CrownRe`s high purity alumina, purity up to 99.99995， could grow to be high quality sapphire crystal materials,which are widely used in electronic, automotive, optic glass etc.

So-called “sapphire glass” refers to crystalline sapphire used as an optical window or cover. Some windows are made from pure sapphire boules that have been grown in a specific crystal orientation, typically along the optical axis, the c-axis, for minimum birefringence for the application. The boules are sliced up into the desired window thickness and finally polished to the desired surface finish. Sapphire optical windows can be polished to a wide range of surface finishes due to its crystal structure and its hardness. The surface finishes of optical windows are normally called out by the scratch-dig specifications in accordance with the globally adopted MIL-O-13830 specification.

Sapphire windows were to be used in Apple’s iPhone 5s, iPhone 6 and iPad mini 3 but those products were released with Gorilla Glass screens instead. Two of the Apple watch models’ screens are made from sapphire.

The sapphire windows are used in both high pressure and vacuum chambers for spectroscopy, crystals in various watches, and windows in grocery store barcode scanners since the material’s exceptional hardness and toughness makes it very resistant to scratching.

It is used for end windows on some high-powered laser tubes as its wide-band transparency and thermal conductivity allow it to handle very high power densities in the infra-red or UV spectrum without degrading due to heating.