The optimization of mixed conductivity in fluorite compounds based upon zirconia was considered. Phase relationships in the new systems, YbO1.5–NbO2.5–ZrO2, and CaO–NbO2.5–ZrO2, were presented. The limit of the cubic defect fluorite phase in YbO1.5–NbO2.5–ZrO2 closely resembled that in the system, YO1.5–NbO2.5–ZrO2, while that in CaO–NbO2.5–ZrO2 was narrow and extended so as to include the composition, Ca0.255Nb0.15Zr0.595O1.82, at 1500C. The influence of dopant ion size, charge and composition upon ionic conduction was assessed, and there were similarities with the systems, YO1.5–NbO2.5–ZrO2 and YO1.5–TiO2–ZrO2. A comparison of these results with published data on the Ti-containing systems, CaO–TiO2–ZrO2 and GdO1.5–TiO2–ZrO2, showed that the highest mixed conducting compositions could be found only in the system, YO1.5–TiO2–ZrO2, among the systems studied here.

The Systems Zr(Nb,Ti)(R)O2-δ, R = Yb, Ca – Optimization of Mixed Conductivity and Comparison with Results of Other Systems (R = Y and Gd). D.P.Fagg, A.J.Feighery, J.T.S.Irvine: Journal of Solid State Chemistry, 2003, 172[2], 277-87