透過型電子顕微鏡による、セラミックス粒界構造解析

使用透射电子显微镜分析陶瓷晶界结构

• 批准号: 12F02783
• 负责人: 幾原 雄一
• 金额: $ 1.47万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for JSPS Fellows
• 财政年份: 2012
• 资助国家: 日本
• 起止时间: 2012-04-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-12F02783/
• 关键词: grain boundary; electron microscopy; ceramics; 走査透過型電子顕微鏡; セラミックス; 界面原子構造; 構造解析

In this study, we fabricated a bicrystal, possessing bi-crystallographic relations of (310)[001]||(310)[001] between upper and lower crystals. Analysis of diffraction patterns confirms these orientations to within a small misfit tilt angle, and high-resolution TEM(HRTEM) reveals a perfect joining at atomic level. The HRTEM image of the grain boundary(GB) of the MgO bicrystal shows that MgO atoms were arranged symmetrically on the GB and the stronger bright spots are arranged periodically at intervals of 0.62 nm on the GB. Since this periodic arrangement of atoms is the very property of the Σ5 GB, we can　confirm that a Σ5 symmetric tilt GB is manufactured. In addition, from the HAADF (High-Angle-Annular-Dark-Field) and EELS (Electron Energy-Loss Spectroscopy) mapping images, the very small amount impurities of calcium (Ca) and titanium (Ti) atoms are segregated at the GB at the same time, and formed the ordered array at the atomic scale which was not present in the natural three-dimensional structure. According to the theoretical calculations, the defects and the charge were strongly combined and formed a complex stable structure. This structure results in a significant change in properties of the sintered material. The strongly bound grain boundary which has such a stable structure, will increase the strength of the bulk material. It was found that the trace amounts of impurities in the ceramic grain boundary will make the ordered superstructure self-assembled, and greatly affect the physical properties of the ceramics materials.

在这项研究中，我们制造了一个双晶体，具有双晶体关系（310）[001]||（310）[001]在上下晶体之间。衍射图案的分析证实了这些取向在一个小的错配倾斜角，和高分辨率TEM（HRTEM）揭示了在原子水平上的完美连接。MgO双晶晶界的HRTEM图像表明，MgO原子在晶界上呈对称排列，较强的亮斑以0.62nm的间隔周期性排列。由于这种原子的周期性排列正是105 GB的特性，我们可以确认制造了105对称倾斜GB。另外，从HAADF（High-Angle-Annular-Dark-Field）和EELS（Electron Energy-Loss Spectroscopy）映射图像来看，钙（Ca）和钛（Ti）原子的极少量杂质同时在GB处偏聚，并形成了在自然三维结构中不存在的原子尺度上的有序阵列。理论计算表明，缺陷与电荷强烈结合，形成了复杂的稳定结构。这种结构导致烧结材料的性能发生显著变化。具有这种稳定结构的强结合晶界将提高块体材料的强度。研究发现，陶瓷晶界中的微量杂质会使有序超结构自组装，从而极大地影响陶瓷材料的物理性能。