Development of Diffraction Techniquesfor Studying Phase Transformation (Synchrotron Radiation and High-Resolution Electron Microscopy)

主要研究结果如下：1）在普通电子显微镜中引入Ω型磁铁，建立了能量过滤电子衍射方法。利用这种方法，可以消除电子衍射中由于非弹性散射而产生的强背景，并可以定量分析由于相变而产生的复杂漫散射。例如，利用能量过滤电子衍射和原位暗场电子显微镜研究了先驱体对Ti 50 Ni 48 Fe 2马氏体相变的影响，首次阐明了含有横向原子位移的微畴的存在和生长过程。同时，利用能量过滤电子衍射方法定量测定了Cu 3 Pd的短程有序参数。2）成核和长大过程动力学是研究非平衡态一级相变机制的有效途径。在旋转装置上安装了精确的温度控制器和高灵敏度的探测器，获得了Au-47.5at% Cd-0.75at.Cu单晶的原位X射线衍射数据。低温相的晶核是从表面开始逐渐向内部生长的。3）将高分辨电子显微术中备受关注的高角环形探测器暗场扫描透射电子显微术应用于十次对称准晶的结构研究。发现了有序准晶，它可以从NaCl和CsCl型超立方晶格的投影得到解释。

The results in the present work are summarized as follows.1) By introducing the omega-type magnet into a conventional electron microscope, the energy-filtering electron diffraction method was established. With this method, the strong background in the electron diffraction due to the inelastic scattering could be removed and complicated diffuse scattering resulting from the phase transformation could now be analyzed quantitatively. For example, the precursor effects on the martensitic transformation in Ti50Ni48Fe2 were investigated by the energy-filtering electron diffraction and in situ dark field electron microscopy, and the existence and the growth process of microdomains containing a transverse atomic displacement were clarified for the first time. Also, the short-range order parameter in Cu3Pd was determined quantitatively by the energy-filtered electron diffraction method.2) The kinetics on the nucleation and growth process is an effective approach to investigate the mechanism of first-order phase transformations for non-equilibrium state. In-situ X-ray diffraction data with an accurate temperature controller and highly sensitive detector attached to rota-unit has been obtained from Au-47.5 at%Cd-0.75at.Cu single crystal. It is understood that the nucleus of the low-temperature phase starts from the surface and grows into the inner part gradually.3) High-angle annular detector dark-field scanning transmission electron microscopy, which is much attention as a new technique for high-resolution electron microscopy, is applied for studying the structure of decagonal quasicrystals. Ordered quasicrystals, which can be interpreted from the projection of NaCl-and CsCl-type hypercubic lattices, have been found.