Artini Cristina, Pani Marcella, Lausi Andrea, Masini Roberto, Costa Giorgio A
DCCI, Department of Chemistry and Industrial Chemistry, University of Genova , Via Dodecaneso 31, 16146 Genova, Italy.
Inorg Chem. 2014 Oct 6;53(19):10140-9. doi: 10.1021/ic5011242. Epub 2014 Sep 5.
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-x)Gd(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 ≤ T ≤ 1073 K at the Elettra synchrotron radiation facility located in Trieste, Italy. In the whole temperature span a boundary was found at x ∼ 0.2 between a CeO2-based solid solution (for x ≤ 0.2) and a structure where Gd2O3 microdomains grow within the CeO2 matrix, taking advantage of the similarity between Gd(3+) and Ce(4+) sizes; the existence of the boundary at x ∼ 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.
在固体氧化物燃料电池的工作温度下研究了钆掺杂二氧化铈的晶体学特征，在该温度下这些材料用作固体电解质。通过混合草酸盐的共沉淀制备了（Ce(1-x)Gd(x))O(2-x/2)样品（x = 0.1、0.3、0.5、0.7），在空气中于1473 K进行处理，并在位于意大利的里雅斯特的Elettra同步加速器辐射设施中在673 K≤T≤1073 K的温度范围内通过同步加速器X射线衍射进行分析。在整个温度范围内，在x ∼ 0.2处发现了基于CeO2的固溶体（x≤0.2）与在CeO2基体中生长Gd2O3微区的结构之间的边界，这利用了Gd(3+)和Ce(4+)尺寸的相似性；通过阻抗谱进行的离子电导率测量也证实了在x ∼ 0.2处存在边界。与在室温下观察到的情况类似，晶胞参数的趋势显示存在最大值；随着温度升高，对应于最大值的组成向较低的钆含量移动。通过分析热膨胀系数随组成的变化行为可以解释这一现象。
