Characteristic of Tungsten Crucible for Sapphire Growth

Sapphire single crystal growth furnace often works with wolfram products which produce production by 99.95% purity of tungsten raw materials, including wolfram crucible, wolfram plate, wolfram sheet, wolfram electrode shield, wolfram tube, wolfram heat shield and other wolfram products. Thanks to the highest melting point of all metals, wolfram crucible is widely applied in sapphire single crystal growth furnace.

It is uncommonly to use wolfram crucible itself as the heating element for single crystal growth furnace, and wolfram crucible would volatize wolfram atoms at high temperatures. It is also possible to adopt wolfram crucible itself as a heat element, but the choice of the manufacturing process and the setting of operation temperature are the most critical factors. Due to differences in manufacturing process of wolfram crucible, sapphire single crystal growth furnace generally use sintering tungsten crucible in China.

Characteristic of tungsten crucible for sapphire growth is that wolfram crucible can avoid sticking the pot. During the process of sapphire single crystal growth, it is easy to stick the pan, but wolfram crucible is high temperature resistant refractory metal which is difficult to produce the chemical reaction. So wolfram crucible can protect purity of sapphire well. Sapphire growth by kyropoulos method requires for a better temperature field device, the quality of spinning wolfram crucible is excellent, the purity and density is relatively high, but prices are high.

On the other hand, wolfram crucible cannot be placed immediately on a cold metal table after heating, otherwise it will crack. Most of the thickness of the wolfram crucibles are relatively thin which is not conducive to long-term using, the number of reusing is poor which will increase the cost of sapphire single crystal growth.

As an important technology, sapphire crystal has been widely used in many fields of science and technology, defense and civilian industries, electronic technology. Chemical properties of sapphire crystal are very stable which would not dissolve in water. In addition,  it would not corroded by acid and alkali, only at a higher temperature (300 ℃) can it be corroded by hydrofluoric acid, phosphoric acid and molten potassium hydroxide eroded. Therefore, the choice of wolfram crucible for a sapphire single crystal growth furnace should base on the manufacturing process of sapphire single crystal and the conditions of single crystal sapphire single crystal growth furnace.