. 



I. CHECKS 

After a samj 
conductor. 1 
mine whethi 
superconduc 
ity sample. . 
the magneti 
sharp, high 
— 1/4tt. Thi 
of the susce] 
the fraction 

In additic 
chemical coi 
tion is deduc 
material. CI 
XPS, electa 
probe that is 
investigator: 
tent is much 
back-scatter 
tents, and n 

The struc 
ily checked 
Constantsa, 
or orthorhoi 
indicate a g( 
for LaSr* (S 
used to com 



CHECKS ON QUALITY 69 



:h easier 

oriented 
s so that 
ial corn- 
icles ex- 
Epoxy- 
aagnetic 

ystalline 
i grains, 
i axis of 
ed mag- 
perpen- 



sensitive 
lateriais. 
and car- 
c to oxy- 
chemical 
ular and 
tions. 
;ed to an 
;ids, and 
th water 
cts of ac- 
carboxyl 

I forms a 
ntrations 
:cts of ex- 
issed sev- 
ers makes 
om long- 
rotection 
Is such as 
SrCuO or 
with gold 



H. THERMOGRAVIMETRIC ANALYSIS 

Thermogravimetric analysis (TGA) consists of monitoring the weight of a sam- 
ple during a heating or cooling cycle. For example, one might determine the 
oxygen content of a superconducting material by measuring its weight change in 
an oxidizing (0 2 or air) or reducing (e.g., 4% H 2 in Ar) atmosphere. Typical 
procedures consist of heating or cooling at 20°C/min. The relative accuracy of 
the method is about 0.005 (Ongzl). Many workers (e.g., Beye3, Hauck, Huanl, 
John4, Leez7, Maruc, Ohish, Ongzl, Tara7, Zhuzz) are now using TGA or dif- 
ferential thermal analysis (DTA) routinely during their sample preparation 
procedures. 



I. CHECKS ON QUALITY 

After a sample has been prepared it is necessary to check its quality as a super- 
conductor. Most investigators employ the four-probe resistivity check to deter- 
mine whether it superconducts, and at what temperature it transforms to the 
superconducting state. A sharp, high T c transition is an indicator of a high-qual- 
ity sample. Another widely used quality control method is the determination of 
the magnetic susceptibility of the specimen. Good quality is indicated by a 
sharp, high T c transition with both the flux exclusion and flux expulsion close to 
- 1/47T. This is, in a sense, a more fundamental check on quality since the value 
of the susceptibility far below the transition temperature is a good indicator of 
the fraction of the sample that is superconducting (see Section III-D) ; 

In addition to its superconducting properties, it is also of interest to know the 
chemical composition and the structure of the specimen. The nominal composi- 
tion is deduced from the relative proportions of the various cations in the starting 
material. Chemical analysis and some more sophisticated techniques such as 
XPS, electrospectroscopic chemical analysis (ESCA), and an electron micro- 
probe that is favorable for low-atomic-weight elements are applicable here. Most 
investigators only report the cation concentrations in the specimen. Oxygen con- 
tent is much more difficult to determine, but is important to know. Rutherford 
back-scattering experiments (Johnl, Wuzzl, Wuzz4) can provide oxygen con- 
tents, and metallography characterizes grain sizes. 

The structures of the oxide superconductors described in Chapter VI are eas- 
ily checked by the X-ray powder pattern method. Many articles list the lattice 
constants a, b y c of samples and mention whether they are tetragonal (a = b ± c) 
or orthorhombic (a ~ b c). Narrow lines and the absence of spurious signals 
indicate a good, single-phase sample. Typical X-ray diffraction powder patterns 
for LaSr* (Skelt) and YBa* presented in Figs. V-3 and V-4, respectively, may be 
used to compare with patterns obtained from freshly prepared samples. 



M 

1 

s 



•3 



70 PREPARATION AND CHARACTERIZATION OF SAMPLES 



J. RESIST 




ANGLE IDEG) 

Fig. V-3. Room-temperature (upper curve) and 24-K (lower curve) X-ray diffraction 
powder patterns of (Lao^sBa^shCuC^ (Skelt). 



A measure: 
temperatui 
becomes si 
sharp drop 
to apply a v 
such a two 
Most resisl 
described t 
method (K 
silver glazi: 
portance ol 
port Jc me; 

The spe< 
in a suitab: 
probe conf 
and out of 
between tw 
conducting 
with the cc 
ment volta 




2 9 (DEG) 

Fig. V-4. Room-temperature X-ray diffraction powder pattern of YBa 2 Cu 3 0 7 . (Provided 
by C. Almasan, J. Estrada, and W. E. Sharp.) 




RESISTIVITY MEASUREMENT 71 

J. RESISTIVITY MEASUREMENT 

A measurement of the resistance R(T) or resistivity p(T) of a material versus the 
temperature is the principal technique employed to determine when a material 
becomes superconducting. The transition temperature manifests itself by a 
sharp drop in resistivity to zero. The simplest way to make this measurement is 
to apply a voltage across the sample and measure the current flow through it, but 
such a two-probe method (Baszy) is not very satisfactory, and is seldom used. 
Most resistivity determinations are made with the four-probe technique to be 
described below, although more sophisticated arrangements such as a six-probe 
method (Kirsc) can also be used. The fabrication of low-resistance contacts by 
silver glazing has been reported (Vand2). These researchers pointed out the im- 
portance of a low-contact resistance (p < 10 /xfl/mm 2 at 77 K) for making trans- 
port Jq measurements. 

The specimen resistance as a function of temperature is generally determined 
in a suitable cryostat by attaching leads or electrodes to it in the standard four- 
probe configuration. Two leads or probes carry a known constant current / into 
and out of the specimen, and the other two leads measure the potential drop 
between two equipotential surfaces resulting from the current flow. For super- 
conducting specimens the leads are often arranged in a linear configuration, 
with the contacts for the input current on the ends, and those for the measure- 
ment voltage near the center. 



VI 



CRYSTALLOGRAPHIC STRUCTURES 



B. PEROVSK 

Much has bet 
perovskite type 
This will perm 
structures of tl 

1. Cubic Fom 

Above 200°C 
cubic, so the tl 
contains one f 
special positio 



A. INTRODUCTION 

To properly understand the mechanisms that bring about the superconducting 
state in particular materials it is necessary to know the structures of the com- 
pounds that exhibit this phenomenon. Single-crystal structure studies have been 
carried out to determine the dimensions of the unit cell, the locations of the 
atoms in this cell, electronic charge distributions, and the possible presence of 
atomic irregularities. Neutron powder diffraction has also provided much of the 
detailed structure information found in this chapter (e.g. , Antso, Beech, Cappo, 
Coxzz Dav.1, Dayzz, Greed, John4, Jorge, Jorgl, Paulz, Torar, Vakni, Yamag, 
Yanz2). More routine X-ray powder pattern measurements which can identify a 
known structure and provide the unit cell dimensions are useful for checking the 
quality of samples, as was explained in Section V-I. 

The numerical values of quantities such as lattice parameters and bond 
lengths show some variation in the literature, and many of our quoted values will 
be typical ones. Much of the quantitative structural information is organized in 
the tables. 

In the beginning of this chapter we will introduce the perovskite structure and 
indicate how it is related to the oxide superconductors. Then we will describe the 
21 structure of LaSrCuO and the 123 structure of YBaCuO, we will show how 
each is generated from a perovskite prototype, and we will clarify its layering 
scheme. The chapter will end with descriptions of the structures of the newer 
high-transition-temperature bismuth and thallium compounds. 

72 



where we have 
site which con 
atoms, and so 
0,0,^ for theo 
sponds to pla< 
center, and ar< 
on Fig. VM. 
nated and the 
stant or lengtl 
space group t; 

An alternal 
state texts an 



Fig. VM. Per 

edge-centered i 




PEROVSKITES 73 



B. PEROVSKITES 

Much has been written about the oxide superconductor compounds being 
perovskite types, so we will begin with a description of the perovskite structure. 
This will permit us to develop some of the notation to be used in describing the 
structures of the superconductors themselves. 

1. Cubic Form 

Above 200°C barium titanate crystallizes in the perovskite structure, which is 
cubic, so the three lattice parameters are all equal (i.e., a = b — c). The unit cell 
contains one formula unit BaTiC>3 and the atoms are located in the following 
special positions (Wyck2, p. 390): 



where we have employed the crystallographic notation (la) for an a-type lattice 
site which contains one atom, (3c) for a c-type lattice site which contains three 
atoms, and so on. Each atomic position is given by three coordinates, such as 
0,0,| for the oxygen located atx = 0,y = 0, z = 0.5a. This arrangement corre- 
sponds to placing a titanium atom on each apex, a barium atom in the body 
center, and an oxygen atom on the center of each edge of the cube, as illustrated 
on Fig. VI-1. We see from the figure that the barium atoms are 12-fold coordi- 
nated and the titaniums have sixfold (octahedral) coordination. The lattice con- 
stant or length of the unit cell is a = 4.0118 A at 201°C. The crystallographic 
space group is Pm3m, O x h . 

An alternate way to represent this structure, which is commonly used in solid- 
state texts and in crystallography monographs (e.g., Wyck2), is to locate the 



Ba (la) 

Ti (lb) 0,0,0 

O (3c) 0,0,£; 0,^,0; £,0,0 



(VI-1) 




Fig. VI-1. Perovskite cubic unit cell showing titanium on the apices and oxygen in the 
edge-centered positions. Barium, which is in the body center, is not shown. 



74 CRYSTALLOGRAPHIC STRUCTURES 



origin at the barium site; this places titanium in the center and the oxygens on 
the centers of the cube faces. The representation (Eq. VI-1) given above is more 
convenient for comparison with the structures of the oxide superconductors. 

The compound LaBaCu 2 0 5 was found to have a cubic perovskite subcell with 
the lattice parameter a = 3.917 A (Sishe). 



2. Tetragonal Form 

At room temperature barium titanate is tetragonal with the unit cell dimensions 
a - 3.9947 A and c = 4.0336 A , which is close to cubic. For this lower symme- 
try the oxygens are assigned to two different sites, a single site along the side 
edges and a twofold one at the top and bottom. The atomic positions (Wyck2 



Ba |,i0.488 

Ti 0,0,0 

0(1) 0,0,0.511 

0(2) 0,^-0.026; £,0,-0.026 



(VI-2) 



are shown in Fig. VI-2. The distortions from the ideal structure of Fig VI-1 are 
exaggerated on this sketch. We will see later that a similar distortion occurs in 
the YBaCuO structure. The cubic and tetragonal atom arrangements (VI-1) and 
(VI-2) are compared in Table VI-1, and we see from this table that the deviation 
from cubic symmetry is actually quite small. 

3. Orthorhombic Form 

When barium titanate is cooled below 5°C it undergoes a transition with a fur- 
ther lowering of the symmetry to the orthorhombic space group Amm2, C 2v , and 



TABLE VI-1 Comparison of Atom Positions of BaTiO, in Its Cubic, Tetragonal and 
Urthorhombic Forms" 



Group Atom 




Cubic and Tetragonal 

X y 



0 

2 

0 

0 
i 

2 

0 

2 

0 



Cubic 



Tetragonal 

z 



Orthorhombic 



1 
1 

1 

I 

2 
I 

2 

0 
0 
0 



1 

0.974 
0.974 
0.511 
0.488 
0 

-0.026 
-0.026 



1 
1 
1 

2 
1 

2 

0 
0 
0 



Fig. VI-2. Pei 



an enlargemen 
The enlarged ( 
shown on Fig. 
the factor y/2. 
5.682 = 4.018 
and the atomic 

Ba 
Ti 
0(1 
0(2 



where u = 0 f 
One should 
site with diffei 
of the atoms i 
0.490 and 0.5 
A compari: 
cubic to tetraj 
orthorhombic 
tions within x 

4. Atom Arrs 

The ionic rad 
together they 
smaller Ti 4+ i 
close-packed 
empty the latl 



PEROVSKITES 75 



; oxygens on 
bove is more 
nductors. 
subcell with 



1 dimensions 
)wer symme- 
ong the side 
ons (Wyck2, 



(VI-2) 



Fig. VI-1 are 
ion occurs in 
ts (VI-1) and 
the deviation 



>n with a fur- 
m2, C 2v , and 



tragonal and 

horhombic 

z 

1 
1 

1 

l 

2 
I 
2 

0 
0 
0 

z coordinates are 




Fig. VI-2. Perovskite tetragonal unit cell showing the puckering of the Ti-O layers. 



an enlargement of the unit cell to accommodate two formula units (BaTi0 3 ) 2 . 
The enlarged cell is rotated by 45° relative to the higher-temperature ones, as 
shown on Fig. VI-3, and therefore its a and b lattice parameters are larger by 
the factor >f2. The three lattice constants are a = 5.669 = 4.009VT A, b = 
5.682 = 4.018V2"A, and c — 3.990 A. There are no longer any special sites, 
and the atomic positions are (Wyck2, p. 405): 



Ba 
Ti 

O(l) 
0(2) 



(2a) 
(2b) 
(2a) 
(4e) 



u » 2 > 2 t 2 2 

0,w + i,0;^w,0 with u = 0.510 
0,w + i,|; \,u,\ with u = 0.490 
w,v+£,0; — i/,v+±,0; w + ^,v,0; — w + £,v,0 
with u = 0.253, v = 0.237 



(VI-3) 



where u ~ 0 for Ba. 

One should note that in Eq. (VI-3) Ba and O(l) are in the same (2a) type of 
site with different values of the parameter u. Figure VI-3 shows the coordinates 
of the atoms in the orthorhombic cell drawn using the approximation » j for 
0.490 and 0.510 and * \ for 0.253 and 0.237. 

A comparison of Eqs. VI-1 to VI-3 indicates that the transformation from 
cubic to tetragonal involves only shifts in the z coordinates of atoms, while the 
orthorhombic phrase differs from the cubic one only through shifts in atom posi- 
tions within x,y planes (see Table VI-1). 

4. Atom Arrangements 

The ionic radii of Ba 2 + (1.34 A) and O 2 " (1.32 A) are almost the same, and 
together they form a face-centered cubic (fee) close-packed lattice with the 
smaller Ti 4+ ions (0.68 A) located in octahedral holes. The octahedral holes of a 
close-packed oxygen lattice have a radius of 0.545 A, and if these holes were 
empty the lattice parameter would be a = 3.73, as shown on Fig. VI-4a. If each 



M 



E2 



76 CRYSTALLOGRAPHIC STRUCTURES 



Barium 



Z = 1/2 
Layer 



Z = 0 
Layer 




Oxygen 



Titanium (copper) 



Fig. VI-3. Atom positions of perovskite when the monomolecular tetragonal unit cell is 
expanded to the bimolecular orthorhombic cell with new axes at 45° with respect to the 
old ones. r 



titanium were to move the surrounding oxygens apart to its ionic radius when 

^T n l the h ° ,e ' 35 Sh ° w " 0n Fig - Vh4b ' the lattice Parameter a would be 
4.00 A. The observed cubic (a = 4.012 A) and tetragonal (a = 3.995 A c = 
4 034 A) lattice parameters are close to these values, indicating a pushing apart 
of the oxygens. The tetragonal distortion illustrated on Fig. VI-2 and the 
orthorhombic distortion of Eq. (VI-3) constitute attempts to achieve this 
through an enlarged but distorted octahedral site. This same mechanism is oper- 
ative in the oxide superconductors. 



Fig. VI-4. Th< 

dral hole and ( 
the hole. For e 
parameter is g 



C. BARIUM-LEAD-BISMUTH OXIDE 

In 1983 Mattheiss and Hamann referred to the 1975 "discovery by Sleight et al 
of high temperature superconductivity" of the compound BaPb, ,Bi 0 3 in the 
composition range 0.05 < x < 0.3 with T c up to 13 K (Matt?, Sleig). Many 
consider this system, which disproportionates 2 Bi 4+ Bi 3+ + Bi 5+ in going 
from the metallic to the semiconducting state, as a predecessor to the LaSrCuO 
system. 



