The Ba0.5Sr0.5Zn0.2Fe0.8O3-delta (BSZF) complex oxide with cubic perovskite structure was synthesized and examined as anew cobalt-free cathode for intermediate-temperature solid oxide fuel cells (IT-SOFCs). The electrical conductivity was relatively low with a peak value of 9.4 S cm(-1) at about 590 degrees C, which was mainly caused by the high concentration of oxygen vacancy and the doping of bivalent zinc in B-sites. At 650 degrees C and under open circuit condition, symmetrical BSZF cathode on Sm-doped ceria (SDC) electrolyte showed polarization resistances (R-p) of 0.48 Omega cm(2) and 0.35 Omega cm(2) in air and oxygen, respectively. The dependence of R-P with oxygen partial pressure indicated that the rate-limiting step for oxygen reduction was oxygen adsorption/desorption kinetics. Using B SZF as the cathode, the wet hydrogen fueled Ni + SDC anode-supported single cell exhibited peak power densities of 392 mW cm(-2) and 626 mW cm(-2) at 650 degrees C when stationary air and oxygen flux were used as oxidants, respectively. (c) 2007 Elsevier B.V. All rights reserved.