Optical Silicon vs. Mullite
Optical silicon belongs to the non-glass optical ceramics classification, while mullite belongs to the oxide-based engineering ceramics. There are 19 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 mullite.
Metric UnitsUS Customary Units
Mechanical Properties
| Compressive (Crushing) Strength, MPa | 120 | |
| 800 |
| Elastic (Young's, Tensile) Modulus, GPa | 150 | |
| 110 to 170 |
| Flexural Strength, MPa | 300 | |
| 130 to 160 |
| Fracture Toughness, MPa-m1/2 | 3.5 | |
| 2.0 |
| Knoop Hardness | 1130 | |
| 750 |
| Poisson's Ratio | 0.28 | |
| 0.25 |
| Tensile Strength: Ultimate (UTS), MPa | 110 | |
| 160 |
Thermal Properties
| Maximum Temperature: Mechanical, °C | 1350 | |
| 1680 |
| Specific Heat Capacity, J/kg-K | 700 | |
| 950 |
| Thermal Conductivity, W/m-K | 150 | |
| 3.5 to 11 |
| Thermal Expansion, µm/m-K | 3.0 | |
| 5.8 |
Electrical Properties
| Dielectric Constant (Relative Permittivity) At 1 MHz | 12 | |
| 6.3 |
Otherwise Unclassified Properties
| Density, g/cm3 | 2.3 | |
| 2.7 to 3.0 |
Common Calculations
| Stiffness to Weight: Axial, points | 35 | |
| 22 to 31 |
| Stiffness to Weight: Bending, points | 75 | |
| 58 to 62 |
| Strength to Weight: Axial, points | 13 | |
| 15 to 17 |
| Strength to Weight: Bending, points | 22 | |
| 22 to 24 |
| Thermal Diffusivity, mm2/s | 93 | |
| 1.4 to 3.7 |
| Thermal Shock Resistance, points | 18 | |
| 12 to 19 |