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.
Silver and yttrium dopants influence some physico-chemical properties of BaCeO 3 protonic conduction. Ag-acceptor dopant substituting Ba atom in BaCeO 3 compounds was studied for the first time. Ba 1−x Ag x Ce 1−y Y y O 3−δ (0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.1) materials were synthesized by solid state reaction and by modified Pechini citric acid method. X-ray diffraction (XRD) and electrical properties measurements including open cell voltage (OCV) of electrochemical cells were used as experimental techniques. Basing on XRD results it was found that all synthesized materials crystallized in orthorhombic Pnma phase with some admixtures of other phases. Metallic Ag, CeO 2 or Y 2 O 3 with different concentrations were detected, depending on the composition, synthesis method and preparation details. DC electrical measurements showed that doping by Ag and Y decreased the total and ionic conductivities of the materials. The modification of charge transport properties was also observed, namely introduction of Ag led to the increase of electronic component of total electrical conductivity, especially at higher temperatures.
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