Preparation and conductive properties of double perovskite oxides Ba3Ba1+xTa2-xO9-δ

Abstract

In this work, Ba3Ba1+xTa2-xO9-δ (x = 0, 0.1, 0.3, and 0.5) double perovskite proton conductors were prepared by solid-state reaction process. Phase compositions and microstructures were characterized by X-ray diffraction and field emission scanning electron microscope techniques. valence and semi-quantitative composition of components were identified by X-ray photoelectron spectroscopy. Conductivities of Ba3Ba1+xTa2-xO9-δ were then measured under various vapor and oxygen pressures by AC impedance spectroscopy technique. Results revealed linear increase in total conductivities of Ba3Ba1+xTa2-xO9-δ oxides as a function of temperature. Ba3Ba1.3Ta1.7O8.55 exhibited the highest total conductivity of 8.41 × 10−4 S cm−1 under humidity and 800 °C. The transport numbers calculated by defect equilibria model revealed. Ba3Ba1+xTa2-xO9-δ oxides as pure proton conductors at 400–800 °C. Also, transport numbers of oxide ions and holes both increased with temperature. Ba3Ba1.3Ta1.7O8.55 illustrated the highest protonic transport number of 0.60 at 800 °C. In sum, these results suggest that Ba3Ba1+xTa2-xO9-δ oxides display excellent proton conductivity.