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坩埚下降法生长钨酸镉闪烁单晶的晶体缺陷 总被引:1,自引:0,他引:1
采用坩埚下降法生长出大尺寸CdWO4单晶,通过光学显微镜、电子探针观察分析了所获CdWO4单晶的典型晶体缺陷,包括晶体开裂、丝状包裹物和晶体黑化.结果表明,CdWO4单晶存在显著的解理特性,常出现因热应力导致的沿(010)解理面的晶体开裂;当采用富镉多晶料进行单晶生长时,所获单晶棒的下部常出现沿轴向分布的丝状包裹物,电子探针分析证实这种丝状包裹物是熔体内过量CdO沉积所致;在氮气氛中进行高温退火处理,CdWO4单晶还会出现黑化现象. 相似文献
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坩埚下降法生长钨酸镉晶体的闪烁性能 总被引:1,自引:0,他引:1
以高温固相反应合成CdWO4多晶为原料,采用垂直坩埚下降法生长出大尺寸完整CdWO4晶体,就所生长CdWO4晶体进行了闪烁发光性能的测试表征,包括紫外可见透射光谱、光致发光光谱、光致发射衰减时间、X射线激发发射光谱、相对光产额以及γ射线辐照硬度.结果表明,该单晶在可见光区具有良好的光学透过性,其光致发光与X射线激发发射光的峰值波长位于475 nm左右,其光致发射衰减时间为842 ns;以CsI∶Tl晶体为基准样品,测得γ射线激发发光的光产额相当于基准样品的51.5%~57.4%,在γ射线辐照条件下其辐照硬度达107 rad. 相似文献
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大尺寸金红石(TiO2)单晶体生长条件的实验研究 总被引:7,自引:2,他引:5
采用高纯(99.995;)、超细的金红石(TiO2)粉末为起始原料,用燃熔法制备了尺寸为30mm×50mm的金红石(TiO2)单晶体.讨论了生长气氛、生长速度、温度梯度在晶体生长中的作用,对比了晶体在空气中与在氧气中退火的结果,测定了晶体试样的摇摆曲线和透过率,并与商用晶体的透过率进行了比较.实验表明:生长气氛中的氧分压大于液固界面(即生长界面)处熔体的氧离解压是生长完整晶体的必要条件;在此条件下,能否生长为大尺寸晶体则取决于炉膛的轴向温度梯度;晶体在退火过程中可消除热应力,但退火更重要的作用是通过氧化反应消除氧空位,在氧气氛中退火,可明显缩短退火时间;所制备的晶体完整性较好,透过率与商用晶体基本一致. 相似文献
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以La2O3和Fe2O3粉体为原料,在1400℃,烧结24 h制备出了LaFeO3多晶料棒,采用浮区法生长出LaFeO3单晶。晶体沿(100)晶向生长,晶体的(100)晶面单晶摇摆曲线的半高宽为26″,证实其单晶化程度很高;在298~773 K温度范围内测试了晶体热学性能,晶体比热变化范围为0.58~0.76 J/g.K,热扩散系数变化范围为3.47~0.85 mm2/s,热导率变化范围为13.10~4.21 W/(m.K);研究退火工艺对晶体近红外透过率的影响,在700℃,48h退火可以明显提高透过率达到65%。 相似文献
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采用固相合成和液相合成两种方法成功制备了Ca9Y0.5La0.5(VO4)7晶体的多晶原料,并采用提拉法生长了尺寸分别为30 mm×33 mm(固相合成多晶原料)和20 mm×27 mm(液相合成多晶原料)的Ca9Y0.5La0.5(VO4)7晶体。测试了该晶体在紫外、可见和近红外区域的透过率,采用Kurtz法测试了晶体的粉末倍频效应。结果表明,采用液相合成原料生长的晶体透过率大于采用固相合成原料生长的晶体约10%。前者粉末倍频效应约为KDP的1.8倍,后者约为KDP的2.5倍。晶体化学腐蚀实验表明采用液相合成原料生长的晶体具有更少的缺陷。采用液相合成方法制备多晶原料有利于提高晶体的光学质量。 相似文献
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以CdO和MoO3粉料为初始试剂,通过高温固相烧结合成CdMoO4多晶料,采用坩埚下降法生长出尺寸达φ25 mm×130mm的透明完整CdMoO4单晶;应用DSC、XRD对所获单晶进行了结晶相和热性能表征,测试了单晶的紫外可见透射光谱、紫外光激发发射光谱及其发光衰减时间.结果表明,CdMoO4单晶具有良好的一致熔融析晶特性,采用坩埚下降法较易于生长出大尺寸单晶;该单晶在吸收截止边375 nm以上波长具有良好光学透过性,在300 nm紫外光激发作用下,测得该单晶具有525 nm左右峰值波长的荧光发射,其发光衰减时间为804 ~ 1054 ns.该单晶经氧气氛高温处理呈现出明显的退火消色效应,即经1000℃以上温度的氧气氛退火处理,可使晶体的光学透过性得以明显改善,其荧光发射强度显著增强. 相似文献
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In the current paper we designed a simple glucose reduction route for synthesis of sheet‐like Cu dendrites on a high yield, using CuSO4 as the starting material. The reaction was carried out at 180 °C for 18 h in the absence of any structure‐directing agent. The product was characterized by X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron diffraction (ED). Some factors influencing the shapes of Cu microcrystals, including the reaction temperature, time, and the concentration of the starting CuSO4, were investigated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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The growth morphology of crystals is analysed from macroscopic point of view and the recent developments in this field are surveyed. In particular, it is shown that, for specific geometry characterized by interfacial angles a given face can increase in size