Structure and transport properties of triple-conducting BaxSr1−xTi1−yFeyO3−δoxides

Abstract

In this work, BaxSr1−xTi1−yFeyO3−δperovskite-based mixed conducting ceramics (forx= 0, 0.2, 0.5 andy= 0.1, 0.8) were synthesized and studied. The structural analysis based on the X-ray diffraction results showed significant changes in the unit cell volume and Fe(Ti)-O distance as a function of Ba content. The morphology of the synthesized samples studied by means of scanning electron microscopy has shown different microstructures for different contents of barium and iron. Electrochemical impedance spectroscopy studies of transport properties in a wide temperature range in the dry- and wet air confirmed the influence of barium cations on charge transport in the studied samples. The total conductivity values were in the range of 10−3to 100S cm−1at 600 °C. Depending on the barium and iron content, the observed change of conductivity either increases or decreases in humidified air. Thermogravimetric measurements have shown the existence of proton defects in some of the analysed materials. The highest observed molar proton concentration, equal to 5.0 × 10−2mol mol−1at 300 °C, was obtained for Ba0.2Sr0.8Ti0.9Fe0.1O2.95. The relations between the structure, morphology and electrical conductivity were discussed.