Effect Of The Thermal Field Structure On The Crystal Growth Of Kyropoulos Sapphire

With the continuous development of high technology in the high-tech fields such as space,military and scientific research.has greatly promoted the demand for sapphire crystals.Kyropoulos method is one of the main manufacturing methods of sapphire crystal.During the growth process of sapphire crystals,the flow field and thermal field are affected by the thermal field structure.At the same time,there are problems with long time and high energy consumption.The method of combining numerical simulation with experiment is important to obtain high quality sapphire crystals at low cost.In this paper,the growth theory of sapphire crystal is summarized,and the main growth problems in sapphire growth process are analyzed.The model is a 60kg grade sapphire single crystal furnace used in actual production,established physical and numerical models of crystal growth.In this paper,the commercial CGSim software has been employed to analyze the heat field structure and compared with the experimental results,and comes to the conclusions as follows.(1)Adding zirconia insulation layers will reduce the single crystal furnace energy consumption.However,the built-in oxidation hopper structure presents an obvious effect on the energy consumption of single crystal furnace.(2)With the increase of the number of zirconia layers,the energy consumption of the single crystal furnace is greatly reduced,15-layer zirconia insulation structure furnace power reduced by 38%compared with the traditional 15-layer molybdenum insulation structure,the power change of single crystal furnace tends to be gentle after adding zirconia to 7 layers.(3)The power consumption of growth furnace is obviously improved with the increase of heat-shield spacing,and cause the solid-liquid interface convexity increased,as well the Von-Mises stress decreased.Consideration of the Heat-shield Spacing effects of heat-shield spacing on the power consumption,solid-liquid interface shape and crystal thermal stress,the optimal heat-shield spacing was determined as 5mm.(4)By comparing the results of numerical simulation with the results of specific growth experiments,The rationality of the design optimization of the thermal field structure is verified.After improving the single crystal furnace in accordance with the simulation method,we basically avoided the remelting phenomenon during growth,it reduced bubbles and other defects.Finally,sapphire single crystals with good diameter and no optical scattering were obtained.