Journal of Research of the National Bureau of Standards
The phase equilibrium diagram for the binary system bismuth sesquioxide- niobium pentoxide has been constructed from observations of fusion characteristics and X-ray diffraction data. In the system five binary compounds were observed with Bi2O3: Nb2O5 ratios of 5:3, 1:1, 4:9, 1:5, and 1:6. The 1:1 compound was found to transform irreversibly (in laboratory time) from the orthorhombic bismutotantalite type structure to a triclinic form at about 1,020 �C and melt congruently at 1,24.5 �C. The 5:3 compound melts incongruently at 1,193 �C the 4:9 at 1,183 �C and the 1:6 at 1,242 �C. The 1:5 compound has a maximum temperature of stability at 1,095 �C and the 4:9 and 1:6 compound have minimum temperatures of stability at 1,070 �C and 1,002 �C respectively. Nb2O5 was found to enter into solid solution in Bi2O3, up to about 23.5 mole percent Nb2O5. The melting point is increased and the monoclinic-cubic phase transformation temperature is decreased. A morphotropic phase change occurrs at about 19.5 mole percent Nb2O5 from the cubic to a pseudocubic structure.
J. Res. Natl. Bur. Stand., Vol. 66A, No. 6, p. 451
ABBYY FineReader 8.0
The Journal of Research of the National Institute of Standards and Technology is a publication of the U.S. Government. The papers are in the public domain and are not subject to copyright in the United States. However, please pay special attention to the individual works to make sure there are no copyright restrictions indicated. Individual works may require securing other permissions from the original copyright holder.