Perovskite-type Bi0.3Sr0.7Co0.3Fe0.7O3-delta (BiSCF3737) oxide with perfectly cubic structure based on the Pm-3m space group has been developed and investigated as cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). BiSCF3737 is incorporated into (La0.6Sr0.4)(0.9)Co0.2Fe0.8O3-delta (LSCF) to form a composite cathode called LSCF-BiSCF. X-ray diffraction (XRD) results demonstrate that BiSCF3737 has an extremely desirable chemical compatibility with LSCF as well as with La0.8Sr0.2Ga0.8Mg0.2O3-delta (LSGM) electrolyte. The cells with LSGM electrolyte (0.5 mm thickness) and symmetrical electrodes are fabricated for electrocatalaytic activity test. Compared with the pure constituent (LSCF or BiSCF3737), the composite with optimum composition, i.e., LSCF50-BiSCF50, exhibits better electrochemical activity for oxygen reduction. The LSGM electrolyte-supported (similar to 300 mu M thickness) cell with LSCF50-BiSCF50 composite cathode exhibits higher power densities of 0.617 and 0.802 W cm(-2) at 650 and 700 degrees C, respectively, with humidified H-2 (similar to 3% H2O) as the fuel and ambient air as the oxidant. Over 78 h stability test at 600 degrees C indicates that a little performance decrease occurs but no interfacial damage happens, suggesting that LSCF50-BiSCF50 is a potential material for IT-SOFCs. (C) 2015 Elsevier B.V. All rights reserved.