Journal of Research of the National Bureau of Standards
A large portion of the phase equilibrium diagram for the binary system barium oxide-niobium pentoxide has been constructed from observations of fusion characteristics and X-ray diffraction data. In the system five binary compounds were observed wIth BaO : Nb2O5 ratios of 5 : 2, 1 : 1, 6 : 7, 3 : 5, and 1 : 3 and a 6 : 1 compound was postulated. The 1 : 1 compound was found to melt congruently at 1,455 �C and have only one stable polymorph, although a second metastable polymorph can also be prepared . The 5 : 2 compound melts congruently at 1,542 �C; the 6 : 7, 3 : 5, and 1 : 3 phases melt incongruently at 1,330, 1,290, and 1,315 �C, respectively. The phase relations of the 6 : 1 compound could not be determined due to the reaction between this phase and platinum metal. No 2 : 1 compound was observed in this system.
J. Res. Natl. Bur. Stand., Vol. 65A, No. 4, p. 337
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