A previously developed high-concentration point defect theory was extended so as to treat perovskite-structured ABO3 oxides; using Sr-doped versions of the present material as a model system. The aim of the theoretical framework was to produce an analytical expression for the virtual defect chemical-potential. This expression was obtained from a Gibbs free energy which included contributions from coulombic interactions between defects, as well as that which arose from a configurational entropy that incorporated considerations of generalized defect exclusions. The coulombic energy was obtained by summing contributions from all defects by using a mean field approximation. The concept of a generalized Madelung constant was introduced in order to account for the effect of a variable charge distribution among the 3 sub-lattices. The expression for the chemical potential could then be used to write down modified mass-action equations that governed defect concentrations. This formalism was used to calculate defect concentrations in La0.9Sr0.1CrO3-, as functions of temperature and O partial pressure. The calculated O deficiency was found to agree well with experimental data.

S.Ling: Journal of the Physics and Chemistry of Solids, 1994, 55[12], 1445-60