Crystal s 
BaPb0 3 has 
and at roon 
6.136 = 4.3; 
0 = 90.17° ( 
and has wha 
4.35 A). Thi 
at room temj 
tetragonal t< 



BARIUM-LEAD-BISMUTH OXIDE 77 




a = 3.73 A 



>nal unit cell is 
i respect to the 



c radius when 
:er a would be 
3.995 A,c = 
pushing apart 
VI-2 and the 
o achieve this 
hanism is oper- 



1.52 A 



2.64 A 

_L 




a = 4.16 A 



Fig VI-4 The z = 0 plane of the perovskite unit cell showing (a) the size of the octahe- 
dral hole and (b) the pushing apart of the oxygens by the presence of a transition ,on in 
the hole. For each case the oxygen and hole sizes are indicated on the left and the lattice 
parameter is given on the right. 



by Sleight et al. 
b,^Bi x 0 3 »n the 
7, Sleig). Many 
-1- Bi 5+ in going 
to the LaSrCuO 



Crystal structure determinations indicate that the metallic compound 
BaPb0 3 has the cubic perovskite structure with a = 4.273 A (Wyck2, p. 390, 
and at room temperature semiconducting BaBiOj is monoclinic with a - 
6.136 = 4.339 VTA , b = 6.181 = 4.371 V2 A , c = 8.670 = 4.335 X 2 A , and 
0 = 90.17° (Coxzl, Coxz2). The latter is quite close to orthorhombic (0 - 90°), 
and has what might be called a pseudocubic perovskite lattice parameter (a - 
4.35 A). These two compounds form a solid solution series BaPb^BuOj which 
at room temperature changes as a function of increasing x from orthorhombic to 
tetragonal to orthorhombic to monoclinic. Superconductivity appears in the 



78 CRYSTALLOGRAPHIC STRUCTURES 



tetragonal phase, and the metal-to-insulator transition occurs at the tetragonal- 
to-orthorhombic phase boundary* = 0.35 (Matt7, Sleil). 



TABLE VI-2. 
Charge States" 

7 Eler 



D. PEROVSKITE-TYPE SUPERCONDUCTING STRUCTURES 

In their first report on high-temperature superconductors Bednorz and Miiller 
referred to their samples as "metallic, oxygen deficient . . . perovskite like 
mixed valent copper compounds." Subsequent work has confirmed that the new 
superconductors do indeed have these characteristics. In this section we will 
comment on their perovskite-like aspects. 

1. Atom Sizes 

In the oxide superconductors Cu replaces the Ti 4+ ions (0.68 A) of perovskite, 
and in most cases retains the Cu0 2 layering with two oxygens per copper in the 
layer. Other cationic replacements tend to be Bi, Ca, La, Sr, Tl, and Y for the 
larger Ba, forming "layers" containing only one oxygen or none per cation. We 
see from the following list of ionic radii 



Cu 2+ 


0.72 A 


Bi 5+ 


0.74 A 


Y 3 + 


0.94 A 


X ,3 + 


0.95 A 


Bi 3+ 


0.96 A 


Ca 2+ 


0.99 A 


Sr 2+ 


1.12 A 


La 3+ 


1.14 A 


Ba 2+ 


1.34 A 


O 2 " 


1.32 A 



(VI-4) 



that there are four size groups, with all other cations significantly smaller then 
the Ba of perovskite. The common feature of Cu0 2 layers that are planar or close 
to planar establishes a fairly uniform lattice size in the a,b plane. The parame- 
ters of the compounds LaSrCuO(a = b = 3.77 A), YBaCuO(a = 3 83 A b = 
3.89 A), BiSrCaCuO (a = b = 3.82 A), and TIBaCaCuO (a = b = 3.86 A) 
are all between the ideal fee oxygen lattice value of 3.73 A and the perovskite 
one of 4.01 A . 

Table VI-2 gives the ionic radii of the positively charged ions of various ele- 
ments of the periodic table. These radii are useful for estimating changes in lat- 
tice constant when ionic substitutions are made in existing structures. They also 
provide some insight into which types of substitutions will be most favorable 



3 
11 
19 

37 
55 



4 
12 
20 
38 
56 



5 
13 
31 
49 
81 



6 
14 

32 
50 
82 



15 
33 
51 
83 



16 
34 
52 



21 

22 
23 
24 
25 



tetragonal- 



and Miiller 
ovskite like 
that the new 
tion we will 



f perovskite, 
;opper in the 
L nd Y for the 
:r cation. We 



(VI-4) 



y smaller then 
planar or close 
. The parame- 
= 3.83 A,fe = 
b = 3.86 A) 
the perovskite 

of various ex- 
changes in lat- 
ares. They also 
)st favorable. 



TABLE VI-2. Ionic Radii in Angstroms of Selected Elements for Various Positive 
Charge States" 



3 
11 
19 

37 
55 



Element 



Li 
Na 
K 
Rb 

Cs 



+ 1 



+ 2 



+ 3 



Alkali 



0.68 
0.97 
1.33 
1.47 
1.67 



Alkaline earths 



4 


Be 


A A A 

U.44 


U.JO 


12 


Mg 


0.82 


u.oo 


20 


Ca 


1.18 


0.99 


38 


Sr 




1.12 


56 


Ba 












Group HI 


5 


B 


V.JO 


0.23 


13 


Al 




0.51 


31 


Ga 


0.81 


0.62 


49 


In 




0.81 


81 


TI 


1.47 


0.95 








Group IV 


6 


C 






14 


Si 


0.65 




32 


Ge 




0.73 


50 


Sn 




0.93 


82 


Pb 




1.20 








Group V 


15 


P 




0.44 


33 


As 




0.58 


51 


Sb 


0.89 


0.76 


83 


Bi 


0.98 


0.96 








Chalcogenides 


16 


S 






34 


Se 


0.66 




52 


Te 


0.82 





+4 



+5 



+ 6 



0.16 
0.42 
0.53 
0.71 
0.84 



0.35 
0^46 
0.62 
0.74 



0.37 
0.50 
0.70 



0.30 
0.42 
0.56 



First transition series (3d n ) 



21 


Sc 






0.81 




22 


Ti 


0.96 


0.94 


0.76 


0.68 


23 


V 




0.88 


0.74 


0.63 


24 


Cr 


0.81 


0.89 


0.63 




25 


Mn 




0.80 


0.66 


0.60 



0.59 



0.52 




39 


Y 






40 


Zr 


1.09 




41 


Nb 


1.00 




42 


Mo 


0.93 




43 


Tc 






44 


Ru 






45 


Rh 






46 


Pd 




0.80 


47 


Ag 


1.26 


0.89 


48 


Cd 


1.14 


0.97 



72 


Hf 


73 


Ta 


74 


W 


75 


Re 


76 


Os 


77 


Ir 


78 


Pt 


79 


Au 


80 


Hg 


57 


La 


58 


Ce 


59 


Pr 


60 


Nd 


61 


Pm 


62 


Sm 


63 


Eu 


64 


Gd 


65 


Tb 


66 


Dy 


67 


Ho 


68 


Er 


69 


Tm 


70 


Yb 


71 


Lu 


"Three anion radii are 


Physics). 





Second transition series (4d n ) 
0.94 



0.68 



Third transition series (5d a ) 



0.79 
0.74 
0.70 

0.67 

0.65 



1.37 
1.27 



1.39 
1.27 



0.80 
1.10 



0.78 

0.70 
0.72 
0.88 
0.68 
0.65 



0.85 



Rare earths (4f n ) 



1.14 

1.07 

1.06 

1.04 

1.06 

1.00 

0.98 

0.62 

0.93 

0.92 

0.91 

0.89 

0.87 

0.86 

0.85 



0.94 
0.92 



0.81 



0.69 



0.62 



0.68 



0.62 
0.69 



2. Unit Cell 

Three and f< 
ducting unil 
removed in 1 
cell to be les 

YB; 
LaS 

Similar stac 



E. LANTH 

The structu: 
is usually Si 
will describe 
The structu 
correspondi 
supercondu< 
divalent cat: 
gen is — 2, il 
becomes trr 
The com 
some invest 
perhaps of a 
Skell, Skei: 

1. Tetragoi 

The tetragc 
K 2 NiF 4 stru 
cell (e.g., Bi 
and one of 1 
oms are all 
ated with th 



with u = 0. 
c = 13.18 i 
5a provides 



80 




PEROVSKITE-TYPE SUPERCONDUCTING STRUCTURES 



2. Unit Cell Stacking 

Three and four fundamental fee unit cells stack vertically to form the supercon- 
ducting unit cells of YBaCuO and LaSrCuO, respectively, with some oxygens 
?emove 8 d in the process. This causes the vertical height or c parameter of the unit 
cell to be less than that expected for the stacking of perovskite cells: 

YBaCuO: c « 11.7 A, 3c fcc = 11.19 k, 3 Cper = 12.03 A (yi _ 5) 
LaSrCuO: c - 13.18 A, 4c fcc = 14.92 A, 4c per = 16.04 A 

Similar stackings occur in the BiSrCaCuO and TIBaCaCuO compounds. 



E. LANTHANUM-COPPER OXIDE 

The structure of LaSrCuO, (La,_,M,) 2 Cu0 4 _ 5 , called the 21 structure where M 
is usually Sr or Ba, is tetragonal in some cases and orthorhomb.c in others. We 
win describe the tetragonal case first and then the orthorhombic distortion of rt. 
The structures will be described in terms of the prototype compound La 2 CuO< 
corresponding** = 6 = 0 in the above expression, keeping m m.nd that in the 
^oJLg compounds themselves some of the La atoms are rep aced by a 
divalent cation such as Sr or Ba. Since lanthanum has a charge of+3 and oxy 
genis -2, it follows that all of the copper is divalent (+2) when* - O.andsome 

becomes trivalent for x > 0. ,„+:„„ v, n + 

The compound La 2 Cu0 4 itself is considered to be nonsuperconducting but 

some investigators claim that it or portions of it ^J^.^-?"^ 
perhaps of afilimentary type (Brill, Coopl, Dvora, Granl, Pickl, Shahe, Skelt, 

Skell, Skel2). 

1. Tetragonal Form 

The tetragonal LaSrCuO superconductors crystallize in what is called the 
K^NirCstructure with space group Wmmm, D» and two formula units per unit 
X g Burns, Colli Hiro" Mossz, Onoda; Wyck3, p. 68) The copper atoms 
and one of the oxygen types O(l) are in special positions and 
oms are all in general positions, with a single undetermined parameter assoc. 
ated with the z coordinate. The positions are 

La (4e) 0,0,w; 0,0,-u; j,i>» + b i-i _u + ^ 

Cu (2a) 0,0,0AAA (VI-6) 

O(l) (4c) 0,i0; ±,0,0,^0,^0,^ 

0(2) (4e) 0,0,v; 0,0,-v; i,5,v+ 5 ; 2-2. v+ 2 

with u = 0.362 and v = 0.182. Typical lattice dimensions are a = b = 3.77 A 
c = 13 18 A Table VI-3 gives more details on the atom positions and big. VI- 
5a provides a sketch of thfs 21 structure. Table VI-4 lists the measured lattice 



CRYSTALLOGRAPHIC STRUCTURES 



St?^ VI " 3 * At ° m Positions of Re S u,ar and Alternate La 2 Cu0 4 Structure, Both of 
Which Correspond to Space Group IMmmm, D l ^ a 



Regular Structure 



Alternate Structure 



Complex Ideal 



Cu0 2 
OLa 

LaO 

0 2 Cu 

LaO 

OLa 
CuO? 



= 0.833 



= 0.667 



0.333 



= 0.167 



Atom 


bite 


X 


y 


z 


Atom 


Site 


X 


y 


z 


( CXI) 


4c 


i 

2 


0 


1 


0(1) 


4c 


i 

2 


o 


1 
i 


! o(i) 


4c 


0 


i 

2 


1 


O(l) 


4c 


o 


i 

2 


1 


^Cu 


2a 


0 


0 


1 


Cu 


2a 


o 


o 


1 


[La 


4e 


1 

2 


I 
2 


0.862 


La 


4e 


2 


2 




CO(2) 


4e 


0 


0 


0.818 






















0(2) 




yj 


1 

2 


3 
4 












0(2) 




i 

2 


A 
U 


3 


f0(2) 


4e 


I 

2 


I 


0.682 










4 


(La 


4e 


0 


0 


0.638 


La 


4e 


o 


n 


n Ala 


C O(l) 


4c 


0 


1 


i 

2 


O(l) 


4c 


o 


2 


i 


J O(l) 


4c 


1 

2 


0 


I 
2 


O(l) 


4c 


2 


0 


2 




2a 


1 

2 


2 


1 


Cu 


2a 


1 

2 


1 

2 


2 


[La 


4e 


0 


0 


0.362 


La 


4e 


0 


0 


0.362 


(.0(2) 


4e 


1 

2 


1 

2 


0.318 




















0(2) 


4d 


2 


0 


4 












0(2) 


4d 


0 


1 


1 


\OQ) 


4e 


0 


0 


0.182 








2 


4 


I^La 


4e 


2 


2 


0.138 


La 


4e 


2 


2 


0.138 


'O(l) 


4c 


2 


0 


0 


0(1) 


4c 


1 

2 


0 


0 


O(l) 


4c 


0 


1 

2 


0 


CXI) 


4c 


0 


2 


0 




2a 


0 


0 


0 


Cu 


2a 


0 


0 


0 



"Superconducting compounds crystallize in the regular structure 
z values in column 2 are for the prototype perovskite. 



(Oguch; see also Onoda). The ideal 



Fig. VI-5. 

with the su 
the right (( 
the two eel 



constants for tetragonal LaSrCuO superconductors with various values of x y 
and 8 m the formula (La,. Jr Sr x ) 2 _ J ,Cu0 4 . 5 . 

2. Alternate Tetragonal Form 

In the previous section we discussed the tetragonal structure which is adopted by 
LaSrCuO superconductors. It has a variant (Hutir, Oguch) called the Nd 2 Cu0 4 
structure in which the oxygens 0(2) are in special sites (4d) instead of the general 
(4e) sites in the same space group, corresponding to 



0(2) (4d) 0 - ± 0 i- i 0 ^- n 1 3 

V * K } W '2»4> 2J U »4» 2» U »4» "»2»4 



(VI-7) 



The remaining atoms are in the positions given by Eq. (VI-6) and listed in Table 
VI-3, and the unit cell is sketched on the right-hand side of Fig. VI-5. This struc- 
ture tends to be unstable relative to its K 2 NiF 4 counterpart, and is not known to 
superconduct. 



3. Orthoi 

The21ort 
logue give 
structure 
means tha 
ones, and 
similar to 
5.409 A = 
times 
bic values 
little char 
orthorhon 



listed in c 



PEROVSKITE-TYPE SUPERCONDUCTING STRUCTURES 



Jothof 



:ture 



0 1 

k * 

0 1 

1 0.862 



I 
2 

0 

1 

2 

0 



0 0.638 



0.362 



2 

0 

2 

0 



0.138 
0 
0 
0 




oda). The ideal 



Fi e VI-5 Lanthanum copper oxide tetragonal unit cell. The regular cell («) associated 
Sle superconducting compounds is shown on the left and the alternate one « is on 
SfwS see also Ohbal). The oxygens denoted by * have different pos.t.ons ,n 
the two cells. 



ilues of x,y, 



is adopted by 
the Nd 2 Cu0 4 
of the general 



(VI-7) 

listed in Table 
-5. This struc- 
; not known to 



3. Orthorhombic Form 

The 21 orthorhombic LaSrCuO structure (Longo) is related to its tetragonal ana- 
logue given by Eq. (VI-6) in the same way that the orthorhombic perovskite 
Sctu (VI 3) is related to its tetragonal (VI-2) and cubic (VI-1) forms. Th,s 
meansthattheorthorhombicbasisd^ 

ones, and the number of formula units in the eel is doub led The stfuat. on is 
similar to that described by Fig. VI-3. with a = 5.363 A = 3 792V 2 !A *- 
5 409 A = 3 825V2 A, c = 13.17 A. Writing the a and b lattice parameters 
times VI compensates for the new choice of axes and shows that the orthorhom- 
b^alnes arec.ose to the tetragonal a = 3.81 A given earlier. There is also ^ 
little change in c. Table VI-5 lists the measured lattice constants for several 
orthorhombic compounds. The anisotropy factors ANIS 



ANIS = 



100 \b - a\ 



(VI-8) 



0.5 {b + a) 

listed in column 6 give the percentage deviation from tetragonality. 



