Spatial modulation of diffracted X-ray beam by bulk acoustic waves

Laue-geometry X-ray diffraction has been studied experimentally in quartz crystals excited by bulk acoustic waves. These waves deform reflecting atomic planes, which leads to spatial modulation of diffracted beams. We show that in the beam section perpendicular to the diffraction vector the intensity stripes appear whose number depends on the order of harmonic of the excited acoustic field. The intensity of appearing fringes depends on the amplitude of alternative voltage applied to the crystal.     

基于XRD的晶体温度计的设计及其应用

在XRD衍射仪上搭建控温测温装置,扫描不同温度下的晶体衍射图谱,得到晶面间距随温度的变化关系,设计了基于XRD的晶体温度计.使用该温度计获得了VO2的相变温度.     

劳厄对晶体衍射的发现

介绍了劳厄提出晶体衍射思想的科学背景及当时的实验过程,并探讨在劳厄发现晶体衍射的过程中其科学思想的形成及X射线晶体衍射的发现带给我们的启示及影响．     

晶体X射线劳厄衍射分束特性研究

本文基于X射线衍射动力学分析了劳厄晶体的分束特性,模拟了晶体吸收和入射光角发散对于透射光和衍射光摇摆曲线的影响,定量给出晶体衍射面内角调节范围和晶体加工厚度对于劳厄衍射分束比的调制.在实验中,采用分析晶体和分束晶体的消色散配置限制入射光角发散的影响,实现300μm厚Si(220)晶体面内角调节劳厄衍射分束的精确测量,并得到300μm, 400μm和500μm厚度Si晶体分束比的调节范围,实现了透射光和衍射光强度的定量调制.     

诊断LiF单晶弹性变形的瞬态X射线衍射

利用瞬态X射线衍射技术对LiF单晶沿晶向［100］方向冲击加载的晶格变形进行了诊断研究。实验在神光Ⅱ装置的球形靶上进行,北四路激光驱动Cu靶获得的类He线作为X射线背光源,第九路为加载光源,对大小为7 mm7 mm、厚300 m的受激光加载的LiF单晶衍射,实验获得了LiF单晶晶面(200)压缩和未压缩状态的衍射信号。实验结果表明：LiF单晶在激光沿［100］方向冲击加载下,晶格发生了弹性变形,(200)晶面间距变小,衍射线上移,晶格压缩量为11%;该瞬态X射线衍射技术可用于冲击加载下的微观动态响应特性测量。     

晶体X射线衍射实验的数据分析模式

针对粉末X射线衍射谱分析软件CSM的特点,利用CSM软件附带的用户程序库功能,实现了固溶体的物相分析和固溶度的定量计算,扩展了CSM软件的使用范围,提高了物相分析的准确程度.     

Lateral field excitation properties of langasite single crystal

In this work, bulk acoustic wave propagation properties of langasite single crystal excited by lateral electric field have been investigated. Three important crystal cuts have been identified for different operational modes of lateral field excitation (LFE) on langasite substrate, namely the (yxl)65o (pure-LFE mode), (yxl)45o (quasi-LFE mode), and (yxl)0o (pseudo-LFE mode). Devices on langasite substrate with the above cuts were fabricated and tested, and the experimental results agree well with the theoretical analysis. It is found that a pure thickness shear mode exists in the (yxl)65o langasite LFE device with the bare side facing liquid, and no spurious mode is found due to its moderately large piezoelectric coupling factor. In addition, (yxl)0o langasite LFE device is also found suitable for liquid phase sensing applications.     

A system for doing low temperature-high pressure single crystal X-ray diffraction with a synchrotron source

Abstract

A new diamond anvil cell and a helium flow cryostat have been developed for X-ray diffraction on single crystals at low temperatures and high pressures using white radiation of a synchrotron beam. This novel instrument especially enables continuous change of temperature and pressure of the sample without any adjustment of alignment. Automatic search for diffraction peaks can be performed since less than 30 pm eccentricity can be maintained during the rotation of the cell in the cryostat and the rotation of the cryostat on the goniometer head. The minimum temperature reached is 46 K. Measurements of solid 4He at 11.8 GPa are presented which confirm the stability of the hcp phase on this isobar.     

Prediction of the frequency spectrum of AT-cut contoured quartz resonators by means of X-ray diffraction topography

This paper presents some important relationships relating to frequencies in contoured AT-cut quartz resonators. It is shown that frequency interval relations are not affected by the piezoelement geometry but are functionally related solely to the indices of the Hermite functions. According to the analysis of trapped-energy resonators, an X-ray technique for predicting the frequency spectrum can be derived. It is based on the use of X-ray patterns of two wave motions and enables one to determine the whole frequency spectrum in the vicinity of any odd harmonic overtone of vibration. Two contoured resonator analyses show that the X-ray topography predictions are in good agreement with experimental data.     

Neutron forward diffraction by single crystal prisms

We have derived analytic expressions for the deflection as well as transmitted fraction of monochromatic neutrons forward diffracted by a single crystal prism. In the vicinity of a Bragg reflection, the neutron deflection deviates sharply from that for an amorphous prism, exhibiting three orders of magnitude greater sensitivity to the incidence angle. We have measured the variation of neutron deflection and transmission across a Bragg reflection, for several single crystal prisms. The results agree well with theory.      

