Abstract:The tetragonal perovskite oxide ceramics Sm0.9Ca0.1Al1−xGaxO3−δ(SCAG, x=0.1−0.5) with low content of impurity phase were synthesized by conventional solid-state reaction method. Their microstructure, morphology, electrochemical performance and transport mechanism were studied by X-ray diffractometry, scanning electron microscopy, alternating current impedance technology and oxygen concentration cell method, respectively. The results show that doubly doping of Ca and Ga can notably improve the electrochemical performance of SmAlO3. The total conductivities of doped samples become large initially while then decreases with increasing Ga content, and reach a maximum value at x= 0.3. Sm0.9Ca0.1Al0.7Ga0.3O3−δ sintered at 1 550 ℃ for 6 h has the highest electrical conductivity of 1.83 S/m at 900 ℃ and relative density of 95.5%. The relationship between ln(T) and T−1 is basically linear for the Sm0.9Ca0.1Al0.7Ga0.3O3−δ sample, which shows that the temperature dependence of conductivity conforms to the Arrhenius equation in 400−900 ℃, and the activation energy is 111.09 kJ/mol. Sm0.9Ca0.1Al0.7Ga0.3O3−δ is a mixed conductor of oxygen ion and electron hole in air. Its oxygen ion transference number is around 0.8 in the measuring temperature range of 600−900 ℃, and slightly increases with increasing temperature. By means of oxygen ion transference numbers measured in air, the relative contribution of oxygen ion conductivity and electron hole conductivity are separated. Activation energy for oxygen ion conduction of 101.08 kJ/mol is appreciably larger than that for electron hole conduction of 92.92 kJ/mol.

Key words: Sm0.9Ca0.1Al1−xGaxO3−δ; mixed oxide ionic; electronic conductor; electrochemical performance; activation energy