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KDP晶体中包裹体形成机制的探讨 总被引:8,自引:8,他引:0
本文介绍了包裹体对KDP晶体质量的影响,并从两个方面探讨了KDP晶体生长过程中包裹体的形成机制.通过分析KDP晶体表面原子结构研究了不同杂质的吸附情况以及杂质对生长台阶的阻碍作用,通过分析晶体生长过程中流体动力学和质量输运条件的变化研究了旋转晶体的流体切应力和表面过饱和度,结果表明吸附杂质对生长台阶的阻碍和表面过饱和度的不均匀造成了生长台阶的弯曲和宏观台阶的形成,导致生长台阶形貌的不稳定是包裹体形成的重要原因. 相似文献
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本文采用坩埚下降法,在真空密封的石英坩埚中成功生长出CsI-LiCl与CsI-LiCl:Na共晶闪烁体。通过扫描电子显微镜(SEM)观察晶体微结构表明该共晶中LiCl相与CsI相存在周期性的层状排列,CsI相的厚度在5 μm左右。共晶样品的X射线激发发射谱显示在CsI-LiCl和CsI-LiCl:Na共晶样品存在缺陷发光,在CsI-LiCl样品中还观察到了纯CsI的自陷激子(STE)发光。CsI-LiCl样品在α粒子激发下的多道能谱中观察到明显的全能峰,这一结果证明CsI-LiCl共晶可用于热中子探测的潜力。 相似文献
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以聚丙烯腈(PAN)为载体,六水合硝酸铈[Ce(NO3)3·6H2O]为原料,采用静电纺丝法制备了Ce(NO3)3/PAN纤维,在空气中热处理得到CeO2微纳米纤维,通过XRD、BET和SEM对CeO2微纳米纤维进行表征。采用静态吸附实验探讨了CeO2微纳米纤维去除水溶液中氟离子的性能,考察了溶液pH值、初始氟离子浓度及共存阴离子等对吸附性能的影响。结果表明,pH=3时,CeO2微纳米纤维对F-的吸附性能最佳,CeO2吸附量随着F-浓度的增大呈上升趋势。CeO2微纳米纤维对F-的吸附等温线遵循Langmuir模型,二级动力学模型能很好地描述CeO2微纳米纤维对F-的吸附过程。CeO2微纳米纤维的除氟性能优良,可为其实际应用提供理论参考。 相似文献
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Sideroxol (1), a kaurane diterpene which has the ent-7α,18-dihydroxy-15β,16β-epoxykaurane structure (MW = 320.47, C20H32O3) was obtained from the acetone extract of Sideritis leptoclada plant as well as from some other Sideritis species. It crystallizes in the orthorhombic space group P21, 21, 21 with a = 10.967(3), b = 24.555(5), c = 6.372(4) Å, Dc = 1.240 g cm−3, Z = 4, and refines to R = 0.065 for 721 independent reflections. The skeleton consists of three fused six-membered rings and a five-membered ring with fused epoxide. The six membered rings exhibited slightly distorted chair conformation. In addition to sideroxol, two kaurane and five kaurene diterpenes were isolated from the hexane and acetone extracts of the studied plant. 相似文献
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A. Yilmaz L. Tatar Yldrm X. Bu M. Kizilyalli G. D. Stucky 《Crystal Research and Technology》2005,40(6):579-585
Two new isostructural open‐framework zeotype transition metal borophosphate compounds, (H)0.5M1.25(H2O)1.5[BP2O8]·H2O (M = Co(II) and Mn(II)) were synthesized by mild hydrothermal method. The structure of compounds were characterized by single‐crystal X‐ray diffraction which have ordered, alternating, vertex‐sharing BO4, PO4, and (MO4)OM(H2O)2 groups with hexagonal, P 61 2 2 (No 178) space group and unit cell parameters for Co a = 9.4960(6) Å, c = 15.6230(13) Å, for Mn a = 9.6547(12) Å, c = 15.791(3) Å, Z = 1 for both of them. TGA/DTA analysis, IR spectroscopy were used for characterization. Magnetic susceptibility measurements for both of the compound indicate strong antiferromagnetic interaction between metal centers. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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K. Subba Ramaiah Y. K. Su S. J. Chang F. S. Juang C. H. Chen 《Journal of Crystal Growth》2000,220(4):405-412
We have studied the optical, structural and surface morphology of doped and undoped GaN thin films. The p- and n-type thin films have been successfully prepared by low-pressure MOCVD technique by doping with Mg and Si, respectively. The different carrier concentrations were obtained in the GaN thin films by varying dopant concentrations. Photoluminescence (PL) studies were carried to find the defect levels in the doped and undoped GaN thin films at low temperature. In the undoped GaN thin films, a low intensity and broad yellow band peak was observed. The donor–acceptor pair (DAP) emission and its phonon replicas were observed in both the Si or Mg lightly doped GaN thin films. The dominance of the blue and the yellow emissions increased in the PL spectra, as the carrier concentration was increased. The XRD and SEM analyses were employed to study the structural and surface morphology of the films, respectively. Both the doped and the undoped films exhibited hexagonal structure and polycrystalline nature. Mg-doped GaN thin films showed columnar structure whereas Si-doped films exhibited spherical shape grains. 相似文献
