Perovskite oxides Sr0.9K0.1FexCo1-xO3-delta (SKFCx, x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) are investigated as potential cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) on Sm0.2Ce0.8O1.9 (SDC) electrolyte. The cubic phase of the SKFCx oxides is demonstrated by x-ray diffraction. The SKFCx cathode shows good compatibility with the SDC electrolyte up to 900 degrees C. Among the investigated compositions, SKFC0.1 displays the highest electrical conductivity of 443-146 S.cm(-1) from 350 degrees C to 800 degrees C in flow air. The area specific resistances (ASRs) of the SKFCx (x = 0.1, 0.3, 0.5, 0.7, 0.9 and 1.0) cathodes are 0.047, 0.058, 0.066, 0.101, 0.155 and 0.175 Omega cm(2) at 650 degrees C in air on an SDC electrolyte. Among the five tested cathodes, SKFC0.1 exhibits the lowest area specific resistances between 550 degrees C and 750 degrees C, when tested on its symmetric cell configuration of cathode vertical bar SDC vertical bar cathode. The thermally stabilized cubic perovskite structure of the SKFC0.1 powder is demonstrated by high-temperature XRD. The average linear thermal expansion coefficient alpha(L) of SKFC0.1 is 18.9 x 10(-6) K-1. A peak power density of 1643 mW.cm(-2) is achieved on SKFC0.1 vertical bar SDC vertical bar Ni-SDC anode supported fuel cell at 650 degrees C. These features, and excellent electrocatalytic activity and good stability, indicate the potential of alkaline metal doped strontium cobalt ferrite perovskites are promising cathode materials for IT-SOFCs. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.