The structure and conductivity of LaMn_1−zCr_zO₃ and (La, A)_1−yMn_1−zCr_zO₃ (A=Sr, Ca) as air cathodes in solid oxide fuel cells

Abstract

Doped LaMnO₃ systems are used as cathodes in solid oxide fuel cells, mainly due to their high electronic conductivity, thermal matching to the electrolyte material and good catalytic activity towards oxygen reduction. Lanthanum deficient LaMnO₃ has been shown to have a higher electronic conductivity than stoichiometric LaMnO₃, however, the material has been found to sinter more readily causing a reduction in the efficiency of the cathode. This paper discusses the effect of imparting non-stoichiometry to the LaMnO₃ system with the incorporation of a B site dopant, Cr. The paper examines the effect on the conductivity and phase present with increased Cr content, and shows that Cr in LaMn_1−zCr_zO₃, up to z=0.15, does not produce an unacceptably large decrease in the electronic conductivity, especially for a Ca doped, A site deficient system. Thus, a B site doped system is considered as a possible candidate for solid oxide fuel cell cathode systems.