Characterization of (1 - x) La0.83Sr0.17 Ga0.83Mg0.17O2.83 - xLa0.8 Sr0.2MnO3 (0≤x≤1) composite cathodes

Composites prepared by mixing La0.83Sr0.17GaO0.83Mg0.17O2.83 (LSGM) and La0.8Sr0.2MnO3 (LSM) powders (1-x)LSGM-xLSM (x=0, 0.01, 0.05, 0.25, 0.50, 0.75 and 1), have been studied. Composites have been sintered at 1300 degrees C in air for 2 h, and their relative densities vary in the range 89-85%. Characterization includes phase analysis based on X-ray powder diffraction data taken at room temperature after thermal treatments at temperatures suitable for IT-SOFCs, scanning electron microscopy for detecting the grain size, the porosity and the homogeneity of the samples, and complex impedance spectroscopy measurements of the electrical conduction properties in the temperature range 300-800 degrees C. The total conductivity was about 2 x 10(-2) S cm(-1) at 800 degrees C for samples with 1% and 5% LSM; such low conductivity is consistent with the values found in the literature for pure LSGM sintered at 1400 degrees C and may account for the low relative densities and the small grain size of the samples. Present results have been compared with those obtained by electrical measurements and EDX analysis on LSGM thick films sandwiched between LSM electrodes. In both experiments there was no evidence of the formation of new phases. (c) 2005 Elsevier Ltd. All rights reserved.