84 CRYSTALLOGRAPHIC STRUCTURES 



TABLE VI-4. Selected Lattice Parameters for (R t JVi x ) 2 Cu0 4 -6 Type Superconductors 
with Tetragonal Structure 0 

Lattice Parameters 6 



TABLE VI-5. S< 
with the Orthorh 



R-M 


X 


a = Z> (A) 


c(A) 


Ref. 


i -Ba 


0.4 


O.OZO 


17 Aft 
lz.OO 




La-ba 


O.Uo 


^ 7ft') 
o. /oz 


1*5.1 OO 


Skelt 




0.075 


1 7ft 1 7 
J. /ol / 


i-i 74ft7 
1 0 . z*to / 


Yll'7'7'7 




O.O/o 


1 7ft7 

J. /o/ 


1 1 11 
10. ox 


Fni it 

ST UJ It 




A 1 
0.1 


1 7Q1 


10. OO 


Piiiit 


La- or 


A AC 
O.OO 


1 7ft7Q 

O. /OJ7 


11711 
lO.Zll 






A AC 
0.05 


1 7ft 
O. /o 


11 9<\ 
10. ZO 


mucin. 




A A/i.1 

O.OoJ 


1 77ftA 


1 1 71 f\ 
lO.ZIO 


T ar o 1 
1 ai ai 




A ATC 

O.O/o 


1 77Q1 


11 7 

io.z 






A A7C 

O.O/o 


"5 7771 


11 77A 
10.ZZO 


1 alal 




0.075 


3.776 


13.234 


Shelt 




0.075 


3.772 


13.247 


Brunz 




0.087 


3.7739 


13.232 


Taral 




0.1 


3.7739 


13.23 


Taral 




0.1 


3.777 


13.2309 


Przys 




0.112 


3.7708 


13.242 


Taral 




0.125 


3.7685 


13.247 


Taral 




0.132 


3.7666 


13.255 


Taral 




0.15 


3.7657 


13.259 


Taral 



"The table is sorted by cations and then by increasing x, the dopant parameter (prepared by M. M. 
Rigney). 

b The a and b lattice parameters were converted from measured values of a 0 , b 0 of Fig. VI-3 through 
the expression a = a Q /\f2, b = b 0 /\f2. 



R-M 
La-Ba 



La-Ba 
La-Ca 



0.0 
0.0 
0.0 
0.1 
0.0 



"AN1S is the aniso 
fc The a and b latti 
through the expres 



(Lao/jBao.ihCU 
5.408 = 3.824 



4. Phase Trail 

The compoum 
temperatures < 
tivity has beei 
Dayzz, Dvora, 
prototype com 
bic transition. 



Copper atoms and one of the oxygen types O(l) are in special positions; the 
remaining two atoms La and 0(2) are in general positions with a single undeter- 
mined parameter associated with the z coordinate. The space group is Fmmm, 
D^jJ, and the positions of the atoms are as follows: 



(VI-9) 



where the parameters u = 0.362 and v = 0.182 have the same values as in the 
tetragonal case presented above. Since u and v are the same and the lattice con- 
stants are so close to the tetragonal values, the sketch of the tetragonal unit cell 
in Fig. VI-5a applies here also. Another work (Hirot, see also Onoda) assigned 




Fig. VI-6. Pha 

transition line 
spin-density wa 
pounds have ab 



PEROVSKITE-TYPE SUPERCONDUCTING STRUCTURES 



conductors 



Ref. 

AUge 

Skelt 

Yuzzz 

Fujit 

Fujit 

Taral 

Hidak 

Taral 

Decro 

Taral 

Shelt 

Brunz 

Taral 

Taral 

Przys 

Taral 

Taral 

Taral 

Taral 



repared by M. M. 
Fig. VI-3 through 



TABLE VI-5. Selected Lattice Parameters for (R^M^CuO^ Type Superconductors 
with the Orthorhombic Structure* 1 



Lattice Parameters 



R-M 



a (A) 



6(A) 



c(A) 



ANIS 



Ref. 



La-Ba 


0.02 


3.786 


3.811 


13.17 


0.66 


Fujit 


0.075 


3.786* 


3.808* 


13.257 


0.58 


Shelt 




0.075 


3.798* 


3.803* 


13.234 


0.13 


Onoda 


La-Ba 


0.1 


3.786* 


3.824* 


13.264 


1.00 


Hirot 


La-Ca 


0.075 


3.772* 


3.808* 


13.168 


0.95 


Shelt 



"AN lb is the anisotropy iacior iw\u u\sv.^\v • w** r *> *>- 

»The a and b lattice parameters were converted from the measured values of a 0 , b 0 of Fig. VI-J 
through the expressions a — a 0 / V2~, b = b 0 / V2~. 

(Lao 9830.0204 to the space group Pccm,p 3 2h with a = 5.354 = 3.786^2 A , b = 
5.408 = 3.824VIA, andc = 13.264 A. 



4. Phase Transition 

The compounds (La.^M^CuO* with M = Sr and Ba are orthorhombic at low 
temperatures and low M contents, and tetragonal otherwise, and superconduc- 
tivity has been found on both sides of this transition (Baris, Bedn3, Birge, 
Dayzz, Dvora, Fujit, Greel, Kangz, Koyam, Mihal, Paulz; see also Heldz). The 
prototype compound La 2 Cu0 4 itself also exhibits the tetragonal-to-orthorhom- 
bic transition. The phase diagram of Fig. VI-6 shows the tetragonal, orthorhom- 



1 positions; the 
single undeter- 
roup is Fmmm, 



(VI-9) 



ng m) 



; values as in the 
d the lattice con- 
tragonal unit cell 
Onoda) assigned 



400 



200 



T 1 


r™. 1 




Tetragonal 


Ortho- 




*\ rhombic £\ 




I (SDW) 


\ (Super- 


\^// Conducting) _ 


1 1 / . 





0.05 



0.10 



0.15 



Fig. VI-6. Phase diagram showing data points along the tetragonal -to-orthorhombic 
transition line for (La.^Ba^CuO^s (O, Fujit) and (La,. Jt Sr x ) 2 Cu0 4 C, Moret). The 
spin-density wave (SDW) and superconducting • regions are indicated. These two com- 
pounds have about the same superconducting region. 



86 CRYSTALLOGRAPHIC STRUCTURES 



bic, superconducting, and spin-density wave (SDW) regions for the barium 
compound (Fujit), and data points for the strontium compound (Moret, 
More8). An alternate phase diagram has been proposed (Aharl). Alkaline metal 
contents much larger than those shown on the figure (e.g., x « 0.5) can be non- 
superconducting. The SDW region occurs below the minimum concentration for 
the onset of superconductivity. Another work (Geise) showed that LaSr(0.04) 
undergoes a structural phase transition between 180 and 300 K. 



6.6 A 



5. Generation of LaSrCuO Structures 

The LaSrCuO tetragonal structures may be visualized as being derived from four 
LaCu0 3 perovskite unit cells of the type illustrated in Fig. VI-1 stacked one 
above the other along the z or c axis. To generate La 2 Cu0 4 in the K 2 NiF 4 struc- 
ture the layers of Cu0 2 atoms on the z = \ and z = | levels of this four-cell 
stacking are removed, La and O are interchanged on two other layers, and the 
middle layer Cu atom is shifted from the edge to the center point of the 

unit cell. Then the cell is compressed vertically from 14.9 to 13.2 A (Table VI-4) 
to take up the space formerly occupied by the removed Cu0 2 layers. Finally, the 
lanthanums along the c axis and the oxygens along the side edges are shifted 
vertically to accommodate the new atom arrangement. 

To generate La 2 Cu0 4 with the Nd 2 Cu0 4 arrangement from this same four-cell 
stacking all of the oxygens on the vertical edges are removed, and two lan- 
thanums are moved to edge sites. Copper is handled the same way as before, so 
in both cases the generated structure lacks two Cu0 2 layers. 



c-~-!- 



6.6 A 



Fig. VI-7. La 

perpendiculai 



6. Layering Scheme of LaSrCuO 

When we described the LaSrCuO structures we left out what is perhaps their 
most important characteristic, namely, their layered aspect. Lanthanum copper 
oxide may be looked upon as consisting of Cu-O layers of square-planar coordi- 
nated copper ions with lanthanum and 0(2)-type oxygen ions populating the 
spaces between the layers. These Cu-O layers are stacked equally spaced, per- 
pendicular to the c axis, as shown in Fig. VI-7, and their oxygens are aligned 
along the c axis, as indicated by the vertical dotted line on the left side of the 
figure. The copper ions, on the other hand, are not aligned vertically, but rather 
alternate between (000) and (Hi) sites in adjacent layers, as illustrated in Figs. 
VI-5 and VI-7. 

The copper is actually octahedrally coordinated with oxygen, but the Cu-O 
distance of 1 .9 A in the Cu0 2 planes is much less than the vertical distance of 
2.4 A between copper and the oxygens above and below, as shown in Fig. VI-8. 
When the structure is distorted orthorhombically the Cu-O spacings in both the 
planes and the c direction remain quite close to their tetragonal counterparts. 

The copper ions and the 0(l)-type oxygens in the planes are both in special 
sites in the tetragonal and orthorhombic forms, in accordance with Eqs. (VI-6) 
and (VI-9), and as a result the plane is perfectly flat in both cases. When the 



structure is 
course the pi 
planes coulc 
The copp 
indicated on 
octahedra. 1 
axis. The su 
planes are 
themselves. 



F. YTTRU 

The YBaCi 
terparts, cc 
scribed in 1 
perovskite 
defect stru( 



PEROVSK1TE-TYPE SUPERCONDUCTING STRUCTURES 



he barium 
d (Moret, 
aline metal 
:an be non- 
ntration for 
LaSr(0.04) 



ed from four 
stacked one 
: 2 NiF 4 struc- 
this four-cell 
yers, and the 
U ,i)ofthe 
(Table VI-4) 
>. Finally, the 
es are shifted 

same four-cell 
and two lan- 
y as before, so 






13.18 A 


+ — La 


11.36 


+ — 0 


10.78 


+ — 0 


8.99 


< — La 


8.41 




r' 



3.78 A 



-Cu 0 2 6.59 



La 4.77 
O 4.19 



O 2.40 
La 1-82 



Cu 0 2 0.0 



Fig. VI-7. Layering scheme of the LaSrCuO superconducting structure. The layers are 
perpendicular to the c axis. 



s perhaps their 
thanum copper 
-planar coordi- 
populating the 
t lly spaced, per- 
;ens are aligned 
\ left side of the 
cally, but rather 
ustrated in Figs. 

n, but the Cu-0 
rtical distance of 
own in Fig- VI-8. 
icings in both the 
ial counterparts, 
re both in special . 
s withEqs.(VI-6) | 
, cases. When the i 



structure is tetragonal the square-planar arrangement is also perfect and of 
couS^ 

planes could influence the superconducting properties. 

The copper-oxygen planes are bound together by Cu-O and La-O ^bonds as 

octahedra This figure also makes clear how the copper ions alternate along the c 
" superconducting properties are probably less influenced by the way t h 
planes are bound together than by the internal characteristics of the planes 
themselves. 



F. YTTRIUM-BARIUM-COPPER OXIDE 

The YBaCuO compounds such as Y, x Ba 2 ,Cu 3 0 7 . s , like their LaSrCuO coun- 
terparts, come in tetragonal and orthorhombic varieties, and both be ^ 
scribed in turn. Then we will show how to generate the *™^J^^ 
perovskite prototypes, we will explain the layering scheme, and finally related 
defect structures will be discussed. 



88 CRYSTALLOGRAPHIC STRUCTURES 




Fig. VI-8. Ordering of the LaSrCuO copper atoms and their associated octahedra of 
oxygen nearest neighbors along the c axis. The LaSrCuO structure consists of alternately 
displaced octahedra with axes parallel to c. 

In much of the early work the formula YBa 2 Cu 3 0 9 _ 6 was used for YBaCuO 
because there are nine oxygens in the prototype perovskite structure. When the 
crystallographers showed that the 14-atom unit cell of YBaCuO contains 8 oxy- 
gen sites, the formula Y,Ba 2 Cu30 M began being widely used, and finally when 
structure refinements demonstrated that one of the oxygen sites is systematically 
vacant, the more appropriate expression Y 1 Ba 2 Cu 3 07-5 was introduced, and it is 
the one that we will use throughout this work. 



The orthorh 
some reported 
duce the ortho 
as81K(Xiao3 
phase transfor 
(3) replacing o 
a tetragonal st 
(Felnl, Ovshi) 



1. Tetragonal 

The tetragona 
6 > 0.5, was ; 
Earlier assign 
one formula u 
tions, and the 
mined param 

I 
( 
< 
< 



The w, v, w, i 
The unit cell 
reported by c 
only partly o< 
this structun 
basal plane a 
The lack of 
yttrium aton 
VI-2. 

The semi 
D\ h (Borde, 
version of oi 
that none re 
"ideal" pen 
quate fit to 

The corr 

Cu 6 Oi4-6 (IV 

tural with tt 



YTTRIUM-BARIUM-COPPER OXIDE 



89 



I octahedra of 
j of alternately 



for YBaCuO 
re. When the 
mtains 8 oxy- 
l finally when 
;ystematically 
iced, and it is 



The orthorhombic phase is ordinarily superconducting. There are, however, 
some reported exceptions: (1) doping with gallium in copper chain sites can in- 
duce the orthorhombic-to-tetragonal transformation with T c remaining as high 
as 81 K (Xiao3); (2) replacing one oxygen by sulfur in EuBa 2 Cu 3 0 7 . 5 induces this 
phase transformation with a small change in T c from 92 to 85 K (Feln2); and 
(3) replacing one oxygen with two fluorines to form YBa 2 Cu 3 0 6 F 2 could produce 
a tetragonal structure with all eight oxygen sites occupied and an enhanced T c 
(Felnl, Ovshi). 



1. Tetragonal Form 

The tetragonal YBa 2 Cu 3 0 7 _ 6 structure, which is stable above about 650°C with 
6 > 0.5, was assigned to space group PMmmm, L>J h (Jorge, see Eagle, Lepag). 
Earlier assignments were P4m2, D S 2A or possibly P4mm, C\ y (Hazen). There is 
one formula unit per unit cell. Yttrium and one copper atom are in special posi- 
tions, and the remaining atoms are all in general positions with a single undeter- 
mined parameter associated with the z coordinate of each: 



(VI-10) 



Y 


(Id) 


1 I 1 

2>2 > 2 






Ba 


(2h) 


2 » 2 » W » 2 > 2 » W 


u 


= 0.1914 


Cu(t) 


(la) 


0,0,0 




= 0.3590 


Cu(m) 


(2g) 


0,0,v;0,0,-v 


V 


O(t) 


(2f) 


0,i,0; £,0,0 






0(m,m') 


(4i) 


0,5,w; 5,0,w 










0,i,-w; 5.0,-w 


w 


= 0.3792 


O(b) 


(2g) 


0,0,jc; 0,0, -x 


X 


= 0.1508 



The u , v, w, and x parameters (from Jorge) are used in column 10 of Table VI-6. 
The unit cell dimensions are a = 3.9018 A, c = 11.9403 A (Jorge), and those 
reported by other investigators are listed in Table VI-7. Oxygen site O(t) may be 
only partly occupied. The atom positions are given in Table VI-6 and a sketch of 
this structure is presented on the right side of Fig. VI-9. The oxygen sites in the 
basal plane at z = 0 are about half occupied in a random or disordered manner. 
The lack of planarity of the CuO z layers immediately below and above the 
yttrium atom is reminiscent of tetragonal perovskite, which is sketched in Fig. 
VI-2. 

The semiconducting compound YBa 2 Cu 3 0 6 was also assigned to PMmmm, 
D\ h (Borde, Renau, Swinn, Torar), as shown in the table. This is a tetragonal 
version of orthorhombic YBa 2 Cu 3 0 7 formed by removing the chain oxygens so 
that none remain on the basal plane. A claim has been made (Relle) that the 
"ideal" perovskite z values shown in column 6 of Table VI-6 provide an ade- 
quate fit to X-ray powder diffraction data from YBa 2 Cu 3 0 7 . 

The compounds La 3 Ba 3 Cu 6 0 14+4 (Davil, see also Golbl), (La^BaoA 
Cu 6 0 14 _ 5 (Iwaz3), and LaBa 2 Cu 3 . I 0 7 -« (Nakai) have been reported as isostruc- 
tural with tetragonal YBa 2 Cu 3 O s . 



a * 

w 

1 

CO 



C3 



ft 

m 



> 
< 



lift! 



