Tungsten Crucible for Crystal Sapphire Growth

Single crystal sapphire is playing an ever-increasingly important role as a vector for high reliability electronics today which belongs to synthetic crystal. Thanks to a good optical permeability, thermal conductivity and mechanical properties, single crystal sapphire is mainly applied to wear resistant elements, window materials and electronics devices. With the rapid development of science and technology, the demand for single crystal sapphire is rising. As a necessary vector for single crystal sapphire growth, the quality of tungsten crucible will directly determine the outcome of sapphire crystal growth.

Manufacturing technologies for sapphire crystal include Flame Fusion, Czochralski, Heat Exchanger method, Kyropoulos, Bridgman-Stockbarge method, Edge Defined Film, Vertical Horizontal Gradient Freezing.

Czochralski: First of all, put the polycrystalline material which has been prepared before in tungsten crucible, heat them to above 2050 ℃ and the raw material will be melted into flux. There are some seed crystals under the lift rod of the tungsten crucible. Reducing the lift rod to make seed crystals insert flux, at an appropriate temperature circumstances, and the seed is in a fixed state then pulling up it in a certain rate. Heat exchanger method is to put seed crystals at the bottom of the tungsten crucible, through controlling the flow of helium gas of the tungsten crucible bottom to ensure that seed can keep in a cold condition. After all the tungsten crucible material being melted, increase the flow of helium gas, so that the solid liquid interface moves upward.

Bridgman-Stockbarge method is to put a seed in bottom of tungsten crucible, after all the raw materials being melted, welding the seed crystal and the melt. And then crystal would obtain a temperature gradient through moving the high temperature zone and low temperature zone of tungsten crucible. Finally, solid-liquid interface move upward to finish sapphire crystal growth.

Tungsten crucible applied in sapphire single crystal growth furnace can avoid sticking the pan when sapphire crystal growth. The internal wall and external wall of tungsten crucible are smooth without any crack which can greatly improve the efficiency sapphire crystal growth.

On the other hand, due to the high melting point 3410 ℃of tungsten, the tungsten crucible is widely used as the core container in sapphire growth furnace, quartz glass melting furnace, rare earth smelting furnace and other industrial furnace.

• < Prev
• Next >