Kyropoulos Method Of Large-size Single-crystal Sapphire

Because of its excellent physical and chemical properties, sapphire crystal has become the first choice for the LED substrate, high-grade watches, smart watches and wearable electronics products. It is interesting to study the growth procedure of large size and high quality sapphire crystal. With the development of LED and consumer electronics market, the demand for high quality sapphire is greatly increased.In this paper, the Kyropoulos sapphire crystal growth procedure was studied and sapphire single crystal was characterized. There are four problems with the 60 kg crystal: high cracking rate; bubble; crystal lower part remelting; small diameter. The results of the experiments show that the following two methods can effectively solve the problem that the remelting of the lower part of 60 kg crystal and the bubble in the bottom:(1) moving the 5?6 tungsten hoop to the 7 position,(2) increasing the crystal growth rate in the middle and late stages, and reducing the crystal growth rate in the final phase of the crystal.Modeling the 60 kg temperature field by sapphire crystal growth simulator CGSim. There were two problems in shouldering:(1) crystal growth angle was too small and the crystal shape was irregular;(2) three eddies was in melt. Which make the bubbles hard to discharge. The temperature of the solid liquid crystal surface became not stable by those eddies, which leads to crystal cracking. In view of the above problems, we updated the temperature field. The radial size of new temperature field increased by 40mm; the crystal growth angle is 45 degrees; melt flow rule, only a large vortex in the melt in shouldering.Using infrared thermometer and platinum rhodium thermocouple wire to measure the temperature of the crystal during annealing. In the early stage of annealing, the cooling rate was very low; in the middle stage, the cooling gradually become faster; in the late stage, the cooling rate was high. In view of the characteristics of this cooling, combined with the nature of sapphire, the three stage annealing process is proposed, which successfully solves the problems of large stress, easy cracking and so on. And this annealing process can shorten the growth period of the crystal.We're building seeding observation system. The system can quantitatively analyze seeding, guarantee seeding quality, reduce the dependence of crystal seeding workers and the difficulty of sapphire growth by Kyropoulos method.