Preparation and conductive properties of double perovskite Ba3Sr1+xTa2−xO9−δ and application for hydrogen sensor

Abstract

A series of Ba3Sr1+xTa2−xO9−δ (x = 0,0.1,0.2,0.3,0.4) double perovskite proton conductors were fabricated at 1400 °C for 10 h and further sintered at 1650 °C for 10 h via a solid-state reaction process. Their phase composition, microstructure characterization and valence were investigated by XRD, FESEM and XPS techniques. Conductivities of these proton conductors were measured under the atmosphere of various water vapor and oxygen pressures by the electrochemical impedance spectra technique. It was found that the grain boundary thicknesses of Ba3Sr1+xTa2−xO9−δ were significantly higher than other perovskite proton conductors. The total conductivities of Ba3Sr1+xTa2−xO9−δ increased with the increase of both temperature and stoichiometric proportion of Sr, and Ba3Sr1.4Ta1.6O8.4 exhibited the highest conductivity of about 4.4 × 10−3 S cm−1 at 750 °C. Additionally, the transport numbers of proton, oxide ion and hole were measured using defect equilibria model. The results indicated that Ba3Sr1+xTa2−xO9−δ oxides were almost pure proton conductors at 400–550 °C and mixed proton-oxide ion-hole conductors at 550–850 °C, and Ba3Sr1.3Ta1.7O8.55 exhibited the highest protonic transport number. The performance of the hydrogen sensor using Ba3Sr1.3Ta1.7O8.55 was also measured in various hydrogen partial pressure, a good linear relationship between EMF and pH2 was observed at 400–800 °C, and the response time was around 10s.