ICSM-UMR5257 CNRS/CEA/UM2/ENCSM , Site de Marcoule, Bât. 426, BP 17171, 30207 Bagnols/Cèze, France.
Inorg Chem. 2011 Aug 1;50(15):7150-61. doi: 10.1021/ic200751m. Epub 2011 Jun 29.
Several CeO(2)-based mixed oxides with general composition Ce(1-x)Ln(x)O(2-x/2) (for 0 ≤ x ≤ 1 and Ln = La, Nd, Sm, Eu, Gd, Dy, Er, or Yb) were prepared using an initial oxalic precipitation leading to a homogeneous distribution of cations in the oxides. After characterization of the Ce/Nd oxalate precursors and then thermal conversion to oxides at T = 1000 °C, investigation of the crystalline structure of these oxides was carried out by XRD and μ-Raman spectroscopy. Typical fluorite Fm ̅3m structure was obtained for relatively low Ln(III) contents, while a cubic Ia ̅3̅ superstructure was evidenced above x ≈ 0.4. Moreover, since Nd(2)O(3) does not crystallize with the Ia ̅3̅-type structure, two-phase systems composed with additional hexagonal Nd(2)O(3) were obtained for x(Nd) ≥ 0.73 in the Ce(1-x)Nd(x)O(2-x/2) series. The effect of heat treatment temperature on these limits was explored through μ-Raman spectroscopy, which allowed determining the presence of small amounts of the different crystal structures observed. In addition, the variation of the Ce(1-x)Ln(x)O(2-x/2) unit cell parameter was found to follow a quadratic relation as a result of the combination between increasing cationic radius, modifications of cation coordination, and decreasing O-O repulsion caused by oxygen vacancies.
几种 CeO(2)-基混合氧化物，通式为 Ce(1-x)Ln(x)O(2-x/2)（0 ≤ x ≤ 1，Ln = La、Nd、Sm、Eu、Gd、Dy、Er 或 Yb），采用初始草酸沉淀法制备，该方法可使阳离子在氧化物中均匀分布。在对 Ce/Nd 草酸盐前体进行特性研究之后，将其在 T = 1000°C 的条件下转化为氧化物，通过 XRD 和 μ-Raman 光谱对这些氧化物的晶体结构进行了研究。对于相对较低的 Ln(III)含量，获得了典型的萤石 Fm ̅3m 结构，而当 x ≈ 0.4 以上时，可证实立方 Ia ̅3̅超结构的存在。此外，由于 Nd(2)O(3) 不以 Ia ̅3̅型结构结晶，因此在 Ce(1-x)Nd(x)O(2-x/2)系列中，当 x(Nd) ≥ 0.73 时，得到了由额外的六方 Nd(2)O(3)组成的两相体系。通过 μ-Raman 光谱研究了热处理温度对这些极限的影响，该方法可确定观察到的不同晶体结构的存在。此外，Ce(1-x)Ln(x)O(2-x/2) 单元晶格参数的变化被发现是由于阳离子半径的增加、阳离子配位的改变以及氧空位引起的 O-O 排斥力的减小的共同作用的结果，遵循二次关系。
