The A-cation Deficient Perovskite Series La2-xCoTiO6-δ (0≤x≤0.20): new Potential Cathodes for Solid Oxide Fuel Cells.

Abstract

La2-xCoTiO6- are presented as promising new cathode materials for solid oxide fuel cells. The B-site ordering characteristic of double perovskites is present in the whole series. Additionally, increasing amounts of La-vacancies gives rise to ordering of alternating La-rich and -rich ( = vacancy) layers perpendicular to the c-axis. The introduction of La vacancies produces both oxidation of Co2+ to Co3+ and oxygen vacancies inducing a change of both electrical and electrochemical properties. The best electrochemical performances are obtained for low x due to a compromise between sufficiently high amount of defects to provide electronic and ionic conductivities, but not so high to induce defect clustering. The material with x= 0.05 exhibits the best performances of the series. Symmetrical cells made of composites of this material and Ce0.9Gd0.1O2-δ deposited on pellets of this electrolyte show a polarization resistance of 0.39 Ωcm2 at 1073 K.