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Ferroelectric crystals of Ammonium Hydrogen Tartrate (AHT) have been synthesised using the controlled reaction between NH4Cl and (CHOHCOOH)2 by diffusion process in silica gel medium. (010) cleavages of AHT crystals have been etched in 1.0 M and 1.5 M solutions of SrCl2 solution. The lateral and normal velocities of the growth of pits were measured at different temperatures. The time dependence of the growth of the pit dimensions is found to be linear, whereas the temperature dependence of the growth of pits is found to be exponential, viz. \documentclass{article}\pagestyle{empty}\begin{document}$ \[V = A\,\exp \left({\frac{E}{{kT}}} \right)\] $\end{document}. The dissolution parameters, e.g. the activation energies and the pre-exponential factors for dissolution along the surface and along the dislocation lines have been computed. It is observed that the activation energy (E1) of dissolution along [001] direction is found to be greater than the activation energy (Eb) along [100] direction and the implications are discussed. 相似文献
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A. G. Saraf K. B. Saraf P. A. Wani S. V. Bhoraskar 《Crystal Research and Technology》1986,21(4):449-452
Dendritic growth of Ammonium tartrate single crystals in silica gel at 30 °C is reported. Main stem parallel to the ‘C’ axis is observed. Dendritic growth in initial and final stages with its surface structures are illustrated and described. Growth features are correlated to the growing conditions and reacting components. 相似文献
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Stadnyk V. Yo. Shchepanskyi P. A. Brezvin R. S. Rudysh M. Ya. Kohut Z. A. Onufriv O. R. Kost Ya. P. 《Crystallography Reports》2019,64(5):787-792
Crystallography Reports - An effect of uniaxial pressure on the spectral and temperature dependences of birefringence of K1.75[NH4]0.25SO4 single crystals has been studied. Different changes in the... 相似文献
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H.-R. Xia L.-X. Li H. Yu X.-L. Meng L. Zhu L.-J. Hu 《Crystal Research and Technology》1999,34(7):901-910
Neodymium-modified barium sodium niobate (Ba2Na)1-xNdxNb5O15(BNN:Nd), with x = 0.025, crystallizes with a filled tungsten bronze (TB) type structure in the tetragonal system, conforming to the space group P4bm and Z = 2. The lattice constants are a = 1.2446(1) and c = 0.3991(1) nm at room temperature. Tc = 537 +- 2 °C. The experiments show that the Nd-ions effectively improve crystal structural quality. The lattice vibrational spectrum, studied by Raman and infrared reflectivity spectroscopy, shows that the crystal microscopic structure and lattice dynamics, thereby the microstrain and microstress, are very stable in a temperature range from 22 to approaching 500 °C. 相似文献
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氮(N)元素和硼(B)元素为金刚石晶体中常见的两种杂质元素,它们对金刚石的物理化学性质有着重要的影响.本文使用高温高压温度梯度法合成了分别含有氮和硼杂质的金刚石单晶,并使用Raman光谱对晶体进行分析研究.研究发现:随着金刚石生长体系内杂质的引入,晶体的质量变差;当生长体系含有氮杂质时,生长的含氮金刚石晶体的特征峰谱线向低波数偏移,晶体的应力表现为拉应力;当生长体系含有硼杂质时,生长的含氮金刚石晶体的特征峰谱线向高波数偏移,晶体的应力表现为压应力.本研究将有助于丰富金刚石单晶掺杂的认识. 相似文献
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Using optical techniques, a study was carried out of the etch patterns produced, by diluted oxalic acid and sodium hydroxide solution, at 30°C. Point bottomed and flat bottomed rectangular etch pits nucleated at the sites of dislocations parallel to ‘C’ axis of the crystal are observed. Mostly they are isolated, and randomly distributed. Further, on prolonged etching they penetrate deeper and their eccentricity can be attributed to the inclined nature of dislocations. 相似文献
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Growth and Characterisation of Pure and Nickel-doped Strontium Tartrate Tetrahydrate Single Crystals
F. Jesu Rethinam D. Arivu Oli S. Ramasamy P. Ramasamy 《Crystal Research and Technology》1993,28(6):861-865
Strontium tartrate tetrahydrate single crystals doped with nickel have been grown in silica gel. The grown crystals have been characterized by X-ray, atomic absorption spectroscopy (AAS), thermogravimetric analysis (TGA), and etching technique. 相似文献
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C. J. Eckhardt H. Müller H. Eckhardt R. R. Chance 《Molecular Crystals and Liquid Crystals》2013,570(1):269-270
