ACRT过程中的温度变化与测量

TEMPERATURE VARIATION AND MEASUREMENTS DURING ACRT PROCESS

ＡＣＲＴ是一种新型的晶体生长技术，已成功地制备了一些优良的功能材料作者利用自制的测温装置，测量了ＡＣＲＴ过程中的温度变化结果表明：ＡＣＲＴ过程中液相保持时间明显延长，生长界面前沿的温度梯度极大提高．

CRT (Accelerated Crucible Rotation Technique) is a newly developed functional crystal growth technique and has been successfully employed to grow some functional crystals of superior quality, such as antiferromagnetic semiconductor MuTe, IR crystal CMT, ferroelectric oxide-peroviskite KNbO3. But there still remain many important aspects untouched. In the paper, the temperature distribution during ACRT process was first measured accurately by a specially designed set up. It has been shown that the slip ring / carbon brush structure with a magnifying electric circuit and an aid-thermocouple is very suitable for the temperature measurement of a rotation system. The results indicate that liquid phase can remain much longer time for ACRT process than non-ACRT process, and that the temperature gradient G ahead of the growth interface can be greatly increased during ACRT process. For a given angular acceleration α, the greater the rotation speed Ω(max), the steeper the temperature gradient; for a given rotation speed, the larger the angular acceleration, the steeper the temperature gradient. In our experiments, G=2902℃ / mm for non-ACRT process. Ifα=25rpm / s and Ω(max) is increased from 100 to 400 rpm, G can be enhanced from 3400 to 4693℃ / mm; if Ω(max)=400rpm and α is increased from 25 to 100rpm / s, G can be increased from 4693 to 4921℃ / mm. The main reasons for the above variations are as follows: (1) Spiral shear flow and Couette flow in the liquid greatly speed up the thermal transportation rate, (2) Ekman laminar flow ahead of the growth interface seriously compresses the thermal boundary layer.