Compatibility of La2NiO4 cathodes with LaGaO3 electrolytes: A computational approach

The available literature information on the phase equilibria for the La–Ga–Ni–O system has been assessed. Based on the known thermodynamics of boundary oxygen containing systems, La–Ni–O, La–Ga–O, and Ga–Ni–O, and experimental data on phase equilibria in the La2O3–Ga2O3–NiO quasiquaternary system, models have been defined to describe the Gibbs energy of the individual phases. The model parameters have been optimized by least-squares fit to selected experimental information using the CALPHAD-method (Calculation of Phase Diagrams). Chemical potential diagrams of the systems representing fabrications and cathode–anode side operation conditions of LaGaO3-based solid oxide fuel cells (SOFC) were calculated. It has been determined that, neither in fuel cell fabrication conditions nor in operation conditions un-doped LaGaO3 electrolytes and La2NiO4 cathodes are stable in equilibrium with each other but will react to form another phases.