Optical Silicon vs. Alumina
Optical silicon belongs to the non-glass optical ceramics classification, while alumina belongs to the oxide-based engineering ceramics. There are 20 material properties with values for both materials. Properties with values for just one material (9, in this case) are not shown.
For each property being compared, the top bar is optical silicon and the bottom bar is alumina.
Metric UnitsUS Customary Units
Mechanical Properties
| Compressive (Crushing) Strength, MPa | 120 | |
| 1920 to 2750 |
| Elastic (Young's, Tensile) Modulus, GPa | 150 | |
| 220 to 370 |
| Flexural Strength, MPa | 300 | |
| 260 to 430 |
| Fracture Toughness, MPa-m1/2 | 3.5 | |
| 3.7 to 7.2 |
| Knoop Hardness | 1130 | |
| 960 to 1660 |
| Poisson's Ratio | 0.28 | |
| 0.22 to 0.24 |
| Tensile Strength: Ultimate (UTS), MPa | 110 | |
| 210 to 290 |
Thermal Properties
| Maximum Temperature: Mechanical, °C | 1350 | |
| 650 to 1730 |
| Melting Onset (Solidus), °C | 1560 | |
| 2040 |
| Specific Heat Capacity, J/kg-K | 700 | |
| 870 to 940 |
| Thermal Conductivity, W/m-K | 150 | |
| 14 to 30 |
| Thermal Expansion, µm/m-K | 3.0 | |
| 6.7 to 8.2 |
Electrical Properties
| Dielectric Constant (Relative Permittivity) At 1 MHz | 12 | |
| 7.8 to 11 |
Otherwise Unclassified Properties
| Density, g/cm3 | 2.3 | |
| 3.4 to 4.1 |
Common Calculations
| Stiffness to Weight: Axial, points | 35 | |
| 35 to 53 |
| Stiffness to Weight: Bending, points | 75 | |
| 57 to 62 |
| Strength to Weight: Axial, points | 13 | |
| 14 to 23 |
| Strength to Weight: Bending, points | 22 | |
| 19 to 28 |
| Thermal Diffusivity, mm2/s | 93 | |
| 3.7 to 10 |
| Thermal Shock Resistance, points | 18 | |
| 4.9 to 14 |