Knowledge of radiation-induced structural changes in complex oxides is of technological importance for the development of container materials for the immobilization of nuclear waste. Fluorite structural derivatives are candidates for container materials, but their disordering processes under radiation environments are still unclear. In the present study, ion irradiation was performed on the Sc₂O₃-HfO₂ pseudo-binary system in which fluorite-related structural compounds such as β-Sc₂Hf₇O₁₇, γ-Sc₂Hf₅O₁₃, and δ-Sc₄Zr₃O₁₂ exist, and the short-range ordered structures were investigated by transmission electron microscopy (TEM). The pristine long-range ordered rhombohedral phase was found to transform into a long-range disordered cubic oxygen-deficient fluorite phase upon ion irradiation. The atomic arrangements are not completely disordered, but a more ordered structure was present in the disordered fluorite matrix. A characteristic diffuse scattering was observed in the electron diffraction patterns, and dark-field TEM observations revealed that it is due to microdomains, defined as small regions where the degree of order is higher than that of the disordered matrix. Although the parent phase was different before irradiation, the short-range organization is the same. A comparison of diffuse scattering with the location of superlattice reflections suggested that the microdomains have a structure similar to the δ-phase. With increasing Sc₂O₃ concentration, the microdomains of δ-type structures were suggested to change to short-range ordered bixbyite structures, which are not present in the equilibrium phase diagram.

中文翻译：

---

Sc2O3-HfO2 中离子辐照萤石结构衍生物的短程有序


了解复杂氧化物中辐射诱导的结构变化对于开发用于固定核废料的容器材料具有技术意义。萤石结构衍生物是容器材料的候选者，但它们在辐射环境下的无序过程仍不清楚。在本研究中，对 Sc₂O 3-HfO₂ 伪二元系统进行离子照射，其中存在 β-Sc₂Hf₇O₁₇、γ-Sc₂Hf₅O₁₃ 和 δ-Sc₄Zr₃O₁₂ 等萤石相关结构化合物，并通过透射电子显微镜 （TEM） 研究了短程有序结构。发现原始的长程有序菱面体相在离子照射后转变为长程无序立方缺氧萤石相。原子排列不是完全无序的，但在无序的萤石基质中存在更有序的结构。在电子衍射图谱中观察到特征性漫散射，暗场 TEM 观察表明这是由于微域引起的，微域定义为有序度高于无序矩阵的小区域。虽然照射前母相不同，但短程组织是相同的。漫散射与超晶格反射位置的比较表明，微畴具有类似于δ相的结构。随着 Sc₂O₃ 浓度的增加，δ型结构的微畴转变为短程有序的 bixbyite 结构，这在平衡相图中不存在。