The rare earth hexaborides are known for their tendency towards very high crystal perfection. They can be grown into large single crystals of very high purity by inert gas arc floating zone refinement. The authors have found that single-crystal cerium hexaboride grown in this manner contains a significant number of inclusions of an impurity phase that interrupts the otherwise single crystallinity of this prominent cathode material. An iterative approach is used to unequivocally determine the space group and the lattice parameters of the impurity phase based on geometries of convergent-beam electron diffraction (CBED) patterns and the symmetry elements that they possess in their intensity distributions. It is found that the impurity phase has a tetragonal unit cell with space group P4/mbm and lattice parameters a = b = 7.23 ± 0.03 and c = 4.09 ± 0.02 Å. These agree very well with those of a known material, CeB4. Confirmation that this is indeed the identity of the impurity phase is provided by quantitative CBED (QCBED) where the very close match between experimental and calculated CBED patterns has confirmed the atomic structure. Further confirmation is provided by a density functional theory calculation and also by high-angle annular dark-field scanning transmission electron microscopy.

中文翻译：

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会聚束电子衍射鉴定高纯 CeB6 中的杂质相

稀土六硼化物以其晶体完美度非常高的倾向而闻名。通过惰性气体电弧浮区精炼，它们可以生长成纯度非常高的大单晶。作者发现，以这种方式生长的单晶六硼化铈含有大量杂质相夹杂物，该杂质相破坏了这种重要阴极材料的单晶性。基于会聚束电子衍射 (CBED) 图案的几何形状以及它们在强度分布中拥有的对称元素，采用迭代方法明确确定杂质相的空间群和晶格参数。发现杂质相具有空间群的四方晶胞磷4/MBM和晶格参数A=乙= 7.23 ± 0.03 和C= 4.09 ± 0.02 埃。这些与已知材料 CeB 的结果非常吻合4。定量 CBED (QCBED) 证实了这确实是杂质相的身份，其中实验和计算的 CBED 模式之间非常接近的匹配证实了原子结构。密度泛函理论计算和高角度环形暗场扫描透射电子显微镜进一步证实了这一点。