Why choose Single Crystal Sapphire products?
Single crystal sapphire possesses excellent optical, physical and chemical properties. It is the hardest oxide crystals, and remains high strength and chemical resistance at high temperatures. It also features a wide transmission wavelength range, great electrical insulation, and good thermal conductivity at low temperatures.
Physical Properties of Sapphire
| Chemical formula | Al2O3（99.999%） |
| Crystal class | Hexagonal system, rhomboidal class 3m |
| Lattice constants, A | a=4.785, c=12.991 |
| Density, g/cm3 | 3.98 |
| Hardness | 2000 with 2000 g identer (Knoop) 9 (Mohs) |
| Optical transmission range, μm | 0.17 - 5.5 |
| Refractive index at 0.532 μm | no=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 |
Thermal Properties of Sapphire
| Meling point, K | 2303 |
| Specific heat, J/(kg x K) | 105 at 91K 761 at 291K |
| 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 |
Electrical Properties of Sapphire
| Resistivity, Ohm x cm at 200-500 °C | 1011 - 1016 |
| Dielectric constant | 10.0 |
| Dielectric strength, V/cm | 4 x 105 |
| Loss tangent | 1 x 10-4 |
Transmission spectrum of 2 mm-thick sapphire window
|
Sapphire Refractive Index vs Wavelength
|
l, mm
|
No
|
Ne
|
|
0.193
|
1.92879
|
1.91743
|
|
0.213
|
1.88903
|
1.87839
|
|
0.222
|
1.87540
|
1.86504
|
|
0.226
|
1.87017
|
1.85991
|
|
0.244
|
1.85059
|
1.84075
|
|
0.248
|
1.84696
|
1.83719
|
|
0.257
|
1.83932
|
1.82972
|
|
0.266
|
1.83304
|
1.82358
|
|
0.280
|
1.82437
|
1.81509
|
|
0.308
|
1.81096
|
1.80198
|
|
0.325
|
1.80467
|
1.79582
|
|
0.337
|
1.80082
|
1.79206
|
|
0.351
|
1.79693
|
1.78825
|
|
0.355
|
1.79598
|
1.78732
|
|
0.442
|
1.78038
|
1.77206
|
|
0.458
|
1.77843
|
1.77015
|
|
0.488
|
1.77530
|
1.76711
|
|
0.515
|
1.77304
|
1.76486
|
|
0.532
|
1.77170
|
1.76355
|
|
0.590
|
1.76804
|
1.75996
|
|
0.633
|
1.76590
|
1.75787
|
|
0.670
|
1.76433
|
1.75632
|
|
0.694
|
1.76341
|
1.75542
|
|
0.755
|
1.76141
|
1.75346
|
|
0.780
|
1.76068
|
1.75274
|
|
0.800
|
1.76013
|
1.7522
|
|
0.820
|
1.75961
|
1.75168
|
|
0.980
|
1.75607
|
1.74819
|
|
1.064
|
1.75449
|
1.74663
|
|
1.320
|
1.75009
|
1.74227
|
|
1.550
|
1.74618
|
1.73838
|
|
2.010
|
1.73748
|
1.72973
|
|
2.249
|
1.73232
|
1.72432
|
|
2.703
|
1.719
|
1.711
|
|
2.941
|
1.712
|
1.704
|
|
3.333
|
1.701
|
1.693
|
|
3.704
|
1.687
|
1.679
|
|
4.000
|
1.674
|
1.666
|
|
4.348
|
1.658
|
1.65
|
|
4.762
|
1.636
|
1.628
|
|
5.000
|
1.623
|
1.615
|
|
5.263
|
1.607
|
1.599
|