O 
CQ 



O 
fa 

c 
o 
M 



I 

OO 

o 
s 
*o 
c 
o 

Si 
a 

o 
15 

E 

o 

■£ 

O 

O 



0 
n 



o 



o 

S 
3 



w 

CO 



OX) 

> 



O 0 s lO no vo 

v© 1^ On O O 

o H (N (N 

I ^ I 00 00 s© vo vO 

o o o o o 



o o o> 00 00 O vO • sO 

^^oooooo 



CN O 00 00 

On 00 o o 

tT O (N (N 

d © d © d 



00 i/) o o 

iT) O <N On CO 

Tj" ^ (N 

I 00 00 vO O \D 

d © d © © 



i - 



Tt TT m *^ O 

On On O (N 

r-* t- »© on to 

< 1 1 1 ^. 

d © d d d 



on oo On lO CO 
n n n ^ h o _ 

-IN d odd do 



N (N O 00 

On On On ^ O 

«in rO ro ^ ^ ° 

d d d d d 



^ i/) <n 

o o r- On 

oo i/i oo i/) _ 

-lw co ro co ^ < ^ O 

© © d © © 



to lO 

H -I 00 

r-- r*» co 

q oo oo ^ 

^ n ^ 



On On 

co i/} iO — ' 

O iO 0O 00 

d d n n h 

i + 



V oo oo n 

^ ^ o 

*o o o 

0> ON On 



o o 



ro n ^ 



d 



tO 



o o 



V On On CD 
iuO — 

00 On 00 



co CO ^ 



i/) On O 



(N nO 
CO tT , 

i-i ^- <n rsi 

00 00 sO ^ 

© © © © d 



O ^ i/) ^ oo 

ONoommvo 

l^(^LO00LO^^^^<N0000 
-lis rrjrocOi-H^OOOOoOOOO 



+ 



N 3 > X >> 

I I I 1 I 



o o o o o 



-l<s >> X > 3 N 



n ro h 



* ° I I 



ro co 

CO CO 

CO co 

00 00 

d d 



r- 

\0 co co co o ^-o 

vOvOvO cOCOCOOnO 
O \0 CO CO CO '-h 

odd -in-im dddddooorN 



II 



II II II 



i/>|vOl/)1<£>CM]r)r>)lr*)<N|r*l 



O O -Km O -Im O -1c* O O -I<n O *-I<n O -lis O O O -In 



-1<n O O O -Iin O O -If* O ~In-i<n O O -Irs O -Ir* o o 



ihhh(N(n)M(N(N I w<N(NM(N(Nhhh 



s§S £ « ills lil«ss§S 

OUOOfflUOOO^OOUfflOOuO 



o 
u 



o 

CQ 



o 



o 
u 



o 

CQ 



o 

u 



GO 

o 



2? 

o 



00 

6 



c o 



C3 «£ 



3 

O 



cd 
> 



£ 
O 

o 

N 

c 

x: 



5 > * 



(/3 



o 

T3 



o 



So « 

" c 

x: _ 
+*> c 

U O 

.5: 

oo o 

?S2 



00 3 

2 u 



CQ 
a> "J 
x: o 



TABLE VI-7. : 
Tetragonal Stn 

R-M 

Y-Ba 



Dy-Ba 

Er-Ba 

Eu-Ba 

Gd-Ba 

Ho-Ba 

Tm-Ba 



"The table is soi 
fc Thea and b 1 at 
the expressions « 



Fig. VI-9. S 

copper oxide 
basal plane : 
the atoms. 



90 



YTTRIUM-BARIUM-COPPER OXIDE 91 



5 



O 

c 



oo 
o 



TABLE VI-7. Selected Lattice Parameters for RBa 2 Cuj0 7 - 6 Type Copper Oxides with 
Tetragonal Structure" 



R-M 


6 


a = b(k) 


c(A) 


Ref. 


Y-Ba 


0.5 


3.859 


11.71 


Hazen 




0.5 


3.859 


11.71 


Hemle 






3.87* 


11.67 


Ihar2 




0.0 


3.87* 


11.67 


Hirab 


Dy-Ba 


0.72 


3.8656 


11.783 


Tara3 


Er-Ba 


0.84 


3.854 


11.796 


Tara3 


Eu-Ba 


0.41 


3.86 


11.73 


Boole 


Gd-Ba 


0.48 


3.877 


11.81 


Tara3 


Ho-Ba 


0.87 


3.8601 


11.791 


Tara3 


Tm-Ba 


0.93 


3.8491 


11.788 


Tara3 



"The table is sorted by cations (prepared by M. M. Rigney). 

6 The a and b lattice parameters were converted from the measured values a 0 , b 0 of Fig. VI-3 through 
the expressions a = a 0 / V?, b = b 0 / V2~. 



s*1 



a 

C/3 



c 

CD 
> 

00 

o 

a> 
rt 
t/j 
a> 
_3 

> 



o 



c 

o 



o 



> 



£ 

o 

o 



— — < c 

s > t 

35 . a) 

1 ts & 

° 

2 U o 

S £ N 

rt c 8 

£ C 3 
« * K • 

00 O 2 <-> 



C 3 > ^ 

U 2 H >< 

3 <^ -C 



YBa 2 Cu 3 0 7 
Orthorhombic 



YB32CU307 
Tetragonal 





Fig. VI-9. Sketches of the orthorhombic (left) and tetragonal (right) yttrium-barium- 
copper oxide unit cells. (Adapted from Jorgl.) Oyxgens are randomly dispersed over the 
basal plane sites in the tetragonal structure. Thermal vibration ellipsoids are shown for 
the atoms. 



m. 
33 



< 



92 CRYSTALLOGRAPHIC STRUCTURES 



I 

lit* 
t list 



1 1!'! 



IS 

IL'; 1; 
I*)* 

i !i,r 



Y 


(lh) 


1 1 1 

2>2>2 




Ba 


(2t) 


1 1 u . 1 1 

2 » 2 > 2 i 2 » 


— u 


Cu(t) 


(la) 


0,0,0 




Cu(m) 


(2q) 


0,0, v; 0,0,- 


-v 


O(t) 


(lb) 


£,0,0 




O(t') 


(le) 


o.i.o 




O(m') 


(2r) 




— JC 


O(m) 


(2s) 






O(b) 


(2q) 


0,0,2; OA" 


— z 



2. Orthorhombic Form 

Orthorhombic YBa 2 Cu 3 0 8 with the 123 structure was assigned to the space 
group Pmmm, D\ h (Antso, Beech, Benoz, Cales, Cappo, Coxzz, Greed, Jorge, 
Siegr, Yosh3, Yanz2, Youzz) with one formula unit per unit cell and the repre- 
sentative lattice parameters a = 3.827 A, b = 3.882 A , and c — 11.682 A. 
Yttrium, one copper, and two oxygens are in special positions, and the remain- 
ing atoms are all in general positions with a single undetermined parameter as- 
sociated with the z coordinate: 



u = 0.1854 



v = 0.3555 

(VI-11) 

x = 0.3790 
y = 0.3781 
z = 0.1568 



The u, v, x, y, and z parameters correspond to the average atom positions given 
in column 8 of Table VI-6. Lattice dimensions a, b, and c and atom positions for 
several structure determinations are given in Table VI-6. Table VI-8 lists lattice 
parameters for a number of orthorhombic YBaCuO compounds. Variable tem- 
perature crystallographic data are also available (Antso, Cappo, Hewal, Jorge, 
Jorgl Momin, Renau). Sketches of this structure are presented on the left side 
of Fig VI-9 (see also Steil). We see from this figure that the O(t) oxygen site is 
empty, which corresponds to the presence of -Cu-0(t ' )-Cu(t ' )-0- chains along 
the b direction. The vacancy of the O(t) site causes the unit cell to compress 
slightly along a to render a < b. The compound TmBa 2 Cu 3 0 7 . a (Andrl) and 
other rare earth analogues (Lepal) are isostructural with YBa 2 Cu 3 0 7 _ 6 . 

Table Vl-9 gives the bond distances and bond angles of this structure (Beech, 
Benoz, Borde, Cales, Coxzz, Greed, Hazen, Lepag, Siegr, Yanz2) and their tem- 
perature dependence has also been reported (Antso, Cappo). 

A transmission electron microscope examination of YBa 2 Cu 3 0 7 -a in the su- 
perconducting state indicated that it is orthorhombic with the space group 
Pmlm, C\ and the lattice constants a = 3.80, b = 3.86, and c = 11.55. The a 
and b axes alternate across an antiphase boundary which runs parallel to the 
[110] direction. 16 

A yttrium-rich phase of YBaCuO was found to have the structure Pnma, 
with a = 13.5 A, b = 6.3 A, and c = 7.6 A (Eagle). GdBa 2 Cu 3 0 7 -6 has a - 
3 909 b = 3.849, and c = 11.682 A with the following possible space groups: 
Pmm'm,D l 2h ; Pmm2, C\ v ; P222, D\ (Xuzzl). YBa 2 Cu 3 0 7 . 5 has also been assigned 



TABLE VI-8. 
with Orthorhc 



R-M 



Y-Ba 



Dy-Ba 



Er-Ba 



Eu-Ba 



Gd-Ba 



Ho-Ba 



Lu-Ba 
Nd-Ba 



he space 
:d, Jorge, 
he repre- 
1.682 A. 
t remain- 
meter as- 



TABLE VI-8. Selected Lattice Parameters for RM 2 Cu 3 0 7 -6 Type Superconductors 
with Orthorhombic Structure" 



(VI-11) 



ons given 
ritions for 
sts lattice 
able tem- 
il, Jorge, 
e left side 
gen site is 
lins along 
compress 
ldrl) and 

•6- 

*e (Beech, 
their tern- 

in the su- 
ice group 
55. The a 
tlel to the 

*nma,D£ 
6 has a — 
:e groups: 
i assigned 









Lattice Parameters 






R-M 


5 


a (A) 


MA) 


c(A) 


A Klf C 


Ket. 


Y-Ba 


0.62 


3.85 


3.86 


11.78 


0.26 


Kuboz 




0.57 


3.85 


3.87 


11.77 


0.52 


Kuboz 




0.47 


3.84 


3.88 


11.75 


1.04 


Kuboz 




0.28 


3.8237 


3.8874 


11.657 


1.65 


Tara3 




0.19 


3.8231 


3.8864 


11.6807 


1.64 


Benoz 




0.15 


3.8282 


3.8897 


11.6944 


1.59 


Bonnl 




0.1 


3.8591 


3.9195 


11.8431 


1.55 


Jorge 




0.1 


3.83 


3.89 


11.7 


1.55 


Kuboz 




0 


3.8124 


3.8807 


11.6303 


1.75 


Cappo 




0 


3.825 


3.886 


11.660 


1.58 


Relle 




0 


3.856 


3.870 


11.666 


0.36 


Siegr 




0 


3.825 


3.883 


11.68 


1.50 


Ginle 




0 


3.825 


3.883 


11.68 


1.50 


Ventu 




0 


3.816 


3.892 


11.682 


1.97 


Greed 




0 


3.84 


3.88 


11.63 


1.04 


Dingl 




0 


3.82 


3.88 


11.67 


1.56 


Crabt 




0 


3.817 


3.882 


11.671 


1.69 


Coxzz 




0 


3.8271 


3.8771 


11.7086 


1.30 


Larbl 




0 


3.83 


3.89 


11.71 


1.55 


Worth 


Dy-Ba 


0 


3.828 


3.886 


11.66 


1.50 


Mapll 




0 


3.941 


3.894 


11.673 


1.37 


Yamad 




0.18 


3.828 


3.889 


11.668 


1.58 


Tara3 


Er-Ba 


0 


3.844 


3.885 


11.532 


1.06 


Kuzzz 




0 


3.845 


3.884 


11.53 


1.01 


Lynnz 




0 


3.813 


3.874 


11.62 


1.59 


Mapll 




0 


3.832 


3.88 


11.639 


1.24 


Yamad 




0.18 


3.815 


3.884 


11.659 


1.79 


Tara3 


Eu-Ba 


-0.1 


3.8449 


3.9007 


11.704 


1.40 


Tara3 




0 


3.8152 


3.8822 


11.6502 


1.74 


Golbe 




0 


3.843 


3.897 


11.7 


1.40 


Mapll 




0 


3.851 


3.901 


11.746 


1.29 


Yamad 


Gd-Ba 


-0.08 


3.840 


3.899 


11.703 


1.52 


Tara3 




0 


3.836 


3.894 


11.62 


1.50 


Mapll 




0 


3.845 


3.898 


11.732 


1.37 


Yamad 


Ho-Ba 


0 


3.845 


3.886 


11.547 


1.06 


Kuzzz 




0 


3.8253 


3.8856 


11.6578 


1.56 


Leez2 




0 


3.821 


3.886 


11.66 


1.69 


Mapll 




0 


3.841 


3.883 


11.676 


1.09 


Yamad 




0.29 


3.822 


3.888 


11.670 


1.71 


Tara3 


Lu-Ba 


0 


3.835 


3.886 


11.531 


1.32 


Kuzzz 




0 


3.791 


3.859 


11.57 


1.78 


Mapll 


Nd-Ba 


-0.16 


3.8546 


3.9142 


11.736 


1.53 


Tara3 




0 


3.867 


3.906 


11.71 


1.00 


Mapll 




0 


3.873 


3.902 


11.761 


0.75 


Yamad 



s- 

SI 

w 

5 



S3 
< 



93 



TABLE VI-8. (continued) 



f 

■ft 
HSl 

m 
i:;,t x 

I' 

it* 



' ,l Hi* 

1! 

! J» I iiii't 
htfil 



R-M 


6 




Lattice Parameters 




Ref. 


a(A) 


D \t\) 


r ( A 1 


ANIS 


Sm-Ba 


— 0.11 


3.855 


3.899 


11.721 


1.13 


Tara3 




o 


3.843 


3.906 


11.72 


1.63 


Mapll 




o 


3.867 




1 1 7^ 
1 1 . /o 


1.08 


Yamad 


Tm-Ba 


0 


3.836 


3.885 


11.529 


1.27 


Kuzzz 




0 


3.845 


3.881 


11.618 


0.93 


Yamad 




0 


3.802 


3.878 


11.63 


1.98 


Mapll 




0.35 


3.810 


3.882 


11.656 


1.87 


Tara3 


Yb-Ba 


0.29 


3.7989 


3.8727 


11.650 


1.92 


Tara3 




0 


3.834 


3.884 


11.531 


1.30 


Kuzzz 




0 


3.798 


3.87 


11.61 


1.88 


Mapll 




0 


3.832 


3.83 


11.61 


0.05 


Yamad 



"The table is sorted by cations and then by decreasing oxygen deficiency parameter, 6. ANSI is the 
anisotropy factor 100|6 - a\/0.$(b + a) (prepared by M. M. Rigney). 



TABLE VI-9. Selected Bond Distances and Angles in YBa 2 Cu 3 0 7 , Where n is 
Number of Equivalent Bonds" 



Bond 


Distance ( A ) 


n 


Mean ( A ) 


Cu(t)-0(t') 


1.941 


2 


1.886 


-O(b) 


1.831 


2 




Cu(m)-0(b) 


2.285 






-O(m) 


1.931 


h 


1.943 


-O(m') 


1.955 






Ba-O(t') 


2.891 


2 




-O(m) 


2.976 


2 




-O(m') 


2.963 


2 


2.864 


-O(b) 


2.747 


4 




Y-O(m) 


2.404 


4 


2.394 


-O(m') 


2.383 


4 





Configuration 


Angle (deg) 


Cu(t)-O(t')-Cu(0 


180 


Cu(m)-0(m)-Cu(m) 


163.6 


Cu(m)-0(m')-Cu(m) 


164.0 



"The bond distances are averages of those reported by various investigators (Beech, Benoz, Borde, 
Cappo, Coxzz, Greed, Lepag, Siegr); the angles are from Coxzz. 



to the orthorh* 
andc = 3.89; 

3. Temperatu 

The structure 
Benoz, Cappc 
square displa< 
thermal vibra 
that there is a 
investigators, 
investigators » 
(Antso, Capp< 
averages over 
tions in thex. 
We see from 
chain coppers 
the oxygens ( 

4. Phase Tra 

The compoui 
second-order 
perature orth 
Jorg3, Sagee 
phase sketch* 
are disordere 
and ordered 1 
This occurs t 
and random] 
orthorhombi< 
superlattice < 

Figure VI 
plane as a fui 
sphere (Jorge 
the fractiona 
5 in the form 
pound (T ~ 
occupancies 
gen. An anoi 
ducting tran 

The orthc 
The tetragor 
above the pr 
does not fori 
tioned in Se< 



94 



YTTRIUM-BARIUM-COPPER OXIDE 95 



Ref. 



