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温度梯度法(temperature gradient technique,TGT)生长的Al_2O_3晶体因石墨发热体在高温时的挥发和原料中过渡性金属离子的存在,在不同部位呈现不同颜色,一般上部为浅红色,尾部为浅黄绿色.将TGT法生长的Al2O3晶体(110×80mm3)依次经过高温氧化气氛、高温还原气氛脱碳、去色退火实验,即“两步法”退火实验,晶体变成无色、透明.经测试,Al2O3晶体的完整性、光学透过率和光学均匀性均有显著提高.
Al_2O_3 crystal grown by TGM (temperature gradient technique) is different in color due to the volatilization of graphite heating element at high temperature and the presence of transitional metal ions in the starting material. The upper part of the Al_2O_3 crystal generally has a light red color at the upper part and a light yellowish green at the tail part The Al2O3 crystal (110 × 80mm3) grown by TGT method was subjected to a high temperature oxidation atmosphere followed by decarbonization in a high temperature reducing atmosphere and a color removal annealing experiment, ie a “two-step” annealing experiment, in which the crystals became colorless and transparent. , Al2O3 crystal integrity, optical transmittance and optical uniformity are significantly improved.