Optical Silicon vs. Synthetic Sapphire
Optical silicon belongs to the non-glass optical ceramics classification, while synthetic sapphire belongs to the oxide-based engineering ceramics. There are 23 material properties with values for both materials. Properties with values for just one material (2, in this case) are not shown.
For each property being compared, the top bar is optical silicon and the bottom bar is synthetic sapphire.
Metric UnitsUS Customary Units
Mechanical Properties
| Compressive (Crushing) Strength, MPa | 120 | |
| 2700 |
| Elastic (Young's, Tensile) Modulus, GPa | 150 | |
| 450 |
| Flexural Strength, MPa | 300 | |
| 1090 |
| Fracture Toughness, MPa-m1/2 | 3.5 | |
| 1.9 |
| Knoop Hardness | 1130 | |
| 1860 |
| Poisson's Ratio | 0.28 | |
| 0.28 |
| Shear Modulus, GPa | 80 | |
| 150 |
| Tensile Strength: Ultimate (UTS), MPa | 110 | |
| 2470 |
Thermal Properties
| Maximum Temperature: Mechanical, °C | 1350 | |
| 2000 |
| Melting Onset (Solidus), °C | 1560 | |
| 2050 |
| Specific Heat Capacity, J/kg-K | 700 | |
| 760 |
| Thermal Conductivity, W/m-K | 150 | |
| 30 |
| Thermal Expansion, µm/m-K | 3.0 | |
| 5.3 |
Electrical Properties
| Dielectric Constant (Relative Permittivity) At 1 MHz | 12 | |
| 10 |
Otherwise Unclassified Properties
| Density, g/cm3 | 2.3 | |
| 4.0 |
| Light Transmission Range, µm | 1.2 to 15 | |
| 0.17 to 5.5 |
| Refractive Index | 3.5 | |
| 1.8 |
Common Calculations
| Stiffness to Weight: Axial, points | 35 | |
| 63 |
| Stiffness to Weight: Bending, points | 75 | |
| 64 |
| Strength to Weight: Axial, points | 13 | |
| 170 |
| Strength to Weight: Bending, points | 22 | |
| 100 |
| Thermal Diffusivity, mm2/s | 93 | |
| 9.9 |
| Thermal Shock Resistance, points | 18 | |
| 74 |