Optical Silicon (Si)
Optical silicon is a non-glass, inorganic optical material. It has the highest thermal conductivity among non-glass optical ceramics. In addition, it has a fairly low density and a fairly high melting temperature. The graph bars on the material properties cards below compare optical silicon to other non-glass optical ceramics (top) and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.
Mechanical Properties
Compressive (Crushing) Strength
120 MPa 17 x 103 psi
Elastic (Young's, Tensile) Modulus
150 GPa 21 x 106 psi
Flexural Strength
300 MPa 44 x 103 psi
Fracture Toughness
3.5 MPa-m1/2 3.2 x 103 psi-in1/2
Knoop Hardness
1130
Poisson's Ratio
0.28
Shear Modulus
80 GPa 12 x 106 psi
Tensile Strength: Ultimate (UTS)
110 MPa 16 x 103 psi
Thermal Properties
Maximum Temperature: Mechanical
1350 °C 2460 °F
Melting Onset (Solidus)
1560 °C 2830 °F
Specific Heat Capacity
700 J/kg-K 0.17 BTU/lb-°F
Thermal Conductivity
150 W/m-K 88 BTU/h-ft-°F
Thermal Expansion
3.0 µm/m-K
Other Material Properties
Density
2.3 g/cm3 150 lb/ft3
Dielectric Constant (Relative Permittivity) At 1 MHz
12
Light Transmission Range
1.2 to 15 µm
Refractive Index
3.5
Common Calculations
Stiffness to Weight: Axial
35 points
Stiffness to Weight: Bending
75 points
Strength to Weight: Axial
13 points
Strength to Weight: Bending
22 points
Thermal Diffusivity
93 mm2/s
Thermal Shock Resistance
18 points
Followup Questions
Further Reading
Handbook of Optical Materials, Marvin J. Weber, 2003
Handbook of Optical Constants of Solids, Edward D. Palik (editor), 1998