Tara3 

Mapll 

Yamad 

Kuzzz 

Yamad 

Mapll 

Tara3 

Tara3 

Kuzzz 

Mapll 

Yamad 



, 6. ANSI is the 



re /i is 



Mean (A) 



1.886 

1.943 

2.864 
2.394 



:h, Benoz, Borde, 



to the orthorhombic space group Pmml, D l 2v with a = 3.820 A , b — 11.688 A , 
and c = 3.893 A (Beyel), and to Pmlm, C\ s . 

3. Temperature Factors 

The structure refinements provided temperature factors B = &k 2 (u 2 ) (Beech, 
Benoz, Cappo, Coxzz, Greed, Lepag, Siegr) which are a measure of the mean 
square displacement <w 2 > in A 2 of an atom about its equilibrium position due to 
thermal vibrations, and these are listed in Table VI-10. We see from the table 
that there is a great deal of scatter in the temperature factors reported by various 
investigators. This is in sharp contrast to the close agreement among these same 
investigators on the atom positions. The vibrations themselves are anisotropic 
(Antso, Cappo, Youzz), and the values listed in the table may be looked upon as 
averages over thermally excited normal modes. The extent of the atomic vibra- 
tions in the jc, y, and z directions is indicated in Fig. VI-9 by ellipsoids (Jorge). 
We see from the figure that the light oxygen atoms O(t') and O(b) bonded to 
chain coppers Cu(t) on the basal plane undergo larger amplitude vibrations than 
the oxygens O(m) and O(m') on the Cu0 2 planes. 

4. Phase Transition 

The compound YBaCuO is tetragonal at high temperatures and undergoes a 
second-order (Freil) order-disorder transition at about 700°C to the low-tem- 
perature orthorhombic phase (Bakke, Beyer, Eatou, Iwaz2, Jorge, Jorgl, Jorg2, 
Jorg3, Sagee, Schul, Torar, Vant2). Quenching can produce the tetragonal 
phase sketched on the right side of Fig. VI-9 at room temperature. The oxygens 
are disordered on the basal (z = 0) plane sites in the high-temperature phase 
and ordered to form chains at low temperature, as indicated on the two figures. 
This occurs because the two oxygen sites O(t) and O(t'), which are equivalent 
and randomly occupied in the tetragonal phase, become inequivalent in the 
orthorhombic phase, where all of the basal plane oxygens reside on O(t'). A 
superlattice associated with this ordering has been observed (Vant2). 

Figure VI- 10 shows the fractional site occupancy of the oxygens in the basal 
plane as a function of the heating temperature of the sample in an oxygen atmo- 
sphere (Jorge). The central curve in the orthorhombic region gives the mean of 
the fractional occupancies of the a and b sites. This curve also gives the value of 
8 in the formula YBa 2 Cu 3 07_ 6 . One should note that the low-temperature com- 
pound (T ~ 25°C) of Fig. VI-10 corresponds to the formula YBa 2 Cu 3 0 6 .9. Site 
occupancies were also obtained for heating in different partial pressures of oxy- 
gen. An anomaly found in the orthorhombic distortion of YBa* at the supercon- 
ducting transition (Hornz) was interpreted as evidence for anisotropic pairing. 

The orthorhombic 123 structure is the superconducting phase of YBaCuO. 
The tetragonal phase can be obtained at room temperature by quenching from 
above the phase transition, and it is found to be semiconducting. Ordinarily it 
does not form a superconductor (Chen2, Kwok2), but some exceptions are men- 
tioned in Section VI-F. 



M 

w 

Jo 
8? 



33 
< 



* 

lllill 



'if*;. 



,J l4tl- 

IS H|, 



1 

H 

9 

O 



3 

U 

CO 



s 

o 



3 
c 

E 



GO 



3 

cr 
on 



ao 



3 

fa 

s 

I 

I! 

hI 

. I 

o eu 
»i § 

> 9 

si 

PQ *5 



o o o o o 

« o n oo o in 



M « fN ^ O O 



oot^^rorvioo 

000^0 0^<N^(N 



O O O O O O O O O O --5 



o o 
t^ioro^Tfvomior- 



o tt 



OO^hOOOOOOOOO*-h 



0^00000000000^0^ 



00 n H H H OO f- 1 H H o\ n 

or^ooooooooooo 



o^ooooooooooo 



00 



to 
to 



coaoio^iot^vor^too^tooo 



O^hOOOOOOOOOOO 



o to 
o 



tO 

to 



O U 



O 
3 
U 



O O m 



o 

ctf 



u o o > 



o 

3 

u 



OOuraOOuO 



o 

3 

u 



o 

cd 
DQ 



o 

3 

u 



isotropic values, 




, Cappo, Jorge) give an 


Fig. VMO. D 

(bottom) sites 
right) on the c 
the two sites. 


<u 

T3 




O 
PQ 

6 


5. Oxygen-S 


s are shown; some (Ants 


Various worl 
eral of them ; 
convention, ; 
the letters t 
and m ' for 1 
the barium 1 

i 


tigation 


i 

| 6. Generatu 


"The results of several invesl 


The YBaCu( 
j prototype f o 
above the ol 
Column 6 of 
1 erate the YB 
replaced by 
moved, as ir 
removed 0x3 



YTTRIUM-BARIUM-COPPER OXIDE 97 



Temperature (K) 



1.0- 



J L 



400 600 800 1000 1200 
i ■ i i I 1 1 l_ 



YBa 2 Cu 3 0 7 . 6 




-1.0 



--0.5 



- 0.0 



-+0.5 



+1.0 



Temperature (°C) 

Fig. VI-10. Dependences of the fractional occupancies of the (0, j, 0) (top) and (£,0,0) 
(bottom) sites (scale on left) and of the oxygen content parameter 6 (center curve, scale on 
right) on the quench temperature. This latter curve is the average of the occupancies of 
the two sites. (Adapted from Jorge.) 



5. Oxygen-Site Nomenclature 

Various workers use different numbering schemes for the oxygen sites, and sev- 
eral of them are compared in Table VI- 1 1 . We have adopted the more mnemonic 
convention, given in column 3 of the table and illustrated in Fig. VI-9, of using 
the letters t and t' for top (and equivalent bottom) copper oxide layer, and m 
and m' for the median copper oxide layers, with O(b) denoting the oxygen on 
the barium level. 

6. Generation of YBaCuO Structure 

The YBaCuO tetragonal structure may be visualized as being derived from three 
prototype fee oxygen unit cells of the type illustrated on Fig. VI- 1, stacked one 
above the other along the z or c axis, as shown in the center of Fig. VI-11. 
Column 6 of Table VI-6 gives the z parameter values for this ideal case. To gen- 
erate the YBaCuO tetragonal unit cell the barium centered in the middle cube is 
replaced by yttrium, and the oxygens on the edges of this middle cube are re- 
moved, as indicated on the left side of Fig. VI-11. To take up the space of the 
removed oxygens and that arising from the smaller size of yttrium, the center 



I- 



"t*:i 



til 



I I,.. 



'I* 

t|: -in:i 

* is: 

itii,iii 



CO 



o> 

4> 

o 



XI 

I-* 
o 
CO 



G 
< 



N N 

N N 

O O 

O N 

CU N 

cu 3 

U 

5 o 



" o 



o 

o 



98 



^ ^ m ^ <n m ciCi-^cd^ 

I uOOfflUOO^OOUfflO 



u o 



uOOoauOO^OOucoO 



3 
U 



^ (^^^ ^ ^ <N — 

OwuOO^OOudqO 



(N ^ n j SG^ « ^ 
UOOfflUOOJnOOUDQO 



c^? §S3 SS§ « s 



U O 



3 



do 



do 



\Q, w ^ Ch w 

SuOOmuOO 



OOuSoSuO 



6 e ? 



OuOOfflUOO^OOUtflOOuO 



c 





OJ 




<u 








C 


c 


c 
j2 


c 


c 






■ 


aS 


i3 




"cL 


a- 


a 


cx 


"cL 




£ 


e 


u 
aj 


c 


£ 






c 




.2 






-3 










oar 




o 


CD 


bat 


an 


E 


£ 


E 


IX 




CD 


.2 




u 


Cu 




cu 


*n 






o 


ex 


cu 


Yt 


o 


o 


H 











o 

3 

u 



o 

05 



O 
3 



o 

3 

u 



o 

CO 



E 
o 

o 
PQ 



O 

3 

u 



-IN 



CUD 
C 

o 



Z 3 

c ^ 

4> CO 
GO CO 
>~> a- 
X o 
O ^ 



(Ba Cu 0 3 ) 



(YCu 0 3 ) 



(Ba Cu 0 3 ) i 



Fig. VM1. G 

stacked BaCu 
level where Y 



cube is com{ 
moved along 
dinated for 
Cu-O distan 
shown in Fig 
pyramidal c 
1.94 A in 
6 = 0 comp 
the left side 

7. Layering 

In Section V 
conductors. 
Fig. VI-13, 
threefold la 
much close 
indicated ii 
median lay* 
between th« 



YTTRIUM-BARIUM-COPPER OXIDE 99 



-373- 



3.83- 



O 

3 

u 

i QQ 



Remove 
Oxygens 
(for 5 = 0) 



(Ba Cu 0 3 ) 



Remove 
Oxygen 
Layer 



(YCu 0 3 ) 



(Ba Cu 0 3 ) 




3.88 
/ 



5.84A Cu 0 

4.01 0, 
3.68 (Ba) 

1.59 Cu0 2 



0.0 



-1.59 Cu 02 
-3.68 (Ba) 
-4.01 0 

-5.84 CuO 




4.25 A 



3.18 



4.25 



Perovskite Remove 
Structure Oxygen 
(for 6 = 0) 



YBa 2 Cu 3 0 7 



Fig. VI-11. Generation of the yttrium-barium-copper oxide unit cell (right) from three 
stacked BaCu0 3 perovskite unit cells (left) by the removal of the oxygens on the yttrium 
level where Y replaces Ba. 

cube is compressed along the c direction. Finally, the vertical edge oxygens are 
moved along c toward the apical Cu(t) ions. This copper ion Cu(t) is sixfold coor- 
dinated for YBa 2 Cu 3 0 8 and square-planar coordinated for YBa 2 Cu 3 0 7 with 
Cu-O distances of 1 .94 A in the basal xy plane and 1 .83 A vertically along c, as 
shown in Fig. VI-12. The two other coppers, Cu(m) and Cu(m' ), exhibit fivefold 
pyramidal coordination, as indicated in Fig. VI-14, with Cu-O spacings of 
1.94 A in the basal plane and 2.29 A vertically. One should note that the final 
5 = 0 compound only differs in composition from the prototype perovskite on 
the left side of Fig. VI-11 by the deficiency of two oxygens. 

7. Layering Scheme of YBaCuO 

In Section Vl-E-6 we discussed the Cu0 2 layering scheme of the LaSrCuO super- 
conductors. The layering scheme of the YBaCuO case, which is illustrated in 
Fig. Vl-13, is somewhat more complicated than the LaSrCuO case. There is a 
threefold layering sequence with the two median planes adjacent to the yttrium 
much closer together (3.18 A) than they are to the basal plane (4.25 A), as 
indicated in the figure. The basal plane copper ions Cu(t) are coupled to the 
median layer coppers Cu(m) through oxygens, and such coupling does not exist 
between the two median planes. The basal plane coppers and oxygens are in 



W 

HI 
W 

P 

HI* 



Ml 



■n 

23 



< 



100 



BSlS 
tti; 

to* 

.r 



If.,, 



"Mai 



! n':>, 
1; ' tJhtu 



CRYSTALLOGRAPHIC STRUCTURES 
1.93 A 




1.93 A 



t 

2.42 A 
i 

1.83 A 

„JL_ 

1.83 A 

2.42 A 
I 



3.18 A 





YBa 2 Cu 3 0 8 



YBa 2 Cu 3 0 7 



Fig. VI-12. Ordering of the YBaCuO copper atoms and their associated oxygen nearest 
neighbors along the c axis. The arrangement is a stacking of pyramid-octahedron-in- 
verted-pyramid groups in the tetragonal structure (left) and of pyramid-square-planar- 
inverted-pyramid groups in the orthorhombic structure (right). 



special sites so the plane is perfectly flat, as shown. In contrast to this the median 
plane coppers and oxygens are both in general sites with slightly different z pa- 
rameters, so the median planes have a puckered appearance with a thickness of 
about 0.23 A, as indicated in Figs. VI-9 and VI-13. 

The case illustrated in Fig. VI-13 corresponds to YBa 2 Cu 3 07_ 6 with 5 = 0, so 
the oxygen sites along the a direction of the basal plane are all empty and those 
along the b direction are all occupied. This produces Cu-O-Cu-O chains along 
the b direction, as shown in the figure. The missing oxygens cause the coppers to 
move slightly closer together along a, thereby inducing the orthorhombic distor- 



4.25 



3.18 



4.25 



Fig. VI-13. La; 

The layers are ] 
layers is indica 



tion with a < 
occupy the va 

8. YBaCuO 1 

Since yttrium 
that for the h 
copper is triv 
strong tender 
YBa 2 Cu 3 0 7 * 
O-Cu-O cooi 
ordered and \ 
case correspo 
of +2 and + 
an average c< 
cussed at gre 
An extra 1 
(Zandl) cons 



M 



YTTRIUM-BARIUM-COPPER OXIDE 



101 



? 




;d oxygen nearest 
i-octahedron-in- 
d-square-planar- 



»this the median 
i y different z pa- 
th a thickness of 

7 _ 6 with5 = 0, so 
empty and those 
i-O chains along 
ise the coppers to 
lorhombic distor- 




CuO 11.68* 



O 9.85 
Ba 9.52 



Cu0 2 7.43 



Y 5.84 



Cu0 2 4.25 



4 Ba 2.16 

< O 1.83 



CuO 0 



Fig. VM3- Layering scheme of the YBaCuO superconducting (orthorhombic) structure. 
The layers are perpendicular to the c axis. The extent of puckering of the median Cu0 2 
layers is indicated. 



tion with a < b. When the oxygen content increases (5 < 0), oxygens begin to 
occupy the vacant sites along a, 

8. YBaCuO Defect Structures 

Since yttrium has a charge of +3, barium is + 2, and oxygen is — 2, it follows 
that for the hypothetical compound YBa 2 Cu 3 0 8 which has 5 = —1, all of the 
copper is trivalent ( + 3). This compound cannot be prepared because of the 
strong tendency toward oxygen deficiency. We have seen that the compound 
YBa 2 Cu 3 0 7 with 5 = 0 has all of its oxygen loss in the basal plane where linear 
O-Cu-O coordination replaces square planar Cu0 4 . The oxygen vacancies are 
ordered and hence the copper ions form (Cu-0)„ chains in this plane. This 5 = 0 
case corresponds to an average copper charge of 2.33, which suggests a mixture 
of +2 and +3 copper valence states. Samples with 5 = 0.5 (e.g., Hazen) have 
an average copper charge of 2.0. This subject of copper valence has been dis- 
cussed at greater length in Section III-J. 

An extra layer of yttrium atoms (Ourma) or an extra or double CuO plane 
(Zandl) constitute common planar defects in the YBaCuO structure. The pres- 



HI 



JO 



s 

ftstj 

23 



nnui 

< 



I 



102 CRYSTALLOGRAPHIC STRUCTURES 



I;? 



tot. 



filial 



■ ill !■'"■'*• 
:!!! |W 



ence of such a planar defect may be visualized as enlarging a unit cell on the 
right-hand side of Fig. VI-11 from, in the yttrium case, a threefold Ba, Y, Ba 
sequence to a fourfold Ba, Y, Ba, Y sequence, with this sequence continuing 
indefinitely in the horizontal direction. Other unit cells are left unchanged. 
Square planar Cu0 2 has been found in the structures of (Y, ^BaJaCujOa and 
(Y l . jr Ba T ) 3 Cu 2 0 7 (Kitaz). 



