Sapphire single crystal

Sapphire is a single crystal aluminum oxide (Al2O3). Its Mohs hardness is 9, it is one of the hardest materials. Sapphire has good mechanical strength, and it is also transparent from visible to IR spectrum. So, it is always used as window material where scratch resistance is required. Lattice Constant: a =4.75 A; c =12.97A Transparent Range: 180nm ~ 4500nm Density: 3.98g/cm3 Mohs Hardness: 9 Melting Point: 2030℃ Thermal Conductivity: 0.04W/m/K Expansion Coefficient: 8.4x10-6/K Refractive Index: 1.755@1um