Abstract Doping is one of the most popular strategies to modify the properties of polycrystalline materials, because the dopants prefer to segregate at the grain boundaries (GBs) and influence the structural and electronic properties of the materials. Understanding how dopants segregate at GBs and how they affect the resultant GB properties are essential. Here, we experimentally characterized the atomic structures and the electronic band structures of Ti-doped Σ7 { 4 5 ¯ 10 } and Σ7 { 2 3 ¯ 10 } GBs in α-Al2O3 by atomic resolution scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDXS) and valence electron energy-loss spectroscopy (EELS). It was found that Ti preferentially segregated at specific atom sites driven by ionic size mismatch between Ti3+ and Al3+, which leads to structural transformations in both GBs. Direct valence EELS measurement revealed the segregation of Ti3+ ions introduces impurity band within the bandgap in Al2O3 GBs. These results provide an in-depth understanding of the local atomic and electronic band structures for Ti-doped GBs.

中文翻译：

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Ti掺杂Al2O3晶界的原子和电子能带结构

摘要 掺杂是最流行的改变多晶材料性能的策略之一，因为掺杂剂更喜欢在晶界（GB）处偏析并影响材料的结构和电子特性。了解掺杂剂如何在 GB 处分离以及它们如何影响最终的 GB 特性至关重要。在这里，我们通过原子分辨率扫描透射电子显微镜（STEM）、能量-Al2O3 实验表征了 Ti 掺杂的 Σ7 { 4 5 ¯ 10 } 和 Σ7 { 2 3 ¯ 10 } GBs 在 α-Al2O3 中的原子结构和电子能带结构。色散 X 射线光谱 (EDXS) 和价电子能量损失光谱 (EELS)。研究发现，由于 Ti3+ 和 Al3+ 之间的离子尺寸不匹配，Ti 优先偏析在特定的原子位置，这导致两个 GB 的结构转变。直接价 EELS 测量显示 Ti3+ 离子的偏析在 Al2O3 GB 的带隙内引入了杂质带。这些结果提供了对 Ti 掺杂 GB 的局部原子和电子能带结构的深入理解。