RAMAN AND X-RAY STUDIES OF CE1-XREXO2-Y, WHERE RE=LA, PR, ND, EU, GD, AND TB
RAMAN AND X-RAY STUDIES OF CE1-XREXO2-Y, WHERE RE=LA, PR, ND, EU, GD, AND TB
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DOI：
10.1063/1.357593
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发表时间：
1994-08-15
影响因子：
3.2
通讯作者：
WEBER, WH
中科院分区：
文献类型：
--
作者：
MCBRIDE, JR;HASS, KC;WEBER, WH
从稀土的硝酸盐溶液开始，在0 ≤ x ≤ 0.5的范围内合成Ce 1-xRExO 2-y型粉末样品，其中RE=La、Pr、Nd、Eu、Gd和Th。用X射线衍射和拉曼散射对样品进行了分析。这些化合物，至少在低掺杂制度和严格的三价掺杂剂，形成固溶体，保持CeO 2的萤石结构与晶格常数的变化，这是大约成比例的掺杂剂离子半径。单一允许的拉曼模式，发生在465 cm-1的纯CeO 2，观察到移动到较低的频率与所有的稀土掺杂水平的增加。然而，在从晶格膨胀校正Gruneisen位移之后，对于所有严格的三价离子，频率偏移实际上是正的。此外，拉曼线变宽并变得不对称，具有低频尾部，并且在光谱中在约570 cm-1处出现新的宽特征。拉曼光谱中的这些变化归因于O空位，每当三价RE取代Ce 4+时，O空位被引入晶格中。这一结论得到了一个简单的模型计算的O空位的拉曼光谱的影响。该模型采用了绿色函数技术的空位处理为零质量的点缺陷。
Powdered samples of the type Ce1-xRExO2-y, where RE=La, Pr, Nd, Eu, Gd, and Th, are synthesized over the range 0 less-than-or-equal-to x less-than-or-equal-to 0.5 starting from nitrate solutions of the rare earths. X-ray diffraction and Raman scattering are used to analyze the samples. These compounds, at least in the low doping regime and for strictly trivalent dopants, form solid solutions that maintain the fluorite structure of CeO2 with a change in lattice constant that is approximately proportional to the dopant ionic radius. The single allowed Raman mode, which occurs at 465 cm-1 in pure CeO2, is observed to shift to lower frequency with increasing doping level for all the rare earths. However, after correcting for the Gruneisen shift from the lattice expansion, the frequency shift is actually positive for all the strictly trivalent ions. In addition, the Raman line broadens and becomes asymmetric with a low frequency tail, and a new broad feature appears in the spectrum at approximately 570 cm-1. These changes in the Raman spectrum are attributed to O vacancies, which are introduced into the lattice whenever a trivalent RE is substituted for Ce4+. This conclusion is supported by a simple model calculation of the effects of O vacancies on the Raman spectrum. The model uses a Green's function technique with the vacancies treated as point defects with zero mass.