Construction of Crystal Structures of Metal Oxide Phosphates Containing Dynamic Distortions

本研究旨在通过将Mo6八面体单元和XO4四面体单元相结合来开发新材料。在研究的第一阶段，系统地搜索了四面体：八面体比例为1：1的化合物，发现了一系列等结构化合物的存在。这些化合物含有Ti、Zr、Ru、Mn或Nb为M^&lt；IV&Gt；Nb或Ta为M^V，K、Rb或Cs为A。在研究的后期，将研究扩展到四面体：八面体比例小于1：1的化合物，特别是研究了比例为1：3的化合物。本文合成了K_&lt；2+x&gt；Ti_xNb_&lt；3-x&gt；O(PO_4)(0.5&lt；x&lt；0.6)等新化合物。在我们集中努力的Nb-磷酸盐体系中，在研究期间的最后一年发现了意想不到的化合物。X-射线衍射图显示出与烧绿石结构有等结构关系的化合物。焦绿石结构具有仅由Mo6八面体组成的网状结构，而所制备的化合物含有四面体元素(P)。唯一具有相似结构特征的化合物是CsAsTiO5，本研究合成的化合物表明许多化合物中的Mo6八面体被XO4四面体取代的可能性很大。我们还尝试了用磷酸盐以外的XO4单元进行准备。我们在锗酸盐体系中合成了一种新的锗化合物Cs_8Nb_&lt；10&gt；Ge_6O_&lt；41&gt；，得到了一种似乎具有新结构的新的砷酸盐RbZrO(AsO_4)。

This research was aimed to develop new materials by combining MO_6 octahedral units and XO_4 tetrahedral units. At the first stage of the research, compounds with the tetrahedra : octahedra ratio of 1:1 were systematically searched and the existence of a series of isostructural compounds were revealed. These compounds contained Ti, Zr, Ru, Mn, or Nb as M^<IV>, Nb or Ta as M^V, and K, Rb, or Cs as A. The relation of dielectric properties of these compounds with the elements composing the compounds was clarified. At the later stages of the research, the research was extended to the compounds with the tetrahedra : octahedra ratio smaller than 1:1, and especially the compounds with the ratio 1:3 were studied. In this study, new compounds including K_<2+x>Ti_xNb_<3-x>O(PO_4)(0.5 <x <0.6) were synthesized. In the niobium-phosphate system, where we focused our efforts, unexpected compounds were discovered in the last year of the research period. The compounds showing the X-ray diffraction pattern which showed isostructural relationship with pyrochlore structure. The pyrochlore structure has the network consisting only of MO6 octahedra while the compounds prepared contained the tetrahedral element (P). The only compound which has similar structural feature is CsAsTiO_5 and the compounds prepared in this research showed the possibility of many compounds in which MO_6 octahedra were replaced by XO_4 tetrahedra. We attempted also the preparations with XO4 units other than phosphates. We prepared a new germanium compound Cs_8Nb_<10>Ge_6O_<41> ain germanate system, and obtained a new arsinate RbZrO(AsO_4) which seems to have a new structure.