Effect of the ultrasonic frequency on the multiple X-ray scattering from a LiNbO<Subscript>3</Subscript> crystal modulated by a surface acoustic wave

The effect of multiple scattering on the formation of the θ-2θ scan curves for a crystal modulated by a surface acoustic wave (SAW), depending on the ultrasonic frequency, has been investigated in the frame-work of the dynamical theory of X-ray diffraction. A model of a Rayleigh surface wave has been analyzed as applied to X-ray diffraction with allowance for the transverse and longitudinal elastic lattice strains. Using the example of the 127° Y′ cut of the LiNbO₃ crystal, it is established that the effects of multiple scattering can be neglected for ultrasonic frequencies above 650 MHz; this finding significantly simplifies the numerical calculations of X-ray diffraction from a crystal modulated by a short-wavelength SAW. A comparative quantitative analysis of the experimental data on synchrotron scattering from the 127° Y′ cut of a LiNbO₃ crystal modulated by a 952-MHz SAW have been performed, both taking into account and neglecting the effects of multiple scattering. It is shown that the computation time can be reduced by 2 to 3 orders of magnitude.     

碲锌镉晶体晶格畸变的测定与分析

在高分辨X射线衍射仪上,利用不对称布拉格衍射STD技术与单晶摇摆曲线技术相结合的方法,对碲锌镉单晶材料的晶格畸变进行了分析测定.此方法实现了一次装样,多角度、多次测定晶体的摇摆曲线,从而利用多组实验数据完成多元线性回归方程组的求解,避开了一般应变测定方法中难以确定无应力状态下衍射角的问题.所测定的生长态碲锌镉晶片晶格畸变量为10-3～10-2数量级,该畸变量是碲锌镉晶片存在成份偏析、位错和空位等缺陷以及晶片受到的应力综合作用的结果.     

Optical and X-ray studies of a four component cyano liquid crystal mixture: Comparison of properties with that of a similar mixture

Optical and X-ray studies have been conducted on a four component liquid crystal mixture (code name 2013) with cyano–end groups in all the four components and a lateral substitution of fluorine atom in one of them. The variations in the optical birefringence with temperature, have been investigated and the thermal dependence of polarisability anisotropy and orientational order parameter have been evaluated. X-ray studies have been conducted to determine the effective molecular characteristics such as apparent molecular length and inter molecular distance and their variations with temperature. From nature of molecular alignment as envisaged from X-ray photographs the order parameter variation with temperature has been determined and compared with macroscopic order parameter variation as determined from birefringence studies. The results have been compared with these obtained for another structurally similar four-component liquid crystal mixture (code name 2014) with isothiocyanato end group in place of cyano.     

碲铟汞晶体的生长研究

以高纯Hg、In、Te单质为原料,在摇摆合料炉中成功地合成了HgInTe多晶原料,并且利用该多晶原料,在特殊设计的坩埚中,成功地生长了HgInTe单晶体.X射线衍射分析证明,所生长的HgInTe晶体为缺陷闪锌矿结构,晶格常数a=0.6293nm,是一种高质量的完整单晶体.     

Fast ultrasonic wavelength tuning in X-ray experiment

A method of tuning (scanning) X-ray beam wavelength based on modulation of the lattice parameter of X-ray optical crystal by an ultrasonic standing wave excited in it has been proposed and experimentally implemented. The double-crystal antiparallel scheme of X-ray diffraction, in which an ultrasonic wave is excited in the second crystal, is used in the experiment. The profile of characteristic line k_α1 of an X-ray tube with a molybdenum anode is recorded using both the proposed tuning scheme and conventional mechanical rotation of crystal. The results obtained by both techniques are in good agreement.     

低位错密度4 inch GaSb(100)单晶生长及高质量衬底制备

采用液封直拉法(LEC)生长了4 inch直径(100)GaSb单晶并进行了衬底晶片的加工制备.通过优化热场,可重复生长出非掺和掺Te 整锭(100)单晶,单晶锭的重量为5~8 kg, 成晶率可达80;以上.4 inch(100)晶片大部分区域的位错腐蚀坑密度小500 cm-2,其(004)双晶衍射峰的半峰宽为29弧秒,表明晶片衬底的完整性相当好.晶体生长过程中固液界面较为平坦,因而晶片表现出良好的横向电学均匀性.经研磨和机械化学抛光,制备出具备良好平整度和表面粗糙度的开盒即用衬底晶片.通过控制本征受主缺陷浓度和掺杂浓度,制备出具有良好近红外透光率的n型GaSb单晶衬底.     

