About sapphire crystal
Crystal Structure: Hexagonal System
Cell Parameter： a=4.785Å , c=12.991Å
Melting Point： 2050℃
Density： 3.98g/cm3
Moh's Hardness： 9
Coefficient of Thermal Expansion：5.8×10-6/K
Specific Heat： 0.418W s/g/k
Thermal Conductivity： 25.12W/m/k (@100℃)
Refractive Index： no =1.768 ne=1.760
dn/dt： 13x10-6/K(@633nm)
Transmission of Light： T≈80% (0.3～5μm)
Permittivity： 11.5(∥c), 9.3(⊥c)
The direction of single crystal sapphire
Sapphire crystal is the hardest oxide crystal, the most basic monocrystal form of alumina and a colorless crystal.
Features
1. Wear resistance, good hardness, corrosion resistance, low friction coefficient, an ideal material of precision instruments and mechanical bearings;
2. Wear resistance, good hardness, corrosion resistance, good light transparency, a good watch cover material of high-grade watch;
3. High strength, corrosion resistance, high heat conductivity, good light transparency and wide transmittance band (from near ultraviolet to 5.5um middle-infrared band), an ideal window and optic element material;
4. Good electric insulation, hexagonal symmetrical structure, stable chemical performance, a good semiconductor and superconducting substrate material;
5. Sapphire is the most important extension substrate material of GaN blue ray LED.
