CHARACTERIZATION OF SR-DOPED LAMNO3 AND LACOO3 AS CATHODE MATERIALS FOR A DOPED LAGAO3 CERAMIC FUEL-CELL

Energy dispersive spectrometry line scan and ac impedance spectroscopy were used in this study to investigate the chemical reactions between two cathode materials, La0.24Sr0.76MnO3 (LSM), La0.5Sr0.5CoO3-delta ( LSC), and the electrolyte La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM). Significan t interdiffusions of Co into LSGM and Ga into LSC were found at an LSC /LSGM interface even at relatively low fabrication temperatures. In co ntrast, only small interdiffusions of Mn into LSGM and Ga into LSM wer e detected at the LSM/LSGM interface even though it was fired at 1470 degrees C. The ac impedance spectra of the electrolyte LSGM with LSM, LSC, and Pt electrodes indicate a grain-boundary contribution to the t otal conductivity in the intermediate frequency range and a diffusion- controlled impedance in the low-frequency range. Irrespective of chemi cal reactions and a larger thermal expansion coefficient, LSC has the lowest de resistance of all three electrodes investigated. Considering both the small interdiffusion reactions between LSM and LSGM and thei r similar thermal expansion coefficients, LSM could be an appropriate cathode material for LSGM-based fuel cells.