Defect chemical modeling of (La,Sr)(Co,Fe)O3-δ

Different defect chemical models for calculation of ionic and electronic defect concentrations are discussed regarding their applicability to transition metal perovskite-type oxides (ABO(3-delta)) with large ranges of oxygen non-stoichiometry. A point defect model, which allows simultaneous consideration of three different B-site species concentrations as a function of the oxygen partial pressure is compared to a simple point defect model, considering only two different B-site species. Additionally, a model assuming electrons/holes as negative resp. positive electronic charge carriers is presented. Further, models involving association of point defects in different complexes are discussed. Examples are given for fits of experimental data of La1-xSrxBO3-delta (x = 0.6, B = Fe, Co) to selected models in the temperature range 700-900degreesC and oxygen partial pressures 10(-5) < pO(2)/atm < 1.