共查询到19条相似文献,搜索用时 640 毫秒
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本文对采用双坩埚提拉法(DCCZ)生长的化学计量比LiNbO3晶体中出现的机械双晶、组分过冷、包裹体等宏观生长缺陷进行了观察和分析.结果表明机械双晶通常以{102}和{104}面族为双晶面,而不是以前文献报道的{102}和{012}面族;化学计量比LiNbO3晶体双坩埚提拉法生长与同成份晶体生长不同,前者是助熔剂生长体系,生长速度稍快或温度较小的波动就会导致组分过冷,而后者属于纯熔体生长体系,不容易产生组分过冷;包裹体是由于组分过冷生长时界面失稳夹入熔体所造成的.由于这些缺陷的存在都会严重影响单晶的获得率和质量,为此,我们通过大量实验研究后提出了可以减少和避免这些生长缺陷提高晶体质量的方法. 相似文献
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近化学计量比铌酸锂晶体组分测定与缺陷观察 总被引:2,自引:0,他引:2
采用助熔剂提拉法生长得到近化学计量比LiNbO3晶体.用多种方法测定了晶体组分,结果表明生长得到的晶体中[Li2O]含量为49.80;摩尔分数;对晶体缺陷的研究表明晶体质量有待提高,并分析了晶体中出现包裹物的原因. 相似文献
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化学计量比LiNbO3晶体的畴结构及完整性研究 总被引:2,自引:2,他引:0
本文对用助熔剂提拉法生长的两种化学计量比LiNbO3晶体进行了测试分析,并与同成分LiNbO3晶体相比较.通过差热分析和X射线粉末衍射测试,得出随着晶体中Li2O含量的增加,其居里温度变高,晶格常数变小.用酸腐蚀晶体,通过直接观察和金相照片,分析其畴结构,得出SLN11是单畴生长,首次观察出SLN19晶体在Z切面上出现了三块面积较大的对称反畴区,将其称为区域性单畴.另外,还对晶体在(001)方向抛光面的不同位置测量了其回摆曲线,得到了其中SLN19晶体有着较完整的结晶面.期望通过改变生长参数,长出完全单畴且更加接近化学计量比的LiNbO3晶体. 相似文献
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助熔剂提拉法生长化学计量比LiNbO3晶体 总被引:5,自引:2,他引:3
利用助熔剂提拉法,分别从掺入11mol;K2O的同成份LiNbO3熔体中和从掺入19mol;*!K2O的化学配比LiNbO3熔体中生长出高质量近化学计量比LiNbO3单晶.对这两种从不同配比熔体中生长的晶体进行光谱分析表明,与同成份比LiNbO3相比较,其紫外吸收边出现明显蓝移,OH红外吸收峰的位置和线宽也都有显著的变化.室温极化反转测试显示,两种晶体的矫顽场分别为4.4kV/mm和0.8kV/mm.根据所得测量结果,估计两种晶体中Li2O的含量分别为49.6mol;和49.9mol;.其中从掺19mol; K2O化学配比LiNbO3熔体中生长出的LiNbO3单晶的Li2O含量已非常接近50mol;的化学配比.进一步优化生长工艺,获得成份均匀、大尺寸化学计量比晶体的工作正在进行中. 相似文献
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以双中心模型为基础,理论研究了LiNbO3∶Cu∶Ce和近化学计量比LiNbO3∶ Fe晶体在稳态情况下的非挥发全息存储灵敏度.通过考虑了两个晶体在其深能级和浅能级中心之间所有可能的电子交换过程,理论结果显示在低光强连续光范围内LiNbO3∶Fe晶体比LiNbO3∶ Cu∶ Ce晶体有着更高的记录灵敏度.并且通过研究文中得到的记录灵敏度的解析表达式,发现灵敏度与晶体浅能级上可激发离子数密度和泵浦光光强成正比.此外,采用较短波长的泵浦光和更大深能级数密度的晶体是另两种改变晶体灵敏度的方式. 相似文献
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Cerium‐doped lithium gadolinium borate (Li6Gd(BO3)3:Ce) single crystal has been grown by the Czochralski method. Some problems like macro defects and concave growth face were found. The macro defects are suggested to be caused by constitutional supercooling and concave growth face is caused by interface inversion. These problems can be resolved or eliminated through controlling the growth parameters strictly. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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移动加热器法(THM)生长碲锌镉晶体时,界面稳定性对晶体生长的质量有很大影响。本文基于多物理场有限元仿真软件Comsol建立了THM生长碲锌镉晶体的数值模拟模型,讨论了Te边界层与组分过冷区之间的关系,对不同生长阶段的物理场、Te边界层与组分过冷区进行仿真研究,最后讨论了微重力对物理场分布的影响,并对比了微重力与正常重力下的生长界面形貌。模拟结果表明,Te边界层与组分过冷区的分布趋势是一致的,在不同生长阶段,流场中次生涡旋的位置会发生移动,从而导致生长界面的形貌随着生长的进行发生变化,同时微重力条件下形成的生长界面形貌最有利于单晶生长。因此,在晶体生长的中前期,对次生涡旋位置的控制和对组分过冷的削弱,是THM生长高质量晶体的有效方案。 相似文献
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The effect of melt convection on the formation of constitutional supercooling defects was studied simply by changing the shape and size of the Ir crucible. The experimental results show that there is a favourable ratio of crucible diameter d to depth h, i.e. d/h is about 1, and a moderate range of the crystal rotating rate must be avoided to grow a quality Nd: YAG crystal. 相似文献
