Aluminum oxide Sapphire
Sapphire is well known for its hardness. Extreme hardness, high strength and crack resistance make it the best choice of material for high performance optics.
Sapphire resistance to scratches and many types of chemical erosion as well as ability to withstand pressure increase and extreme temperature changes make it the best choice to be used in military, aerospace, medical, industrial and consumer industries.
Our Company grows crystals by the method of Horizontally Directed Crystallization with dimensions up to 300x220x25mm.
|
Main properties |
|
|
Chemical formula |
Al2O3 |
|
Crystal class |
Hexagonal system, rhomboidal class 3m |
|
Lattice constants, A |
a=4.785, c=12.991 |
|
Density, g/cm3 |
3.98 |
|
Melting point, °K |
2303 |
| Hardness |
Knoop(daN/mm2): 1800 parallel to C-axis, 2200 perpendicular to C-axis, Mohs: 9 |
|
Optical transmission range, µm |
0.17 - 5.5 |
| Refractive index at 0.532 µm |
n0=1.7717, ne=1.76355 |
|
Water absorption |
nil |
|
Young Modulus, Gpa |
345 |
|
Shear Modulus, Gpa |
145 |
|
Bulk Modulus, Gpa |
240 |
|
Bending Modulus (Modulus of Rupture), Mpa |
420 at 20°C, 280 at 500°C |
|
Elastic Coefficient |
C11=496, C12=164, C13=115, C33=498, C44=148 |
|
Poisson ratio |
0.25-0.30 |
|
Friction Coefficient |
0.15 on steel, 0.10 on sapphire |
|
Tensile strength, MPa |
400 at 25°, 275 at 500°, 345 at 1000° |
|
Flexural strength, daN/mm2 |
35 to 39 |
|
Compressive strength, GPa |
2.0 |
|
Young’s modulus E, daN/mm2 |
3.6 x 104 do 4.4 x 104 |
|
Specific heat, J/(kg x K) |
105 at 91°K, 761 at 291°K |
|
Thermal coefficient of linear expansion, K-1,at 323K |
6.66 x 10-6 parallel to optical axis, 5 x 10-6 perpendicular to optical axis |
|
Thermal conductivity, W/(m x K) at 300K |
23.1 parallel to optical axis, 25.2 perpendicular to optical axis |
|
Resistivity, Ohm x cm |
1016 (25°), 1011 (500°), 106 (1000°) |
|
Dielectric constant |
1.5 (103 - 109 Hz, 25°) parallel to C-axis, 9.3 (103 - 109 Hz, 25°) perpendicular to C-axis |
|
Dielectric strength, V/cm |
4 x 105 |
|
Loss tangent |
1 x 10-4 |
|
Solubility |
|
|
- in water |
insoluble |
|
- in HNO3,H2SO4, HCl, HF |
insoluble to 300 °C |
|
- in alcalis |
insoluble to 800 °C |
|
- in melts of metals Mg, Al, Cr, Co, Ni, Na, K, Bi, Zn, Cs |
insoluble to 800-1000 ° C |
|
g -radiation stability |
No change in transmission above 2.5 mm after exposure to 107 Rads. No visible coloration after exposure to 108 Rads/hr for 60 minutes at - 195°C |
|
Proton radiation stability |
No change in transmission below 0.3 µm after exposure to 1012 proton/cm2 total dose |
|
Chemical resistance |
Sapphire is highly inert and resistant to attack in most process environments including hydrofluoric acid and the fluorine plasma applications commonly found in semiconductor wafer processing (NF3, CF4) |
