High Temperature Structural Study of Gd-Doped Ceria by Synchrotron X-ray Diffraction (673 K 鈮?T 鈮?1073 K)

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• 作者：Cristina Artini ; Marcella Pani ; Andrea Lausi ; Roberto Masini ; Giorgio A. Costa
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：October 6, 2014
• 年：2014
• 卷：53
• 期：19
• 页码：10140-10149
• 全文大小：525K
• ISSN：1520-510X

文摘

The crystallographic features of Gd-doped ceria were investigated at the operating temperature of solid oxides fuel cells, where these materials are used as solid electrolytes. (Ce_1鈥?i>xGd_x)O_2-x/2 samples (x = 0.1, 0.3, 0.5, 0.7) were prepared by coprecipitation of mixed oxalates, treated at 1473 K in air, and analyzed by synchrotron X-ray diffraction in the temperature range 673 K 鈮?T 鈮?1073 K at the Elettra synchrotron radiation facility located in Trieste, Italy. In the whole temperature span a boundary was found at x 鈭?0.2 between a CeO₂-based solid solution (for x 鈮?0.2) and a structure where Gd₂O₃ microdomains grow within the CeO₂ matrix, taking advantage of the similarity between Gd³⁺ and Ce⁴⁺ sizes; the existence of the boundary at x 鈭?0.2 was confirmed also by measurements of ionic conductivity performed by impedance spectroscopy. Similar to what observed at room temperature, the trend of the cell parameter shows the presence of a maximum; with increasing temperature, the composition corresponding to the maximum moves toward lower Gd content. This evidence can be explained by analyzing the behavior of the coefficient of thermal expansion as a function of composition.