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The crystallization of ice in aqueous dextrose solutions is studied in an adiabatic continuous stirred tank crystallizer with a supercooled feed stream. The effective diameter of the ice crystals was determined for various values of mean crystal residence time, feed supercooling, magma density, stirring rate, and dextrose concentration. For all process conditions the supercooling was measured at 9-12 different locations in the crystallizer. These local supercoolings were averaged algebraically to yield the bulksupercooling. From the experimental results growth and nucleation rates have been calculated. By comparing the experimental growth rates to growth rates calculated by means of a mathematical model kinetics for the inbuilding of water molecules into the ice lattice have been determined. The growth rate appears to be directly proportional to the interface supercooling. The rate constant decreases exponentially with increasing weight percentage of dextrose in the solution. The nucleation rate was found to be directly proportional to total crystal surface per unit volume of suspension and proportional to the bulksupercooling to the power 2.1. Nucleation is believed to occur by breakage of dendrites from the surface of parent crystals. 相似文献
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On the dependence of the critical crystallization rate on the initial impurity concentration in melt
The dependence of the critical crystallization rate on the initial impurity concentration in melt is derived by determining
the condition at which a nonplanar solution to the stationary diffusion problem arises. It is suggested that the conditions
at which defects arise at the interface differ from those obtained when crystallization becomes stationary. The initial transient
process of binary melt solidification under crystal pulling at a constant rate has been studied numerically within a 1D model.
It is shown that the character of the time dependence of the crystallization rate is determined by the ratio of the crystal
pulling rate to solidification rate V
c, when a constitutional supercooling zone is formed in the melt. 相似文献
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K. Chen M. S. Zhang W. C. Chen Q. Chen 《Progress in Crystal Growth and Characterization of Materials》2000,40(1-4):43-50
Raman scattering and photoinduced light scattering in Co-, Cr- and Fe-doped lithium niobate were examined. The A1(TO) modes appear in E symmetry spectrum of the doped lithium niobate. Their intensities vary with different dopings. In the spectrum of z(yy)x geometry, the properties of the lowest-frequency E(TO) mode of the Cr-doped lithium niobate are different from those of pure, Co- and Fe-doped lithium niobate. The intensity of the A1(TO) mode at 637cm-1 I is decreased in doped lithium niobate compared with the pure crystal. We attribute these properties to both the photorefractive effect which is enhanced by dopants and to the different occupation of the doping ions. A light climbing effect was observed in Co- and Cr-doped lithium niobate for the first time. A higher photodamage threshold and quicker light climbing speed were found in Co- and Cr-doped lithium niobate in comparison with the light climbing effect in the Fe-doped lithium niobate. The results from the photoinduced light scattering experiments were compared with those from a Raman spectroscopic study. 相似文献