Sapphire
Sapphire is a single crystal aluminum oxide(AL2O3). It is one of the hardest materials. Sapphire has good transmission characteristics over the visible, and near IR spectrum. It exhibits high mechanical strength, chemical resistance,thermal conductivity and thermal stability. It is often used as window material in specific field such as space technology where scratch or high temperature resistance is required.
Physical Properties
| Crystal Symmetry Hexagonal | System |
| Lattice Constant | a=4.75;c=12.97 |
| Transparence Range | 0.18-4.5um |
| Density | 3.98g/cm³ |
|
Mohs Hardness |
9 |
| Melting Point | 2030℃ |
| Thermal Conductivity | 0.04W/m/k |
| Expansion Coefficient | 8.4*10-6/k |
| Refractive Index | 1.755 |
Silicon(si) Crystals
Silicon(Si) is commonly used as a substrate material for infrared reflectors and windows in the 1.5um-8um region.The strong absorption band at 9um makes it unsuitable for CO2 laser transmission applications but it is frequently used for laser mirrors because of its high thermal conductivity and low density.Silicon is also a useful transmitter in 20um range.
| Material Type | CZ FZ;N or P |
| Crystal Direction | {100}{111} |
| Resistivity (Ohm/cm) | 0.003-50 |
| Thermal conductivity(J/K.M.S) | 163.3@273K |
| Density | 2.33g/cm³ at20℃ |
| Melting point | 1410℃ |
| Boiling point | 3265℃ |
| Knoop Hardness | 1150 |
| Transparency Range | 1000nm-10000nm，30000nm-300000nm |
