Application of (Sm0.5Sr0.5)CoO3 as a cathode material on Zr0.89Sc0.1Ce0.01O1.95 electrolyte for reduced-temperature operation solid oxide fuel cells (SOFCs) was investigated in detail. As a protective layer for preventing the unfavorable solid-state reactions between materials, doped ceria thin films with an apparent density range between 50 and 80% were fabricated on the electrolyte by a cost-effective wet ceramic process using nanometer (Ce0.8Sm0.2)O-1.9 and submicrometer (Ce0.9Gd0.1)O-1.95 powders. The impact of doped ceria interlayers on the performance of (Sm0.5Sr0.5)CoO3 cathode was investigated by X-ray diffraction and ac impedance measurements. It was found that controlling the microstructure of interlayers is important for (Sm0.5Sr0.5)CoO3 cathodic performance. The (Sm0.5Sr0.5)CoO3 cathode deposited on Zr0.89Sc0.1Ce0.01O1.95 electrolyte coated by (Ce0.8Sm0.2)O-1.9 or (Ce0.9Gd0.1)O-1.95 interlayer can reach an interface conductivity of 4.4 or 7.2 S/cm(2), respectively, at 700 degrees C. (c) 2006 The Electrochemical Society.