Electrical properties and water incorporation in A-site deficient perovskite La1−xBaxNb3O9−0.5x

• Barium doped perovskites La1−xBaxNb3O9−0.5x (x=0–0.05) are capable to incorporate water from the gas phase and to exhibit proton transport.
• The hydration is accompanied by the formation of OH− – groups and H3O+ – ions.
• The total conductivity exhibits a minimum on σ−f(x) dependencies as a result of a mixed cation effect.

Barium doped A-site deficient perovskites La1−xBaxNb3O9−0.5x (x=0–0.05) were synthesized by the solid state method, their structure, electrical properties and state of oxygen-hydrogen groups have been investigated. These phases were found to be able to incorporate water from the gas phase and to exhibit proton transport. Hydration is accompanied by the formation of different forms of oxygen-hydrogen groups: OH− – groups and H3O+ – ions. The total conductivities of doped samples increased in a wet atmosphere due to the appearance of proton current carriers (at the temperatures below 700 °C), but the conductivity increased insignificantly (~0.25 order of magnitude) because of a low doping level and, consequently, small concentration of protons. TG-measurements confirmed relatively low water content (below 0.2%). The total conductivity depends substantially on x and exhibits a minimum on σ−f(x) dependencies. It has been suggested that such behavior is a manifestation of a mixed cation effect.

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