Thermodynamic Modeling of the La-Co-O System

A thermodynamic modeling of phase diagrams and thermodynamic properties of the La-Co-O system is presented. Special attention is given to the perovskite LaCoO3−δ phase, due to its outstanding practical importance. In addition to phase equilibria, defect chemistry and charge disproportionation of lanthanum cobaltite were considered during the modeling and are discussed with respect to their thermo-chemical and electrochemical applications. Two sets of optimized parameters are obtained, one for high charge disproportionation (2Co3+ → Co2+ + Co4+) and one for low charge disproportionation. By analyzing both oxygen nonstoichiometry and ion distribution results, it is decided that the parameters for low charge disproportionation will be used in the extensions to multi-component system database (e.g. La-Sr-Co-Fe-O). Calculations with the presented thermodynamic database deliver fundamental materials properties for the optimization of technological materials for industrial applications, including SOFC and oxygen membrane.