直径210mm氟化钙晶体的生长

Diameter 210mm Calcium Fluoride Crystal Growth

采用Bridgman-Stockbarger法生长出直径为210mm的氟化钙晶体。透过率在紫外200nm处接近80%,红外透过率良好,可使用到9μm。通过对原有生长设备的改进,采用更为先进的温控设备和合理的温场控制条件,使生长区温场径向梯度小于0.5℃/mm,轴向生长温度梯度2～3℃/mm。整个生长过程分为:升温化料、熔体均一化、下降坩埚生长和初步退火过程,初退火温度为950℃,退火降温速率为15℃/h。

Diameter 210mm calcium fluoride crystal has been grown by Bridgman- Stockbarger method. In order to grow the crystal we have approved the equipment. The transmittance of the grown crystal at 200nm is about 80% in ultraviolet band, and the grown crystal can be used up to 9μm because of the good transmittance in infrared band. We used the more advanced temperature controller and made a more suitable temperature field condition. The radial gradient of temperature field was below 0.5℃/mm and axial gradient of temperature field was within 2-3℃/mm at the growing zone. The whole growing processes included raising temperature and melting, homogenate of melt, pulling the crucible and growing, and primary annealing. The annealing temperature was 950℃ and temperature descending rate was 15℃/h.