Grain boundary atomic structures and light-element visualization in ceramics: combination of Cs-corrected scanning transmission electron microscopy and first-principles calculations
Grain boundary atomic structures and light-element visualization in ceramics: combination of Cs-corrected scanning transmission electron microscopy and first-principles calculations
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DOI：
10.1093/jmicro/dfr049
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发表时间：
2011-08-01
期刊：
影响因子：
--
通讯作者：
Ikuhara, Yuichi
中科院分区：
文献类型：
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作者：
Ikuhara, Yuichi
晶体的晶界和界面具有特殊的电子结构，这是由周期性的无序引起的，提供了完美晶体中无法观察到的功能特性。在晶界和界面附近，掺杂或杂质经常被分离，它们对决定材料的性能起着至关重要的作用。球差(Cs)校正的扫描电子显微镜(STEM)可以形成亚埃大小的电子探针，可以直接观察晶界分离的掺杂。另一方面，陶瓷材料是由轻元素组成的，这些轻元素对陶瓷材料的性能也起着重要的作用。最近，环状亮场(ABF)-STEM成像被提出，它现在被认为是一种非常强大的技术，可以同时显示轻元素柱和重元素柱。本文结合理论计算，介绍了陶瓷晶界的原子结构测定和晶界偏析掺杂及轻元素的直接观察。举例说明了稀土掺杂的Al_2O_3和ZnO陶瓷、CeO_2和SrTiO_3晶界、锂电池材料和金属氢化物的晶界，并用Cs校正的大角度环形暗场和ABF-STEM进行了表征。结果表明，STEM表征和第一性原理计算相结合，对于解释各种陶瓷的结构信息和理解其性质的来源是非常有用的。
Grain boundaries and interfaces of crystals have peculiar electronic structures, caused by the disorder in periodicity, providing the functional properties, which cannot be observed in a perfect crystal. In the vicinity of the grain boundaries and interfaces, dopants or impurities are often segregated, and they play a crucial role in deciding the properties of a material. Spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM), allowing the formation of sub-angstrom-sized electron probes, can directly observe grain boundary-segregated dopants. On the other hand, ceramic materials are composed of light elements, and these light elements also play an important role in the properties of ceramic materials. Recently, annular bright-field (ABF)-STEM imaging has been proposed, which is now known to be a very powerful technique in producing images showing both light- and heavy-element columns simultaneously. In this review, the atomic structure determination of ceramic grain boundaries and direct observation of grain boundary-segregated dopants and light elements in ceramics were shown to combine with the theoretical calculations. Examples are demonstrated for well-defined grain boundaries in rare earth-doped Al2O3 and ZnO ceramics, CeO2 and SrTiO3 grain boundary, lithium battery materials and metal hydride, which were characterized by Cs-corrected high-angle annular dark-field and ABF-STEM. It is concluded that the combination of STEM characterization and first-principles calculation is very useful in interpreting the structural information and in understanding the origin of the properties in various ceramics.