Transition metal doped LaCaO_3 perovskite fast oxide ion conductor and intermediate temperature solid oxide fuel cell

摘要

Doping transition metal cation is known to enhance the electric conduction of solid electrolytes, however, the ionic conduction can be improved by doping the small amount of transition metal, in particular, doping Co is effective for improving the oxide ion conductivity. In this investigation, oxide ion conductivity of LaGaO_3 based oxide doped with Co were investigated in detial. It was found that LaGaO_3 doped with Co for Ga site (LSGMC) show a notable oxide ion conductivity over a wide range of oxygen partial pressures, although a hole conduction was appeared by addition of excess amount of Co. Considering the electrical conductivifty and transport number of oxide ion, the optimized composition of LSGMC seems to be existed at La_0.8Sr_0.2Ga_0.8Mg_0.115Co_0.0085O_3. Power generation characteristics of fuel cells was greatly improved by using LSGMC for electrolyte and extremely large power density can be obtained on both H_2- O_2 and H_2 - air cells.In particular, the maximum power density was attained to a value of 1.53 and 0.50 W//cm~2 at 1073 and 873 K, respectively, on H_2-O_2 cell when the thickness of electrolyte was 0.18 mm. Furthermore, almost similar large power density was attained when air was used as oxidant. The high power density of cell demonstrated in this study suggests that the operating temperature of SOFC can be decreased by using LSGMC for electrolyte.