Structural Analysis on Quasicrystals and their Approximants.

准晶体及其近似物的结构分析。

• 批准号: 08404021
• 负责人: HIRAGA Kenji
• 金额: $ 22.34万
• 依托单位: Tohoku University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (A)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 1997
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08404021/
• 关键词: quasicrystal; approximant; X-ray diffraction; High resolution electron microscope; projection method; 高分解能電子顕微鏡; quasicrystal; high-resolution electron microscopy; X-ray diffraction; approximant; maximum entropy; higher-dimensional space

Since the first finding of a quasicrystal in Al-Mn system by Schetman, a number of structural studies have been carried out in order to understand the physico-chemical properties of this new materials. The conventional high-resolution electron microscope is known to be one of the most powerful methods to analyze the structures of quasicrystals and their approximants. However, detailed structural information such as transition metal distribution cannot be obtained from the results of the electron microscope only. On the other hand, X-ray diffraction allows us to determine the precise atomic coordinates for individual constituents and such information is strongly required for discussing a variety of physical properties of quasicrystals. In these contexts, the main purpose of this research project is to characterize the structures of quasicrystals and their approximants by the combination of high-resolution electron microscope and X-ray diffraction. It may be added that the projection met … More hod including high dimensional space group theory is intensively used for elucidate the obtained structural results. For the intensity measurement of X-ray diffraction, we developed a new type of weissenberg camera equipped with imaging plates and the intensity reader for them. The rotating anode type X-ray generator with a maximum load of 18kW is employed as a X-ray source, the graphite monochromator is set in the incident beam pass for selecting MoKalpha radiation. Two imaging plates are installed and the measuring time is extensively reduced in comparison with a conventional four-circle diffractometer. It should be added that the mu-axis controlling system is also introduced for the intensity measurement with no special blind region. By using this weissenberg camera, we foundan dodecahedral atom clusters with 1.2nm and 2.0nm in diameter in Al-Pd-Mn system. These atom cluster are classified as essential structural units for the corresponding icosahedral phase, by indicating tau-inflation rule in their sizes. The structural model by using these atom clusters coupled with the projection method allows us to demonstrate a feasible structural model of Al-Pd-Mn icosahedral quasicrystals. These results were appreciated by many material scientists and we are invited to talk these fruitful results at the international conference of quasicrystals in 1997. These atom clusters with dodecahedral symmetry together with a projection method are suggested to shed light upon the real understanding of icosahedral quasicrystals. Less

自从Schetman首次在Al-Mn系中发现准晶以来，为了了解这种新材料的物理化学性质，人们进行了大量的结构研究。传统的高分辨电子显微镜被认为是分析准晶及其近似物结构的最有力的方法之一。然而，仅从电子显微镜的结果不能获得诸如过渡金属分布的详细结构信息。另一方面，X射线衍射使我们能够确定各个成分的精确原子坐标，并且这些信息对于讨论准晶的各种物理性质是非常必要的。在这种背景下，本研究项目的主要目的是通过高分辨率电子显微镜和X射线衍射相结合来表征准晶及其近似物的结构。可以补充的是， ...更多信息 包括高维空间群理论的HOD被广泛用于阐明所获得的结构结果。为了测量X射线衍射强度，我们研制了一种新型的韦森堡照相机，配有成像板和强度读出器。X射线源采用最大负载为18 kW的旋转阳极型X射线发生器，入射光路中设置石墨单色器，用于选择MoK α辐射。与传统的四圆衍射仪相比，安装了两个成像板，测量时间大大减少。为了实现无特殊盲区的光强测量，还引入了μ轴控制系统。利用该相机在Al-Pd-Mn体系中发现了直径为1.2nm和2.0nm的十二面体原子团簇。这些原子团被归类为相应的二十面体相的基本结构单元，通过指示它们的尺寸的τ膨胀规则。利用这些原子团簇结合投影方法建立的结构模型为Al-Pd-Mn二十面体准晶的结构模型提供了一个可行的模型。这些成果得到了许多材料科学家的赞赏，我们受邀在1997年的国际准晶会议上谈论这些丰硕的成果。这些具有十二面体对称性的原子团簇与投影方法的结合，有助于对二十面体准晶的真实的理解。少

项目成果

X.Z.Li, K.Sugiyama, K.Hiraga, A.Sato, A.Yamamoto, H.X.Shi & K.HKuo.: "Crytsal Structure of Orthorhombic epsilon-Al_4Cr." Z.Krist.212. 628-633 (1997)

X.Z.Li、K.Sugiyama、K.Hiraga、A.Sato、A.Yamamoto、H.X.Shi

K.Hiraga et ol.: "An Atom Cluster Model of F-tqpe Icosahedral Quasicrystals,Derived from to Structure of a 1/1 Cubic Approximant Phase." Journal of Physical Society of Japan. 66. 3700-3702 (1997)

K.Hiraga 等人：“F-tqpe 二十面体准晶体的原子簇模型，源自 1/1 立方近似相的结构。”

K.Hiraga: "Advances in Imaging and Electron Physics" High-Resolution Eletion Microscapy of Quasicrystals., 37-98 (1998)

K.Hiraga：“成像和电子物理的进展”准晶体的高分辨率元素显微术。，37-98 (1998)

W. Sun & K. Hiraga: "High-resolution electron microscopy study of the early stage of formation of a Al-Pd-Mn decagonal quasicrystal from crystalline approximant." Philosophical Magazine Letters.73・6. 395-404 (1996)

W. Sun 和 K. Hiraga：“从晶体近似形成 Al-Pd-Mn 十方准晶体的早期阶段的高分辨率电子显微镜研究。”73・6（1996）。

K.Sugiyama et al.: "Crystal struicture of a Cabic Alropd_<23>M_6Si:a2/1 Rafional Approximant of an Icosahedrol Phase" Zeit guir Kristallpgraphy. 213. 90-95 (1998)

K.Sugiyama等人：“Cabic Alropd_23M_6Si的晶体结构：二十面体相的a2/1 Rafional近似”Zeit guir Kristallpgraphy。