| Properties | Units | Sapphire (parallel to C axis) |
Sapphire (perpendicular to C axis) |
Alumina 99.9 % | Alumina 99.5 % | Quartz | Silicon Carbide | Silicon Nitride | Aluminum Nitride | |
 |
Density | g/cm3 | 3.97 | 3.97 | 3.96 | 3.98 | 2.2 | 3.1 | 3.18-3.30 | 3.25 |
| Young’s Modulus | Gpa at R.T | 435 | 386 | 372 | 70 | 393 | 311 | 300 | ||
| Modulus of rigidity (shear) | Gpa at R.T | 175 | 158 | 152 | 31 | 166 | ||||
| Poisson’s Ratio | 0.27-0.30 | 0.27-0.30 | 0.22 | 0.22 | 0.17 | 1.19 | ||||
| Flexural Strength | MPa | 1035 | 760 | 550 | 350 | 80 | 462 | 338-900 | 300 | |
| Compressive Strength | MPa at R.T | 2000 | 3700 | 2600 | 550-1100 | 2500 | ||||
| Hardness | Knoop | 1900 | 2200 | 1440 | 1551 | 1250 | 2500 | 1050 | ||
 |
Volume Resistivity | ohm-cm at R.T | 1 x 10 16 | 1 x 10 16 | 1 x 10 14 | 1 x 10 14 | 7 x 10 7 | 1 x 10 8 | 1 x 10 12 | 1 x 10 14 |
| Dielectric Strength | volts/cm | 480000 | 480000 | 315000 | 331000 | 500000 | ||||
| Dielectric Constant | 10 3 -10 9 Hz | 11.5 | 9.3 | 9.8 | 9.7 | 3.75 | 8.5 | |||
| Loss Tangent | * 10 5 @ 10 10 Hz | 8.6 | 3.0 | 2.0 | 2.0 | 0.4 | ||||
| Magnetic Susceptability | * 10 6 | -0.21 | -0.25 | |||||||
 |
Melting Point | 0C | 2053 | 2053 | 1683 | |||||
| Maximum usable temperature | 0C | 2000 | 2000 | 1900 | 1750 | 1200 | 1400 | 1200-1400 | 1600 | |
| Specific Heat | cal/g0 K at R.T | 0.181 | 0.181 | 0.21 | 0.20 | 0.16 | 0.15 | 0.17 | ||
| Thermal Conductivity | watts/m0 K at R.T | 40 | 40 | 39 | 36 | 1.4 | 125 | 12–15 | 115 | |
| Coefficient of Thermal Expansion | * 10 -6 at 25-10000C | 8.8 | 7.9 | 8.4 | 8.2 | 0.55 | 4.3 | 3.0 | 5.7 | |
 |
Refractive index | 1.768 | 1.76 | opaque | opaque | 1.46 | opaque | opaque | opaque | |
| Optical Transmission Range(80%) | nm (100cm thick) | 200-3500 | 200-3500 | opaque | opaque | 270-2400 | opaque | opaque | opaque | |
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