铌酸锶钠锂单晶折射率及透光曲线的测量

本文首次研究了用提拉法生长的透明不裂铌酸锶钠锂单晶在可见光波段的折射率和透过率。并分析了其误差因素。 关键词：     

铌酸锶钠锂单晶的生长

铌酸锶钠锂单晶具有优良的电光性能,但它在室温下为亚稳相。生长的晶体降温至1200℃以下要通过共析反应区。我们用提拉法采取大温度梯度生长,在共析反应区较快速降温避免分解等措施,获得最大尺寸为直径10mm,长15mm的单晶。文中讨论了引起开裂的原因及生长过程中遇到的主要问题。 关键词：     

Ca2+掺杂铌酸锶钡晶体的光折射变化特性研究

基于Ca2+掺杂铌酸锶钡晶体的透射特性,探讨了Ca2+在晶体中的电子行为机制,分析了Ca2+掺杂而引起的光致折射率变化特性.采用Michelson干涉装置测得了样品折射率随时间变化的特性曲线.实验结果分析表明,适当的ca2+掺杂可以有效改善铌酸锶钡晶体的光折射特性.     

Ca2+掺杂铌酸锶钡晶体的光折射变化特性研究

基于Ca²⁺掺杂铌酸锶钡晶体的透射特性,探讨了Ca²⁺在晶体中的电子行为机制，分析了Ca²⁺掺杂而引起的光致折射率变化特性.采用Michelson干涉装置测得了样品折射率随时间变化的特性曲线.实验结果分析表明，适当的Ca²⁺掺杂可以有效改善铌酸锶钡晶体的光折射特性. 关键词： 2+')" href="#">Ca²⁺ 铌酸锶钡 透射率 光折变     

掺铁铌酸锂晶体中光致散射的锂组分和温度依赖关系研究

研究了单掺铁铌酸锂晶体的光致散射行为随锂组分以及温度的变化关系.实验表明,随晶体组分的升高,光致散射得到了大幅抑制;不同组分晶体光致散射被完全抑制的温度不同.由此提出掺铁铌酸锂晶体在48.9 mol%-49.3 mol%范围内可能存在一临界锂组分,当晶体组分超过这一临界组分时,晶体光致散射被大幅抑制,而光致散射行为的温度依赖关系明显改变.     

导模法生长铌酸锶钠锂单晶并验证相图

引 言 铌酸锶钠锂(简称 SNL) 单晶是5+1型的钨青铜结构的铁电体[1],由于它具有半波电压低、温度系数小的特性[2],近年来一直受到人们的重视.已经用提拉法生长了这种晶体[3]并测试了它的物理特性[4],证明温度系数对晶体中的锂含量是敏感的,增加晶体中的锂含量可使温度系数在较宽的温度范围内近似为零.用提拉法生长时,锂的分凝系数远小于1[3],而用导模法生长时能改善分凝系数[5],使晶体中的锂含量比用提拉法生长时有显著增加,从而可进一步改善晶体的温度系数.另外,采用导模法生长时固液界面高度是不变的,晶体不转动,因而熔体热对流的影响可…     

钾钠铌酸锶钡晶体作为自泵浦相位共轭镜器件的设计

本文给出了钾钠铌酸锶钡晶体作为自泵浦相位共轭镜器件的设计原理及基本考虑,设计了相应的器件并研究了其基本特性。     

铌酸锶钡晶体的光存储实验研究

通过全息存储光路调整,采用适当的曝光时间,在铌酸锶钡晶体中得到清晰的全息存储图象,并通过高压固化存储图象,测得全息存储时间衰减曲线.     

铌酸锶钠锂单晶电光、热电、介电和压电性能

文本研究了用提拉法生长的铌酸锶钠锂(Sr₄NaLiNb₁₀O₃₀)晶体的电光、热电、介电和压电性能。其半波电压与温度的关系与晶体中锂含量密切相关。测得其室温下的热电系数与Ba～0.5的Sr_1-xBa_xNb₂O₆晶体相当,～7×10^-8C/cm²·K。已极化的晶体几乎检测不到退极化现象。将其作成热电器件,其探测度D^*不小于1.7×10⁷Hz^1/2·cm/W。文中还描述了其介电和某些压电性能。 关键词：     

掺铜钾钠铌酸锶钡晶体自泵浦相位共轭研究

用掺铜钾钠铌酸锶钡晶体制成猫式(cat)自泵浦相位共轭器,共轭光反射率高达63%.增加掺铜量,晶体在红光波段效应增强.本文研究了掺杂浓度、激光波段与该器件性能的关系.     

