Melt-Growth of Single Crystals of Cadmium Iodide and Study of Their Polytypsim by X-ray Diffraction

Single crystals of cadmium iodide have been grown from melt using Bridgman-Stockbarger system and their polytypism studied by X-ray diffraction. The initially grown crystals were found to stick to the walls of the ampoule and had black specks of impurity suspended in them. A systematic study has been carried out to determine the effect of degree of vacuum, material of the ampoule and quality of raw material on crystal growth. It has been concluded and later verified using zone-refined material that the observed sticking essentially stems from the presence of impurities in the raw material. From X-ray diffraction it is found that all crystals belong to the most common polytype 4H alone.     

Microstructure of Milled Mesophase Pitch-Based Carbon Fibers as an Anode Material for Li-ion Batteries

Abstract

The microstructure of milled mesophase pitch-based carbon fibers (mMPCFs) that have been developed as an anode material for Li ion batteries have been studied as a function of heat treatment temperature (HTT), by SEM, X-ray diffraction, and Raman spectroscopy. And the results obtained are compared with those by X-ray diffraction (XRD) and SEM observations, for the characterization of specific structural features of mMPCFs as a promising anode material.     

Analysis of Structural Features of Periodic Fe/Pd/Gd/Pd Multilayered Systems

Crystallography Reports - The structure of a material promising for magnetic memory elements based on Fe/Pd/Gd/Pd superlattices has been investigated by X-ray analysis and electron microscopy....     

Synthesis, growth and characterization of Bis S-benzylisothiouronium tetrachlorido zincate (II) a semiorganic nonlinear optical crystal

A new semiorganic nonlinear optical (NLO) crystal, Bis S-benzylisothiouronium tetrachloridozincate (II) (SBTTZ), has been synthesized and good optical quality needle shaped single crystals of the title material were grown by solvent evaporation solution growth method at room temperature. Powder X-ray diffraction pattern confirms the crystallinity of the material. Single X-ray diffraction study was carried out to establish the existence of intermolecular hydrogen bonding in the crystal. The UV–Vis–NIR spectrum indicates that the crystal has very good transmittance in the entire visible and near IR regions of the spectrum suggesting the suitability of the material for NLO applications. The presence of various functional groups was confirmed by FT IR spectroscopic technique. The ¹H NMR spectrum confirms the molecular structure. The thermal and mechanical stabilities have been confirmed by TG/DTA analyses and Vickers microhardness study respectively. The SHG in the grown crystal was identified by modified Kurtz–Perry method using Nd:YAG laser as the source.     

Dielectric Properties of Diphasic Composites of BaTiO3 and LiFe5O8

A composite material has been prepared by sintering a mixture of a piezoelectric BaTiO₃ and a piezomagnetic ferrite phase. The two-phase nature of the composite has been characterised by X-ray analysis. The electrical resistivity and dielectric properties of the composite material are studied as a function of the volume fraction of the components. The effect of poling on the dielectric constant is also discussed.     

Röntgenographische Untersuchungen zum Abbau von bleihaltigen Stabilisatoren im PVC

Investigation methods of X-ray diffraction cannot only be used for characterizing technical crystalline admixtures of plastic material. In the case of stabilizers „dibasic lead stearate”︁ and „three-basic lead sulphate”︁ in PVC, there has been shown that the degradation of these substances at thermal stress of the material can be illustrated by diffractograms proving basic lead oxichlorides in cristalline intermediate stages. As final product of the reaction of lead stabilizers with HCl liberated when PVC decomposes, lead chloride appears, and in this connection the conversion of the sulphate part of th three-basic lead sulfate in this compound must also be taken into account. The intensities of the interferences of the three-basic lead sulphate and of the lead chloride on the X-ray diffractograms show the degree of degradation of the material after a processing operation due to the thermal stress. There is also the possibility of comparing the thermal stability of various lead stabilized PVC materials.     

[(Epy)2][MnBr2I2]配合物的合成、晶体结构及发光性能

室温下,以N-乙基吡啶碘盐(Epy)I和四水溴化锰(MnBr2·4H2 O)为原料合成了一种零维发光材料[(Epy)2][MnBr2 I2].对该配合物进行元素含量分析、红外光谱、单晶X射线衍射、粉末X射线衍射、紫外可见吸收光谱、光致发光光谱及X射线激发发射光谱等测试.单晶X射线衍射结果表明:配合物为单斜晶系,C2/c...     

