采用FLUENT软件对分离结晶Bridgman法生长CdZnTe晶体进行了全局数值模拟.模拟对象为:熔体上部边界条件分别为固壁和自由表面时两种晶体生长系统.重点考虑坩埚和晶体之间狭缝宽度e和重力对分离结晶过程的影响.在计算中分别取e=0 mm、0.5 mm和1 mm三种狭缝宽度,得到了在微重力和常重力条件下的温度分布、结晶界面形状以及流函数分布图.结果表明:在微重力条件下,当熔体上部为固壁时,随着狭缝宽度的增大,热毛细力作用增强,流动强度增强;当熔体上部为自由表面时,则与之相反.在常重力条件下,由于浮力-热毛细对流的共同作用,随着狭缝宽度的增加,流动强度逐渐减弱,有助于提高晶体生长质量.
CdZnTe single crystal growth process with detached vertical Bridgman method by FLUENT was simulated. Two kinds of boundary condition of the upper melt were calculated: (1)non-slip wall;(2) free surface. The gap width (e) between the crucible wall and crystal and gravity were the two key factors for the crystal growth process. The temperature distribution, stream function distribution and the solidification interface shape were displayed and analyzed both in the microgravity and the gravity condition with e equals to 0 mm, 0.5 mm and 1 mm, respectively. The simulation results showed that in the microgravity condition, when the upper of melt is non-slip wall, the flow strength of thermocapillary convection increases with the wider gap width. However, when the upper of melt is free surface, the flow strength shows the opposite trend with the increase of the gap width. In the gravity condition, the flow strength decreases with the increase of the gap width, which will improve the crystal quality.
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