Nano-composite powders consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) were synthesized by spray pyrolysis using different cation concentration solutions, and the effect of this cation concentration on the electrochemical performance of electrodes fabricated using the powders was investigated. Regardless of the cation concentration, spherical particles consisting of nano-order fine SSC and SDC crystallites were successfully obtained. Although the crystal size of all the synthesized powders was almost the same, the particle size increased with increasing cation concentration. The microstructure of the cathodes fabricated using the nano-composite powders clearly depended on the particle size of the starting powders; the microstructure became coarser with increasing particle size and the original particle shapes partially remained in the cathode network. Also, electrochemical measurements for solid oxide fuel cells with these cathodes revealed that the electrode performance was related to the microstructure. The electrode polarization resistance decreased with decreasing particle size, and a relatively fine microstructure cathode exhibited lower electrode polarization resistance, resulting in a high performance of 1.52 W cm (2) at 700 degrees C. These results indicate that controlling the particle size, as well as controlling the nanostructure within the particles, is crucial to attain high performance electrodes. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.