Reactions between La1-xCaxMnO3 and CaO-stabilized ZrO2 -: Part I -: Powder mixtures

The chemistry and microstructure of the interface between calcium substituted lanthanum manganite and cubic calcia stabilized zirconia have been studied. The aim was to investigate the chemical stability of these materials as a model system for, respectively, the cathode and the electrolyte in solid oxide fuel cells. The relative amounts and time dependence of the formation of secondary phases (La2Zr2O7 and CaZrO3) and inter-diffusion between the primary phases were observed to depend on temperature, partial pressure of oxygen, and composition of the manganite. 30 mole % Ca on La-site and A-site deficiency of the manganite were shown to stabilize the heterophase interface in air. Reducing conditions were shown to destabilize the primary phases and increase the rate of formation of secondary phases. Pore-coarsening with increasing amount of Ca in the manganite was the most striking feature in the time dependence of the microstructure. The present findings are discussed in relation to the thermodynamic and kinetic stability of the cathode/electrolyte interface of conventional solid oxide fuel cells consisting of yttria stabilized zirconia and strontium substituted lanthanum manganite. (C) 1999 Kluwer Academic Publishers.