G. OTHER LaSrCuO AND YBaCuO STRUCTURES 

The system La(Ba,. jr La r ) 2 Cu 3 07 + 6 has the region of solubility 0.125 < x < 0.25. 
These compounds are disordered isomorphs of the orthorhombic YBa 2 Cu 3 0 7 
structure (Segre). The highest T c = 60 K occurs for x = 0.065 and x = 0, the 
latter stoichiometric compound LaBa 2 Cu 3 0 7 . 5 being outside the range of solubil- 
ity. The compounds La 2 SrCu 2 0 62 , La 4 BaCu s O, 3 , and La 5 SrCu 6 0 I5 are not su- 
perconducting (Torrl). 

Studies of related superconducting compounds such as (La,. 6 Bao. 4 )Cu0 4 _ 5 , 
(La 0 . 8 Ba 0 . 2 )CuO 4 _ 5 , and (Y 0 . 8 Bao. 2 )Cu0 4 _ 6 (Kirsl, Kirs2), and (Y 0 . 4 Bao. 6 )Cu0 3 
(Luozz) have been reported. See also Bedn4. 

The green semiconducting phase Y 2 BaCuO s which is often found admixed 
with superconducting YBa* is orthorhombic and was assigned to the space 
group Pbnm, Z)|£ or Pna2 u C 9 2v (Hazen, Kitan, Mansf, Mich2, Raozz, Rossz) 
with a = 7.1 A, b = 12.2 A, and c = 5.6 A. 

The compound La 2 Cu0 4 was identified as the first member (n = 1) of the 
homologous series of composition R n+1 M /1 0 3 „ +1 with R = La and M = Cu in 
the present case (Davie). Several members of the series were prepared with n in 
the range from 1 to 6, and their crystallography consisted of slabs of (LaCu0 3 )„ 
groups containing Cu0 6 octahedra with a perovskite-type structure separated by 
layers of LaO with the La and O atoms in an NaCl-type structure, as shown on 
Fig. VI- 14. The perovskite LaCu0 3 , which plays the role of the limiting struc- 
ture of La„+,Cu„0 3/1 + i as n -* oo, is shown for comparison. 

Other oxide types have also been mentioned in the literature/such as the pos- 
sible lower symmetry space groups of the R 2 M0 4 structure arising from rigid 
octahedral tiltings at phase transitions (Hatch). 



H. BISMUTH-STRONTIUM-CALCIUM-COPPER OXIDE 

Early in 1988 two new superconducting systems were discovered which have 
transition temperatures considerably above those attainable with the YBaCuO 
compounds, namely, the bismuth- (Chuz2, Maeda, Zand2) and the thallium- 
(Gaoz2, Hazel, Sheng, Shenl) based materials. In this section we will discuss 
the structure of BiSrCaCuO, and in the next we will treat TIBaCaCuO. 

The 2212 compound Bi 2 (Sr,Ca) 3 Cu 2 O s+6 crystallizes in the same tetragonal 
space group IA/mmm, D\l as La 2 Cu0 4 with two formula units per unit cell and 




Fig. VI-14. Ides 
La„ + |Cu„0 3/ , + i v 
squares are CuO, 
gonal cell is proj< 



the lattice parai 
the atoms are: 



where the aton 
those for site 0 
following atom 

(8« 



Table VI-12 gi 
have been repo 



BISMUTH-STRONTIUM-CALCIUM-COPPER OXIDE 103 



cell on the 
Ba, Y, Ba 
continuing 

unchanged. 

3 Cu 2 0 6 and 



< x < 0.25. 
YBa 2 Cu 3 0 7 
ix = 0, the 
ge of solubil- 
5 are not su- 

3ao.4)Cu0 4 -6, 
M Bao.6)Cu0 3 

ind admixed 
to the space 
*aozz, Rossz) 

t = 1) of the 
J M = Cu in 
ired with n in 
of (LaCu0 3 )„ 
; separated by 
, as shown on 
imiting struc- 

lch as the pos- 
ing from rigid 



ed which have 
i the YBaCuO 
1 the thallium- 
we will discuss 
:aCuO. 

ame tetragonal 
er unit cell and 




Fig, VI-14. Idealized representations of the structures of the series of compounds 
La„ +1 Cu„0 3 „ +1 with (a)» = l ( (6)n = 2, (c) n = 3, and (d) LaCu0 3 (n = oo). The 
squares are Cu0 6 octahedra and the solid circles denote La atoms. In (a)-(c) the tetra- 
gonal cell is projected down [010] and the c axis is vertical (Davie). 



the lattice parameters a = 3.817 A, c = 30.6 A (Tara9). The parameters for 
the atoms are: 



Ca 


(2a) 








Sr 


(4e) 


u 


= 0.1097 




Bi 


(4e) 


u 


= 0.3022 


87% occupancy 


Bi 


(4e) 


u 


= 0.2681 


13% occupancy 


Cu 


(4e) 


u 


= 0.4456 




O(l) 


(8g) 


u 


= 0.446 




0(2) 


(4e) 


u 


= 0.375 




0(3) 


(4e) 


u 


= 0.205 




0(4) 


(4d) 






6.5% occupancy 



where the atom positions for sites (2a) and (4e) are given above in Eq. VI-6, 
those for site (4d) are given by Eq. VI-7, and the remaining site (8g) has the 
following atom positions: 

(8g) 0,£,w; 0,£, — w; ^,0,w; ^,0, — u\ 13) 

Table VI-12 gives more details on the atom positions. Superlattice structures 
have been reported along a and b (Iqba6). 



104 CRYSTALLOGRAPHIC STRUCTURES 



TABLE VI-12. Atom Positions of Bi 2 Sr 2 CaCu 2 0 8+5 Structure with Two Formula 
Units per Unit Cell 0 



Complex 


Vertical 
Position 


Atom 


Site 


X 




2 


ca 


30.6 


Ca 


2a 


0 


0 


1.0 




29.0 


O(l) 


8g 


0 


1 

2 


0.9460 




29.0 


O(l) 


8g 


1 

2 


0 


0.9460 




28.9 


Cu 


4e 


1 

2 


1 

2 


0.9456 


c 


27.2 


Sr 


4e 


0 


0 


0.8903 




26.8 


0(2) 


4e 


2 


t 
2 


0.8750 


UBl 


24.5 


Bi 


4e 


2 


2 


0.8022 




24.3 


0(3) 


4e 


0 


0 


0.7950 


biU 2 


23.0 


Bi' 


4e 


1 

2 


2 


0.7681 




23.0 


0(4) 


2d 


0 


1 

2 


3 
4 




23.0 


0(4) 


2d 


1 

2 


0 


3 
4 




22.4 


Bi' 


4e 


0 


0 


0.7319 


d:/"\ 


21.6 


0(3) 


4e 


2 


1 

2 


0.7050 




21.4 


Bi 


4e 


0 


0 


0.6978 


AC- 

05>r 


19.1 


0(2) 


4e 


0 


0 


0.6250 




18.7 


Sr 


4e 


2 


1 

2 


0.6097 


Cu0 2 


17.0 


Cu 


4e 


0 


0 


0.554 




17.0 


O(l) 


8g 


0 


1 

2 


0.554 




17.0 


0(1) 


H 


2 


0 


0.554 


Ca 


15.3 


Ca 


2a 


1 

2 


1 

2 


2 


CuC) 2 


13.6 


0(1) 


8g 


2 


0 


0.4460 




13.6 


0(1) 


8g 


0 


I 

2 


0.4460 




13.6 


Cu 


4e 


0 


0 


0.4456 


OSr 


11.9 


Sr 


4e 


2 


1 

2 


0.3903 




11.5 


0(2) 


4e 


0 


0 


0.3750 


BiO 


9.25 


Bi 


4e 


0 


0 


0.3022 




9.03 


0(3) 


4e 


1 

2 


1 

2 


0.2950 


DIU2 


8.20 


Bi' 


4e 


0 


0 


0.2681 




7.65 


0(4) 


2d 


1 

2 


0 


4 




7.65 






n 


2 


l 




7.10 


Bi' 


4e 


I 
2 


2 


0.2319 


OBi 


6.27 


0(3) 


4e 


0 


0 


0.2050 




6.05 


Bi 


4e 


1 

2 


2 


0.1978 


SrO 


3.83 


0(2) 


4e 


1 

2 


2 


0.1250 




3.36 


Sr 


4e 


0 


0 


0.1097 


0 2 Cu 


1.66 


Cu 


4e 


2 


1 

2 


0.0544 




1.65 


O(l) 


H 


1 

2 


0 


0.0540 




1.65 


Oil) 


8g 


0 


2 


0.0540 


Ca 


0 


Ca 


2a 


0 


0 


0 


"The space group is IA/mmm t D^ h . 


The unit cell dimensions are a 


= 3.817 A,c 




30.6 A (Tara9). 



TABLE VI-13. At< 
IMmmm, D" h with 



Complex 



Ve 
Pc 



Ca 

0 2 Cu 



BaO 

OT1 

TIO 

OBa 

Cu0 2 



Ca 

Cu0 2 



OBa 

TIO 

OT1 

BaO 

0 2 Cu 

Ca 



"The unit cell dime 



I. THALLIUR 

The compounc 
IMmmm, D\l 
units per unit 
(Subra). The s 



BISMUTH-STRONTIUM-CALCIUM-COPPER OXIDE 



105 



» Formula 



TABLE VI-13. Atom Positions of Tl 2 Ba 2 CaCu 2 0 8 Structure Belonging to Space Group 
IMmmm, D< h with Two Formula Units per Unit Cell" 









Vertical 

▼ V»l liVHl 














z 


Complex 


Position 


A tntn 

/AlUIll 




X 


y 


z 


) 


1.0 


Ca 


29.32 


Ca 


2a 


0 


0 


1.0 


I 

2 


0.9460 


0 2 Cu 


27.76 


O(l) 


8g 


0 


i 

2 


0.9469 


) 


0.9460 




27.76 


O(l) 


8g 


i 

2 


0 


0.9469 


1 

2 


0.9456 




27.74 


Cu 


4e 


1 
2 


1 

2 


0.946 


D 


0.8903 


BaO 


25.75 


Ba 


4e 


0 


0 


0.8782 


i 

2 


0.8750 




25.04 


0(2) 


4e 


2 


1 

2 


0.8539 


1 

2 


0.8022 


OT1 


23.06 


Tl 


4e 


2 


1 

2 


0.7864 


3 


0.7950 




22.91 


0(3) 


16n 


0.104 


0 


0.7815 


i 

2 


0.7681 


TIO 


21.07 


0(3) 


16n 


0.604 


1 

2 


0.7185 


1 

2 


3_ 
4 




20.92 


Tl 


4e 


0 


0 


0.7136 


D 


3 
4 


OBa 


18.94 


0(2) 


4e 


0 


0 


0.6461 


0 


0.7319 




18.23 


Ba 


4e 


i 

2 


1 

2 


0.6218 


i 

2 


0.7050 


Cu0 2 


16.24 


Cu 


4e 


0 


0 


0.5540 


0 


0.6978 




16.22 


O(l) 


8g 


0 


t 

2 


0.5531 


0 


0.6250 




16.22 


O(l) 


8g 


1 

2 


0 


0.5531 


2 


0.6097 


Ca 


14.66 


Ca 


2a 


2 


2 


I 

2 


0 


0.554 


Cu0 2 


13.10 


O(l) 


8g 


2 


0 


0.4469 


1 

2 


0.554 




1 J.1U 


O(l) 


8g 


0 


1 

2 


0.4469 


0 


0.554 




13.08 


Cu 


4e 


0 


0 


0.4460 


1 

2 


2 


OBa 


11.09 


Ba 


4e 


2 


2 


0.3782 


0 


0.4460 




10.38 


0(2) 


4e 


0 


0 


0.3539 


1 

2 


0.4460 


TIO 


8.40 


Tl 


4e 


0 


0 


0.2864 


0 


0.4456 




8.25 


0(3) 


16n 


0.604 


2 


0.2815 


1 

2 


0.3903 


OTI 


6.41 


0(3) 


16n 


0.104 


0 


0.2185 


0 


0.3750 




6.26 


Tl 


4e 


2 


1 

2 


0.2136 


A 

u 




BaO 


4.28 


0(2) 


4e 


1 

2 


2 


0.1461 


1 

2 


0.2950 




3.57 


Ba 


4e 


0 


0 


0.1218 


0 


0.2681 


0 2 Cu 


1.58 


Cu 


4e 


1 

2 


2 


0.0540 


0 


i 

4 




1.56 


O(l) 


8g 


1 

2 


0 


0.0531 


i 

2 






1.56 


O(l) 


8g 


0 


1 

2 


0.0531 


1 

2 

0 
1 
2 


0.2319 
0.2050 
0.1978 


Ca 


0 


Ca 


2a 


0 


0 


0 


"The unit cell dimensions are a 


= 3.8550 A,c 


= 29.318 A (Subra). 






1 

2 


0.1250 
















0 


0.1097 
















2 


0.0544 
















0 


0.0540 
















1 

2 


0.0540 
















0 


0 


I. THALLIUM-BARIUM-CALCIUM-COPPER OXIDE 







= 30.6 A (Tara9). 



The compound TI 2 Ba 2 CaCu 2 0 8 crystallizes in the same tetragonal space group 
14/rnmm, D\l as the bismuth compound described above, with two formula 
units per unit cell and the lattice parameters a = 3.8550 A, c — 29.318 A 
(Subra). The atoms are at the following sites: 



M 
S 



S3 

ft 



ft 



< 



106 CRYSTALLOGRAPHIC STRUCTURES 



■IB 

%: 

9k' 

•*« 

r 

IfLtfW 

If* 

'Mil*, 



nEt 11*.* 

'Jit Itaitii 



Ca 


(2a) 






Tl 


(4e) 


u 


= 0.21359 


Ba 


(4e) 


u 


= 0.12179 


Cu 


(4e) 


u 


= 0.0540 


O(l) 


(8g) 


u 


= 0.0531 


0(2) 


(4e) 


u 


= 0.1461 


0(3) 


(16n) 


V 


= 0.604, 



(VI-14) 



u = 0.2815 



where the atom positions for sites (2a), (4e), and (8g) are the same as in the 
previous section. The remaining i occupied site (16n) has two parameters v and 
u, and the following possible atom positions: 

(16n) 0,v,u; 0,v,-w; 0,-v,u; 0,-v,-u; \,v+±,u + $; 

i,v+i-« + i; 0,-v+±,u+\; 0,-v+£,-u + * (yi . 15) 
v,0,u; v,0,-m; -v,0,u; -v,0,-m; v+±,\,u + \\ 





1WT 





TI 2 Ba 2 Cu0 6 



Tl2Ba 2 Ca2Cu30 10 



TI 2 Ba 2 CaCu208 

Fig- VMS. Tetragonal unit cells of three thallium-copper oxide superconductors, 
Tl 2 Ba 2 Ca /I Cu H+1 0 6+2/1 with, from left to right, n = 0, 1, 2. Metal atoms are shaded and 
Cu-O bonds are shown (Tora2). 



Table VI-13 gi 
sketch of the s 



J. SITE SYM 

Some experirr 
spectroscopy, 
metry of parti' 
symmetries at 
These symmel 
for point grou 



TABLE VI 14. 
(with 100% sto 

Space Group 



Pm3m, Ol 



Amm2, 



lA/mmm, D x l 



PA/mmm, D A] 



SITE SYMMETRIES 107 



Table VI-13 gives more details on the atom positions and Fig. VI-15 presents a 
sketch of the structure. 



J. SITE SYMMETRIES 

Some experiments such as electron spin resonance of transition ions, optical 
spectroscopy, and infrared spectroscopy provide data that depend upon the sym- 
metry of particular lattice sites. Table VI- 14 lists for reference purposes the site 
symmetries at all of the lattice sites in the various structures mentioned above. 
These symmetries are given in both the International and Schoenflies notations 
for point groups. 



TABLE VI- 14. Point Symmetries at Lattice Sites of Various Compounds 
(with 100% stoichiometry)" 



Space Group 



Site 



Atom 



Point Symmetry 



Cubic Perovskite BaTiO? 



Pm3m, O l h 



Amml, C\l 



14/ mmm, D\l 



Fmmm, Df h 



P4/mmm, D\ 



Ah 



(la) 


Ba 


m3m 


o h 


(lb) 


Ti 


m3m 


o h 


(3c) 


O 


4/mmm 




Orthorhombic Perovskite BaTiOj 






(2a) 


Ba,0(l) 


mm 




(2b) 


Ti 


mm 


Civ 


(4e) 


0(2) 


m 


c s 




Tetragonal La 2 Cu0 4 






(2a) 


Cu 


4/mmm 




(4c) 


O(l) 


mmm 


£> 2h 


(4d) 


0(2)(alt.str.) 


