Synthetic sapphire is an anisotropic crystalline material consisting of single crystals of aluminum oxide (Al2O3). Sapphire is a very important optical material that is widely used in UV, visible and near-infrared applications because of its high transmittance and excellent mechanical strength properties at high temperatures. Alfa Chemistry can custom manufacture optical components of virtually any shape and size using sapphire material according to customer requirements. If you need help, please contact us.
Advantages and Uses of Sapphire Materials
To create customized optical products, Alfa Chemistry uses high-grade optical grade sapphire. It is basically 100 percent pure. The orientation of the sapphire crystal within the crystal with respect to the optical axis determines its varied qualities. Its transmission spectrum ranges from 150 nm to 6.0 µm. Due to its high melting point, superior thermal conductivity, and minimal thermal expansion, it performs exceptionally well in hot settings.
Fig 1. Transmittance of regular and UV grade sapphire windows (2 mm thickness) as a function of temperature. (Lee G. W, et al. 2011)
In the UV to NIR band, there is excellent transmittance. IR windows, lenses, and spherical lenses are just a few of the optical components that sapphire may be manufactured into. Sapphire is suitable for harsh situations due to its great chemical inertness to acids, alkalis, and water as well as its resistance to temperatures up to 1000 ℃.
Sapphire is incredibly hard, making it challenging to polish with conventional methods. High optical quality finishes on sapphire are not always feasible.
Properties of Sapphire Materials
| Density | 3.97 g/cc |
| Molecular Weight | 101.96 |
| Solubility | 98 x 10-6g/100g water |
| Class/Structure | Trigonal (hex), R3c |
| Melting Point | 2040 ℃ |
| Hardness | Knoop 2000 with 2000g indenter |
| Refractive Index | No 1.75449; Ne 1.74663 at 1.06 μm |
| Transmission Range | 0.17 ~ 5.5 μm |
| Reflection Loss | 14% at 1.06 μm |
| Reststrahlen Peak | 13.5 μm |
| Absorption Coefficient | 0.3x10-3 cm-1 at 2.4 μm |
| dn/dT | 13.1x10-6 at 0.546 μm |
| Youngs Modulus (E) | 400 GPa @ 20℃ |
| Shear Modulus (G) | 148.1 GPa |
| Bulk Modulus (K) | 240 GPa |
| Tensile Strength | 300 ~ 400 MPa |
| Thermal Expansion | 5.6 (para) and 5.0 (perp) x 10-6/K |
| Thermal Conductivity | 27.21 W/m/K at 300K |
| Dielectric Constant | 11.5 (para) 9.4 (perp) at 1MHz |
| Specific Heat Capacity | 763 J Kg-1 K-1 at 293K |
| Poisson Ratio | 0.25 |
| Elastic Coefficients | C11=496, C12=164, C13=115, C33=498, C44=148 |
About refractive index parameters.
"No" means ordinary light, "Ne" means extraordinary light.
| µm | No | Ne | µm | No | Ne | µm | No | Ne |
|---|---|---|---|---|---|---|---|---|
| 0.193 | 1.9288 | 1.9174 | 0.213 | 1.8890 | 1.8784 | 0.222 | 1.8754 | 1.8650 |
| 0.226 | 1.8702 | 1.8599 | 0.244 | 1.8506 | 1.8407 | 0.248 | 1.8470 | 1.8372 |
| 0.257 | 1.8393 | 1.8297 | 0.266 | 1.8330 | 1.8236 | 0.280 | 1.8244 | 1.8151 |
| 0.308 | 1.8110 | 1.8020 | 0.325 | 1.8047 | 1.7958 | 0.337 | 1.8001 | 1.7921 |
| 0.351 | 1.7969 | 1.7882 | 0.355 | 1.7960 | 1.7883 | 0.442 | 1.7804 | 1.7721 |
| 0.458 | 1.7784 | 1.7702 | 0.488 | 1.7753 | 1.7671 | 0.515 | 1.7730 | 1.7649 |
| 0.532 | 1.7717 | 1.7636 | 0.590 | 1.7680 | 1.7600 | 0.633 | 1.7659 | 1.7579 |
| 0.670 | 1.7643 | 1.7563 | 0.694 | 1.7634 | 1.7554 | 0.755 | 1.7614 | 1.7535 |
| 0.780 | 1.7607 | 1.7527 | 0.800 | 1.7601 | 1.7522 | 0.820 | 1.7596 | 1.7517 |
| 0.980 | 1.7561 | 1.7482 | 1.064 | 1.7545 | 1.7466 | 1.320 | 1.7501 | 1.7423 |
| 1.550 | 1.7462 | 1.7384 | 2.010 | 1.7375 | 1.7297 | 2.249 | 1.7323 | 1.7243 |
| 2.703 | 1.719 | 1.711 | 2.941 | 1.712 | 1.711 | 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 |
Reference
- Peixoto C, et al. (2022). "Injection Molding of High-Precision Optical Lenses: A Review." Precision Engineering. 76: 29-51.