Sapphire Crystal Growth Furnace Process

sapphire crystal growth furnace

(1)Sapphire Introduction

Also known as α-Al2O3 single crystal sapphire , commonly known as corundum , is a simple ligand type oxide crystals. Sapphire crystal has excellent optical properties, mechanical properties and chemical stability , high strength, hardness, resistance to erosion, close to 2000 ℃ high temperature in the harsh conditions of work , which is widely used in military infrared devices , satellite space technology , high-intensity laser window material. Its unique lattice structure , excellent mechanical properties, good thermal properties make sapphire crystal as the practical application of semiconductor GaN/Al2O3 light-emitting diode (LED), LSI SOI and SOS and nanostructured superconducting films such as the most ideal substrate material . Low-cost, high-quality large-size sapphire single crystal growth has become an urgent task facing .

Sapphire Dan Changjing Furnace

Sapphire crystal growth method can be divided into solution growth , melt growth , the growth of three kinds of gas , which has a melt growth method due to fast growth rate , high purity and crystal integrity and good features, but is preparing to become a large size and a specific shape crystal the most common way of crystal growth . Currently available to melt growth method to artificial sapphire crystal growth methods include melting flame method , Czochralski method , zone melting method , the crucible moving method, heat exchange, the temperature gradient and Kyropoulos law. However, these methods have their own shortcomings and limitations , is more difficult to meet the future large-size sapphire crystal , high-quality, low-cost development needs. For example, the melting flame method , Czochralski method , zone melting crystal growth methods such as quality and size are limited , it is difficult to meet the performance requirements of optical devices ; heat exchange method, temperature gradient and Kyropoulos grown sapphire and other methods large crystal size , better quality , but requires a lot of heat exchange of helium as a coolant , the temperature gradient method, the foam raw sapphire crystal ingot grown by a high temperature annealing required , subsequent processing of the blank process more complicated and costly .

(2)Micro-Pulling Rotation Kyropoulos Prepared Sapphire Crystal Craft

Micro- pulling rotation Kyropoulos prepared on sapphire crystal method Kyropoulos and improved Czochralski method developed on the basis for the growth of large-size sapphire crystal method , mainly in Ukraine Donets produced Ikal-220 crystal growth furnace based on the improvement and development. Crystal growth system mainly comprises a control system, vacuum system , heating element , cooling systems and thermal protection systems. Micro- pulling rotation Kyropoulos large sapphire crystal growth technology mainly through the regulation of heat transport within the system to control the entire crystal growth process, so the heating body and the thermal protection system design, the choice of the working fluid heat exchanger , heat ability to design, crystal growth rate , cooling rate and other process control problems of high quality can grow sapphire crystals are essential.

Micro- pulling rotation Kyropoulos prepared sapphire crystal growth equipment catchment , electricity and gas in one , mainly by the energy supply and control system , transmission system , the crystal growth chamber , vacuum system , cooling system and other ancillary equipment and other components. Transmission as a seed rod ( heat exchanger) pulling and rotating movement of the guide and drive mechanism is connected with the column top of the furnace tube , the main by the seed rod ( heat exchanger) for lifting , rotating device component. Pulling gear from the seed rod ( heat exchanger ) of fast and slow lift system composed of two parts . Seed rod ( heat exchanger ) system consists of a slow lifting magnet DC torque motor , precision ball screw through harmonic reducer and connected by rolling linear guide rail , drag the slider to achieve seed rod ( heat exchange device ) in the slow process of pulling down movement . Seed rod ( heat exchanger ) quick lift system by the fast servo motor via a worm on a harmonic reducer , worm gear and harmonic linkage implementation. Seed rod rotary motion by a rare earth permanent magnet servo motor through the wedge belt drive implementation. The drive has a high positioning accuracy , load capacity , speed, stable, reliable, no vibration, no crawling and so on. Precision heating , which is simple to operate , easy to control characteristics. In the thermal protection system, the design is capable of regulating the atmosphere insulation cover , radiation resistance, thermal insulation layer of small thermal conductivity , thermal stability, long-term work not the dregs , can not afford leather , with a pair of crystal growth of environmental pollution small , easy to clean and so on. Optional molybdenum crucible and crystal growth according to the design dimensions , the design quality of the inner diameter of the crucible , the net depth , thickness and other geometric dimensions , each furnace can be prepared maximum D200mmX200mm, 25Kg weight sapphire single crystal . Al2O3 raw purity of raw materials used in crystal growth 5N high purity alumina powder prepared by flame or melt broken sapphire crystal .

Crystallization from the melt synthetic gemstones is the basic process : raw material powder melting → ​​cooling → ​​heating → ​​→ → exceeds the critical undercooling crystallization .

99.99% purity alumina powder is added an organic binder , the green body is formed in the press ; first state of the body previously fired alumina semi block burn into the furnace , the furnace was evacuated exhaust impurity gas , has started mechanical pump , diffusion pump , vacuum to 10 ↑ [-3] -10 ↑ [-4] Pa, when the furnace temperature of 1500-1800 ℃ filled with protective gas mixture , continue to heat up to the set temperature (2100 - 2250 ℃); (3) furnace temperature reached the set temperature , the heat 4-8 hours , adjust the position of the furnace temperature and the crucible and the seed crystal at the top of the raw material melt to achieve inoculation growth , the temperature gradient of the solid-liquid interface is set at 10 - 50 ℃ / cm, until the end of the crystal growth , in-situ annealed.