Zircon-type Ce1-xAxVO4+δ (A = Ca, Sr; x = 0 to 0.2) were stable in air up to approximately 1300K, while further heating or reducing O partial pressure led to the formation of A-site deficient zircon and CeO2-δ phases. The stability boundaries of the Ce1-xAxVO4+δ were comparable to those of vanadium dioxide and calcium orthovanadate. At O pressures below 10-15atm, perovskite-type CeVO3-δ was formed. The O ion transference numbers of Ce1-xAxVO4+δ, determined by Faradaic efficiency measurements in air, varied from 2 x 10-4 to 6 x 10-3 at 973 to 1223K; increasing with temperature. The O ionic conductivity had an activation energy of 87 to 112kJ/mol and was essentially independent of the A-site dopant content. Contrary to the ionic transport, the p-type electronic conductivity and Seebeck coefficient of Ce1-xAxVO4+δ were influenced by the divalent cation concentration. The average thermal expansion coefficients of Ce1-xAxVO4+δ, calculated from high-temperature X-ray diffraction and dilatometric data in air, were between 4.7 x 10-6 and 6.1 x 10-6/K.

Stability and Oxygen Ionic Conductivity of Zircon-Type Ce1-xAxVO4+δ (A = Ca, Sr). E.V.Tsipis, V.V.Kharton, N.P.Vyshatko, A.L.Shaula, J.R.Frade: Journal of Solid State Chemistry, 2003, 176[1], 47-56