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

In this work, Ba 3 Ba 1+ x Ta 2- x O 9- 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 Ba 3 Ba 1+ x Ta 2- x O 9- δ were then measured under various vapor and oxygen pressures by AC impedance spectroscopy technique. Results revealed linear increase in total conductivities of Ba 3 Ba 1+ x Ta 2- x O 9- δ oxides as a function of temperature. Ba 3 Ba 1.3 Ta 1.7 O 8.55 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. Ba 3 Ba 1+ x Ta 2- x O 9-δ oxides as pure proton conductors at 400–800 °C. Also, transport numbers of oxide ions and holes both increased with temperature. Ba 3 Ba 1.3 Ta 1.7 O 8.55 illustrated the highest protonic transport number of 0.60 at 800 °C. In sum, these results suggest that Ba 3 Ba 1+ x Ta 2- x O 9- δ oxides display excellent proton conductivity.