The equilibrium between gaseous O (870Pa to 20kPa) and high surface-area Ce1-xZrxO2 powders, where x ranged from 0 to 0.36, was studied by means of thermogravimetry in order to improve understanding of the nature and behaviour of the point defects in the solid solutions. By measuring the weight changes between 2 different O pressures, it was possible to deduce the variation in the O vacancy concentration at the surface of the solutions as a function of the O pressure and Zr concentration. The anionic sub-lattice was shown to obey an ideal thermodynamic behaviour, with an O-vacancy concentration which was proportional to the reciprocal of the one-sixth power of the O pressure. By comparing experimental and theoretical variations in the O vacancy concentration versus Zr concentration, it was found that the cationic sub-lattice could be described by a non-ideal regular model in which the activity coefficients of the structural elements and associated defects differed from unity.

Thermodynamic Description of the Nonstoichiometric Defect Structure in (Ce,Zr)O2 Solid Solution Powders. C.Janvier, M.Pijolat, F.Valdivieso, M.Soustelle: Solid State Ionics, 2000, 127[3-4], 207-22