In-situ high pressure X-ray diffraction studies of orthoferrite SmFeO_3

The high-pressure behaviors of SmFeO3 are investigated by angle-dispersive synchrotron X-ray powder diffraction under a pressure of up to 40.3 GPa at room temperature. The crystal structure of SmFeO3 remains stable at up to the highest pressure. The different pressure coefficients of the normalized axial compressibility are obtained to be βa = 0.60 × 10-3 GPa-1,βb = 0.79 × 10-3 GPa-1, βc = 1.28 × 10-3 GPa- 1, and the bulk modulus （B0） is determined to be 293（3） GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. Furthermore, the larger compressibility of the FeO6 octahedra suggests the evolution of the orthorhombic structure towards higher symmetry configuration at high pressures.     

Compression mechanism of GaF3 and FeF3: a high-pressure X-ray diffraction study

The VF₃-type compounds MF₃ with M = Fe and Ga have been studied by high-pressure energy-dispersive X-ray diffraction. The compression mechanism was found to be highly anisotropic for both compounds, with the c-axis showing little pressure dependence. The volume reduction is mainly achieved through coupled rotations of the MF₆ octahedra around the c-axis, which reduces the length of the a-axis. The compression mechanism of both compounds is reasonably well described in terms of deformation of an 8/3/c2 sphere-packing model up to the pressures where the fluorine atoms become hexagonally close-packed. It is proposed that both compounds enter a phase with the fluorine atom arranged in a “super-dense” sphere packing at higher pressures. The zero pressure bulk modulus of FeF₃ and GaF₃ was determined as 12(2) and 37(3) GPa, respectively, and a scaling relation between the zero pressure bulk modulus and unit cell volumes was found for TiF₃, CrF₃, FeF₃ and GaF₃.     

X-ray diffraction from single Al6CuLi3 grains showing five-fold symmetry

We present here the detailed results of X-ray diffraction from single quasicrystals of Al₆CuLi₃. X-ray precession photographs taken down the two-, three- and five-fold axes along with rotation and zero-level Weissenberg photographs are shown. Preliminary analysis of the diffraction data rules out the twin hypothesis.     

X射线双晶衍射技术的发展及应用

简要介绍了X射线双晶衍射技术的原理;描述了双晶衍射技术的发展与演化,中简要讲述了多晶衍射技术的应用范围及应用鑫晶衍射仪所能做的工作。     

稀土金属间化合物的晶体结构及其标准X射线衍射数据

文章结合作者的科研工作,介绍了新的稀土金属间化合物及其晶体结构与标准X射线衍射数据的研究.     

Thiourea-doped ammonium dihydrogen phosphate: A single crystal neutron diffraction investigation

Thiourea-doped ammonium dihydrogen phosphate (TADP) exhibits nonlinear optical property and the second harmonic generation efficiency of these crystals is three times that of pure ammonium dihydrogen phosphate (ADP) crystal. In this context, the study of structural distortion in the thiourea-doped ADP crystal is significant, hence single neutron diffraction investigations were undertaken. The final R-factors are: R[F ² > 2σ(F ²)] = 0.11, Goodness of fit(S) = 1.15. Though the dopant could not be located from the difference Fourier map, the cell parameters (a = b = 7.531(3) A, c = 7.544(5) Å) were found to be significantly greater than that of pure ADP at RT (a = b = 7.502(1) Å, c = 7.546(1) Å). This indicates that the dopant concentration in the crystals is small but enough to bring changes in the overall average structure.     

合肥X射线衍射光束线单色仪中晶体反射曲线的测量

合肥X射线衍射光束线装备了一台以两晶体无色散 ( +n ,-n)排列 ,能量可连续扫描 ,空间位置固定输出为特点的双晶单色仪。选用单晶硅作为分光元件 ,它所对应的不同能量产生的全反射的本征宽度决定了双晶单色仪的分辨率。因此 ,晶体在投入使用之前 ,测量它的本征宽度 ,为单色仪的调试提供依据是非常必要的。介绍了用于合肥X射线衍射光束线单色仪中两块晶体的测量 ,包括测试方法、装置、测量结果和分析。     

Laboratory set-up for X-ray diffraction at high pressures

We describe here a simple set-up for X-ray diffraction under high pressure using a diamond anvil cell employing a sealed tube. The set-up works in angular dispersive geometry and is built using rather common components that are available in a research laboratory. We show that using this set-up one can routinely acquire good-quality data for the determination of structural properties under pressure and the equations of state. Technical details are presented along with examples of experimental results for sodium chloride and LiV₂O₄.     

Synchrotron X-ray diffraction study of phenacite at high pressure

We report the results of a natural phenacite from 0 to 30.9 GPa using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at the National Synchrotron Light Source, Brookhaven National Laboratory. Over this pressure range, no phase change or disproportionation has been observed. The isothermal equation of state was determined. The values of V₀, K₀, and K₀′ refined with a third-order Birch-Murnaghan equation of state are V₀=1116.1±1.2 ų, K₀=223±9 GPa, and K₀′=5.5±0.8. Furthermore, we confirm that the linear compressibilities (β) along a and c directions of phenacite are elastically isotropic (β_a=1.50×10^-3 and β_c=1.34×10^-3 GPa^-1). Consequently, it can be concluded that the compressibility of phenacite under high pressures has been accurately constrained.     

1310nm波段石英晶体旋光性的温度效应测试研究

为了测试温度对1310nm波段石英晶体旋光性的影响,采用高低温试验箱作为温控器,设计了双光路检测系统对石英晶体在1310nm波段旋光性的温度效应进行测试研究。实验结果表明,在-10～20℃温度范围内,对于确定波长的光,随温度的升高,石英晶体的旋光率增大;在25～50℃温度范围内,随温度的升高旋光率减小;对于同一温度,波长越长旋光率越小。根据测试结果求解Sellmeier方程得出了Sellmeier方程的常数与温度的关系式,从而可以得出任意温度下不同波长对应的石英晶体的旋光率。