This study presents the electrochemical performance of (Ba0.5Sr0.5)(0.9)Sm0.1CO0.8Fe0.2O3-delta (BSSCF) as a cathode material for intermediate temperature solid oxide fuel cells (IT-SOFC). AC-impedance analyses were carried on an electrolyte supported BSSCF/Sm0.2Ce0.8O1.9 (SDC)/Ag half-cell and a Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF)/SDC/Ag half-cell. In contrast to the BSCF cathode half-cell, the total resistance of the BSSCF cathode half-cell was lower, e.g., at 550 degrees C; the values for the BSSCF and BSCF were 1.54 and 2.33 ohm cm(2), respectively. The cell performance measurements were conducted on a Ni-SDC anode supported single cell using a SDC thin film as electrolyte, and BSSCF layer as cathode. The maximum power densities were 681 mW cm(-2) at 600 degrees C and 820 mW cm(-2) at 650 degrees C. (c) 2006 Elsevier B.V. All rights reserved.