Abstract The spectra of polydiacetylene crystals may be categorized such that they form two distinct classes. There are the long wavelength reflectors with their peaks of reflectivity from 15,000 to 16,000 cm?1 and the short wavelength reflectors with their reflection peaks from 18,000 to 19,000 cm?1. In the former set where the crystals reflect a reddish-gold color, the vibrational structure is greatly enhanced compared to the spectra for the systems of the second class which reflect in the green. X-ray crystallographic determinations have shown that in the case of the gold-reflecting crystals the polymer may be represented by an acetylenic backbone: 相似文献
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Spherulitic growth of gadolinium tartrate dihydrate crystals by controlled diffusion in silica gel is reported. The influence of growth parameters e.g., reactant concentration, gel pH and gel ageing, on the size, quality and nucleation density of the spherulites has been studied. It is observed that under varying experimental conditions involving change in reactant concentrations, gel pH and gel ageing, the material crystallizes in the form of spherulites. The results of growth kinetics are discussed. Scanning electron microscopy confirms spherulites to be aggregates of single crystallites, with each micro-sized crystal exhibiting a cuboid morphology. Surface structures exhibited by the micro-sized crystals indicate their growth by two-dimensional nucleation mechanism. 相似文献
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《Journal of Non》2007,353(18-21):2020-2024
Glasses from the xMnO · (100−x)[3B2O3 · 0.9PbO · 0.1Ag2O] system with 0 ⩽ x ⩽ 20 mol% have been prepared and studied by means of FT-IR absorption and Raman scattering. We interpreted the spectroscopic data in conjunction with the structural information obtained by X-ray diffraction and scanning electron microscopy (SEM). The X-ray patterns have showed homogenous glasses over the entire compositional range while the SEM pictures have detected metallic silver or Ag2O clusters dispersed in the glass network. Acting as complementary spectroscopic techniques, both types of measurements, FT-IR and Raman, revealed that the network structure of the studied glasses is mainly based on BO3 and BO4 units placed in different structural groups, the BO3 units being dominant. The influence of manganese-ion content (x), on the NBO4/NBO3 ratio evolution was investigated. 相似文献
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Raman scattering has been used to study the vibrational spectra of GaSexS1‐x layered mixed crystals at 10 K. We report the frequency dependencies of different modes on composition x, with particular emphasis on A′1(2) (A1g1) and A′1(4) (A1g2) intralayer compressional modes having low dispersion in the Brillouin zone. The appearance of additional bands is attributed to multimode behavior typically exhibited by mixed crystals of anisotropic compounds. 相似文献
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Growth of spherulitic crystals of iron tartrate by controlled diffusion in sodium metasilicate gels has been described. Infrared spectroscopic, thermogravimetric and elemental analysis have been conducted to characterize the crystals. The results are interpreted and explained. 相似文献
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Single crystals of potassium pentaborate were grown by the solution growth method. The grown crystals were characterised by optical transmission spectrum, differential thermal analysis, and thermogravimetric analysis. The coefficient of thermal expansion was also determined and the results discussed. 相似文献
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用电阻加热提拉法生长了一系列较大尺寸,组分离子均匀性较好的铌酸钾锂晶体.利用X射线荧光光谱法测量了不同配比的熔体中生长出的晶体组成,用同步辐射X射线测量了晶体结构,结果表明随晶体组成变化,晶体的晶格常数发生了变化.根据晶体组分离子浓度与折射率的关系研究了晶体折射率变化情况,结果表明用本方法生长的大尺寸KLN晶体,寻常折射率no在测量误差范围内没有变化,非寻常折射率ne的变化率在820nm仅为1.22×10-4/mm,在410nm仅为1.93×10-4/mm.晶体的干涉条纹证明了晶体有良好的光学均匀性.结合晶体生长实验,探讨了改进晶体组分离子浓度分布均匀性的方法,结果表明采用籽晶和坩锅向相同方向旋转可以改善晶体生长界面处组分离子浓度的波动,提高晶体组分离子均匀性.晶体的缺陷研究表明晶体结构完整性较好,位错形状与晶体结构相一致,密度为7.5×104,[001]轴是晶体的极化轴.晶体对890~960nm波长范围的cw-Ti:sapphire激光倍频结果表明晶体有良好的倍频性能. 相似文献