Samples of Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ), 0 < x < 0.1, with Improved Chemical Stability in CO(2)-H(2) Gas-Involving Atmospheres as Potential Electrolytes for a Proton Ceramic Fuel Cell

Comparative studies were performed on variations in the ABO(3) perovskite structure, chemical stability in a CO(2)-H(2) gas atmosphere, and electrical conductivity measurements in air, hydrogen, and humidity-involving gas atmospheres of monophase orthorhombic Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ) samples, where 0 < x < 0.1. The substitution of strontium with barium resulting in Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ) led to an increase in the specific free volume and global instability index when compared to BaCe(0.9)Y(0.1)O(3−δ). Reductions in the tolerance factor and cell volume were found with increases in the value of x in Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ). Based on the thermogravimetric studies performed for Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ), where 0 < x < 0.1, it was found that modified samples of this type exhibited superior chemical resistance in a CO(2) gas atmosphere when compared to BaCe(0.9)Y(0.1)O(3−δ). The application of broadband impedance spectroscopy enabled the determination of the bulk and grain boundary conductivity of Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ) samples within the temperature range 25–730 °C. It was found that Ba(0.98)Sr(0.02)Ce(0.9)Y(0.1)O(3−δ) exhibited a slightly higher grain interior and grain boundary conductivity when compared to BaCe(0.9)Y(0.1)O(3−δ). The Ba(0.95)Sr(0.05)Ce(0.9)Y(0.1)O(3−δ) sample also exhibited improved electrical conductivity in hydrogen gas atmospheres or atmospheres involving humidity. The greater chemical resistance of Ba(1−x)Sr(x)Ce(0.9)Y(0.1)O(3−δ), where x = 0.02 or 0.05, in a CO(2) gas atmosphere is desirable for application in proton ceramic fuel cells supplied by rich hydrogen processing gases.