Investigation of aliovalent transition metal doped La0.7Ca0.3Cr0.8X0.2O3-δ (X= Ti, Mn, Fe, Co, and Ni) as electrode materials for symmetric solid oxide fuel cells

The crystal phase, chemical stability, thermal expansion behavior, oxygen non-stoichiometry, electrical conductivity, and electro-catalytic activity of La0.7Ca0.3Cr0.8X0.2O3-delta (X= Ti, Mn, Fe, Co, and Ni) electrode materials have been investigated. All the compositions are chemically stable with a single-phase perovskite structure in both reducing and oxidizing atmospheres at high temperature. The linear thermal expansion coefficients of La0.7Ca0.3Cr0.8X0.2O3-delta are approximately 10 x 10(-6) K-1. The total electrical conductivity of La0.7Ca0.3Cr0.8X0.2O3-delta increases in the order of X= Ti < Ni < Fe < Co < Mn, which is correlated to the porosity, valence orbital ionization potential, and oxygen nonstoichiometry upon the reduction process. The overall reaction process of the hydrogen oxidation for the La0.7Ca0.3Cr0.8X0.2O3-delta anodes is limited by the charge transfer process that requires higher activation energy. In a similar trend observed in electrical conductivity, La0.7Ca0.3Cr0.8X0.2O3-delta exhibits the lowest polarization resistance value of 0.12 Omega cm(2) at 800 degrees C. Finally, the symmetric single cell with La0.7Ca0.3Cr0.8X0.2O3-delta as both the cathode and anode shows a maximum powder density of 220 mW cm(-2) at 800 degrees C. (C) 2015 Elsevier Ltd and Techna Group S.r.l. All rights reserved.