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31 citations found for Shimomura,

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An imaging plate was applied to the large-volume press MAX80 for quantitative in-situ X-ray diffraction. A combination of the two-dimensional detector with the uniform pressure and temperature environments of MAX80 and the wide energy range of synchrotron radiation resulted in high-quality diffraction data. A modified cell assembly with a disc-type heater was used to minimize extrinsic diffraction peaks from the surrounding materials. To demonstrate the high-quality data obtained from the imaging-plate system, the crystal structure of the high-pressure and high-temperature polymorph of the highly absorbing element bismuth (Bi IV) was determined.

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A position-sensitive detector (PSD) for Mo K[alpha] radiation has been successfully applied to detect very weak X-rays diffracted from an extremely small volume of specimen compressed in a diamond-anvil high-pressure cell. The PSD can cover a scattering-angle range of 22.6° with an angular resolution of 0.038: in a single measurement. Remarkably rapid recording of diffraction patterns with a high S/N ratio is performed with this method at pressures higher than 10 GPa. Some diffraction patterns of iodine near the insulator-metal transition around 16-18 GPa are shown to demonstrate the usefulness and power of this PSD system.

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A diffractometer for powder samples of very small amount has been developed to collect high-quality diffraction patterns under extreme conditions. Performance, examples of application and practicability are presented.

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A standard two-circle diffractometer with a Ge(Li) solid-state detector controlled by a microcomputer has been constructed. Its characteristics [good signal-to-noise (s/n) ratio, simple optical collimation, without any monochromator or filter] are described. A single angle-dispersive scan with this system can give diffraction patterns with K[alpha], K[beta] and fluorescence radiation simultaneously: diffractometry with the present system can be carried out in a shorter time than with a conventional diffractometer and a proportional or scintillation counter and will give a better s/n ratio. Powder or amorphous samples of small volume can be more easily studied with the present system; typical examples reported include crystalline InSb and amorphous GaSb, both in a diamond-anvil high-pressure cell.


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A new method for density measurements by means of X-ray absorption under high pressure and high temperature using synchrotron radiation has been developed. The method has been modified for a large-volume Paris-Edinburgh press and combined with intense high-energy X-rays at the ESRF. In order to overcome effects of deformation of sample shape under pressure, a ruby cylinder was used as a sample container. The density was determined from the intensity profile of transmitted X-rays. The densities of crystalline and liquid Bi were successfully measured up to 750 K at 1 GPa.

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Two germanium polymorphs of the diamond type and the ST-12 structure were used to investigate the accuracy of extended X-ray absorption fine structure (EXAFS) analysis with a phase-difference method. This method gives similar accuracies to both conventional curve-fitting and Fourier-transform methods in determining the difference of the first- neighbor distances for these two polymorphs. The number of first-shell atoms of the ST-12 structure was determined to be 4.0 ± 0.2 with the diamond-type phase as a standard. In addition, the first-neighbor coordination of amorphous germanium was analyzed with this method. These results suggest that the phase-difference method is useful for structure analysis of materials and that it is especially useful for structure analyses under high pressure.

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Results are reported of an investigation using synchrotron radiation into the effects of temperatures up to 1173 K on pressure-induced phase transitions in phosphorus. A cubic type multi-anvil press was employed and a diffraction pattern in an energy-dispersive mode was taken for a period of time, typically 200 s, without suffering from a deterioration of the sample material. The pressure of the first transition, orthorhombic-rhombohedral (As-type), decreases with increasing temperature at a rate of 2.3 MPa K-1 and the As-type structure is stable at a pressure as low as 2.6 GPa at a temperature of 1073 K. The volume discontinuity at the transition, [Delta]V, is 10% at room temperature and remains almost unchanged with increasing temperature. The axial ratio c/a, when the rhombohedral structure is referred to the hexagonal system, changes mostly with pressure but only slightly with temperature, approaching [square root]6 = 2.45 on going to the second transition, rhombohedral-simple cubic. The pressure of this transition, in contrast to the first one, is independent of temperature but [Delta]V at this transition, 3.7%, continuously decreases with increasing temperature.

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Acta Cryst. (1996). A52, C531
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Acta Cryst. (1996). A52, C533
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The experiment under high pressure using a diamond anvil cell (DAC) requires the utilization of synchrotron radiation. High-pressure experiments were performed using a DAC on CdS microcrystals, both in the far-IR and in the X-ray regions, in order to study the lattice dynamics and lattice stability concerned with the phase transitions. From these experiments, experimental evidence is presented indicating that a CdS microcrystal of smaller diameter shows a higher transition pressure for lattice transformation under pressure. The origin of such an increase in the transition pressure in the microcrystals is discussed in relation to the surface tension.


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Two-dimensional small-angle X-ray scattering measurements were performed on highly oriented pyrolytic graphite. The observed radial streak patterns are discussed in the context of double Bragg scattering.


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High-pressure apparatus for Compton scattering experiments has been developed to study the momentum distribution of conduction electrons in metals and alloys at high pressure. This apparatus was applied to observe the Compton profile of metallic Li under pressure. It was found that the Compton profile at high pressure could be obtained within several hours by using this apparatus and synchrotron radiation. The result on the pressure dependence of the Fermi momentum of Li obtained here is in good agreement with that predicted from the free-electron model.

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Acta Cryst. (1996). A52, C542
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A method for nondestructively visualizing multisection nanostructures of integrated circuits by X-ray ptychography with a multislice approach is proposed.

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Acta Cryst. (1993). A49, c301
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