STRUCTURE ANALYSIS OF DECAGONAL QUASICRYSTALS USING THE HIGH-ANGLE ANNULER DARK-FIELD SCANNING TRANSMISSION ELECTRON MICROSCOPE METHOD.

〇Al_<72>Ni_<20>Co_8, Al_<73>Ni_<22>Fe_5十方准晶我们利用HAADF方法首次揭示了原认为具有十倍旋转对称的Al_<72>Ni_<20>Co_8十方准晶的原子团不是十倍对称而是镜像对称，并且发现Al_<72>Ni_<20>Co_8是由基本原子团组成的准晶，存在于近似Al_<13>Fe_4的单斜准晶中。在此近似结构的基础上，建立了Al_<72>Ni_<20>Co_8的新结构模型。HAADF法还发现Al_<73>Ni_<22>Fe_5十方准晶具有与Al_<72>Ni_<20>Co_8相似的结构。Al-Ni-Fe非中心对称的十方准晶体我们以前通过传统的高分辨率电子显微镜发现，Al_<70>Ni_<15>Fe_<15>准晶体是由具有五重旋转对称的原子团簇形成的。我们首次将HAADF方法应用到准晶体中，验证了原子团簇确实是五重对称的。在HAADF图像和近似结构的基础上，建立了结构模型。利用HAADF方法，成功地实现了以往未实现的反演域边界反相移的直接观测。〇Al-Fe和Al-Co晶体近似物通过HAADF对一个结构已解的Al_<13>Fe_4晶体近似物的观测，证实了HAADF图像选择性地呈现过渡金属原子位置。我们发现，O^2膨胀的Al_<13>Co_4近似物的HAADF图像显示出与直径为2nm的十方准晶体原子团簇相似的图像。基于HAADF图像和Al_<13>Fe_4的结构，构建了O^2膨胀Al_<13>Co_4近似结构模型。此外，通过与十方准晶及其近似结构的比较，提出了由O^2膨胀的Al_<13>Co_4形成十方准晶的模型。少

○Al_<72>Ni_<20>Co_8, Al_<73>Ni_<22>Fe_5 decagonal quasicrystalsWe, using the HAADF method, revealed that the atom cluster of an Al_<72>Ni_<20>Co_8 decagonal quasicrystal, which had been believed to be of tenfold rotation symmetry, is not of tenfold but of mirror symmetry for the first time, Furthermore, we found that Al_<72>Ni_<20>Co_8 is composed of basic atom clusters, which exist in a basic quasicrystalline approximant of monoclinic Al_<13>Fe_4. On the basis of the approximant structure, a new structural model of Al_<72>Ni_<20>Co_8 was constructed. It was also found using the HAADF method that an Al_<73>Ni_<22>Fe_5 decagonal quasicrystal has a similar structure to that of Al_<72>Ni_<20>Co_8.○Al-Ni-Fe non-centrosymmetric decagonal quasicrystalWe previously found, by conventional high-resolution electron microscopy, that an Al_<70>Ni_<15>Fe_<15> quasicrystal is formed by an atom cluster with fivefold rotation symmetry. We applied the HAADF method to the quasicrystal for the first time … More , and verified that the atom cluster is truly of fivefold symmetry. Furthermore, a structural model was constructed on the basis of the HAADF image and an approximant structure. The direct observation of an antiphase shift at an inversion domain boundary, which had not been carried out, was successfully performed by the HAADF method.○Al-Fe and Al-Co crystalline approximantsFrom the HAADF observations of an Al_<13>Fe_4 crystalline approximant, whose structure was already solved, it was confirmed that the HAADF images exhibit transition-metal-atom positions selectively. We found that HAADF images of a O^2-inflated Al_<13>Co_4 approximant show a similar image of the 2nm-diameter atom-clusters of decagonal quasicrystals. On the basis of the HAADF images and the structure of Al_<13>Fe_4, a structural model of O^2-inflated Al_<13>Co_4 approximant was constructed. Furthermore, by the comparison between the decagonal quasicrystal and its approximant structures, a formation model of decagonal quasicrystals from the O^2-inflated Al_<13>Co_4 was proposed. Less