Yb:FAP晶体生长

采用中频感应提拉法生长了Yb：FAP晶体。对晶体生长中影响晶体质量的因素特别是原料的处理、CaF2的挥发等进行了研究和讨论。运用ICP-AES测定Yb^3＋离子在Yb：FAP晶体中的分凝系数。对Yb：FAP晶体进行了高分辨X射线的四圆衍射实验,结果表明晶体具有比较高的晶格完整性。     

Growth and characterization of calcium lithium tantalum gallium garnet single crystal

A new disordered garnet single crystal, calcium lithium tantalum gallium garnet (CLTGG) was grown by the Czochralski method. The lattice parameter of the crystal has been determined to be a=12.508±0.001 Å by X-ray powder diffraction (XRPD). The melting point of CLTGG was measured to be 1548 °C. The crystal possesses a wide transmission range from the ultraviolet to infrared, which is advantageous for applications as a laser host material. The refractive indices were also measured by the V-prism method.     

Lattice Parameter Local Determination for Trigonal,Hexagonal, and Tetragonal Crystal Systems Using Several Coplanar X-Ray Reflections

The method for determining the local lattice parameters using quasi-multiple X-ray diffraction (which was proposed and used only for crystals of the cubic system) has been expanded to measure the local crystal lattice parameters for the trigonal, hexagonal, and tetragonal systems. Local variations in the lattice parameters in the tetragonal paratellurite (TeO₂) and trigonal lanthanum-gallium tantalate (La₃Ga_5.5Ta_0.5O₁₄) crystals have been investigated. Reflections necessary for implementing the quasi-multiple X-ray diffraction scheme are found for these crystals. The pairs of reflections that were found were used to complete quasi-multiple X-ray diffraction schemes on a laboratory X-ray source and determine the variation in the lattice parameter a along the surface of these crystals. The relative measurement error was 4 x 10^-6 at a spatial resolution of 140 μm. The accuracy of the method and the parameters determining this characteristic were analyzed based on the results. The locality of the method and the limits of the spatial resolution of an X-ray diffraction measurement of lattice parameters are estimated.     

X-Ray Study of Strained CdTe Powders

Lattice strains have been produced in cadmium telluride by grinding for different durations. X-ray diffractograms have been obtained at different stages of grinding. The lattice constants, particle size, lattice strain and Debye-Waller factors have been determined. From the correlation between the strain and the effective Debye-Waller factor, the Debye-Waller factor for zero strain has been estimated.     

Synthesis,characterization, crystal structure and NLO properties of a new mixed crystal potassium sodium ammonium dihydrogenphosphate K0.23Na0.23(NH4)0.54H2PO4

Potassium sodium ammonium dihydrogenphosphate K_0.23Na_0.23(NH₄)_0.54H₂PO₄ (KSADP), a new mixed crystal has been grown in aqueous medium by the slow evaporation of equimolar mixture of ammonium dihydrogenphosphate (ADP), potassium dihydrogenphosphate (KDP) and sodium dihydrogenphosphate (SDP). Crystal composition as determined by single crystal X-ray diffraction analysis reveals that it belongs to the tetragonal system with noncentrosymmetric space group I-42d and it is structurally similar to ADP with cell parameter values, a=7.4794(4) Å; b=7.4794(4) Å; c=7.2974(11) Å; υ=408.23(7) Å³; z=4. The presence of sodium and potassium in ADP matrix was confirmed by inductively coupled plasma emission spectrometry and energy dispersive X-ray spectroscopy. The partial cationic substitution results in defect centers influencing the physical properties. Slight shifts in vibrational patterns could be attributed to strains in the lattice. Refinement of structure by single crystal XRD analysis reveals that potassium, sodium and ammonium coexist in the mixed crystal. The surface morphology of the as-grown specimen, which is changed as a result of cationic incorporation, was studied by scanning electron microscopy. The relative second harmonic generation (SHG) efficiency measurements revealed that the mixed crystal has a superior NLO activity than ADP.     

Magnesium-doped potassium lithium niobate crystal and its properties

High quality magnesium-doped potassium lithium niobate (designated as KLN:Mg) single crystal was grown for the first time. The tetragonal tungsten bronze structure of the Mg:KLN crystal was determined by X-ray powder diffraction, in which the lattice parameters were A=1.262nm and C=0.398nm. High temperature X-ray diffraction patterns showed that the expansion of the lattice with increasing temperature was less than that of the undoped crystal. The transmittance of the as-grown crystal was measured. It increased by 80% from the cutoff wavelength 380nm to 450nm. The transmittance for 404nm was 50%, which is larger than that of the undoped crystals. The frequency-doubling property of KLN crystal was analyzed. Preliminary frequency doubling experiments showed that the crystal could generate blue light of 404nm through noncritical phase matching (NCPM) second harmonic generation (SHG) using a 808nm diode laser at room temperature.     

