Application of DTA-TG-MS for determination of chemical stability of BaCeO3−δ-based protonic conductors

Thermogravimetry (TG) and Differential Thermal Analysis (DTA) techniques coupled with mass spectrometry were applied to evaluate the chemical stability of BaCeO 3−δ -based materials in the CO 2 - and H 2 O-rich atmosphere. The different groups of materials were investigated: solid solutions of BaCeO 3 –BaTiO 3 and BaCeO 3 –BaSnO 3 acceptor doped by Y or In and composite materials with nominal composition (1−x)BaCe 0.9 Y 0.1 O 3−δ -xYPO 4 . To evaluate the chemical stability towards carbon dioxide and water vapour samples were exposed to atmosphere containing CO 2 /H 2 O (7 % of CO 2 in air, 100 % RH) at temperature of 25 °C for 350 h. Thermal analysis (TG/DTA) was applied to analyse the materials before and after the test. To support the interpretation of TG/DTA results, the analysis of gaseous products evoluted during thermal treatment of the samples was provided using mass spectrometer. This combined analysis clearly shows that during the exposition test, the conversion of barium cerate to barium carbonate and barium hydroxide occurs. The amount of BaCO 3 and the degree of BaCeO 3−δ conversion depend on the type of barium cerate modification. The mass loss observed after the exposition test can be treated as a measure of chemical instability of BaCeO 3−δ -based materials. The correlation of chemical stability, described by the mass loss, on Goldschmidt tolerance factor, describing the deviation from ideal perovskite structure, was found in most of the materials investigated. However, the influence of the microstructure and the modification the grain boundaries on the chemical stability of BaCeO 3−δ -based materials cannot be neglected.