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pp.470-475
La1-xSrxMnO3(LSM,0≤x≤0.5) powders as the air electrode for solid oxide fuel cell were synthesized by a glycine-nitrate combustion process. The powders were then examined by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The as-formed powders were composed of very fine ash particles linked together in chains. X-ray maps of the LSM powders milled for 1.5 h showed that the metallic elements are homogeneously distributed inside each grain and in the different grains. The powder XRD patterns of the LSM with x< 0.3 showed a rhombohedral phase; the phase changes to the cubic phase at higher compositions(x≥0.3) calcined in air at 1200˚C for 4 h. Also, the SEM micrographs showed that the average grain size decreases as Sr content increases. Composite air electrodes made of 50/50 vol% of the resulting LSM powders and yttria stabilized zirconia(YSZ) powders were prepared by colloidal deposition technique. The electrodes were studied by ac impedance spectroscopy in order to improve the performance of a solid oxide fuel cell(SOFC). Reproducible impedance spectra were confirmed using the improved cell, which consisted of LSM-YSZ/YSZ. The composite electrode of LSM and YSZ was found to yield a lower cathodic resistivity than that of the non-composite one. Also, the addition of YSZ to the La1-xSrxMnO3 (0.1≤x≤0.2) electrode led to a pronounced, large decrease in the cathodic resistivity of the LSM-YSZ composite electrodes.
