Water Uptake and Transport Properties of La1-xCaxScO3-α Proton-Conducting Oxides.

Alyona Lesnichyova,Anton Kuzmin,Anna Stroeva,Igor Khromushin,Maxim Ananyev,Tatyana Aksenova,Maksim Plekhanov,Andrey Farlenkov,Nikita Shevyrev,Semyon Belyakov

doi:10.3390/ma12142219

Alyona Lesnichyova, Anton Kuzmin + Show 8 more

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https://doi.org/10.3390/ma12142219

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Abstract

In this study, oxide materials La1−xCaxScO3−α (x = 0.03, 0.05 and 0.10) were synthesized by the citric-nitrate combustion method. Single-phase solid solutions were obtained in the case of calcium content x = 0.03 and 0.05, whereas a calcium-enriched impurity phase was found at x = 0.10. Water uptake and release were studied by means of thermogravimetric analysis, thermodesorption spectroscopy and dilatometry. It was shown that lower calcium content in the main phase leads to a decrease in the water uptake. Conductivity was measured by four-probe direct current (DC) and two-probe ascension current (AC) methods at different temperatures, pO2 and pH2O. The effects of phase composition, microstructure and defect structure on electrical conductivity, as well as correlation between conductivity and water uptake experiments, were discussed. The contribution of ionic conductivity of La1−xCaxScO3−α rises with decreasing temperature and increasing humidity. The domination of proton conductivity at temperatures below 500 °C under oxidizing and reducing atmospheres is exhibited. Water uptake and release as well as transport properties of La1−xCaxScO3−α are compared with the properties of similar proton electrolytes, La1−xSrxScO3−α, and the possible reasons for their differences were discussed.

Highlights

Oxide materials with proton conductivity have been attracting attention as key materials for highly efficient and environment friendly protonic ceramic fuel cells (PCFC)
The X-ray diffraction (XRD) analysis demonstrated that La0.97 Ca0.03 ScO3−α (LCS3), LCS5 and LCS10 samples are single-phase
Ca2+LCS3, concentration increasing in LCS. are means that the diffraction peaks in each pattern were indexed assuming a LaScO3‐type orthorhombic distorted effective volume of [La

Summary

Introduction

Oxide materials with proton conductivity have been attracting attention as key materials for highly efficient and environment friendly protonic ceramic fuel cells (PCFC). The use of proton-conducting electrolytes in comparison with oxygen-ion conductors has several advantages. The proton transfer process has significantly lower activation energy than oxygen-ions, which leads to a reduction in the operating temperature of devices without any loss of their power characteristics [1,2,3]. Researchers have focused on the study of solid oxides with A2+ B4+ O3 -type perovskites (where A = Ba, Sr; and B = Ce, Zr) because of their high proton conductivity. Some of these materials can decompose in atmospheres containing water vapor and carbon dioxide due to the high content of alkaline earth-metal cations [4,5,6].

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