Research on behavior of lattice imperfection and phase transformation at low temperature by atom resolution analytical electron microscope

本研究采用加速电压为200kv、4OOkV、8OOkV的原子分辨电子显微镜，具有液氦和液氮温度的低温试样阶段，并配有电子能量损失谱仪，在原子尺度上研究各种材料在包括极低温在内的不同温度下的结构变化。采用GATAN电视摄像机和索尼电视监视器以及照相法记录图像。进行了以下观察。Nb_3Sn超导体在液态氦和室温下的原子结构观察。对具有较高临界温度Tc的陶瓷超导材料Y.Ba_2Cu_3O_x、ErBa_2Cu_3O_x、Bi_2Sr_2CaCu_2O_x（85K）和Bi_2Ca_2Cu_3O_x（110K）进行了类似的观察。将含有重原子Th的长链分子负载在石墨薄膜上，用超导物镜在200kv电子显微镜下观察，进一步降低试样温度至液- he温度。结果表明，即使在液- he温度下，在200kv电子的照射下，暗场中Th原子的亮点图像仍在移动。3.1在室温和液- he温度下，用200kv电子显微镜观察到t - tas_2和In_xNb_3 Te_4 （X=1.3 ~ 1.5）由于电荷密度波引起的周期性晶格畸变，并在电子衍射图和电子显微图上观察到它们的相变。利用200kv电子显微镜和电子能量分析仪，在室温和低温条件下研究了低温下严重损伤的沸石晶体的辐射损伤效应。结果表明，即使试样的晶体变为无定形，晶体中的水仍然存在于试样中，并在几分钟后随ca原子一起消失。这一现象可以用沸石结构通道中水和钙离子同时逸出来解释。为了研究高能电子辐照下原子的位移和辐射效应，利用美国加州大学的lMeV原子分辨电子显微镜和冈山大学的4OOkV原子分辨电子显微镜分别观察了Si和Th原子在晶体和分子中的行为。采用试样加热装置研究了Ni - Ti形状记忆合金在相变温度以上和以下的原子排列和缺陷结构。观察了两相边界的原子结构和重复孪晶在温度每升高一个循环时的结构变化。少

The present research aimed to study the structure change of various materials in atomic scale at various temperature including very low temperature by using atom resolution electron microscopes with the accelerating voltage of 2OOkV, 4OOkV, 8OOkV, which have low temperature specimen stages of liquid helium and liquid nitrogen temperature and an electron energy loss spectrometer. The images were recorded by using GATAN TV camera and Sony TV monitor as well as photographic method.The following observations have been carried out.1. Observation of the atomic structure of Nb_3Sn superconductor at liq.-He and room temperature. Similar observations are carried out for the ceramic super conducting materials with high critical temperature Tc i.e. Y.Ba_2Cu_3O_x, ErBa_2Cu_3O_x, Bi_2Sr_2CaCu_2O_x(85K), and Bi_2Ca_2Cu_3O_x(110K).2. Long chain molecules containing heavy atom Th were supported on graphite thin films and observed in the 2OOkV electron microscope with superconducting objective lens, wh … More ich lower the specimen temperature to be at liq.-He temperature. It was observed that even at the liq.-He temperature, bright spots images of Th atoms in the dark field still moved under the irradiation of 2OOkV electrons.3.1T-TaS_2 and In_xNb_3 Te_4 (X=1.3-1.5) which produce the periodic lattice distortion due to Charge Density Wave were observed at room and liq.-He temperature by 2OOkV electron microscope and their phase transformation were observed in electron diffraction patterns and electron micrographs.4. Radiation damage effect of Zeolite crystal, which shows heavy damage at low temperature was studied at room and low temperatures by an 2OOkV electron microscope with electron energy analyzer. It was noted that even the specimen crystal changes to amorphous, water in crystal are still in the specimen and disappear together with Ca-atoms some minutes later. This phenomena was interpreted by the escape of water and Ca ions in channels of zeolite structure at the same time.5. In order to investigate displacement of atoms and radiation effect under high energy electron irradiation, lMeV Atom Resolution Electron Microscope in California University and 4OOkV one in Okayama were used to see the behavior of Si and Th atoms in crystals and molecules respectively.6. Atomic arrangements and defects structure of Ni Ti shape memory alloy at above and below of the phase transformation temperature were studied by a specimen heating device. The atomic structure of the boundary of two phases and the structure change of repeating twins in every cycle of elevation of the temperature are observed. Less