Electrical conduction behaviors of isovalent and acceptor dopants on B site of (La0.8Ca0.2)CrO3−δ perovskites

The electrical conduction behaviors of isovalent and acceptor dopants on B site of (La0.8Ca0.2)CrO3−δ perovskites at high and low oxygen activities were investigated systematically. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of electron hole with the electrical conductivity. The information of charge compensation mechanisms and defect formation may be valuable for a better understanding of the interconnect of (La0.8Ca0.2)CrO3−δ-based ceramics used for solid oxide fuel cells (SOFCs). Since (La0.8Ca0.2)CrO3−δ-based specimens belong to p-type conductors, their conductivities are proportional to the concentration of electron hole. In reducing atmosphere, the oxygen may be lost and ionic compensation may be take place through the formation of oxygen vacancies and the electrical compensation may arise by changing the valence of Cr from tri-valence to tetra-valence in reducing atmosphere. However the formation of oxygen vacancies has no contribution to electrical conductivity, the compensation mechanism is dominated by the electrical compensation, i.e. the take place a transition of Cr3+ → Cr4+ rather than that of ionic compensation, i.e. the formation of oxygen vacancies. Based on the defect chemical reactions and the results of electrical conductivity, the concentration of electron hole at high oxygen activity is larger than that at low oxygen activity. Therefore the electrical conductivity of (La0.8Ca0.2)CrO3−δ-based ceramics at air is larger than that at 5% H2–95% Ar forming gas. The compensation mechanisms contain ionic and electrical compensation and the ratios of electrical to ionic compensation varied with the kind of dopant which significantly effects the electrical conductivity. The results suggest that the (La0.8Ca0.2)Cr0.9Co0.1O3−δ specimen shows high electrical conductivity in air (σ850 °C = 59.59 S/cm) and 5% H2–95% Ar forming gas (σ850 °C = 47.98 S/cm) leading it a promising candidate as an interconnect material for SOFCs applications.