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Combined effects of crucible geometry and Marangoni convection on silicon Czochralski crystal growth
F. Mokhtari A. Bouabdallah M. Zizi S. Hanchi A. Alemany 《Crystal Research and Technology》2009,44(8):787-799
In order to understand the influence of crucible geometry combined with natural convection and Marangoni convection on melt flow pattern, temperature and pressure fields in silicon Czochralski crystal growth process, a set of numerical simulations was conducted. We carry out calculation enable us to determine temperature, pressure and velocity fields in function of Grashof and Marangoni numbers. The essential results show that the hemispherical geometry of crucible seems to be adapted for the growth of a good quality crystal and the pressure field is strongly affected by natural and Marangoni convection and it is more sensitive than temperature. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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由于Nd3 离子半径0.112nm和Y3 离子半径0.101nm相差10.9%,使得Nd3 离子非常难于进入YAG晶体中。我们用温度梯度法生长了大尺寸高浓度(2.8 at%)的Nd:YAG晶体,同时与用提拉法Nd:GGG晶体进行了比较。分析了高浓度掺杂Nd:GGG和Nd:YAG晶体浓度猝灭问题。研究了不同浓度掺杂的猝灭效应。在同样的掺杂浓度下,我们发现它们的猝灭程度不同,其原因是两种晶体中ΔE(m is-)m和ΔE(m i s )m不同。 相似文献
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Nd∶NaY(WO4)2激光晶体生长 总被引:7,自引:0,他引:7
采用提拉法生长出了四方晶系白钨矿结构的Nd:NaY(WO4)2(简称Nd∶NYW)激光晶体,尺寸为20mm×30mm.通过TG-DTA差热分析得到晶体的熔点为1211℃,从XRD分析得到晶胞参数为a=b=0.5212nm ,c=1.1268nm ,晶胞体积V=0.3062nm3.讨论了Nd∶NYW晶体的生长工艺,给出了晶体生长的最佳工艺参数.通过比较Nd∶NaBi(WO4)2(简称Nd∶NBW)和Nd:NYW的XRD、红外光谱和拉曼光谱测试结果,认为二者结构基本相同,为四方晶系白钨矿结构、I(4)空间群. 相似文献
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In this paper, photorefractive properties of Mg:Ce:Cu:LiNbO3 crystals were studied. The crystals doped with different concentration of Mg ions have been grown by the Czochralski method. Mg concentrations in grown crystals were analyzed by an inductively coupled plasma optical emission spectrometry (ICP‐OE/MS). The crystal structures were analyzed by the X‐ray powder diffraction (XRD), ultraviolet‐visible (UV‐Vis) absorption spectra and infrared (IR) transmitatance spectra. The photorefractive properties of crystals were experimentally studied by using two‐beam coupling. In this experiment we determined the writing time, maximum diffraction efficiency and the erasure time of crystals samples with He‐Ne laser. The results showed that the dynamic range (M/#), sensitivity (S) and diffraction efficiency (η) were dependent on the Mg doping concentration, and the Mg(4.58mol%):Ce:Cu:LiNbO3 crystal was the most proper holographic recording media material among the six crystals studied in the paper. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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L. Lipiska W. Ryba‐Romanowski A. Rzepka S. Ganschow R. Lisiecki R. Diduszko A. Pajczkowska 《Crystal Research and Technology》2009,44(5):477-483
The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neodymium were investigated. Nanopowders of GGG:Nd were prepared by modified sol‐gel method using acetic acid as complexing agent. This way permitted to incorporate large amounts of dopant (up to 10 %) without destroying garnet structure. Small single crystals of Nd:GGG were grown by a μ‐pulling down method and spectroscopic features of nanopowders and their single crystal counterparts were compared. It has concluded that the Nd3+ ions are located preferentially in the same type of sites in crystal lattices of GGG:Nd nanopowders and their single crystal counterparts. In addition, it follows from the perfect agreement of emission wavelengths and line width recorded for nanopowders and single crystal samples that the crystal lattice of GGG in nanopowders is not distorted. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Jiecai Han Huaixin Guo Mingfu Zhang Ningning Song Chenghai Xu 《Crystal Research and Technology》2012,47(5):485-490
Nd3+‐doped Y3Al5O12 single crystals have been grown by the horizontal directional solidification (HDS) method in different thermal zone. The Grashof (Gr), Prandtl (Pr), Marangoni (Ma) and Rayleigh (Ra) numbers of melt in HDS system have been discussed for our experimental system to understand the mechanism of melt flow patterns and concentration gradient of dopant. The concentration gradient of Nd3+ ions was explained with melt flow processes during crystal growth in different thermal zone, and results indicated that high growth temperature will be helpful for uniformity of dopant in HDS‐grown single crystal. The main microscopic growth defects such as bubbles and irregular inclusions in HDS‐grown Nd:YAG crystals were observed, and the causes were discussed as well. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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F. Mokhtari A. Bouabdallah A. Merah M. Zizi S. Hanchi A. Alemany 《Crystal Research and Technology》2010,45(6):573-582
