Synergy effects of mixing Pr2NiO4 and La(Ba)CoO3 on cathodic performance were investigated using a LaGaO3-based oxide electrolyte. It was observed that cathodic overpotential could be suppressed significantly by mixing Pr2NiO4 with La(Ba)CoO3 base oxide, in spite of a decrease in the electrical conductivity. Because LaCoO3-doped with Ba shows high oxygen dissociation activity and Pr2NiO4 shows high oxide ion and hole conductivity, the active sites for oxygen dissociation could be extended in three dimensions. In response to the improved number of active sites, diffusion overpotential was decreased significantly by mixing Pr2NiO4-based oxide with LaCoO3-based oxide. The maximum power density of 117 mW cm(-2) was achieved at temperatures as low as 673 K using a LaGaO3 thin film electrolyte (5-mu m thick) and a composite oxide of Pr2NiO4-La(Ba)CoO3 cathode. (C) 2012 Elsevier B.V. All rights reserved.