Zinc Sulfide and Cleartran®
Zinc sulfide is a robust optical material for windows, domes and other optical elements in the infrared range. The high breaking strength and hardness of zinc sulfide makes it suitable for use in demanding environments.
Cleartran® is a converted form of zinc sulfide that has been modified using a hot isostatic process. This process removes zinc hydrides from the crystal lattice, normalises the crystal structure and purifies the material. This improves transmission in the visible and infrared range (from 0.35 to 14 µm).
Thanks to low absorption and scattering as well as high optical quality, Cleartran® is particularly suitable for multispectral applications.
Resistant materials for VIS and IR applications
Vickers Hardness of Cleartran®
150
[kg mm-2]
to operate in harsh enviroments
Chemical purity of Cleartran®
99.9996
%
more homogeneous crystal structure
Transmission of Cleartran®
0.37 – 14
µm
multispectral in VIS and IR
CVD Ceramics’ chemically vapour-deposited zinc sulfide is the cost-effective alternative for infrared windows, domes and optical elements. With twice the breaking strength of zinc selenide and high hardness, zinc sulfide is successfully used in many military applications that require mechanical resistance to harsh environments.
With its low absorption and scattering over the entire transmission range and high optical quality, it is particularly suitable for multispectral applications that require a single aperture for the beam path of several wavelength ranges. Zinc sulfide and Cleartran® are chemically inert, non-hygroscopic, highly pure, theoretically dense and easy to machine.
Special diameters, rectangles, CNC-profiled blanks, generated lens blanks, prisms and near-net-shape domes can be manufactured to your specifications.
Properties of our zinc sulfide and Cleartran®
| Zinc sulfide | Cleartran® | |
|---|---|---|
| Optical properties | ||
| 10 % transmission limit (t = 6 mm) | 1.0 µm – 14 µm | 0.37 µm – 14 µm |
| Refractive index Inhomogeneity (∆n/n) | < 100 ppm @ 10.6 µm | < 20 ppm @ 633 nm |
| Thermo-optical coefficient dn/dT (298-358 K) K-1 @ 0.6328 µm K-1 @ 1.15 µm K-1 @ 3.39 µm K-1 @ 10.6 µm | 4.6 x 10-5 4.3 x 10-5 4.1 x 10-5 | 5.43 x 10-5 4.21 x 10-5 3.87 x 10-5 |
| Absorption coefficient cm-1 @ 1 .3 µm cm-1 @ 2.7 µm cm-1 @ 3.8 µm cm-1 @ 9.27 µm cm-1 @ 10.6 µm | 2.0 x 10-1 | 6.0 x 10-4 1.0 x 10-3 6.0 x 10-4 6.0 x 10-3 2.0 x 10-1 |
| Mechanical properties | ||
|---|---|---|
| Knoop hardness: 50 g load [kg mm-2] Vickers hardness: 1 kg load [kg mm-2] | 200 – 235 230 | 160 150 |
| Flexural strength (modulus of rupture) 4pt. Load [psi] 4pt. Load [MPa] Disc bursting [MPa] | 15 x103 103 84 | 1.09 x104 75 50 |
| Fracture toughness (critical stress intensity factor, KIC values) [MPa √m, Vickers, 1 kg] | 0,8 | 1,0 |
| Modulus of elasticity [psi] [GPa] | 10,8 x106 74.5 | 10,8 x106 74.5 |
| Poisson’s ratio | 0.29 | 0.28 |
| Physical properties | ||
|---|---|---|
| Crystal structure | cubic | cubic |
| Grain size [µm] | 2 – 8 | 20 – 35 |
| Density [g cm-3] at 298 K | 4.09 | 4.09 |
| Specific resistance [Ω cm] | ~ 1012 | ~ 1013 |
| Chemical purity [%] | 99.996 | 99.9996 |
| Thermal properties | ||
|---|---|---|
| Coefficient of thermal expansion [K-1] @ 273 K [K-1] @ 373 K [K-1] @ 473 K [K-1] @ 208 – 573 K | 6.6 x 10-6 7.3 x 10-6 7.7 x 10-6 | 6.3 x 10-6 7.0 x 10-6 7.5 x 10-6 6.5 x 10-6 |
| Thermal conductivity [JK-1m-1s-1] @ 298 K | 16.7 | 28.4 |
| Heat capacity [Jg-1K-1] @ 298K [Jg-1K-1] @ 273K [Jg-1K-1] @ 323K [Jg-1K-1] @ 373K | 0.469 | 0.474 0.489 0.504 |
| Thermal diffusivity [m2s-1] | 1.46 x 10-5 |
| Refractive indices | ||
|---|---|---|
| Wavelength [µm] | n | n |
| 0,4358 | 2.48918 | 2.48918 |
| 0,6438 | 2.34731 | 2.34731 |
| 1,0140 | 2.29165 | 2.29165 |
| 2,0581 | 2.26442 | 2.26442 |
| 3,0 | 2.25772 | 2.25772 |
| 4,0 | 2.25231 | 2.25231 |
| 5,0 | 2.24661 | 2.24661 |
| 8,0 | 2.22334 | 2.22334 |
| 9,0 | 2.21290 | 2.21290 |
| 10,0 | 2.20084 | 2.20084 |
| 12,0 | 2.17101 | 2.17101 |
| 13,0 | 2.15252 | 2.15252 |
