Electrochemical evaluation of La0.6Sr0.4Co0.8Fe0.2O3-δ-La0.9Sr0.1Ga0.8Mg0.2O3-δ composite cathodes for La0.9Sr0.1Ga0.8Mg0.2O3-δ electrolyte SOFCs

The composite cathodes consisting of perosvkite material La0.6Sr0.4Co0.8Fe0.2O3-delta (LSCF) and La0.9Sr0.4Co0.8Fe0.2O3-delta (LSGM) were prepared, and then studied for potential applications in intermediate temperature solid oxide fuel cells (SOFCs) with LSGM electrolyte. Both ac impedance spectroscopy and dc polarization measurements were performed in air within the temperature range of 600-800 degrees C under open circuit potential. The results showed that the addition of 40 wt% LSGM to LSCF (LSCF-LSGM40) resulted in lower interfacial resistance (0.24 Omega cm(2) at 800 degrees C) than other composite cathodes and was slightly lower than the single-phase LSCF cathode (0.28 Omega cm(2) at 800 degrees C). Although adding LSGM electrolyte material to the LSCF electrode did not improve the electrode performance much, it could buffer the thermal expansion coefficient (TEC) of LSCF, which is larger than that of LSGM electrolyte. (C) 2008 Elsevier B.V. All rights reserved.