4m2 




(4e) 


La,0(2) 


4mm 




Orthorhombic La2Cu0 4 (Longo) 






(4a) 


Cu 


mmm 




(8e) 


O(l) 


2/m 


Cm, 


(8i) 


La,Q(2) 


mm 


Civ 


Tetragonal YBa^CujOg (Borde, Jorge) 






(la) 


Cu(t) 


4/mmm 


D 4h 


(Id) 


Y 


4/mmm 


£>4h 


(2f) 


O(t) 


mmm 




(2g) 


Cu(m), 0(b) 


4mm 


c 4v 


(2h) 


Ba 


4mm 




(4i) 


0(m) = O(m') 


mm 





108 



CRYST ALLOC RAPHIC STRUCTURES 



I* 1 
•it 

lift 



'Hi 

iff-" 

'If; 
kr 

If 1 ; 

Hi'' 
to*- 

If* 



Knit 



'I IE; 



'Sitlj! 



TABLE VM4. (continued) 



Space Group 



Site 



Atom 



Point Symmetry 



Tetragonal YBa 2 Cu 3 0 8 (Hazen) 



P4m2, D 5 2d 



(la) 


Cu(t) 


42m 


Du 


(lc) 


Y 


42m 


Du 


(2e) 


Cu(m),0(b) 


mm 


Civ 


(20 


Ba 


mm 


C2v 


(2g) 


O(0,O(m),O(m') 


mm 


C2v 



Pmmm, D x 2h 



Pbnm,D\l 
"Green Phase" 



Orthorhombic YBafiu 3 0 8 b 

(la) Cu(t) 

(lb) O(t') 

(le) O(t) 

(lh) Y 

(2q) Cu(m),0(b) 

(2r) O(m') 

(2s) O(m) 

(2t) Ba 

Orthorhombic Y 2 BaCu0 5 (Hazen) 

(4c) Cu,Ba,Y(l),Y(2),0(3) 
(8d) 0(1),0(2) 



mmm 

mmm 

mmm 

mmm 

mm 

mm 

mm 

mm 



m 
1 



Tetragonal Bi2Sr 2 CaCu 2 0 8 TlfiafiaCufis (Tara9, Subra) 
Wmmm,D x l (2a) Ca 4 /mmm 



(46) 0(4) 

(4e) Ba,Bi,Cu,0,Sr,Tl 

(8g) O 

(16n) O 



4m2 
4mm 



D 2h 

D 2h 
D 2h 
D 2h 

C 2v 

C 2v 

c 2v 

C 2v 



D 4h 

c 4v 



"In particular, sites such as Cu(t) in YBa 2 Cu 3 0 7 with nearest-neighbor oxygens missing have point 
symmetries lower than those given. 
*See Table VI-6. 



K. STRUCTURAL ORIGIN OF SUPERCONDUCTIVITY 

Various types of evidence presented throughout this review support the conten- 
tion that the copper oxide planes play a crucial role in the origin of the supercon- 
ductivity of the LaSrCuO and YBaCuO compounds. It has also been proposed 
that the CuO chains are required for the superconductivity of YBaCuO (Bardl , 
Toral, Vandl), perhaps through coupling to the Cu0 2 planes (Engl2, Murp2). 
Opinions of this type were widely held prior to the discovery of the bismuth and 
thallium compounds described in the sections above. These new materials are 
tetragonal with all of the oxygen sites occupied on the Cu0 2 planes, and hence 
no chains are present. The commonalities of these various superconductor types 
have been discussed (PoolS). 



VII 



OTHER 



A. INTRODl 

The previous c 
YBaCuO, BiSi 
details such a* 
ments were str 
will be treated 
. tropies, and la 
We mentioi 
conductors we 
ties of the new 
in their cation 
or trivalent ca 
deficiency and 
begin the cha 
instabilities wi 
tions, the isot" 
on elastic and 



B. OXYGEN 

The newer ox: 
many of the c 
oxygen atoms 
lated (Tara7). 



ATTACHMENT B 



Jim Leonard 
05/24/98 02:38 PM 



To: Daniel P Morris/Watson/IBM@IBMUS 

cc: 

From: 

Subject: Layered Like or Type 
Dan, 

For Layered Like or Type, here are some article abstracts. One book was found for Layered Type. 

Article listing are from a search of INSPEC on DIALOG. 

If citation information is needed, let me know. 

All the best, 

Jim 

James W. Leonard, Reference Librarian, Watson Library Services. Room 16-240 
IBM TJ Watson Research Center, 
Route 134, YorktownHts. NY 10598. 
jwl@us.ibm.com 

Voice=(914) 945 3468; Fax=(914) 945 4144 
★♦♦♦♦★a********************************************** 



File 2: INSPEC 19 69 - 199 8/May W3 

(c) 1998 Institution of Electrical Engineers 



********************************^^ 



Layered like 

?»s layered () like 

23991 LAYERED 
136878 LIKE 

513 5 LAYERED () LIKE 
?*s sl3 and py=1969:1985 

5 S13 

2642109 PY=1969 : PY=1985 

514 1 S13 AND PY=1969:1985 
?*t 14/7/1 

14/7/1 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

02401641 INSPEC Abstract Number: A85032877 

Title: Polymorphism of diphthalocyanine-neodymium. Molecular and crystal 
structure of beta phase 

Author(s): Darovskikh, A.N.; Tsytsenko, A.K.; Frank-Kamenetskaya, O.v.; 
Fundamenskii, V.S.; Moskalev, P.N. 



Author Affiliation: Inst, of Nucl. Phys., Acad, of Sci., Leningrad, USSR 
Journal: Kristallograf iya vol.29, no. 3 p. 455-61 
Publication Date: May-June 1984 Country of Publication: USSR 
CODEN: KRISAJ ISSN: 0023-4761 

Translated in: Soviet Physics - Crystallography vol.29, no. 3 p. 273-6 
Publication Date: May-June 1984 Country of Publication: USA 
CODEN: SPHCA6 ISSN: 0038-5638 

U.S. Copyright Clearance Center Code: 0038-5638/84/030273-04$03.90 
Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: X-ray structural analysis reveals that diphthalocyanine-neodymi 
urn, with the composition PcNdPc/sub ox/ (Pc=(C/sub 32/H/sub 16/N/sub 
8/) /sup 2-/, Pc/sub ox/=(C/sub 32/H/sub 16/N/sub 8/) /sup 1-/) exists in 
three polymorphic modifications- tetragonal alpha , orthorhombic gamma , and 
monoclinic beta . Determination of the crystal structure of the beta phase 
(P2/sub 1/ automatic dif f ractometer, theta -2 theta method, Mo K alpha , 
R=0.052) revealed that it is of the structural type Pc/sub 2/U. The 
sandwich molecules are packed in layers parallel to the ac plane. The 
metal -ligand distance in the structure of Pc/sub 2/M (where M is a metal 
ion) is explained by the ratio between the ionic radii (r/sub Nd/>r/sub 
u/>r/sub Sn/) . The angle of relative rotation of the ligands is apparently 
determined by the character of the packing. Comparing the identity periods 
T/sub perpendicular to / perpendicular to the layers of molecules in the 
alpha , beta , and gamma modifications of diphthalocyanine-neodymium 
(2T/sup alpha //sub (001)/=T/sup beta //sub (001) /sin beta =T/sup gamma 
//sub (101)/)/ one sees that the M-ligand distances are stable in these 
structures. The relation between the periods T/sup beta //sub (100)/ 
approximately=T/sup beta //sub (010)/ approximately=l/2T/sub (110) //sup 
alpha / in the alpha and beta phases shows that the tetragonal structure is 
evidently layered like the beta phase. (10 Refs) 

******************************************* 



Layered type 



?«s layered () type 

23991 LAYERED 
419473 TYPE 

515 80 LAYERED () TYPE 
?*s sl5 and py=1969:1985 

80 S15 
2642109 PY=1969 : PY=1985 

516 15 S15 AND PY=1969:1985 
?«t 16/7/1-15 

16/7/1 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

02616964 INSPEC Abstract Number: B86015292 

Title: A study of the breakdown mechanism in dual -layer MOS capacitor 
dielectrics 

Author (s): Domangue, E.; Hickman, T.; Pyle, R. ; Rivera, R. 
Author Affiliation: Motorola Inc., Austin, TX, USA 

Conference Title: 35th Electronic Components Conference (Cat. No. 
85CH2184-0) p. 396-9 

Publisher: IEEE, New York, NY, USA 

Publication Date: 1985 Country of Publication: USA 516 pp. 
U.S. Copyright Clearance Center Code: 0569-5503/85/0000-0396$01.00 
Conference Sponsor: IEEE; Electron. Ind. Assoc 

Conference Date: 20-22 May 1985 Conference Location: Washington, DC, 
USA 



Language: English Document Type: Conference Paper (PA) 
Treatment: Experimental (X) 

Abstract: The time to break down distribution of MOS capacitors 
fabricated with a multilayer dielectric was studied- The dielectric was 
composed of 10 nm of thermal silicon dioxide, 15 nm of LPCVD silicon 
nitride, and 1-3 nm of SiO/sub 2/ thermally grown on the Si/sub 3/N/sub 4/ 
layer. The test capacitor was constructed with paralleled storage cells in 
a 64K dynamic memory device. Various electric fields and temperatures were 
used to stress the layered type of capacitors and a control group 
consisting of the same vehicle but having a 39 nm silicon dioxide 
dielectric- Stressed units were physically analyzed to isolate the failure 
sites. The type and location of the dielectric breakdown faults were found 
to be similar in both types of dielectric structure. The layered dielectric 
demonstrated superior reliability, however, which is attributed to lower 
detectivity or the spatial variation of the applied electric field within 
the structure. (9 Refs) 



16/7/2 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

02506581 INSPEC Abstract Number: A85096207 

Title: Reflectivity, joint density of states and band structure of group 
ivb transition-metal dichalcogenides 

Author (s): Bayliss, S.C.; Liang, W.Y. 

Author Affiliation: Cavendish Lab., Cambridge Univ., UK 
Journal: Journal of Physics C (Solid State Physics) vol.18, no. 17 
p. 3327-35 

Publication Date: 20 June 1985 Country of Publication: UK 
CODEN: JPSOAW ISSN: 0022-3719 

U.S. Copyright Clearance Center Code: 0022-3719/85/173327+09$02.25 
Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: Optical joint density of states (OJDOS) functions have been 
obtained from Kramers -Kronig analysis of reflectivity measurements for the 
layered-type materials TiS/sub 2/, TiSe/sub 2/, ZrS/sub 2/, ZrSe/sub 2/, 
HfS/sub 2/ and HfSe/sub 2/. The reflectivity measurements were made at 
near-normal incidence over the photon energy range 0.6-14 eV at 77K. 
Comparison of the OJDOS functions shows that there are many similarities in 
the band shapes which can be explained in terms of the amount of trigonal 
distortion present in the crystal lattice and the differences in binding 
energy of electron levels in the atoms. (9 Refs) 



16/7/3 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

02225943 INSPEC Abstract Number: A84041348, B84023254 

Title: Hydriodic acid photodecomposition on layered- type transition metal 
dichalcogenides 

Author (s): Bicelli, L.P.; Razzini, G. 

Author Affiliation: Dept. of Appl. Phys. Chem., Milan Polytech., Milan, 
Italy 

Journal: Surface Technology vol.20, no. 4 p. 393-403 
Publication Date: Dec. 1983 Country of Publication: Switzerland 
CODEN: SUTED8 ISSN: 0376-4583 

U.S. Copyright Clearance Center Code: 0376 -4583/83/$3 . 00 
Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: The photodecomposition of hydriodic acid on platinized 
n-WSe/sub 2/ single crystals immersed in an aqueous 1 M HI solution was 
studied. During the photodecomposition process, hydrogen evolution only 



occurred on the microscopic defects of the sample surface, whereas iodine 
was produced on the smooth areas where a diffuse orange -red colouring 
appeared. For polycrystalline specimens/ however, hydrogen gas bubbles were 
formed over the entire surface, the rate of process being markedly slower 
than on single crystals. The results are discussed with the assumptions 
that the n-WSe/sub 2/ single crystals behave as Schottky- type photochemical 
diodes, that the cathodic reaction takes place on the stepped 
platinum- covered areas and that the anodic reaction occurs on the smooth 
unplatinized areas. (26 Refs) 



16/7/4 

DIALOG (R) Pile 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

02085031 INSPEC Abstract Number: A83077984, B83041973 
Title: Mechanistic studies of reversible layer- type electrodes 
Author(s): Rouxel, J.; Molinie, P.; Top, L.H. 
Author Affiliation: Lab. de Chimie des Solides, Nantes, France 
Journal: Journal of Power Sources vol.9, no. 3-4 p. 345-57 
Publication Date: April-May 1983 Country of Publication: Switzerland 
CODEN: JPSODZ ISSN: 0378-7753 

U.S. Copyright Clearance Center Code: 0378-7753/83/0000 -0000/$3 . 00 
Conference Title: International Meeting on Lithium Batteries 
Conference Date: 27-29 April 1982 Conference Location: Rome, Italy 
Language: English Document Type: Conference Paper (PA); Journal Paper 
(JP) 

Treatment: Theoretical (T) 

Abstract: In layered type intercalation electrodes ions are stored 
reversibly during the functioning of secondary batteries. The behaviour of 
the system depends on geometrical and electronic factors. The geometrical 
factors are concerned with the localization of the ions in the host 
structure; they deal with average structure determinations and local 
ordering problems. The diffusion properties of the intercalated ions depend 
on the site geometry, the population of the Van Der Waals gap, the ionicity 
of the bonds in the host, the stoichiometry of the host, and the mechanical 
properties of its slabs. Electrons have to be accommodated by the host. The 
band structure of the host plays an important role in respect of the 
ability to intercalate, the phase limit, and the stability of the products. 
Metal -insulator transition may be induced. Other possible factors such as 
Jahn-Teller effects have also to be considered. (23 Refs) 



16/7/5 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

01994480 INSPEC Abstract Number: A83023215 

Title: Structure of tungstic acids and amorphous and crystalline WO/sub 3/ 
thin films 

Author(s): Ramans, G.M.; Gabrusenoks, J. v.; Veispals, A. A. 
Author Affiliation: Inst, of Solid State Phys., P. Stucka Univ., Riga, 
USSR 

Journal: Physica Status Solidi A vol.74, no.l p.K41-4 
Publication Date: 16 Nov. 1982 Country of Publication: East Germany 
CODEN: PSSABA ISSN: 0031-8965 

Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: The authors compare the Raman spectra of a -wo/sub 3/ with 
spectra of crystalline WO/sub 3/.H/sub 2/0, WO/sub 3/.2H/sub 2/0 and 
amorphous bulk WO/sub 3/.H/sub 2/0. It is concluded from the results that 
the structure of a-wo/sub 3/ films consists of a layered type structure of 
tungsten hydrates and of a framework structure of tungsten anhydride. The 
band at 59 0 cm/sup -1/ is attributed to stretching modes of the terminal 



oxygen. By dehydration of amorphous WO/sub 3/. 1.74 H/sub 2/0 one can get 
amorphous bulk samples with a structure similar to the a -WO/sub 3/ thin 
films. (12 Refs) 



16/7/6 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

01973788 INSPEC Abstract Number: A83008001 

Title: Synthesis of new layered- type and new mixed- layered- type bismuth 
compounds 

Author (s): Kodama, H.; Watanabe, A. 

Author Affiliation: Nat. Inst, for Res. in Inorganic Materials, Ibaraki, 
Japan 

Journal: Journal of Solid State Chemistry vol.44, no. 2 p. 169-73 
Publication Date: Sept. 1982 Country of Publication: USA 
C0DEN: JSSCBI ISSN: 0022-4596 

U.S. Copyright Clearance Center Code: 0022-4596/82/110169 - 05$02 . 00/0 
Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: Four new compounds, PbBi/sub 2/TiTaO/sub 8/F, PbBi/sub 
2/TiNbO/sub 8/F, Bi/sub 5/Ti/sub 2/WO/sub 14/F, and Bi/sub 7/Ti/sub 5/O/sub 
20/F, were prepared and identified by X-ray diffraction analysis. Two of 
them are new members of a family called layered bismuth compounds. The 
other two are new members of a family called mixed- layered bismuth 
compounds. Thermal properties of the new compounds were studied. Moreover, 
the possibility of the existence of other new members belonging to the 
family called mixed- layered bismuth compounds is discussed. (14 Refs) 



16/7/7 

DIALOG (R) File 2 : INSPEC 

(c) 1998 institution of Electrical Engineers. All rts. reserv. 

