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中动力学现象的必要条件。设计了一种新的分析系统，用于观测地球物质在相变、分解、熔化、再结晶过程中，随周围物理条件、压力、温度和应力的变化而发生的晶体结构变化。（1）用于时间分辨衍射研究的角色散测量一种用于压力下时间分辨研究的新系统由四圆衍射仪和计算机辅助测量和控制系统组成，该系统带有一个工作角区为120 °的位置灵敏探测器。高光子计数效率是高压X射线衍射研究的一大优势。(2)高压装置在四环金刚石压砧上安装了油压控制器， ...更多信息 le衍射仪设置在旋转阳极X射线发生器上。采用压力传感器对压力进行精确控制，并根据压力的可压缩性，采用红宝石荧光法和氯化钠内标物平衡状态法进行测量。本文研究了压力下不同温度下GeO_2从六方晶系（石英型P321，z=3）向四方晶系（金红石型P4/mmm，z=2）多晶型转变的动力学。(1)在7 GPa和62 ℃时，六方晶系GeO_2转变为非晶相，而在85 ℃和0.6GPa时，GeO_2很容易转变为金红石相。在室温下，非晶相连续保持到25 GPa。(2)半高宽（FWHM）的衍射峰变得线性加宽，由于减少晶粒尺寸，表明增强的更精细的域。积分衍射强度随压力的增加而降低。(3)用EXAFS和拉曼谱分析了室温下Ge离子在淬灭非晶相中的局域结构。结果表明，非晶相部分由六配位的Ge离子组成，其结构与熔融玻璃的结构有很大的不同。(4)非晶相被证实是介稳的. Ca（OH）_2和Mg（OH）_2的脱水过程用钨旋转阳极X射线和同步辐射能量色散衍射对脱水过程进行了时间分辨观察。在10 keV-40 keV的能量范围内，用本征Ge SSD进行了900 μ C以下的光谱原位测量。通过曲线拟合获得的积分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