Aluminum oxide (Al2O3) Appearance: colorless transparent pellets or blue half-transparent pellets Density: 3.97 g/cm3 Vapor pressure: 1 Pa at 2000centigrade 10 Pa at2200centigrade Hardness(Mohs hardness): 9 Melting point: 2040centigrade Solubility: non-soluble in water, soluble in acid and alkali Transmittance scope: 200-5000nm Refractive index(500nm): 1.63 Vapour deposition condition: evaporated by electron gun Vapour deposition temp.: 2000-2200centigrade Purity: >99.99% Applications: anti-reflection film, multi-layer film, interference filter, protection film, etc. Usual specs: 1-3mm 1-5mm