Study of Microscopic Pattern Formation in Structural Phase Transition by Electron Microscopy

本研究的目的是研究几种结构相变中产生的微观图案的结构和物理性质，并利用带有纳米探针的电子显微镜研究其图案形成的动力学性质。主要结果分为以下三类。利用电视摄像系统和成像板系统，对Rb2ZnCl4和BaZnGeO4在C-IC相变过程中失约（DC）晶格的模式演变进行了观察，并对其性质进行了研究，分析了暗场图像和衍射图中的漫射强度分布。观察到条纹和反条纹的产生和湮灭，条纹和平面直流电的相互作用，并伴随着直流电的重排。几个相变的新发现发现电子束辐照后，zn - GeO4发生相变，至少出现了三个不同的相。在Pb3(PO4)2中，在铁弹性相变温度以上用漫射散射法获得了高分辨率图像，表明铁弹性相存在微畴。在Ba2NaNb5015的C-IC相变过程中，在IC相中形成了10nm大小的铁弹性畴，形成了IC相的四方对称和准usi2-q态。通过对直流电畴和铁弹性畴壁运动的观察，研究了IC-C相变和记忆效应。微观区域的物理测量我们试图发展一种测量纳米尺度区域物理性质的方法，以及通过电子显微镜观察得到的结构性质。研究发现，利用精细汇聚电子束的光收集系统检测切伦科夫辐射和跃迁辐射可以提供纳米尺度区域介电函数的信息。少

The purpose of this research is to study structural and physical properties of microscopic patterns arising in several structural phase transitions, and to find the dynamical properties of their pattern formations by means of an electron microscope with a nanometer-size probe. The main results are divided into the following three categories.1. Pattern formation in commensurate-incommensurate phase transitionPattern evolution of the discommensuration(DC) lattices during the C-IC phase transitions in Rb2ZnCl4 and BaZnGeO4 was observed and their properties were studied from the analyzes of the dark field images and also the diffuse intensity profiles in the diffraction patterns, using the TV camera system and the imaging plate system. The creation and annihilation of stripples and antistripples were seen and the interactions between stripple and planer DC were observed, which accompany the rearrangements of DCs.2. New founding in several phase transitionsIt is found that the electron beam … More irradiation induces phase transition in BaZn GeO4, and at least three distinct phases were observed to appear. In Pb3(PO4)2 the high resolution image using the diffuse scattering was taken above the ferroelstic phase transition temperature, which indicates the existence of microdomains of the ferroelastic phase. In the C-IC phase transition of Ba2NaNb5015 the ferroelastic domains of the order of 10nm in size are found to be created in the IC phase, which result in the tetragonal symmetry and the qusi2-q state of the IC phase. The IC-C phase transition and the memory effect were studied through the observation of DC and ferroelastic domain wall motion.3. Physical measurement of microscopic regionWe try to develop the method to measure physical properties of nanoscale region as well as the structural properties obtained from the electron microscopic observation. It is found that the Cherenkov and transition radiation detected by the light collection system using a finely converged electron beam will provide information of the dielectric function of a nanoscale region. Less