A-site cation-ordered PrBaCo2O5+delta (PrBC) double perovskite oxide was synthesized and evaluated as the cathode of an intermediate-temperature solid-oxide fuel cell (IT-SOFC) on a samarium-doped ceria (SDC) electrolyte. The phase reaction between PrBC and SDC was weak even at 1100 degrees C. The oxygen reduction mechanism was investigated by electrochemical impedance spectroscopy characterization. Over the intermediate-temperature range of 450-700 degrees C, the electrode polarization resistance was mainly contributed from oxygen-ion transfer through the electrode-electrolyte interface and electron charge transfer over the electrode surface. An area-specific resistance as low as similar to 0.4 Omega cm(2) was measured at 600 degrees C in air, based on symmetric cell test. A thin-film SDC electrolyte fuel cell with PrBC cathode was fabricated which delivered attractive peak power densities of 620 and 165 mW cm(-2) at 600 and 450 degrees C, respectively. (C) 2008 Elsevier B.V. All rights reserved.