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

Abstract

Thermogravimetry (TG) and Differential Thermal Analysis (DTA) techniques coupled with mass spectrometry were applied to evaluate the chemical stability of BaCeO 3-d-based materials in the CO 2-and H 2 Orich 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 3d-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-d 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 3d-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-d-based materials cannot be neglected.

Effect of microstructure on chemical stability and electrical properties of BaCe0.9Y0.1O3 − δ

“…Thermal analysis combined with mass spectrometry was already established as the proper tool for evaluation of the chemical stability of BaCeO 3 -based materials [19,20]. All samples were exposed to the CO 2 and H 2 O-containing atmosphere for the same period of time which allows the comparative analysis.…”

Structure, chemical stability and electrical properties of BaCe 0.9 Y 0.1 O 3−δ proton conductors impregnated with Ba 3 (PO 4 ) 2

“…Above 450 C degradation of protonic defect, related to liberation of water, occurs similar as it was observed for the sample before the test. According to the literature and our previous i n t e r n a t i o n a l j o u r n a l o f h y d r o g e n e n e r g y x x x ( 2 0 1 6 ) 1 e1 0 studies [34,35] barium carbonate decomposes below 900 C thus the mass loss above 800 C connected with evolving of CO 2 is the result of degradation of BaCO 3 formed during the exposure test. The mass loss observed for this stage of BaCe 0.9 Y 0.1 O 3Àd sample degradation is 0.22% and can be directly treated as the measure of instability of barium cerate in CO 2 containing atmosphere.…”

“…This additional phase modifies the intergranular area, probably blocking kinetically the possibility of formation of secondary carbonates. Another possible explanation of chemical stability improvement, is based on the structure modification of host BaCe 0.9 Y 0.1 O 3Àd material [35,36]. Such modification leads to the change of Goldschmidt tolerance factor, which was found to be directly related to the chemical stability of wide range of perovskites.…”

Fluorine and chlorine doping in oxygen-deficient perovskites: A strategy for improving chemical stability

“…The poor chemical stability in the atmosphere of carbon dioxide and water vapor is the limiting factor for application of the protonic electrolytes as the components of solid oxide fuel cells [9]. A compromise between high proton conductivity and chemical stability must be found to create long-term working electrochemical devices based on solid oxide protonic conductors.…”