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PROPERTIES OF SAPPHIRE
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|
PHYSICAL
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THERMAL
|
| Chemical formula |
Al2O3 |
Thermal conductivity |
0.065 cal cm-1 s-1 °C-1 |
| Crystal structure |
Hexagonal system (rhombohedral) |
(60° to c-axis) at 25 °C |
|
| Unit cell dimension |
a = 4.758 Å , c = 12.991 Å |
Thermal expansion |
8.40 x 10-6 °C-1 |
| Density |
3.98 g cm-3 |
coefficient |
|
| Hardness |
9 mohs, 1525-2000 Knoop |
(60° to c-axis) 25 - 800 °C |
|
| Melting point |
2040 °C |
Specific heat at 25 °C |
0.10 cal g-1 |
| Boiling point |
2980 °C |
Heat capacity at 25 °C |
18.6 cal °C-1 mol-1 |
|
MECHANICAL*
|
ELECTRICAL
|
| Tensile strength |
40,000-60,000 psi (design criterion) |
Volume resistivity |
1014 Ohm-cm |
| Flexural strength |
70,000-130,000 psi (design criterion) |
Dielectric strength |
480,000 V cm-1 |
| Young's modulus |
50 x 106 psi |
Dielectric constant |
|
| Compressive modulus |
55 x 106 psi |
E perpendicular to c-axis |
9.4 |
| Flexural modulus |
52 x 106 psi |
E parallel to c-axis |
11.5 |
| Rigidity modulus |
21.5 x 106 psi |
Dissipation factor, tan delta |
10-4 |
| Volumetric modulus of |
35 x 106 psi |
|
|
| elasticity (bulk modulus) |
|
|
|
| Poisson's ratio |
0.29 |
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|
* psi = 6.9 kPa
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