for a very wide range of relative growth rates and need not be the slow‐growing face. Even growing faster than the neighbouring faces, such a face can increase in its size. However, there are other faces with other specific geometry, which can decrease the size growing more slowly than one of the neighbouring faces. If the growth time is sufficiently long, such a face may disappear and not be represented in the final crystal morphology. In the present survey the concepts given earlier [5] are extended. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Xinxin Zhuang Genbo Su Guofu Wang Guohui Li Zixiang Huang 《Crystal Research and Technology》2004,39(9):754-758
A new crystalline complex zinc nickel sulfate heptahydrate (ZNSH) has been prepared. The crystal structure was investigated by x‐ray single crystal diffraction method and the empirical formula is Zn0.24Ni0.76(SO4)·7H2O. The ZNSH crystal belongs to the orthorhombic space group P212121 with cell parameters a = 6.7742(14) Å, b = 11.748(2) Å, c = 12.009(2) Å. The deep‐green ZNSH single crystal with dimension of 30 × 25 × 25 mm3 has been grown by the cooling solution method. The constituent ratio of ZNSH crystal grown from various compounding solutions at temperature range 40‐50 °C is approximate invariant. The crystal absorption spectra with theoretical analysis are reported. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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P. Di Martino R. Censi L. Malaj D. Capsoni V. Massarotti S. Martelli 《Crystal Research and Technology》2007,42(8):800-806
In the present study, metronidazole was crystallized in several solvents, according to both the “cooling crystallization” and the “crystallization by non‐solvent addition”. Particle properties, such as crystal habit, elongation ratio, and mean particle size, were determined by SEM analysis. Structural changes and development of polymorphic forms were excluded by both Differential Scanning Calorimetry (DSC) and X‐Ray Powder Diffractometry (XRPD). Crystal habit (and thus elongation ratio) was typically influenced by both the solvent polarity index and the crystallization method: solvents with higher polarity index tended to promote acicular or stick‐shaped crystals with a high elongation ratio, while isodimensional crystals were promoted by decreasing the polarity index, as was particle aggregation. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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晶体美丽有用,构造和谐有序。光电功能晶体可实现光能和电能的相互转化,在微电子、光电子、通信、航天及现代军事技术等高科技领域占有重要地位。人类认识晶体,源于天然矿物。从矿物晶体的发现到光电功能晶体的人工生长和应用经历了漫长的发展,晶体种类、晶体质量、生长理论、生长技术以及应用等方面均取得了较大进展。本文简述了从矿物宝石到晶体学发展的历程,介绍了压电晶体、电光晶体、激光晶体、非线性光学晶体和闪烁晶体等几类光电功能晶体发展历程及晶体生长研究的进展,展望了未来光电功能晶体的发展趋势。 相似文献
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晶体形态一些基本概念的实际意义分析 总被引:5,自引:1,他引:4
本文对晶体学中关于晶体形态一些古老的基本概念(单形的正形与负形、左形与右形、一般形与特殊形)进行了深入思考,并从实际晶体形态上发育这些单形的角度,分析了它们的本质区别与内在含义:单形的正形与负形是属于同一几何单形、同一对称型(点群)的两个结晶单形,它们可以相聚;单形的左形与右形也是属于同一几何单形、同一对称型(点群)的两个结晶单形,但它们却具有不同的内部结构,所以它们不能够相聚;单形的一般形与特殊形只有结晶单形意义,无几何单形意义.这些认识阐明了过去我们多年来并没有足够重视的一些理论与实际问题,这有助于晶体形态对称理论的发展,也有助于晶体学教学思路的明确. 相似文献