OXYGEN PERMEATION MODELING OF PEROVSKITES

A point defect model was used to describe the oxygen nonstoichiometry of the perovskites La0.75Sr0.25CrO3, La0.9Sr0.1FeO3, La0.9Sr0.1CoO3 an d La0.8Sr0.2MnO3 as a function of the oxygen partial pressure. Form th e oxygen vacancy concentration predicted by the point defect model, th e ionic conductivity was calculated assuming a vacancy diffusion mecha nism. The ionic conductivity was combined with the Wagner model for th e oxidation of metals to yield an analytical expression for the oxygen permeation current density as a function of the oxygen partial pressu re gradient. A linear boundary condition was used to show the effect o f a limiting oxygen exchange rate at the surface.