Sapphire Properties
Refractory Metals - Composites -Special Alloys - Ceramics -Tungsten - Titanium
SAPPHIRE PROPERTIES
Physical Properties |
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| Chemical Formula | AL2O3 | ||
| Structure | hexagonal-rhombodedral | ||
| Molecular weight | 101.96 | ||
| Lattice Constants Å | a=4.765, c=13,000 | ||
| Density (g/cm3) | 3.98 | ||
| Hardness | 9 Mohs 1800 knoop parallel to C-axis 2200 knoop perpendicular to C-axis |
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| Water Absorption | nil | ||
| Young Modulus (GPa) | 379 at 30° to C-axis 352 at 45° to C-axis 345 at 60° to C-axis 386 at 75° to C-axis |
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| Shear Modulus (GPa) | 145 | ||
| Bulk Modulus (GPa) | 240 | ||
| Bending Modulus/ Modulus of Rupture (MPa) |
350 to 690 | ||
| Tensile strength | 400 at 25°C 275 at 500°C 345 at 1000°C |
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| Elastic Coefficient | C=496, C12=164, C13=115, C33=498, C44=148 |
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| Apparent Elastic Limit (MPa) | 448 to 689 | ||
| Flexural Strength (GPa) | 2.5 - 4.0 | ||
| Poisson ratio | 0.25 - 0.30 | ||
| Friction Coefficient | 0.15 on steel 0.10 on sapphire |
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| Abrasion resistance | 8 times higher than steel | ||
Thermal Properties |
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| Melting Point (°C) | 2040 | ||
| Maximun use temperature (°C) | 1800 | ||
| Specific Heat J/(kg x K) | 105 at 91 K 761 at 291 K |
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| Thermal coefficient of linear expansion at 323 K (K-1) |
66.66 x 10-6 parallel to optical axis 5 x 10-6 perpendicular to optical axis |
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| Thermal conductivity (W/m °K) at 20° C |
41.9 | ||
| Thermal Expansion (20 - 1000° C) | Parallel to C-axis: 9.03 x 10-6 °C Perpendicular to C-axis: 8.31 x 10-6 °C 60° to C-axis: 8.4 x 10-6 °C |
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Optical Properties |
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| Wavelength (m) | Refractive Index | Wavelength (m) | Refractive Index |
| 0.265 | 1.833 | 0.7065 | 1.763 |
| 0.280 | 1.824 | 0.8944 | 1.757 |
| 0.2967 | 1.815 | 1.0139 | 1.755 |
| 0.3130 | 1.809 | 1.1286 | 1.753 |
| 0.3466 | 1.798 | 1.6932 | 1.743 |
| 0.3650 | 1.793 | 2.2492 | 1.732 |
| 0.4046 | 1.785 | 3.3026 | 1.702 |
| 0.5460 | 1.770 | 4.2553 | 1.663 |
| 0.5790 | 1.765 | 5.777 | 1.586 |
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Transission Range
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0.2 - 5.5 microns
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Transmission (thickness of disc 1 mm)
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| Visible light | >85% | ||
| Infrared | 0.75 to 5 µm | 85% | |
| 5.5 µm | 70% | ||
| Ultraviolet | 400 - 300 nm | 80% | |
| 280 nm | 60% | ||
| 200 nm | 50% | ||
| Reflection loss | 14% at 1 micron (2 surfaces) | ||
| Restrahlen Peak | 13.5 micron | ||
| dN/dT | +13 x 10-6 °C | ||
Electrical Properties |
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| Resistivity, Ohm•cm at 20 - 500° C | 1011 - 1016 | ||
| Dielectric Constant | 11.5 parallel to C axis 9.4 perpendicular to C axis |
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| Dielectric strength (V/cm) | 4 x 105 | ||
| Loss Tangent | 10-4 | ||
Stability Parameters |
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Solubility
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| In water | insoluble | ||
| In HNO3, H2SO4, HCI, HF | insoluble up to 300° C | ||
| In alkalis | insoluble up to 800° C | ||
| In melts of metals: Mg, Al, Cr, Co, Ni, Na, K, Bi, Zn, Cs |
insoluble up to 800 - 1000° C | ||
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Radiation Stability
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No change in transmission above 2.5 micron after exposure to 107 Rads. No visible coloration after exposure to 108 Rads/hr for 60 minutes at -195° C |
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Proton Radiation Stability
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No change in transmission below 0.3 micron after exposure 1012 proton/cm2 total dose. |
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