The effects of several growth parameters in cylindrical and spherical Czochralski crystal process are studied numerically and particularly, we focus on the influence of the pressure field. We present a set of three‐dimensional computational simulations using the finite volume package Fluent in two different geometries, a new geometry as cylindro‐spherical and the traditional configuration as cylindro‐cylindrical. We found that the evolution of pressure which is has not been studied before; this important function is strongly related to the vorticity in the bulk flow, the free surface and the growth interface. It seems that the pressure is more sensitive to the breaking of symmetry than the other properties that characterize the crystal growth as temperature or velocity fields. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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Nd3+:d3Ga5O12晶体的室温吸收光谱和荧光光谱 总被引:1,自引:0,他引:1
用提拉法生长了掺钕的钆镓石榴石(Nd3+:GG)激光晶体.研究了室温下的吸收光谱和荧光光谱性质,分析了Nd3+:GG晶体4F3/2→4I11/2能级跃迁与1.06μm附近的荧光谱线之间的关系.吸收系数、发射系数、荧光寿命分别是4.32×10-20 cm-2,2.3×10-19cm-2, 240μs, 比较了Nd3+∶GGG 和 Nd3+∶YAG 的物理参数,实验表明:d3+∶GGG较Nd3+∶YAG有一系列的优点. 相似文献
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For the seeding process of oxide Czochralski crystal growth, influence of the crucible bottom shape on the heat generation, temperature and flow field of the system and the seed‐melt interface shape have been studied numerically using the finite element method. The configuration usually used in a real Czochralski crystal growth process consists of a crucible, active afterheater, induction coil with two parts, insulation, melt, gas and seed crystal. At first, the volumetric distribution of heat inside the metal crucible and afterheater inducted by the RF‐coil was calculated. Using this heat generation in the crucible wall as a source the fluid flow and temperature field of the entire system as well as the seed‐melt interface shape were determined. We have considered two cases, flat and rounded crucible bottom shape. It was observed that using a crucible with a rounded bottom has several advantages such as: (i) The position of the heat generation maximum at the crucible side wall moves upwards, compared to the flat bottom shape. (ii) The location of the temperature maximum at the crucible side wall rises and as a result the temperature gradient along the melt surface increases. (iii) The streamlines of the melt flow are parallel to the crucible bottom and have a curved shape which is similar to the rounded bottom shape. These important features lead to increasing thermal convection in the system and influence the velocity field in the melt and gas domain which help preventing some serious growth problems such as spiral growth. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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用提拉法沿a轴和c轴成功生长出质量优良的Nd:YbVO4新型单晶.采用HRXRD-D5005型高分辨X射线衍射仪测得晶体的摇摆曲线,可以测得(400)面的半峰宽为70.92″,(004)面的半峰宽为19.80″.测得掺杂浓度为1;原子分数Nd:YbVO4晶体中Nd离子的有效分凝系数Keff为0.54.在298.15~573.15K温度范围内测量了晶体的热膨胀系数,αa=2.6×10-6/K,αb=2.5×10-6/K,αc=8.7×10-6/K;测得比热值为0.45~0.65J/g·K.测量了晶体的热扩散系数a,从而得到了其热导率λ. 相似文献
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As a result of our experimental work of mainly practical importance we established that for LiNbO3 single crystals the Mg and Fe dopants promote spirality whereas decreasing of the pulling velocity strongly reduces the propensity of the system to produce spiralshaped crystals. 相似文献
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P. W. Mokruchnikov 《Crystal Research and Technology》1999,34(9):1169-1173
This paper regards the interaction of free and forced convection in the Czochralski configuration. A relationship between the crystal rotation rate and growth parameters at which the crystallization front remains flat, at which the crystallization front remains almost flat, has been studied. This relationship is compared with experimental data. 相似文献
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Nd:LuVO4晶体的生长及其性能研究 总被引:2,自引:0,他引:2
采用提拉(Czochralski)法生长了Nd:LuVO4晶体.利用液相反应法,以V2O5和NH4OH生成NH4VO3,Nd2O3、Lu2O3和HNO3生成Nd(NO3)3和Lu(NO3)3反应制备多晶料;所生长Nd0.01Lu0.99VO4晶体为16×20×21 mm3,质量超过40g.以X射线荧光分析仪测得其生长中各主要元素的分凝系数.其中Nd3+约为0.91,V3+和Lu3+接近1.还测定了其介电常数ε11=27.2,ε33=33.9(30℃,1kHz),以同步辐射X射线白光形貌术观察了其内部质量. 相似文献