Sapphire Wafer Dia 25.4mm, Double Sided Polished, Pk 5

Single crystal sapphire possesses excellent optical, physical and chemical properties. It is the hardest oxide crystals and remains high strength and chemical resistance at high temperatures. It also features a wide transmission wavelength range, great electrical insulation, and good thermal conductivity at low temperatures.

Physical Properties of Sapphire
Chemical formula:     Al2O3（99.999%）
Crystal class:      Hexagonal system, rhomboidal class 3m
Lattice constants, A:     a=4.785, c=12.991
Density, g/cm:    3 3.98
Hardness: 2000 with 2000 g identer (Knoop) 9 (Mohs)
Optical transmission range, μm: 0.17 - 5.5
Refractive index at 0.532 μm: no=1.7717, ne=1.76355
Water absorption: nil
Young Modulus, GPa: 345
Shear Modulus, GPa: 145
Bulk Modulus, GPa: 240
Bending Modulus (Modulus of Rupture), MPa: 420 at 20 °C; 280 at 500 °C
Elastic coefficient: C11=496, C12=164, C13=115, C33=498, C44=148
Poisson ratio: 0.25-0.30
Friction coefficient: 0.15 on steel; 0.10 on sapphire
Surface roughness: Ra ≤0.2 nm

Thermal Properties of Sapphire
Melting point, K: 2303
Specific heat, J/(kg x K): 105 at 91K; 761 at 291K
Thermal coefficient of linear expansion, K-1, at 323K: 6.66 x 10-6 parallel to the optical axis; 5 x 10-6 perpendicular to the optical axis
Thermal conductivity, W/(m x K) at 300K: 23.1 parallel to the optical axis; 25.2 perpendiculars to the optical axis

Electrical Properties of Sapphire
Resistivity, Ohm x cm at 200-500 °C: 1011 - 1016
Dielectric constant: 10.0
Dielectric strength, V/cm: 4 x 105
Loss tangent: 1 x 10-4