Electrochemical and microstructure characteristics of Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) cathodes prepared by citrate precursor method for SOFCs

Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) films as solid oxide fuel cell (SOFC) cathodes were screen-printed on Ce0.9Gd0.1O1.95 (CGO) electrolyte disks using powders prepared from the citrate precursor method. Two different powders were obtained via different calcination schemes: the one obtained with an additional calcination step in nitrogen protection atmosphere (P-NA) consisted of smaller aggregates of fine particles in comparison with that obtained only through a calcination step in air (P-A). X-ray diffraction and scanning electron microscope observation were carried out to examine the structures and morphologies of the BSCF powders and films obtained with different sintering temperatures ranging from 800 to 950,C. AC impedance spectra for BSCF/CGO/BSCF cells were also measured to obtain the interfacial area specific resistances (ASRs). The ASR values varied with sintering temperature and powder used to prepare the electrodes. In particular, the lowest values of 0.78 Omega cm(2) at 500 degrees C, 0.10 Omega cm(2) at 600 degrees C and 0.018 Omega cm(2) at 700 degrees C were obtained from the electrode prepared using a sintering temperature of 900,C and P-NA powder. The results of microstructure examination along with that of the porosity evaluation were analyzed to reveal the effects of sintering temperature and microstructures of powders and electrode films on ASR. (C) 2009 Elsevier B.V. All rights reserved.