Series of Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) samples have been prepared by modified citrate-nitrate combustion method from the precursor solutions with different pH values and citrate/metal ion ratios. The XRD results reveal that BSCF oxide free of impurity phases can be obtained from a precursor solution with a suitable pH value and a suitable C/M value, whereas CO2-TPD profiles show that there are minor carbonates species present in all BSCF samples, but the amount of these carbonates varies with the pH and C/M values of precursor solutions. The current density-voltage characteristics indicate that carbonates in the BSCF samples reduce the cell performance. The electrochemical impedance spectra (EIS) show that carbonates in BSCF lead to increases in ohmic and polarization resistances. High performance is achieved on the cell with a cathode using a pure BSCF calcined under O-2 flow at 900 degrees C. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.