Material - Zinc Sulphide (ZnS)
Used for IR windows and lenses in the thermal band (8 to 14 microns) where maximum transmission and lowest absorption is required.
Also selected for use where visible alignment is an advantage. Zinc Sulphide is produced by synthesis from zinc vapour and H2S gas, forming as sheets on graphite susceptors. It is microcrystalline in structure, the grain size being controlled to produce maximum strength. Multispectral grade is then Hot isostatically pressed (HIP) to improve the mid IR transmission and produce the visibly clear form. Polycrystal ZnS is available.
BASE PROPERTIES
|
PARAMETER |
|
VALUE |
|
|
|
|
|
|
| OPTICAL |
|
| |
Transmission Range |
|
0.37 to 13.5 microns |
|
| |
Refractive Index |
|
2.20084 at 10 microns |
|
| |
Reflection Loss |
|
26.2% at 10 µm (2 surfaces) |
|
| |
dn/dT |
|
+38.7 x 10-6/°C at 3.39µm |
|
| |
Index of Absorption |
|
0.0006 cm-1 at 3.8 microns |
|
| |
Restrahlen Peak |
|
30.5 microns |
|
| PHYSICAL |
|
| |
Density |
|
4.09 g/cm3 |
|
| |
Melting Point |
|
1765°C (dissociates about 700°C)° C |
|
| |
Thermal Conductivity |
|
27.2 Wm-1K-1 at 298K |
|
| |
Thermal Expansion |
|
6.5 x 10-6/°C at 273K |
|
| |
Hardness |
|
Knoop 160 with 50g indenter |
|
| |
Specific Heat Capacity |
|
515 J/(kg K) |
|
| |
Dielectric Constant |
|
8 |
|
| |
Young's Modulus (E) |
|
74.5 GPa |
|
| |
Apparent Elastic Limit |
|
68.9 MPa (10,000psi) |
|
| |
Poisson Ratio |
|
0.28 |
|
| CHEMICAL |
|
| |
Solubility |
|
0.001 g/100g water |
|
| |
Molecular Weight |
|
144.33 |
|
| |
Class/Structure |
|
HIP polycrystalline cubic, ZnS, F43m |
|
REFRACTIVE INDEX
| |
Wavelength, µm |
0.405 |
0.436 |
0.468 |
0.480 |
0.509 |
0.546 |
0.588 |
0.644 |
0.668 |
0.706 |
|
|
Refractive Index |
2.545 |
2.489 |
2.449 |
2.437 |
2.413 |
2.388 |
2.368 |
2.347 |
2.340 |
2.331 |
|
|
|
|
|
|
|
|
|
|
| |
Wavelength, µm |
0.780 |
0.795 |
0.852 |
0.894 |
1.014 |
1.129 |
1.530 |
2.058 |
3.000 |
3.500 |
|
|
Refractive Index |
2.317 |
2.314 |
2.306 |
2.302 |
2.292 |
2.285 |
2.272 |
2.264 |
2.258 |
2.255 |
|
|
|
|
|
|
|
|
|
|
| |
Wavelength, µm |
4.000 |
4.500 |
5.000 |
8.000 |
9.000 |
10.00 |
11.25 |
12.00 |
13.00 |
|
|
|
Refractive Index |
2.252 |
2.250 |
2.247 |
2.223 |
2.213 |
2.201 |
2.183 |
2.171 |
2.153 |
|
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