Method for calculating ionic and electronic defect concentrations in proton containing perovskites

A general numerical method for calculation of concentrations of vacancies and ionic and electronic defects in solids in equilibrium with two gas pressures is presented. The method is applied to 5 at% B-site doped SrCeO3 in equilibrium with oxygen and water vapor. The model includes protons and electronic defects, as well as cation vacancies on the A and B sites. The 10 concentrations in the model are determined uniquely by solving the linear and mass action law type equations in a rational sequence. No approximations or truncations of the equations are necessary. No information on the magnitude of the Schottky-equilibrium constant, K-s, controlling the population of cation vacancies is available. Limiting values of K-s were tested to illustrate suppression and enhancement of cation vacancy formation in perovskites. Deviations from Sieverts law are demonstrated. Deviation of the A/B ratio from unity has the same effect on the proton content as an increase of the dopant level. (C) 1999 Academic Press.