Sapphire is diamond ground using the same general processes as any dense alumina oxide material. While it tends to chip easier than alumina, simple grinding procedure and technic can accommodate this characteristic. Due to the relatively high cost of sapphire care should be taken to remove a minimal amount of material to reach the final specified dimensions. Sapphire is quite unique both physically, chemically and electrical as you will observe below. San Jose Delta has over 40 years of grinding intricate closely tolerance features in sapphire. Contact us today.
| Property | Value |
|---|---|
| General | |
| Chemical Formula: | Al203 (aluminum oxide) |
| Names: | Corundum, Sapphire, Alpha-alumina |
| Crystal System | Trigonal |
| Class: | Hexagonal-scalenohedral |
| Thermal | |
| Melting Point | 2053 °C (3727 °F) |
| Maximum Useful Temperature | ≈2000 °C |
| Specific Heat | 0.181 cal/gm °K (25°C) 0.300 cal/gm °K (1000°C) |
| Thermal Conductivity | 0.4 watts/cm °K(25°C) 0.1 watts/cm °K (1000°C) |
| Thermal Expansion Coefficient | (25-1000°C) 8.8 X 10-6 parallel to C-axis 7.9 X 10-6 perpendicular to C-axis |
| Density | 3.97 gm/cm3 (o.143 lb/in3) (25°C) |
| Young's Modulus | 435 GPa (63 X 106 psi) parallel to C-axis (25°C) 386 GPa (56 X 106 psi) parallel to C-axis (1000°C) |
| Modulus of Rigidity (Shear Modulus) | 175 GPa (26 X 106 psi) |
| Poisson's Ratio | 0.27 - 0.30 orientatium dependent |
| Flexural Strength | 1035 MPa (150 kpsi) parallel to C-axis (25°) 760 MPa (110 kpsi) perpendicular to C-axis (25°) |
| Compressive Strength | ≈2 GPa (300kpsi) 25°C |
| Hardness | 9 Moh's Scale 1900 Knoop parallel to C-axis 2200 Knoop perpendicular to C-axis |
| Optical | |
| Uniaxial Negative Refractive Index | Ordinary ray (C-axis) No = 1.768 Extraordinary ray Ne = 1.760 Birefringence: 0.008 |
| Temperature Coefficient of Refractive Index | 13 X 10-6° C-1 (Visible range) |
| Spectral Emittance | 0.1 (1600°C) |
| Spectral Absorption Coefficient | 0.1-0.2cm-1 (0.66μm, 1600°C) |
| Electrical | |
| Volume Resistivity | 1016 ohm-cm (25°C) 1011 ohm-cm (500°C) 106 ohm-cm (1000°C) |
| Dielectric Strength | 480,000 volts/cm (1200 volts/mil) |
| Dielectric Constant | 11.5 (103-109Hz, 25°C) parallel to C-axis 9.3 (103-109Hz, 25°C) perpendicular to C-axis |
| Loss Tangent | 8.6 X 10-5 (@1010Hz, 25°C) parallel to C-axis 3.0 X 10-5 (@1010Hz, 25°C) perpendicular to C-axis |
| Magnetic Susceptibility | -0.21 X 10-6 parallel to C-axis -0.25 X 10-6 perpendicular to C-axis |
| Chemical | |
| Weathering Resistance | Unaffected by atmospheric exposure |
| Sea Water resistance | Unaffected by marine exposure |
| Biological Resistance | Unaffected by in-vivo exposure Non-thrombogenic Non-reactive with body fluids |