Microstructure and polarization resistance of thermally sprayed composite cathodes for solid oxide fuel cell use

Porous composite cathode coatings containing (La0.8Sr0.2)(0.98)MnO3 (LSM) a nd ZrO2-12% Y2O3 (YSZ) were prepared by vacuum plasma spraying (VPS) and da me spraying (FS) on prefabricated substrate-based planar solid oxide fuel c ells (SOFC) with 60 mm in diameter. Microstructural observations reveal the open porosity of the cathode coatings and prove qualitatively the composit ional gradient from YSZ-LSM I composite to pure I,SM. The electrochemical b ehavior was investigated by impedance spectroscopy. The results of graded c athodes compared with nongradient and bilayered ones are discussed with res pect to the cathodic polarization resistance between 750 and 950 degrees C. Bilayered cathodes indicate the lowest cathodic losses followed by the gra ded ones and the conventional composite. Flame spraying as a rarely used pr ocessing tool for SOFC components can provide cathodes of high electrochemi cal performance.