氟碳铈钡矿的电子衍射和晶格象研究

氟碳铈钡矿Ce₂Ba₃(CO₃)₅F₂是在我国发现的新矿物,其电子衍射斑点按强度可分为两大类:较强的一类是晶体亚结构的贡献;其余衍射斑点是超结构的贡献。晶体的亚结构与黄河矿的相类似,可以划出一个六角的亚晶胞。亚晶胞参数为a₀=5.06?,c₀=9.63?。超结构属单斜晶系,晶胞参数为a=21.2?,b=5.06?,c=13.1?,β=95°。晶体属空间群C2/m、Cm或C2,亚结构与超结构的基矢有如下关系:该矿h00系统衍射形成的晶格象中,常夹有间距较小的条纹,或宽的黑带。本文对此进行了讨论,也讨论了该矿是否会有更大周期的超结构问题。关键词：

ELECTRON DIFFRACTION AND LATTICE IMAGE STUDY ON CEBAITE

Cebaite Ce₂Ba₃(CO₃)₅F₂ is a new mineral discovered in China. Its electron diffraction spots can be divided into two groups according to the intensity. The stronger one results from the substructure which is similar to that of Huanghoite and can be described by a hexagonal subcell with parameters α₀=5.06?, c₀=9.63?, while the other group comes from the superstructure which belongs to monoclinic system. The parameters of the real unit cell are α=21.2? b=5.06? c=13.l? β=95°. The possible space groups are C2/m, Cm and C2. The basic vectors of the substructure and those of the superstructure in the real space are as follows :Some frings with spacing smaller than the original one and some broad black bands often appear in lattice images formed by h00 systematic reflexions. The cause of this is discussed. It is also discussed whether there is any superstructure with longer period in this mineral.
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