微下拉法晶体生长全局数值模拟

发布时间：2018-02-26 15:24

本文关键词： 微下拉法晶体生长感应加热全局模拟　出处：《重庆大学》2016年硕士论文　论文类型：学位论文

【摘要】：本文基于有限体积法对微下拉法生长YAG晶体进行包括感应加热在内的全局数值模拟,并分析各参数对生长炉内温度场和坩埚产热的影响。建立微下拉法晶体生长全局数学物理模型,模型中耦合了感应加热、气体与熔体对流以及固液气三相的热输运,熔体中对流同时考虑浮力与表面张力作用。为统一使用有限体积法离散控制方程,采用复函数法求解电磁场,并与流函数法对比验证了程序的正确性。并分析了整个生长炉内的温度场和流场(包括气体和熔体)分布。由于晶体结晶速率主要受固液交界区温度梯度影响,尤其是轴向温度梯度。为优化晶体生长炉结构,本文详细分析了线圈轴向和径向位置、线圈匝数、通入线圈交流电大小和频率大小以及改进后热器材料对固液交界区温度分布和温度梯度的影响。结果表明:(1)随着线圈向上移动,固液交界区温度降低,固液交界区轴向温度梯度增大。随着线圈径向距离增大,固液交界区温度降低,而固液交界区轴向温度梯度变化并无明显规律,当线圈径向位置为80和85mm时,轴向温度梯度明显增大。随着线圈匝数减小,固液交界区温度降低。线圈匝数为4匝和6匝时,坩埚上的有效感应区面积太小,产热效率太低。(2)当后热器材料采用与保温层相同的氧化锆时,与原始模型相比温度梯度增大,但此时固液交界区的温度降低。当不采用后热器装置时,温度梯度明显增大,但此时温度大幅下降,加热效率非常低,需增大线圈中通入的电流大小。(3)当电流数值增大,炉内温度最大值随之近似线性增长,浮区温度也均匀增长。电流频率增大,炉内温度最大值随之而增大。频率为1kHz-10kHz时,温度急速增大。而频率为20kHz-100kHz时,温度增大平缓。电流频率范围为10kH-20kHz时加热效率最高。本文所建模型能较真实地反映微下拉法的实际晶体生长环境,为优化晶体生长炉结构和生长工艺提供参考。
[Abstract]:Based on the finite volume method, the global numerical simulation of YAG crystals grown by micro-pull-down method, including induction heating, is carried out in this paper. The effects of various parameters on the temperature field and crucible heat generation in the growth furnace are analyzed. A global mathematical and physical model for crystal growth by micro-pull-down method is established. The model is coupled with induction heating, gas and melt convection, and the thermal transport of solid-liquid gas. Both buoyancy and surface tension are considered for convection in melt. In order to discretize the governing equation with finite volume method, the complex function number method is used to solve the electromagnetic field. Compared with the flow function method, the program is proved to be correct. The temperature field and the flow field (including gas and melt) in the whole furnace are analyzed. The crystal crystallization rate is mainly affected by the temperature gradient at the solid-liquid junction. Especially the axial temperature gradient. In order to optimize the structure of crystal growth furnace, the axial and radial positions of the coils and the number of turns of the coils are analyzed in detail in this paper. The effect of AC current and frequency on the temperature distribution and temperature gradient at the solid-liquid junction is studied. The results show that the temperature at the solid-liquid junction decreases with the moving of the coil. The axial temperature gradient at the solid-liquid junction increases with the increase of the radial distance between the coils, but the axial temperature gradient at the solid-liquid junctions does not change regularly. When the radial position of the coils is 80 mm and 85 mm, the axial temperature gradients of the solids and liquid junctions decrease with the increase of the radial distance of the coils. The axial temperature gradient increases obviously. With the decrease of the number of coils, the temperature at the solid-liquid junction decreases. When the number of coils is 4 turns and 6 turns, the effective induction area on the crucible is too small. The thermal efficiency is too low. (2) when zirconia with the same insulation layer is used, the temperature gradient increases compared with the original model, but the temperature at the solid-liquid junction decreases. When the rear thermostat is not used, the temperature gradient increases obviously. However, when the current value increases, the maximum temperature in the furnace increases linearly, and the temperature in the floating zone increases uniformly, and the current frequency increases. The maximum temperature of the furnace increases rapidly when the frequency is 1kHz-10kHz, and the frequency is 20kHz-100kHz. The heating efficiency is the highest when the current frequency range is 10kH-20kHz. The model in this paper can reflect the actual crystal growth environment of micro-pull-down method and provide reference for optimizing the structure and technology of crystal growth furnace.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：O782

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