Short-range order and atomic clusters in liquid Cu–Sn alloys

We report an investigation of the short-range order of liquid Cu–Sn alloys carried out by means of X-ray and neutron diffraction. The diffracted X-ray intensity was evaluated with a model assuming micro-inhomogeneities in the material. Furthermore, the reverse Monte Carlo modelling technique was applied to derive partial correlation functions. The alloys under investigation are found to be micro-heterogeneous with clusters of Cu₃Sn stoichiometry distributed among the remaining Sn atoms.     

Numerical simulation of the recording of diffraction lines with the Bragg-Brentano focusing

The role played by different factors in the broadening of X-ray diffraction lines is evaluated using numerical methods. It is demonstrated that, within the kinematical theory of X-ray scattering, the main factors affecting the linewidth are as follows: the angle of reflection, the number of reflection planes, the focus width, the material of the anode of the X-ray tube, and the angle of misorientation of coherent scattering regions. It is established that, in the case where the number of reflection planes is less than 200, the instrumental component of the linewidth does not exceed 5% of the total linewidth.     

锡溶液中半导体单晶CuSi2P3的生长与结构分析

Single crystals of CuSi2P3 as long as 1cm has been grown by using tin solution growth. X-ray powder photography technique showed that only CuSi2P3 can grow as a pure material without any exchanges of Si with Sn. The structure is in the form of Fcc with a lattice parameters of a=0.5248nm. Electron probemicro anaiysis (EPMA) has supported the X-ray data in regarding the single phase of this compound grown by solution growth.     

Effect of purification on the polytypism in solution-grown cadmium iodide crystals

The effect of purification on the polytypism in cadmium iodide crystals has been studied by X-ray diffraction in three hundred and sixty polytypes. Formation of small period polytype 2H is governed by both temperature and impurities contained in the starting material. 4H is the most stable polytype and higher occurrence of unidentified polytypes in crystals of purified material has been attributed to free movement of edge dislocations during growth. The results have been examined against empirical conclusions of earlier investigations.     

碳热原位合成SiC_w/Al_2O_3复相陶瓷粉体的制备工艺及反应机理

本文以高岭土和纳米碳黑颗粒为原料,采用碳热还原原位合成工艺制备SiC_w/Al_2O_3复相陶瓷粉体.通过研究合成温度、保温时间、原料配比以及氩气流量对合成产物的影响,借助XRD、SEM等技术手段进行测试表征,得到了合成工艺的最优参数,并探讨了碳热还原反应的机理.实验结果表明:高岭土与碳黑的摩尔比为1∶ 8,氩气流量为80 mL/min,在1500 ℃下保温2 h,可获得纯净的SiC_w和Al_2O_3复相陶瓷粉体,SiC晶须的平均直径为300 nm左右,长度大于6 μm,长径比大于20,SiC晶须表面光洁,与氧化铝颗粒呈均匀分布.碳热还原高岭土合成SiC_w/Al_2O_3,包括碳热还原SiO_2 与碳热还原莫来石两个阶段,碳化硅晶须的生成遵循气-固(V-S)生长机理.     

An X-ray scattering study of hydrogenated nanocrystalline silicon with varying crystalline fraction

Using X-ray diffraction (XRD) and small angle X-ray scattering (SAXS), we probed the nanostructural features of several PECVD grown nc-Si:H thin films with varying crystalline volume fraction. XRD results of a mixed phase film, 70% a-Si:H and 30% c-Si:H, show these crystallites have a preferred [220] orientation in the growth direction. Another film with approximately 90% c-Si also shows elongated grains, but with a preferred [111] orientation. The SAXS results also show an increase in scattering intensity when compared to the mixed phase material. In the mixed phase material, models show that the electron density fluctuations between the amorphous and crystalline phases are not enough to explain the measured SAXS scattering. Hydrogen clustered at the crystallite boundaries and in void regions of the a-Si phase must be included as well.     

X-ray,optical and electrical study of melt-grown CdI2 single crystals

CdI₂ has been purified using the zone-refining technique by giving 20 passes. Single crystals grown from the starting material showed arcing in the X-ray oscillation photographs whereas it is absent in the crystals grown from the zone refined material. These crystals are found to be of the 4 H type. DC conductivity studies were made on these crystals at various stages of purification. The surface morphology of these crystals have been studied using an optical microscope.     