LiNbO3单晶体直拉法生长时组分过冷所形成的胞状界面和胞状组织

对于沿[0001]生长的LiNbO₃单晶体,组分过冷形成的胞状界面和胞状组织进行了形态学的研究(组分过冷是由于操作上的原因在熔体中掺入了Al₂O₃而引起的),确定了胞状界面和胞状组织的基本形态。胞状界面是由相毗邻的三角锥组成,三角锥的稜锥面为{0112}面组,毗邻的三角锥体间存在沟漕,其中的熔体中浓集溶质。在长成的晶体中的胞状组织或是由{1210}面构成的其母线平行于[0001]方向的稜柱体,或是由溶质浓集的三{1210}面相交而成的三叉。实验观测证实了白丝、白点、云层及溶质尾迹是胞状组织的某种表现,而温度起伏是形成间歇式胞状组织的原因。通过胞状界面的形态研究,确定了形态干扰的某些具体形式,并证实了破坏界面稳定性的形态干扰与界面邻近流体的动量边界层的稳定性有关。文章最后讨论了高熔点氧化物晶体与金属晶体的胞状组织在形态上的差异,认为是由于两类物质的不同熔化熵而产生的。 关键词：     

生长温度、过冷度对InAsPSb外延层表面形貌影响的研究

本文采用恒温液相外延生长方法,研究了InAsPSb四元材料外延层表面形貌与生长温度、过冷度之间的关系.实验结果表明,生长温度、过冷度对外延晶体质量及表面形貌的影响较为明显,同时对其它因素的影响也做了分析.     

Structural and physical aspects of the formation of salt crystals from solutions

The peculiarities of the crystallization of about 100 solutions of different salts have been experimentally studied. A correlation is established between the maximum attainable supercooling temperature of the solution and the structure of the crystals formed. It is found that the highest supercoolings are characteristic of solutions of acentric crystals.     

直拉法生长的YAG单晶体中组分过冷引起的针状应力区和位错

本文研究了掺钕的YAG(Y₃Al₅O₁₂)晶体在组分过冷条件下,固液界面的形态演变以及产生的钕离子的富集区。该富集区在正交偏光下表现为针状应力区。利用光弹方法确定了该应力为压应力,且应力分布具有圆柱对称性。通过浸蚀法和双折射貌相法观察到在钕富集区边界处存在位错列,并测定了位错的线密度。其结果与根据钕的浓度差值估计的密度大体符合。故认为这些位错是钕富集区边界处点阵失配所引起的。 关键词：     

熔体生长水杨酸苯脂晶体的形貌

在实验上用实时观察法和Kyropoulos技术生长水杨酸苯脂单晶,研究晶体形貌随过冷度的变化关系。在理论上采用Hartman-Perdok的PBC方法,分析水杨酸苯脂单晶形貌和晶体结构的关系。应用木原的核心势能模型,扩展了PBC理论。解析的晶体形貌与实时观察法得到的晶体形貌相当一致。 关键词：     

Growth and characterization of potassium halides mixed l-arginine phosphate monohydrate semi organic nonlinear optical single crystals

Single crystals of pure and potassium halides additive mixed l-arginine phosphate monohydrate have been grown with good optical quality by slow temperature reduction method. Microbial growth aspects and coloration have been studied on the growth solutions. In addition to that the structural properties have been studied by powder X-ray diffraction method and Fourier transform infrared spectral analyses for the grown crystals. Thermal stability of the grown crystals were studied by thermo gravimetric (TG) and differential thermal analyses (DTA) and found that the grown crystals are suitable for device fabrication for frequency conversion applications.     

Dynamic Light Scattering Studies on Crystallization of Isotactic Polystyrene from Dilute Solutions at High Supercoolings

Crystallization of isotactic polystyrene (it‐PS) from dilute solution at high supercooling has been investigated by dynamic light scattering (DLS). We successfully obtained simultaneously, in situ in solutions, the time developments of both random coils of it‐PS molecules and the growing crystals. The size of coils remains constant during growth, while the crystals pass through two stages, that is, an induction period at the early stage with very slow growth rates and a subsequent linear growth stage. It is confirmed that the temperature dependence of the linear growth rates, determined by DLS, agree well with that determined by electron microscopy. The temperature dependences of the growth rate and the inverse of induction time are dependent on the viscosity of solvent, which indicates that all dynamics are dominated by the segmental motion of polymer chains in solution at high supercoolings (low temperatures). Two possibilities are proposed for the induction period.     

Dislocation Generation in Dislocation-Free Germanium

A dislocation structure is studied in germanium single crystals grown in a regime of minimum temperature gradients at the crystallization front and low supercooling. The investigations show that the distortion of the flat crystallization front arising during crystal droplet detachment in the completion growth stage results in the dislocation generation in the lower parts of dislocation-free single crystals. The dislocations are generated at the phase boundary and propagate in the thermoplasticity zone. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 5, pp. 21–24, May, 2005.     

Constitutional supercooling in an organic single crystal

Single crystals of cyclododecane, doped with a range of concentrations of an organic dye, were grown under various physical conditions. Dopant segregation resulted in similar, but not identical, cellular features to inorganic materials. The conditions for the onset of constitutional supercooling are in agreement with the theory applicable to inorganic materials.