The electrolyte materials Ce0.85Sm0.15O1.925-x at.% FeO1.5 (x = 0, 0.5, 1, 2, 3) were synthesized by means of glycine-nitrate process (GNP). Their structures and ionic conductivities were characterized by X-ray diffraction, SEM and AC impedance spectroscopy. All the electrolytes were found to be ceria-based solid solutions of fluorite type structures. Grain size increased with increased Fe2O3 content up to 0.5 at.% and then became almost constant with further addition of Fe2O3. The grain-boundary resistance could be significantly decreased by small addition of Fe2O3. Electrolyte-supported solid oxide fuel cells (SOFC) fabricated with Ce0.85Sm0.15O1.925-x at.% FeO1.5 (x = 0.5, 3) electrolytes were studied and compared with the fuel cell with Ce0.85Sm0.15O1.925 as electrolyte. (C) 2010 Elsevier B.V. All rights reserved.