| As a kind of optical window material, sapphire crystal has become popular in thefields of aerospace and military with its excellent optical properties, mechanicalproperties and chemical stability. Currently,the growth of sapphire by the Kyropoulos iswidely used. Kyropoulos crystal growth process ensures the growth of high qualitysingle crystal sapphire, and the thermal fields determine the quality of the crystalgrowth. In this paper, sapphire crystal growth thermal fields influenced by the up, down,side heat shield and the heater from the crucible, and the heater power allocation basedon the inner structure in the furnace of35kg Kyropoulos sapphire crystal growth, arediscussed using CGSim softwre, including melt flow field and temperature distribution,S/L interface gradients and Von Mises stress.The results show that sapphire growththermal fields are strongly influenced by the position of the heater and the heater powerallocation. Next, the paper analyzes the reason of the Kyropoulos85kg sapphire failuregrowth, such as remelting and polycrystalline, impurities and bubbles, fracture. Thenthe paper studies the thermal fields of85kg sapphire growth by Kyropoulos using theCGSim software, and obtains the conclusions that remelted and polycrystalline is due totwo or more independent vortex in the melt convection causing uneven melt density andgrowth uncoordinatly; impurities and bubbles in the crystal are due to the temperaturegradient causing the S/L interface lower; fracture in the crystal is due to the highthermal stress. At last, the paper makes the structure optimization of85kg Kyropoulossapphire furnace, and obtains a kind of ideal furnace, which can improve the thermalfields of the crystal growth, including the better fluid flow field and temperature field,gradients and Von Mises stress, then designs an experimental to produce sapphire cystalof better quality with the modified furnace successfully. |
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