High-temperature thermodynamic properties of Y-doped barium zirconates, BaZr_1–xY_xO_3−x/2 (x = 0.1, 0.2), with perovskite-type structure

Perovskite-type oxides BaZr_1–xY_xO_3−x/2 (x = 0.1, 0.2) were synthesized and their enthalpy increments were measured by means of high-temperature drop calorimetry in the temperature range of (373–1273) K in air. The data obtained were used for estimating the high-temperature thermodynamic functions (constant pressure heat capacity and entropy increments) of the zirconates BaZr_1–xY_xO_3−x/2 (x = 0.1, 0.2). They were found to be only weakly dependent on the concentration of Y-dopant. Thermal expansion coefficient of zirconates BaZr_1–xY_xO_3−x/2 (x = 0.1, 0.2) was successfully estimated by Grüneisen equation. Also, Neumann-Kopp rule was shown to be inapplicable for accurate estimation of heat capacities of the studied oxides. Thermodynamic analysis showed that BaZr_1–xY_xO_3−x/2 (x = 0.1, 0.2) oxides are prone to chemical interaction with CO₂ at typical working temperatures of proton-conducting solid oxide fuel cells. Some possibilities to overcome this issue have been discussed.