The A-cation deficient perovskite series La2−xCoTiO6−δ (0 ≤ x ≤ 0.20): new components for potential SOFC composite cathodes

Abstract

La_2−xCoTiO_6−δ/Ce_0.9Gd_0.1O_2−δ composites are presented as promising new cathodes 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 give 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 Ce_0.9Gd_0.1O_2−δ deposited on pellets of this electrolyte show a polarization resistance of 0.39 Ω cm² at 1073 K.