Photochemical fabrication of molecular devices

We present a novel way to fabricate electronic devices from a molecular charge transfer salt Ag(DM)₂ by simple illumination, which realizes a junction-structure in the single molecular crystal. The electrical conductivity of the selected parts of samples can be controlled by illimination time and power. The electrical behavior gradually turned semiconducting from metallic one by illumination. X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray absorption fine structure indicated that illumination should transfer some electrons from the conducting DM columns to the Ag ions. The X-ray powder diffraction pattern indicated that original crystal lattice was maintained after the illumination. These observations imply that the illumination practically effected doping (or rather dedoping) on the material.     

Dielectric relaxation and morphologic properties of CaCu3Ti4O12 doped with GeO2

CaCu₃Ti₄O₁₂ (CCTO) is a material with giant dielectric constant, presenting good stability over a wide temperature and frequency ranges. The preparation method and doping has a great influence on the microstructure and dielectric properties of this material. In this work, doping CCTO with 2–10 wt% GeO₂ has been shown to increase the dielectric constant. We studied the prepared samples by X-ray diffraction (XRD), scanning electron microscopy (SEM) and impedance spectroscopy. X-ray diffraction shows the presence of nanocristals. Grains and grain boundaries compositions have been observed by scanning electron microscopy with energy dispersive X-ray spectrometry mapping. Impedance spectroscopy measurements, in the frequency range from 75 kHz to 30 MHz, and temperature from 250 to 325 K, have been performed. The data were analyzed using the Cole–Cole model of dielectric relaxation.     

Fluorozirconate-based nanophase glass ceramics for high-resolution medical X-ray imaging

Two-dimensional indirect digital X-ray detectors use either a storage phosphor or a scintillator as an imaging plate. A storage phosphor forms a latent X-ray image, which is subsequently read as a visible image by a photostimulated luminescence method. A scintillator produces a visible image during X-ray illumination. Commercial storage phosphor plates have a relatively poor spatial resolution due to light scattering in the readout process by the grains of phosphor material that are embedded in the plates. To improve the image resolution of storage phosphors and apply them to high-resolution mammography, we are developing image plates of Eu²⁺-doped fluorozirconate-based nanophase glass ceramics. X-ray imaging tests show that the resolution of these storage phosphor plates exceeds that of commercial ones by about a factor of 10. By using appropriate thermal-processing conditions, we are able to make transparent nanophase glass ceramic scintillators based on the same materials. The imaging tests show that these scintillators have high a resolution and high efficiency compared to a single-crystal CdWO₄ scintillator. These results demonstrate that fluoroziconate-based nanophase glass ceramics are good candidates for medical X-ray imaging, such as high-resolution mammography.     

Synthesis of high-quality CdSiP2 polycrystalline materials directly from the constituent elements

High-purity, single-phase CdSiP₂ polycrystalline materials were synthesized directly from the constituent elements by a new method without graphite boat sealed in silica ampoule. The problem of explosions was solved by careful control of the heating and cooling cycle and adopting the two-zone rocking furnace with specially designed temperature profile. Mechanical and temperature oscillations as well as gradient cooling were introduced in the synthesis process. The mechanism and advantages of this new method are discussed. X-ray diffraction (XRD) analysis and Energy dispersive X-ray (EDX) microanalysis both indicated that the synthesized compound is high-quality CdSiP₂ polycrystalline material.     

Hydrothermal Synthesis and Characterization of a New Strandberg-type Diphosphopentamolybdate (C6N3H18)2[P2Mo5O23] · 6H2O

Crystallography Reports - An inorganic-organic hybrid material formulated as (C6N3H18)2[P2Mo5O23] · 6H2O, has been hydrothermally synthesized and characterized by single crystal X-ray...     

Fabrication,characterization and modification of nanodimensional silica hybrid multilayered materials

A sol–gel derived hybrid material with nanometer dimensional layers is described. The material was fabricated using alternating layers of preformed silica colloids decorated with either epoxide or amine functional groups as a means of providing horizontal ordering to an otherwise amorphous material. The layer thicknesses, as determined by XPS escape depth calculations, are 20 nm for the epoxide and 7 nm for the amine decorated material. The sharpness of the interfaces, the homogeneity of the surfaces and the chemical availability of the functional groups following deposition are demonstrated by X-ray photoelectron spectroscopy, grazing angle infrared spectroscopy and aqueous contact angle measurements. The functional groups of the uppermost layer were readily modified by diethylamine or propylene oxide in tetrahydrofuran at 100 °C.