Phase equilibria in this system (¼Y3NbO7) were studied at 1700C by using solid-state reaction. The use of X-ray diffraction after heat treatment (64h) indicated that all of the compositions were cubic solid solution having a fluorite-type structure. The lattice parameter of the fluorite phase decreased with increasing ZrO2 content. The conductivity at a given temperature increased with increasing ZrO2 content; that is, with decreasing Y and Nb content. However, the concentration of O vacancies in the system remained constant. The variation in conductivity was explained in terms of the association of O ions with Nb, and of O vacancies with Y.

Phase Stability and Electrical Conductivity of the (Zr,Y)O1.75-(Y,Nb)O1.75 System. J.H.Lee, M.Yoshimura: Solid State Ionics, 1999, 124[1-2], 185-91