采用改进的温梯法生长氟化钙晶体

CALCIUM FLUORIDE CRYSTAL GROWTH WITH IMPROVED TEMPERATURE GRADIENT TECHNIQUE

对现有的晶体生长温梯法进行改进,将炉内温场分为坩埚底部温度高于坩埚顶部温度的化料区和坩埚底部温度低于坩埚顶部温度的温梯生长区两部分。通过对坩埚相对于温场位置的控制,获得适宜进行熔体均一化和晶体生长条件。生长了尺寸为φ135mm×150mm氟化钙(CaF2)晶体,生长的CaF2晶体质量较好,位错密度<330/mm2,从190nm到9000nm透过良好,紫外200nm处和红外9μm处透过率可达80%以上。

The temperature gradient technique （TGT） for crystal growth was improved. The temperature field in a furnace was divided into two zone： in the melting zone, the temperature of the crucible＇s bottom is higher than the crucible＇s top; conversely, in the temperature gradient growth zone, the temperature of the crucible＇s bottom is lower than the crucible＇s top, similar to traditional TGT. Controlling the relative position of the crucible according to the temperature field causes the melt to become homogenous and provides good crystal growth conditions. Calcium fluoride （CaF2） crystals with a size of 4,135 mm×150 mm having higher quality grown by the improved TGT. The dislocation density in CaF2 crystal is lower than 330/cm^2. The crystal has a good transmissivity from 190to 9000nm. In the ultraviolet band, the transmissivity of the crystal is above 80% at 200nm, and above 80% at infrared band 9 μm also.