Recent progress in LaGaO₃ based solid electrolyte for intermediate temperature SOFCs

Partial electronic and oxide ionic conduction in LaGaO₃ doped with Sr and Mg, Co for Ga site was studied with the ion blocking method. It was found that doping small amount of Co into Ga site is effective for elevating the oxide ion conductivity. However, it is seen that the partial electronic conduction monotonically increases with increasing Co amount and P_O2 at p-n transition was shifted to lower value. Even at X = 0.1, the oxide ion conductivity in LSGMC is still dominant. Calculation on the theoretical leakage of electrolyte of solid oxide fuel cells suggests that the highest efficiency of the electrolyte was achieved around 100 μm in thickness for La_0.8Sr_0.2Ga_0.8Mg_0.15Co _0.05O₃ (LSGMC). Preparation of LSGMC film on Ni-Sm_0.2Ce_0.8O₂ porous anode was studied with the colloidal spray method. In order to prevent the reaction between substrate and film, La doped CeO₂ was used for the interlayer film. In accordance with the theoretical calculation, open circuit potential of the cell using LSGMC film electrolyte with 40 μm thickness becomes much smaller than the theoretical value. However, fairly large maximum power density (0.21 W/cm²) can be achieved at 873 K and even at 773 K, the maximum power density of the cell as high as 0.12 W/cm² was exhibited on the SOFC using 40 μm thickness LSGMC electrolyte.