01891945 INSPEC Abstract Number: A82076639 

Title: The phase relations in the Yb/sub 2/0/sub 3/-Fe/sub 2/O/sub 3/ -MO 
systems in air at high temperatures (M: Co, Ni, Cu, and Zn) 

Author (s): Kimizuka, N.; Takayama, E. 

Author Affiliation: Nat. Inst, for Res. in Inorganic Materials, 
Ibaraki-ken, Japan 

Journal: Journal of Solid State Chemistry vol.42, no.l p. 22-7 
Publication Date: 15 March 1982 Country of Publication: USA 
C0DEN: JSSCBI ISSN: 0022-4596 

Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract- The phase relations in the Yb/sub 2/0/sub 3/-Fe/sub 2/0/sub 
3/-COO system at" 1350 and 1300 degrees C, the Yb/sub 2/0/sub 3/-Fe/sub 
2/0/sub 3/-N10 system at 1300 and 1200 degrees C, the Yb/sub 2/0/sub 
3/-Fe/sub 2/0/sub 3/-Cu0 system at 1000 degrees C and the Yb/sub 2/0/sub 
3/-Fe/sub 2/0/sub 3/-ZnO system at 1300 degrees c were determined in air by 
means of a classical quenching method. New layered- type compounds, 
YbFeCoO/sub 4/ (a=3.4295(5) AA, C=25. 198(3) AA) , YbFeCuO/sub 4/ 
(a=3 4808 (2) AA, c=24.100 (2) AA) , and YbFeZnO/sub 4/ (a=3.4251(2) AA, 
c=25 282 (2) AA) , which are isomorphous with YbFe/sub 2/0/sub 4/ (space 
group: R3m; a=3. 455(1) AA, c=25. 109(2) AA) , and a new compound, Yb/sub 
2/Cu/sub 2/0/sub 5/, were obtained. In the Yb/sub 2/0/sub 3/-Fe/sub 2/O/sub 
3/-NiO system, there are no quaternary compounds. (10 Refs) 



16/7/8 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 



01816212 INSPEC Abstract Number: C82012609 

Title: Office automation technology- storage and retrieval of information 
Author (s): Kurachi, T. 

Author Affiliation: Toshiba Corp., Ome-shi, Japan 

Journal: Journal of the Institute of Electronics and Communication 
Engineers of Japan vol.64, no. 2 p. 143-9 

Publication Date: Feb. 1981 Country of Publication: Japan 
CODEN: IECJAJ ISSN: 0373-6121 

Language: Japanese Document Type: Journal Paper (jp) 
Treatment: Applications (A); Practical (P) 

Abstract: The file compositions ordered using link and direct using a 
page map and B tree type retrieval order are described. Layered type data 
models as in IBM's IMS, and the MRI System 2000, network type data models 
as in GE's IDS and Cineam Systems 1 TOTAL, relational type data model as in 
IBM's System R and Software AG's ADABAS and distributed type data base are 
also described. The types of retrieval and their call words are discussed 
and exemplified. Floppy disc, magnetic drum, magnetic disk, large capacity 
memory devices and backend systems and database machines are discussed. 
Micrographics and graphic information files are briefly discussed. (13 
Refs) 



16/7/9 

DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

01587609 INSPEC Abstract Number: A80098966 

Title: A method of measurement of the refractive indices of crystals with 
layered structure 

Author(s): Allakhverdiev, K.R.; Guliev, R.I.; Salaev, E.Yu.; Kulevskii, 
L.A.; Savelev, A.D.; Smirnov, V.V. 

Author Affiliation: Inst, of Phys., Acad, of Sci., Baku, Azerbaidzhan 
SSR, USSR 

Journal: Physica Status Solidi A vol.60, no.l p. 309-12 
Publication Date: 16 July 1980 Country of Publication: East Germany 
CODEN: PSSABA ISSN: 0031-8965 

Language: English Document Type: Journal Paper (JP) 
Treatment: New Developments (N) ; Experimental (X) 

Abstract: A method of determining the refractive indices of the ordinary 
(n/sub o/) and extraordinary (n/sub e/) rays in crystals with layered type 
structure are described. The refractive indices of layered CdlnGaS/sub 4/ 
and TllnS/sub 2/ are measured using this technique with the help of laser 
radiation source at 0.63, 1.15, and 3.39 mu m. The experimentally obtained 
values of n/sub o/ and n/sub e/ are extrapolated from 0 . 6 to 4 . 0 mu m by 
the formulas n/sub o//sup 2/=A+B( lambda /sup 2/+C) ; n/sub e//sup 2/=K+L/( 
lambda /sup 2/+M) . The values of the extrapolation coefficients A, B, C, K, 
L, and M for CdlnGaS/sub 4/ and TllnS/sub 2/ crystals are obtained using 
the electronic computer Mir-2. (4 Refs) 



16/7/10 
DIALOG (R) File 2: INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

01496111 INSPEC Abstract Number: B80019231 
Title: Fabrication of 8 turn multi- track thin film heads 

Author(s): Hanazono, M. ; Kawakami, K.; Narishige, S.; Asai, 
E.; Okuda, K.; Ono, K. ; Tsuchiya, H.; Hayakawa, W. 

Author Affiliation: Hitachi Res. Lab., Hitachi Ltd., Ibaraki, 

Journal: IEEE Transactions on Magnetics vol. MAG- 15, no. 6 

Publication Date: Nov. 1979 Country of Publication: USA 

CODEN: IEMGAQ ISSN: 0018-9464 

Conference Title: Joint I NTERMAG - MMM Conference 

Conference Sponsor: IEEE 



0.; Kaneko, 

Japan 
p. 1616-18 



Conference Date: 17-20 July 1979 Conference Location: New York, NY, 
USA 

Language: English Document Type: Conference Paper (PA); Journal Paper 
(JP) 

Treatment: Practical (P) - 

Abstract: To obtain high bit and high track densities, fabrication of 
thin film magnetic recording heads have been studied by a number of 
companies. The authors describe a newly developed method for fabricating 
layered type, multi-turn, multi-track thin film inductive heads with a 
central tap by using photolithographic and thin film deposition techniques. 
(6 Refs) 



16/7/11 
DIALOG (R) File 2 : INSPEC 

(c) 1998 institution of Electrical Engineers. All rts. reserv. 

01406419 INSPEC Abstract Number: A79086309 

Title: A theoretical study of the effects of various laryngeal 
configurations on the acoustics of phonation 
Author (s): Titze, I.R.; Talkin, D.T. 

Author Affiliation: Sensory Communication Res. Lab., Gallaudet Coll., 
Washington, DC, USA 

Journal: Journal of the Acoustical Society of America vol.66, no.l 
p. 60-74 

Publication Date: July 1979 Country of Publication: USA 
CODEN: JASMAN ISSN: 0001-4966 

Language: English Document Type: Journal Paper (JP) 
Treatment: Theoretical (T) 

Abstract: Simulation of glottal volume flow and vocal fold tissue 
movement was accomplished by numerical solution of a time -dependent 
boundary value problem in which nonuniform, orthotropic, linear, 
incompressible vocal fold tissue media were surrounded by irregularly 
shaped boundaries, which were either fixed or subject to aerodynamic 
stresses. Spatial nonunif ormity of the tissues was of the layered type, 
including a mucosal layer, a ligamental layer, and muscular layers. 
Orthotropy was required to stabilize the vocal folds longitudinally and to 
accommodate large variations in muscular stress. Incompressibility and 
vertical motions at the glottis played an important role in producing and 
sustaining phonation. A nominal configuration for male fundamental speaking 
pitches was selected, and the regulation of fundamental frequency, 
intensity, average volume flow, and vocal efficiency was investigated in 
terms of variations around this nominal configuration. Vocal intensity and 
efficiency are shown to have local maxima as the conf igurational parameters 
are varied one at a time. It appears that oral acoustic power output and 
vocal efficiency can be maximized by proper adjustments of longitudinal 
tension of nonmuscular (mucosal and ligamental) tissue layers in relation 
to muscular layers. Quantitative verification of the ■body-cover 1 theory is 
therefore suggested, and several further implications with regard to 
control of the human larynx are considered. (17 Refs) 



16/7/12 
DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

01295844 INSPEC Abstract Number: A79010903 
Title: Optical phonons in TllnS/sub 2/ 
Author (s): Allakhverdiev, K.R.; Adigezalov, U.V.; Nani, R.Kh.; Yusifov, 

Yu G 

Journal: Izvestiya Akademii Nauk Azerbaidzhanskoi SSR, Seriya Fiziko- 
Tekhnicheskikh i Matematicheskikh Nauk no.l p. 21- 5 
Publication Date: 1978 Country of Publication: USSR 
CODEN: IAFMAF ISSN: 0002-3108 



Language: Russian Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: The optical phonons of a wide gap semiconducting TllnS/sub 2/ 
which has a layered type structure have been investigated by the method of 
long -wavelength infra-red (JR) and Raman scattering spectroscopy. The 
splitting of absorption bands is observed when the crystals are cooled down 
to 100K. The comparison of phonon frequencies determined from JR and Raman 
experiments revealed TllnS/sub 2/ to be centresymmetric. (10 Refs) 



16/7/13 
DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

01081136 INSPEC Abstract Number: A77063130 

Title: Field dependence of the susceptibility maximum for two-dimensional 
ant if erromagnet 

Author (s): Mostafa, M.F.; Semary, M.A.; Ahmed, M.A. 

Author Affiliation: Dept. of Phys., Faculty of Sci., Cairo Univ., Cairo, 
Egypt 

Journal: Physics Letters A vol.61A, no. 3 p. 183 -4 

Publication Date: 2 May 1977 Country of Publication: Netherlands 

CODEN: PYLAAG ISSN: 0375-9601 

Language: English Document Type: Journal Paper (JP) 
Treatment : Experimental (X) 

Abstract: The magnetic susceptibility measurements on layered type 
structure (CH/sub 3/NH/sub 3/) /sub 2/FeCl/sub 2/Br/sub 2/ revealed a 
transition temperature T/sub N/(H=0) approximately=100K. The transition 
temperature of (CH/sub 3/NH/sub 3/) /sub 2/FeCl/sub 4/ was previously found 
to be T/sub N/(H=0) approximately^ 5K. The effect of magnetic field on the 
transition temperature and peak intensity for both compounds has been 
investigated. (7 Refs) 



16/7/14 
DIALOG (R) File 2 : INSPEC 

(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

00360679 INSPEC Abstract Number: A72019924 
Title: Magnetic ordering in LiCr/sub 1-x/Fe/sub x/O/sub 2/ 
Author(s): Tauber, A.; Moller, W.M.; Banks, E. 

Author Affiliation: US Army Electronics Command, Fort Monmouth, N.J., USA 

Journal: Journal of Solid State Chemistry vol.4, no.l p. 138 -52 
Publication Date: Jan. 1972 Country of Publication: USA 
CODEN: JSSCBI ISSN: 0022-4596 

Language: English Document Type: Journal Paper (JP) 
Treatment: Experimental (X) 

Abstract: Magnetic ordering in the LiCr/sub 1-x/Fe/sub x/O/sub 2/ system 
has been investigated for polycrystal and single crystal specimens 
characterized by optical and X-ray diffraction techniques. Part of the 
Li/sub 2/O-Fe/sub 2/O/sub 3/-Cr/sub 2/O/sub 3/ system was also 
investigated. Magnetization and susceptibility measurements from 4.2 to 
900K and Mossbauer measurements from 4.2 to 300K indicate that all 
compositions of ordered rocksalt . (space group R3m) order 
antiferromagnetically at low temperatures. The first -order phase transition 
tracked with all Mossbauer parameters. The Weiss molecular field theory for 
a layered- type antif erromagnet was fitted with two exchange constants. The 
dependence of theta on x was found to be theta = theta /sub a/(l-x)/sup 2/+ 
theta /sub b/2x(l-x)+ theta /sub c/x/sup 2/, where - theta /sub a/=Cr/sup 
3+/-Cr/sup 3+/ interaction, + theta /sub b/=Fe/sup 3+/-Cr/sup 3+/ 
interaction and - theta /sub c/=Fe/sup 3+/-Fe/sup 3+/ interaction. A 
spontaneous magnetization associated with iron -substituted crystals 
originated with an epitaxial overgrowth of LiCr/sub 4.75/Fe/sub 0.25/O/sub 



8/. (29 Refs) 



16/7/15 
DIALOG (R) File 2 : INSPEC 

.(c) 1998 Institution of Electrical Engineers. All rts. reserv. 

00301052 INSPEC Abstract Number: C71019443 

Title: A static and dynamic finite element shell -analysis with 
experimental verification 
Author(s): Klein, S. 

Author Affiliation: Aerospace Corp., San Bernardino, CA, USA 
Journal: International Journal for Numerical Methods in Engineering 
vol.3, no. 3 p. 299-316 

Publication Date: July-Sept. 1971 Country of Publication: UK 
CODEN: IJNMBH ISSN: 0029-5981 

Language: English Document Type: Journal Paper (JP) 
Treatment: Theoretical (T) 

Abstract: A system of finite element shell analysis codes, called 
SABOR/DRASTIC, is used to analyse a complex two -layered shell of revolution 
under static and dynamic asymmetric loads. The dynamic analysis is compared 
with experimentally measured response. In this linear elastic analysis, 
emphasis is placed on the inherent flexibility of the finite element method 
in modelling the complex structural geometry of a given test specimen. 
Static studies, which involve variations in important shell parameters, and 
dynamic studies, which provide a successful correlation with experiment, 
are used to illustrate both the detail and the generality with which shell 
analyses may now be performed with confidence. 

**************************************************** ****************** 



Layered Like books = 0 



43=> f (layered -like) or (layered w like) 
Searching . . . 

SEARCH RESULTS 

Search Records Search Term 
ID Found 



543 0 layered- like 

544 1440 layered 

545 57219 like 

546 o (layered- like) or (layered w like) 



*********************** 



****************************** 



Layered Type books = 1 

47=> f (layered- type) or (layered w type) 
Searching . . . 

SEARCH RESULTS 



Search Records Search Term 
ID Found 



S47 
S48 
S49 
S50 



0 

1440 
82277 
1 



layered- type 

layered 

type 

(layered- type) or (layered w type) 



51=> f s50 and yr < 1986 
Searching . . . 

SEARCH RESULTS 



Search 

ID 



Records 
Found 



Search Term 



S51 



1 



s50 and yr < 1986 



52=> d s51 1 f8 
Record 1 of 1 
Copyright 1998 OCLC 
Page: 1 of 1 

AN: 23935341 

AU: Lee, Harry Nai-Shee, 1942- 

TI: Electrical transport properties of some hexagonal layered type 

transition metal chalcogenides . 

YR: 1969 

LN: English 

PT: Book 

PH: ix, 83 1. charts, diagrs. 28 cm. 



**************************************** ****^ 



This Page is Inserted by IFW Indexing and Scanning 
Operations and is not part of the Official Record 

BEST AVAILABLE IMAGES 

Defective images within this document are accurate representations of the original 
documents submitted by the applicant. 

Defects in the images include but are not limited to the items checked: 

□ BLACK BORDERS 

□ IMAGE CUT OFF AT TOP, BOTTOM OR SIDES 

□ FADED TEXT OR DRAWING 

□ BLURRED OR ILLEGIBLE TEXT OR DRAWING 

□ SKEWED/SLANTED IMAGES 

□ COLOR OR BLACK AND WHITE PHOTOGRAPHS 

□ GRAY SCALE DOCUMENTS 

□ LINES OR MARKS ON ORIGINAL DOCUMENT 

□ REFERENCE(S) OR EXHIBIT(S) SUBMITTED ARE POOR QUALITY 

□ OTHER: 

IMAGES ARE BEST AVAILABLE COPY. 
As rescanning these documents will not correct the image 
problems checked, please do not report these problems to 
the IFW Image Problem Mailbox.