New version of the gauge theory of linear defects in crystals with a polyatomic lattice

The gauge theory of dislocations and disclinations has been generalized to the case of crystals with a polyatomic lattice. An infinite anisotropic continuous medium with dislocations and disclinations is used as a real crystal model based on the gauge group SO(3N)λT(3N).     

钙钛矿型层状化合物K2Pr2Ti3O10的合成及XRD研究

在K2CO3-镧系元素氧化物(Pr2O3)-TiO2三元体系中,用固相反应法合成K2Pr2Ti3O10,利用X射线粉晶衍射仪对K2Pr2Ti3O10进行扫描测定,获得X射线衍射数据,进行指标化,得到其晶胞参数。XRD分析结果表明,K2Pr2Ti3O10为四方晶系,空间群I4/mmm。     

双掺离子在KTNNP晶体生长中的协同效应研究

本文采用高温溶液法生长了不同掺质浓度的较大尺寸掺Nd3+和Nb5+KTP(KTNNP)晶体,以X射线单晶衍射仪测定了所生长晶体的晶胞参数,以等离子发射光谱(ICP-AES)法系统测定了晶体中的掺质浓度。实验结果显示,掺Nd3+和Nb5+后,KTP晶体生长习性和形态发生了很大的变化,而且体系中Nd3+的分配系数明显增大,并随Nb5+浓度的增大而增大,从而体现了Nb5+对Nd3+的协同效应。另外,掺质后,晶体的单胞体积一般略有增大,但未呈现出规律性。     

DFT studies,Hirshfeld surface analysis and crystal structure of novel silver complex of sulfapyridine with secondary ligand pyridine

Silver complex of sulfapyridine has been synthesized and characterized by IR, NMR and PL. The crystal structure has been determined by X-ray diffraction technique. Silver complex of sulfapyridine with secondary ligand pyridine crystallizes in monoclinic space group P2₁/n with lattice parameter: a = 17.8075(4)Å, b = 10.7885(3)Å, c = 17.8075(4)Å, β = 94.12(1)Å and Z = 4. To study the nature of intermolecular interactions and their quantitative contributions towards the crystal packing, Hirshfeld surfaces and accordingly the fingerprint plot analysis have been performed. Molecular properties such as NBO analysis, Homo-Lumo energy calculation have been carried out by DFT method. Furthermore, the antimicrobial activity of silver complex of sulfapyridine and free ligand is studied by the dilution method.     

AgGaS2单晶生长与完整性研究

采用二温区气相输运温度振荡方法合成了高纯单相致密的AgGaS2多晶,计算出晶格常数a-5.7535nm,c=10.3008nm,以及S原子位置x=0.279,与PDF值相差很小,表明其是高质量的多晶原料,以此为原料用改进Bridgman法生长出直径15mm长度30mm的单晶体,经外形观测,解理试验和X射线衍射分析表明其是结晶完整的单晶体。     

Influence of the chemical nature of implanted ions on the structure of a silicon layer damaged by implantation

The influence of the implantation of silicon single crystals by fluorine, nitrogen, oxygen, and neon ions on the distribution of strain and the static Debye-Waller factor in the crystal lattice over the implanted-layer depth has been investigated by high-resolution X-ray diffraction. The density depth distribution in the surface layer of native oxide has been measured by X-ray reflectometry. Room-temperature implantation conditions have ensured the equality of the suggested ranges of ions of different masses and the energies transferred by them to the target. It is convincingly shown that the change in the structural parameters of the radiation-damaged silicon layer and the native oxide layer depend on the chemical activity of the implanted ions.     

Study of X-ray diffraction from a surface acoustic wave in the grazing geometry with allowance for the curvature of the unperturbed crystal surface

Fresnel X-ray diffraction from a concave crystal surface in the presence of a surface acoustic wave (SAW) has been considered for grazing angles of incidence in noncoplanar symmetric Laue geometry. It is shown that the main peak and diffraction satellites are focused at different distances from a crystal. The effect of deviation from the Bragg angle, the spectral line width, and the SAW amplitude on the X-ray diffraction pattern has been analyzed. It is established that the contrast of an X-ray diffraction pattern of an SAW in Bragg-Laue grazing geometry is related to the character of irregularities of the crystal surface, and the pattern details depend on the measurement mode. The sensitivity of the method is about a nanometer. The focal image of the SAW serves as a scale landmark for determining the crystal surface characteristics.     

Temperature Dependence of Molecular Motions in Naphthalene and Anthracene Crystals

As some of their lattice properties are estimated in the harmonic approximation, the amplitudes of the molecular motions for naphthalene and anthracene crystals have been calculated. Comparison between the results obtained either by a full dynamical calculation (i.e. tensors L and T) or by the simplified Cruickshank's theory with the values deduced from X-ray experiments is presented. In addition, the temperature dependence of molecular motions in naphthalene crystal is given in a wide range (from 77 K up to sublimation temperature).