Samples of Ba1-xSrxCe0.9Y0.1O3-δ, 0 < x < 0.1, with improved chemical stability in CO2-H2 gas-involving atmospheres as potential electrolytes for a proton ceramic fuel cell

Abstract

Comparative studies were performed on variations in the ABO3 perovskite structure, chemical stability in a CO2-H2 gas atmosphere, and electrical conductivity measurements in air, hydrogen, and humidity-involving gas atmospheres of monophase orthorhombic Ba1-xSrxCe0.9Y0.1O3-δ samples, where 0 < x < 0.1. The substitution of strontium with barium resulting in Ba1-xSrxCe0.9Y0.1O3-δ led to an increase in the specific free volume and global instability index when compared to BaCe0.9Y0.1O3-δ. Reductions in the tolerance factor and cell volume were found with increases in the value of x in Ba1-xSrxCe0.9Y0.1O3-δ. Based on the thermogravimetric studies performed for Ba1-xSrxCe0.9Y0.1O3-δ, where 0 < x < 0.1, it was found that modified samples of this type exhibited superior chemical resistance in a CO2 gas atmosphere when compared to BaCe0.9Y0.1O3-δ. The application of broadband impedance spectroscopy enabled the determination of the bulk and grain boundary conductivity of Ba1-xSrxCe0.9Y0.1O3-δ samples within the temperature range 25-730 °C. It was found that Ba0.98Sr0.02Ce0.9Y0.1O3-δ exhibited a slightly higher grain interior and grain boundary conductivity when compared to BaCe0.9Y0.1O3-δ. The Ba0.95Sr0.05Ce0.9Y0.1O3-δ sample also exhibited improved electrical conductivity in hydrogen gas atmospheres or atmospheres involving humidity. The greater chemical resistance of Ba1-xSrxCe0.9Y0.1O3-δ, where x = 0.02 or 0.05, in a CO2 gas atmosphere is desirable for application in proton ceramic fuel cells supplied by rich hydrogen processing gases.