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

点击翻译按钮获取中文摘要

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