Sapphire crystal is use for optical window lenses and Nitride Based Devices (Blue LEDs). It has the following outing properties: outstanding physical-chemical properties, extraordinary mechanical resistance, high hardness, high optical resistance, resistance against high temperatures, high thermal conductivity, low electric conductivity, extremely low dielectric constant, strength even under extreme temperature conditions, outstanding chemical resistance even against fluorination agents, perfect crystal lattice.
Main properties of Ti: Sapphire crystal:
| Crystal Structure | Hexagonal system |
| Lattice Constants | a=4.785A , c=12.991A |
| Melting Point | 2300K |
| Density | 3.98g/cm3 |
| Mohs Hardness | 9 |
| Coefficient of Thermal Expansion | 5.8 × 10 -6 /K |
| Reflection | 0.418W.s/g/k |
| Thermal Conductivity | 25.12W/m/k (@ 100 ℃ ) |
| Reflective Index | no =1.768 ne =1.760 |
| dn/d | 13x10 -6 /K(@633nm) |
| Transmission Band | T ≈ 82% (0.3 ~5 μ m) |
| Dielectric Constant | 11.5( ∥ c), 9.3( ⊥ c) |
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