真空度对泡生法蓝宝石晶体生长环境的影响

摘要

It is not necessary to grow sapphire crystals by the Kyropoulos method under ultra-high vacuum.Increasing the vacuum degree to below 10-1 Pa cannot improve obviously the heat efficiency of the Kyropoulos furnace for sapphire growth.A lower vacuum degree is helpful for the cooling of sapphire after power off.A high degree of vacuum efficiently prevents the tungsten heater and the thermal shield,made of tungsten and molybdenum,from oxidization.However,it aggravates the evaporation of molten Al2O3 deposited on thermal parts and deteriorates the environment in the thermal field,shortening the life span of thermal parts.An ultra-high vacuum degree will lead to the sublimation of tungsten and molybdenum in Kyropoulos furnace and therefore shorten the life span of thermal parts.The use of an inert gas fill the furnace in order to achieve a lower vacuum degree can protect furnace elements from oxidization and restrain the evaporation of molten Al2O3 so as to keep the field clean at the same time.%指出对泡生法蓝宝石晶体生长,无需采用过高的真空度.炉内真空度达10-1 Pa级时,进一步提高真空度对长晶炉热效率影响不大,较低的真空度有利晶体在出炉前低温段的冷却.研究表明,尽管高真空度可以有效防止热场中钨/钼材料的氧化,但真空度过高容易导致钨钼材料的升华损耗；真空度越高,原料三氧化二铝熔体蒸发越甚,导致热场零部件污染越严重,从而缩短热场零部件的使用寿命；采用惰性气体保护可以在较低真空度下防止热场中钨钼件氧化,同时抑制熔体蒸发、保持热场洁净并延长热场使用寿命.