Kinetic Study on the Crystal Structure Transformation by Time-resolved Measurement of X-ray Diffraction

研究矿物的晶体结构和结构是理解地球科学动力学现象的必要条件。设计了一种新的分析系统，用于观测土材料在相变、分解、熔化、再结晶过程中晶体结构随周围物理条件、压力、温度和应力的变化而发生的变化。(1)时间分辨衍射研究的角色散测量。压力下时间分辨衍射研究的新系统是由四圆衍射仪和位置敏感探测器组成的，工作角范围为120^ <s:1>，由计算机辅助测控系统组成。高光子计数效率是高压x射线衍射研究的一大优势。(2)高压装置在旋转阳极x射线发生器上的四圈衍射仪上安装了一个带油压控制器的金刚石砧。压力由传感器精确控制，采用红宝石荧光法和基于可压缩性的NaCl内标样品方程状态进行测量。结果1。压力下不同温度下GeO_2由六方（石英型P321， z=3）向四方（金红石型P4/mmm， z=2）晶型转变动力学(1)六方GeO_2在7GPa和62ºC时转变为非晶相，而在85ºC和0.6ºC时容易转变为金红石结构。在室温下，非晶态相连续保持到25GPa。(2)由于晶粒尺寸的减小，衍射峰的全宽半最大值（FWHM）呈线性展宽，表明微晶畴的增强。积分衍射强度随压力的增大而减小。(3)室温条件下，用EXAFS和拉曼光谱分析了淬火非晶相中Ge离子周围的局部结构。结果表明，非晶相部分由6重配位锗离子组成，其结构与熔融玻璃有很大的不同。(4)证实了非晶相是热力学亚稳态的。采用钨旋转阳极x射线和同步辐射能量色散衍射对Ca (OH) _2和Mg (OH) _2A的脱水过程进行了时间分辨观察。在10kv -40kev能量范围内，用本质锗固态硬盘对900^ C的光谱进行了原位测量。通过剖面拟合获得的综合强度提供了氧化物产物与水合物的质量比。少

Research of the crystal structure and texture of the minerals are necessary for understanding the dynamical phenomena in earth sciences. A new analytical system is designed for the observation of the crystal structure change in the process of the phase transformations, decomposition, melting, recrystallizaton in response to the variation of the physical, conditions, pressure and temperature and stress surround the earth materials. For these research we have developed the following new systems :(1) Angular dispersive measurement for time-resolved diffraction study A new system for time-resolved studies under pressure was composed of four-circle diffractometer with a position sensitive detector having an working angular region of 120^ﾟ and of computer aided measurement and control system. A high photon count efficiency is a large advantage for high pressure X-ray diffraction studies.(2) High pressure apparatus A diamond anvil with an oil-pressure controller was installed on the four-circ … More le diffractometer set on the rotated anode X-ray generator. Pressure was finely controlled by a sensor and measured by the ruby fluorescence method and equation state of internal standard sample of NaCl based on the compressibility.Result 1. Kinetics of polymorphic transition of GeO_2 from hexagonal (quartz-type P321, z=3) to tetragonal (rutile type P4/mmm, z=2) various temperatures under pressure. (1) Hexagonal GeO_2 was transformed to the amorphous phase at 7GPa and 62ﾟC but easily transformed to rutile structure at 85^ﾟC and 0.6GPa. The amorphous phase was successively retained up to 25GPa at room temperature. (2) Full width half maximums (FWHM) of the diffraction peaks became linearly broadened due to reducing crystallite size, indicating the enhancement of the finer-domain. Integrated diffraction intensities were decreased with pressure. (3) A local structure around Ge ion in the quenched amorphous phase was analyzed by EXAFS and Raman spectra at room condition. It was elucidated that amorphous phase was partly composed of 6-fold coordinated Ge ions and that the structure was quite different from that of melted-glass. (4) The amorphous phase was confirmed to be thermodynamically metastable.2. Dehydration Process of Ca (OH) _2 and Mg (OH) _2A time-resolved observation of the dehydration process was undertaken by energy dispersive diffraction using tungsten rotated anode X-ray and synchrotron radiation. The in situ measurements of the spectra up to 900^ﾟC were carried out by intrinsic Ge SSD in the energy range 10keV-40kev. Integrated intensities obtained by the profile fitting provide the mass ratio of oxide products to hydrates. Less