Atom-resolved imaging of ordered defect superstructures at individual grain boundaries
Atom-resolved imaging of ordered defect superstructures at individual grain boundaries
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DOI：
10.1038/nature10593
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发表时间：
2011-11-17
期刊：
影响因子：
64.8
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
--
作者：
Wang, Zhongchang;Saito, Mitsuhiro;Ikuhara, Yuichi
能够在空间上分辨和识别缺陷中的原子将极大地促进我们对材料结构和性能之间的关系的理解(1)。这在多晶材料中尤其重要，在多晶材料中，晶界对最终材料的性能和应用具有深远的影响(2)。然而，这样的原子分辨率仍然是极其困难的，部分原因是晶界是原子缺陷和杂质(3-5)的有效汇，这可能会驱动晶界的结构转变，从而改变材料的性能(6，7)。无论这些缺陷的来源是什么，缺陷和晶界之间的相互作用使我们难以确定缺陷区域中存在的实体的确切位置和化学成分，从而限制了我们对特定缺陷如何调节性能变化的理解。在这里，我们展示了先进的电子显微镜、光谱学和第一性原理计算的结合，可以提供具有原子分辨率和化学敏感性的复杂的、多组分的晶界的三维图像。这些技术的高分辨率使我们能够证明，即使是具有简单的岩盐结构的氧化镁，晶界也可以容纳复杂的有序缺陷超结构，这些缺陷超结构会在氧化物的带隙中诱导显著的电子陷阱。这些结果提供了对陶瓷中缺陷和晶界之间相互作用的见解，并表明原子尺度分析材料中复杂的多组分结构现在已经成为可能。
The ability to resolve spatially and identify chemically atoms in defects would greatly advance our understanding of the correlation between structure and property in materials(1). This is particularly important in polycrystalline materials, in which the grain boundaries have profound implications for the properties and applications of the final material(2). However, such atomic resolution is still extremely difficult to achieve, partly because grain boundaries are effective sinks for atomic defects and impurities(3-5), which may drive structural transformation of grain boundaries and consequently modify material properties(6,7). Regardless of the origin of these sinks, the interplay between defects and grain boundaries complicates our efforts to pinpoint the exact sites and chemistries of the entities present in the defective regions, thereby limiting our understanding of how specific defects mediate property changes. Here we show that the combination of advanced electron microscopy, spectroscopy and first-principles calculations can provide three-dimensional images of complex, multicomponent grain boundaries with both atomic resolution and chemical sensitivity. The high resolution of these techniques allows us to demonstrate that even for magnesium oxide, which has a simple rock-salt structure, grain boundaries can accommodate complex ordered defect superstructures that induce significant electron trapping in the bandgap of the oxide. These results offer insights into interactions between defects and grain boundaries in ceramics and demonstrate that atomic-scale analysis of complex multicomponent structures in materials is now becoming possible.