Ca9Zn4.5Sb9 Zintl compound is one of the promising thermoelectric materials with excellent performance, which can be further improved by Eu alloying. In this work, a series of Ca9−yEuyZn4.5+δSb9 compounds is investigated by using the advanced Cs-corrected high-angle annular dark field scanning transmission electron microscope (HAADF-STEM) imaging technique at an atomic level. The HAADF-STEM images show that alloying Eu will lead to preferential substitution of Eu atoms at Ca(1) and Ca(5) sites. The further structural analysis and first-principles density functional theory calculation elucidate the origin that the Eu atoms are prone to replace Ca(1) and Ca(5) sites in Ca9−yEuyZn4.5+δSb9. The preferential substitutions may provide a new insight into revealing the structural transformation commonly found in Zintl phase thermoelectric materials.

中文翻译：

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9-4-9 Zintl 相 Ca9− yEuyZn4.5+ δ Sb9 中阳离子位点的优先取代

Ca9Zn4.5Sb9 Zintl化合物是一种很有前途的热电材料，性能优异，可以通过Eu合金化进一步提高。在这项工作中，通过使用先进的 Cs 校正高角度环形暗场扫描透射电子显微镜 (HAADF-STEM) 成像技术在原子水平上研究了一系列 Ca9−yEuyZn4.5+δSb9 化合物。HAADF-STEM 图像显示合金化 Eu 将导致优先取代 Ca(1) 和 Ca(5) 位置的 Eu 原子。进一步的结构分析和第一性原理密度泛函理论计算阐明了Eu原子容易取代Ca9−yEuyZn4.5+δSb9中的Ca(1)和Ca(5)位点的原因。优先取代可能为揭示 Zintl 相热电材料中常见的结构转变提供新的见解。