Characterizations of Fe Doping on B‐Site of (La_0.8Ca_0.2)(Cr_0.9Co_0.1)O_3−δ Interconnect Materials for SOFCs

Abstract

The microstructure, lattice parameters, and electrical conductivity mechanisms for Fe doping on B-site of (La 0.8 Ca 0.2 ) (Cr 0.9 Co 0.1 )O 3 -d were systematically investigated. The oxygen nonstoichiometry was measured by means of thermogravimetry as a function of oxygen partial pressure. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of electron hole with the electrical conductivity. Based on the result of electrical conductivity in air, it is concluded that the concentration of electron hole at high oxygen activity is larger than that at low oxygen activity. This is due to the fact that (La 0.8 Ca 0.2 )CrO 3 -d -based ceramics are p-type conductors, the electrical conductivity is dominated by the concentration of hole. At higher Fe-doping level, the compensation mechanism at high oxygen activity is significantly dominated by the formation of oxygen vacancy, that is, ionic compensation. The compensation mechanism at low oxygen activity is significantly dominated by the formation of the formation of Cr 4+ , that is, electrical compensation at lower Fe-doping level. Based on oxygen nonstoichiometry data, it is found that with increasing Fe-doping amount on B-site of (La 0.8 Ca 0.2 )(Cr 0.9 Co 0.1 )O 3 -d specimens, the initial weight-stable temperature shifted to lower temperature which might be highly related with the change in compensation mechanism at the temperature.