An EXAFS study of rare-earth phosphate glasses in the vicinity of the metaphosphate composition
An EXAFS study of rare-earth phosphate glasses in the vicinity of the metaphosphate composition
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DOI：
10.1016/s0022-3093(98)00466-9
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发表时间：
1998-07
影响因子：
3.5
通讯作者：
R. Anderson;T. Brennan;G. Mountjoy;R. J. Newport;G. Saunders
中科院分区：
文献类型：
--
作者：
R. Anderson;T. Brennan;G. Mountjoy;R. J. Newport;G. Saunders
利用英国达雷斯伯里实验室同步辐射光源的扩展X射线吸收精细结构（EXAFS）装置，在不同温度下对偏磷酸盐组成附近的稀土磷酸盐玻璃进行了研究。偏磷酸盐类玻璃含有稀土元素La，Sm，Eu和Gd作为R3+离子。实验在室温、145和79 K下进行。数据显示，稀土离子周围的第一层壳层仅包含平均距离为1.22 -2.4 μ m的氧原子。可以清楚地观察到“镧系收缩”，即，R-O距离随着原子序数的增加而减小。观察到的R（−O）配位数在5-7之间。第二个关联壳层被发现，与中心稀土原子周围的磷原子有关（13.5），另一个稀土：氧关联也被确定（14.4）。静态无序占主导地位的德拜-沃勒项，但热无序是不可忽略的。在EXAFS数据的准确性内，在研究的温度范围内没有观察到显著的结构变化。我们的结论是，异常的散装性能与任何微妙的结构特征或主要是由于稀土离子的相互作用。
A study of rare-earth phosphate glasses, in the vicinity of the metaphosphate composition, has been undertaken at different temperatures using the extended X-ray absorption fine structure (EXAFS) facility at the Synchrotron Radiation Source, Daresbury Laboratory, UK. The metaphosphate-like glasses examined contained the rare-earth elements La, Sm, Eu and Gd as R3+ions. The experiments were carried out at room temperature, 145 and 79 K. The data show that the first shell surrounding rare-earth ions contains only oxygen atoms at a mean distance of ∼2.2–2.4 Å. The `lanthanide contraction' is clearly observed, i.e., the R–O distance decreases with increasing atomic number. The observed R(−O) coordination numbers are in the range 5–7. A second correlation shell was found, associated with phosphorus atoms around the central rare-earth atom (∼3.5 Å), and another rare-earth:oxygen correlation was also identified (∼4 Å). Static disorder dominates the Debye–Waller term, but thermal disorder is not negligible. Within the accuracy of the EXAFS data, no significant structural variations were observed over the temperature range studied. We conclude that the anomalous bulk properties are associated with either subtle structural features or primarily due to rare-earth ion interactions.