Novel fast oxide ion conductor and application for the electrolyte of solid oxide fuel cell

Effects of Co doping to Ga sites of a LaGaO₃ based oxide on the oxide ion conductivity was investigated. Oxide ion conductivity increased by doping with Co and it was found that usage of a LaGaO₃-based perovskite type oxide, doped with Sr for the A site and Co and Mg for the B site (La_0.8Sr_0.2Ga_0.8Mg_0.115 Co_0.085O₃ denoted as LSGMC), for the electrolyte of the fuel cell gave a notably large power density at an intermediate temperature of 873 K on a cell using H₂ and O₂ as fuel and oxidant, respectively. The power density increased as the thickness of the electrolyte was decreased. The maximum power density was attained at values of 1.4 and 0.5 W/cm² at 1073 and 873 K, respectively, when 0.18 mm thick LSGMC was used for the electrolyte. Electrical conductivity in the LSGMC was also estimated using polarization methods. Electrical conductivity was also increased by doping with Co, resulting in an increased amount of chemically leaked oxygen. Consequently, the theoretical calculation demonstrated that the highest energy conversion efficiency would be achieved when the thickness of the LSGMC electrolyte was 100 μm.