Structural study for hydrolytic condensed amorphous(Y,Zr)O_x.

以金属醇盐和其它金属有机化合物为原料的溶胶-凝胶技术已发展成为制备各种先进材料的新技术，ZrO_2就是其中之一。用溶胶-凝胶法制备的非晶ZrO_2（a-ZrO_2）热分解时，除生成单斜ZrO_2（m-ZrO_2）外，还生成亚稳四方ZrO_2（t-ZrO_2）。为了阐明这种晶化行为，我们对α- ZrO_2的结构进行了系统的分析.以Zr（OC_4H_9）_4和ZrOCl_2+8H_2O水溶液为原料，通过水解缩合反应制备了两种α-ZrO_2。应用反常X射线散射技术获得了锆周围环境的径向分布函数。定量地确定了锆与六个氧原子的配位距离为0.214nm，而这个锆八面体与另外四个氧原子的配位距离为0.341nm。这种典型的局部有序结构与m-ZrO_2结构中的有序结构类似，而与t-ZrO_2结构中的有序结构不同。用类似的方法分析了稀土（Y或Er）取代α-ZrO_2的结构。稀土元素的加入并没有改变a-ZrO_2的典型局部结构，但a-ZrO_2是由稀土元素取代的a-ZrO_2结晶而成的。因此，该体系的晶化行为与α-ZrO_2的结构特征无关。用X射线小角衍射研究a-ZrO_2的结构不均匀性是溶胶-凝胶法制备材料的特征之一。

The sol-gel technique using metal alkoxides and other metal organic compounds as master materials has been developed for making various advanced materials and ZrO_2 is known to be included in this category. Thermal decomposition of amorphous-ZrO_2(a-ZrO_2) obtained by this sol-gel method produces a metastable tetragonal-ZrO_2(t-ZrO_2) in addition to monoclinic-ZrO_2(m-ZrO_2). In order to clarify this crystallization behavior, we analyzed the structure of a- ZrO_2 systematically. Two kinds of a-ZrO_2 were prepared by the hydrolytic condensation of Zr(OC_4H_9)_4 and the aqueous solution of ZrOCl_2+8H_2O. The anomalous X-ray scattering technique has been applied to obtain the environmental radial distribution function around a zirconium. Zirconium is quantitatively confirmed to be coordinated by six oxygens at a distance of 0.214nm and this Zr-octahedron is surrounded by other four octahedra at a distance of 0.341nm. This typical local ordering is suggested to be similar to that in the structure of m-ZrO_2 rather than that of t-ZrO_2. The structure of REE(Y or Er) substituted a-ZrO_2 have been analyzed in similar way. The typical local structure was not changed by the addition of REE elements to the a-ZrO_2, although cubic-ZrO_2 is produced by the crystallization of REE substituted a-ZrO_2. Therefore, it is rather suggested that the crystallization behavior is independent of the structural feature of a-ZrO_2 in this system. The research by using X-ray small-angle diffraction is strongly required for discussing the structural inhomogeneity in a-ZrO_2, which is one of the characteristic natures of the materials produced by sol-gel technique.