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The solubility of Ag2O was measured for the Na2O–B2O3 and Na2O–B2O3–Al2O3 system with the rotating crucible method and static method, respectively, under air atmosphere at temperatures ranging from 1273 to 1423 K. The contamination of melts from crucibles could be avoided by the rotating crucible method, with which it became possible to measure the solubility of Ag2O for the Na2O–B2O3 system above the melting point of Ag for the first time. It was found that the addition of Na2O decreases the solubility of Ag2O while the addition of Al2O3 had little effect on the solubility. The effect of Na2O and Al2O3 on the solubility of Ag2O is expressed by interaction coefficients and is analyzed in terms of the basicity of melts. The solubility of Ag2O in Na2O–B2O3–Al2O3 melts increased with increased temperature. This phenomena was explained by a small enthalpy change in oxidation of silver. 相似文献
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H. Doweidar 《Journal of Non》2011,357(7):1665-1670
Data of density, refractive index and thermal expansion coefficient for B2O3-SiO2 and GeO2-SiO2 glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B2O3, GeO2 and SiO2. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO3, GeO4 and SiO4 units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B2O3 or GeO2 in the concerned glasses. 相似文献
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S. Kumar Gertraud Koellner Thomas Steiner K. Subramanian 《Journal of chemical crystallography》1998,28(2):149-152
The X-ray crystal structure of 1,6-bis(N-cyano-p-methoxy-anilino)-2,4-hexadiyne, C22H18N4O2, is determined. The crystal packing is dominated by phenyl stacking interactions. Weak C–H···N hydrogen bonds help align the molecules. C–H··· hydrogen bonding is not apparent. 相似文献
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Cd1 − xFexTe single crystals were prepared by vapour phase growth method in the composition range of 0 ≤ x ≤ 0.03. Chemical analysis, surface morphology, structural investigations and electrical properties were carried out by EDAX, SEM, XRD, TEM and transport technique, respectively. Microscopic variations between the target and actual compositions were noticed. Morphology studies revealed that dislocation aided growth is active in the present crystals. TEM and XRD studies confirmed that the samples of all compositions crystallized in zinc blende structure, and the lattice parameters varied almost linearly decreases with Fe content. At room temperature, the resistivity of the Cd1 − xFexTe crystals of all compositions (x = 0.01, 0.015, 0.02, 0.025 and 0.03) lies in the range of 3.5-6.5 M Ω, the activation energies lie in the range of 63-133 meV, and the samples were show the ‘p’ type conductivity. 相似文献
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本文基于密度泛函理论的平面波超软赝势方法,采用第一性原理研究了含Cd空位缺陷CdS和含S空位缺陷纤锌矿CdS的几何结构、能带结构、电子态密度及光学性质。通过计算分析可知,含Cd空位缺陷的CdS体系均为p型半导体,含S空位缺陷的CdS体系跃迁方式均由直接跃迁变为间接跃迁。Cd、S空位缺陷的CdS体系的态密度总能量降低。空位CdS体系相较于本征CdS体系的静介电常数均有提高,并随着空位浓度的增大而增大,Cd空位缺陷体系更为明显,极化能力得到显著提升。空位Cd的CdS体系相较于本征CdS体系在红外波段存在明显的吸收,空位S的CdS体系相较于本征CdS体系在可见光波段存在明显的吸收。 相似文献