Defect analysis and thermodynamic modeling of LaCoO3−δ

The defect structures of the LaCoO3−δ perovskite are analyzed through thermodynamic modeling by means of the CALPHAD technique. It is discovered that charge disproportionation exists for Co3+ in order to describe the relationship between the oxygen partial pressure and the oxygen deficiency. Based on available experimental data, a compound-energy model, (La3+,Va)1(Co2+,Co3+,Co4+,Va)1(O2−,Va)3, where Va stands for vacancy, is proposed and model parameters evaluated. It was consequently predicted from the thermodynamic model that the amounts of Co2+ and Co4+ are about 20% each when there is no oxygen deficiency.