Zinc Sulphide (ZnS)
Zinc Sulfide (ZnS) is a valuable material in optics, especially noted for its broad transparency range from the visible to the infrared spectrum. This makes it ideal for use in multispectral applications, such as imaging systems and IR optics. ZnS is often used in lenses, windows, and domes for military and aerospace applications due to its excellent optical properties and good mechanical strength. Additionally, it can be manufactured in both cubic (clear) and hexagonal (multispectral) forms, offering versatility for various optical requirements. ZnS’s ability to withstand harsh environments and high durability further enhance its suitability for demanding optical applications.
| Optical Properties | IR Grade | Multispectral Grade |
| Refractive Index Inhomogeneity @ 0.6328μm | < 100 x 10-6 | < 20 x 10-6 |
| Thermal co-efficient of Refractive Index @ 10.6μm | 4.1 x 10-5/°C | 5.4 x 10-5/°C |
| Bulk Absorption Coefficient @ 10.6μm | ≤ 0.24 /cm | ≤ 0.20 /cm |
| Thermal Properties | ||
| Thermal Linear Expansion | 6.8 x 10-6 /°C @ 20°C | 6.5 x 10-6 /°C @ 20°C |
| Thermal Conductivity | 0.167W/cm/°C @ 20°C | 0.27W/cm/°C @ 20°C |
| Specific Heat | 0.469 J/g/°C | 0.527 J/g/°C |
| Mechanical Properties | ||
| Density | 4.08 g/cc | 4.09 g/cc |
| Knoop Hardness | 210-240 kg/mm² | 150-160 kg/mm² |
| Young Modulus | 74.5GPa | 85.5 Gpa |
| Poisson’s Ratio | 0.27 | 0.27 |
| Rupture Modulus | 103.4 MPa | 68.9 Mpa |
| Fracture Toughness | 0.8 x 10⁶ N/m3/2 | 1.0 x 10⁶ N/m3/2 |
| λ (μm) | IR Grade Index | λ (μm) | Multispectral Index |
| 0.42 | 2.516 | 0.40 | 2.5451 |
| 0.50 | 2.419 | 0.50 | 2.4127 |
| 0.62 | 2.355 | 0.64 | 2.3473 |
| 0.70 | 2.332 | 0.70 | 2.3307 |
| 0.82 | 2.310 | 0.85 | 2.3065 |
| 0.90 | 2.301 | 0.89 | 2.3018 |
| 1.00 | 2.292 | 1.01 | 2.2916 |
| 2.20 | 2.263 | 2.05 | 2.2644 |
| 3.00 | 2.257 | 3.00 | 2.2577 |
| 4.20 | 2.251 | 4.00 | 2.2523 |
| 5.00 | 2.246 | 5.00 | 2.2466 |
| 6.20 | 2.238 | 8.00 | 2.2233 |
| 7.00 | 2.232 | 9.00 | 2.2129 |
| 8.20 | 2.221 | 10.00 | 2.2008 |
| 9.00 | 2.212 | 11.25 | 2.1831 |
| 10.20 | 2.198 | 12.00 | 2.1710 |
| 11.0 | 2.186 | 13.00 | 2.1525 |
| 12.20 | 2.167 | – | – |
| 13.00 | 2.152 | – | – |
| 14.20 | 2.126 | – | – |
| 15.00 | 2.106 | – | – |
| 16.20 | 2.072 | – | – |
| 17.00 | 2.045 | – | – |
