Development Of Thermal Field Measurement Technology For Sapphire Bubble Crystalline Furnace

With the development of semiconductor lighting industry in recent years, the demand of the sapphire substrate is increasing rapidly. With the advantages of excellent mechanical and optical properties, there is a huge market for the application of sapphire single crystal in LED light source. Consequently, the demand of sapphire crystal growth equipment is growing. Though the current widespread Kyropoulos technique of growing sapphire single crystal is mature, the thermal field of the growth furnace crucible cannot be real-time measuring, and the temperature gradient cannot be optimized. Thus the yield does not improve a lot, leading to high production cost. Besides, how to produce sapphire single crystals with large size, low cost and high quality has been the emphasis and difficulty of the sapphire growth technology. Therefore, in order to improve the furnace heating field and then to improve the quality of crystal, a new method to measure the sapphire crystal growth furnace is urgently needed.The present paper, with the basic theoretical knowledge of blackbody radiation, analyzes the two mainly used methods in the infrared radiation temperature measurement technology:monochromatic method and colorimetric method. By measuring the thermal field in the crystal furnace with traditional infrared thermometer, and with the help of thermal field simulation, the feasibilities of two methods are compared. And then a suggestion on setting a temperature measurement system, which is simple in structure, precise in temperature measurement and cheap in price, and can be used for the thermal field measurement of the sapphire crystal growth by the Kyropoulos technique, is put forward. This paper designs and produces a radiation thermometry system utilizing portable optical fiber. The system is made up by a high-power fiber coupler, power delivery fiber, photoelectric detector, preamplifier module, ADC module and the signal processing module etc. In the paper, the role of each module and data processing method of the system are specifically described, and performance of the system is verified.The research shows that the radiation thermometry system utilizing portable optical fiber introduced in the paper is stable in function and reliable in precision, and its measurement range is suitable for sapphire growth process. The system, with advantages of portability, ease of use and accuracy of measurement, can be used for the thermal field measurement of the sapphire crystal growth by Kyropoulos technique.