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Properties of
Synthetic Sapphire and Ruby
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| Generally properties |
Chemical composition
|
Al2O3 |
| Crystal structure |
Hexagonal |
| Purity |
99.99% |
| Thermal properties |
Melting point |
2050¡ãC |
| Softening point |
1800¡ãC |
| Specific heat |
0.18 cal/g.¡ãC (25¡ãC) |
Thermal expansion
|
Parallel to C-axis: 6.7¡Á10-6/¡ãC |
| Perpendicular to C-axis: 5.0¡Á10-6/¡ãC |
| Thermal conductivity |
0.09 cal/sec.cm.¡ãC (25¡ãC) |
| Mechanical properties |
Density |
3.98--4.1 g/cm3 |
| Hardness Mohs |
9 |
| Knoop |
1800 face parallel to C-axis |
| 2200 face perpendicular to C-axis |
| Modulus of elasticity |
3.40--3.80¡Á106 kg/cm2 |
| Compressive strength |
21000 kg/cm2 |
| Tensile strength |
1900 kg/cm2 |
| Bending Strength |
4000 kg/cm2 |
| Optical properties |
Index of refraction |
Parallel to C-axis: 1.769 |
| Perpendicular to C-axis: 1.76 |
| Index of infrared Transmission |
83% |
Electrical properties
|
Electrical resistance |
1011 ohm/cm at 500¡ãC |
| 106 ohm/cm at 1000¡ãC |
| 103 ohm/cm at 2000¡ãC |
| Dielectric constant |
7.5--10.5 |
| Chemical properties |
Acids and alkalis attack |
0 £¨300¡ãC£© |
| Porosity |
0 |
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