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本文报道了坩埚下降法生长大尺寸白宝石单晶。我们使用大尺寸异型钼坩埚 ,高纯氧化铝原料 ,在中性气氛下 ,结晶区温度梯度为 2 5～ 30℃ /cm ,生长速度为 0 .8～ 1.8mm/h ,生长方向选C面 [0 0 0 1]取向 ,成功生长出直径 80mm ,高度 90mm的完整透明的白宝石单晶 ,在 30 0～ 550 0nm范围内 ,其光学透过率均在 80 %以上。实验中采用高性能保温材料使生长过程所需加热功率由 2 0kW下降到 15kW ,能耗降低达 2 5% ;采用双回路加热系统 ,提高温场稳定性 ,缩短晶体生长周期。晶体的主要缺陷为顶部 (生长后期 )出现有 5～ 10mm淡黄色色带 (经在氧化性气氛中退火后已消除 )和底部有细丝状条纹。
This paper reports the growth of large-sized white sapphire single crystals by the crucible descent method. We use a large-size shaped molybdenum crucible, high purity alumina raw materials, in a neutral atmosphere, the crystallization temperature gradient of 25 ~ 30 ℃ / cm, the growth rate of 0.8 ~ 1.8mm / h, the growth direction of the election C [0 0 0 1] orientation, a completely transparent white crystal of 80 mm in diameter and 90 mm in height was successfully grown. The optical transmittance of the pure white crystal was above 80% in the range of 30 0 ~ 550 0 nm. In the experiment, the high-performance thermal insulation material was used to reduce the heating power required for the growth process from 20kW to 15kW, and the energy consumption was reduced by 25%. The double-loop heating system was used to improve the stability of the temperature field and shorten the growth cycle of the crystal. The main defects of the crystal are the appearance of a 5 to 10 mm light yellow band on top (late growth) (eliminated after annealing in an oxidizing atmosphere) and filamentous streaks on the bottom.