Structure and Electrical Properties of Bace1− X Laxo3− Δ Mixed Conductors

In this paper, BaCe1− x La x O3− δ (x = 0.05, 0.1, 0.2, 0.3) oxides were calcined at 1100 °C for 5 h and further sintered at 1550 °C for 5 h via a citrate-nitrate combustion method. The crystal structure, conductivity, and chemical properties were investigated by X-ray diffraction (XRD), alternating current (AC) impedance technique, X-ray photoelectron spectroscopy (XPS). XRD analysis showed that all samples had an orthorhombic perovskite-type structure and lattice volumes increased with the increasing of La doping contents. XPS results showed that the valence states of Ba, Ce, La were bivalent, tetravalent, trivalent, respectively. And there were two types of O binding states in the perovskite structure: O-H groups/ oxygen vacancies and lattice oxygen. AC impedance spectra results indicated that all samples were proton-oxide ion-electron hole conductors at 400~800 °C under wet O2 atmosphere and proton-electron conductors at 400~800 °C under wet Ar atmosphere. Among these samples, BaCe0.9La0.1O3− δ and BaCe0.95La0.05O3− δ displayed the highest conductivities at below 500 °C and above 500 °C, respectively. Furthermore, the BaCe0.95La0.05O3− δ exhibited the highest total conductivity of 1.05×10−2 S·cm−1 at 800 °C under PO2 ≈ 1 atm and PH2O=0.006 atm