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ZnS Zinc Sulfide Technical Data

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Summary Description

ZnS is a medium refractive index material (2.4 @ 10 microns) with good long wavelength transmission in the infrared. It’s popularity as a material has largely decreased over the last 10-15 years in favor of ZnSe. As a result, the relative cost of optical parts from the 2 materials is about the same. However, in many applications ZnS can be a much better choice than ZnSe and in ATR measurements will provide similar depth of penetration and spectral results. Both materials have zero water solubility and can be coated with a BBAR (Broad Band Anti-reflection coating)

Advantages compared to ZnSe:

  1. ZnS is on the GRAS list and can be used in food, beverage and pharmaceutical process streams.
  2. Better chemical resistance, acids and bases.
  3. Better abrasion resistance
  4. Higher tensile strength
  5. Full transmission of the visible spectrum for applications requiring simultaneous visible and infrared measurements.

Disadvantages compared to ZnSe:

  1. The spectral range is about 200cm-1 less than ZnSe in the important long wavelength region.
  2. Although the cost and availability are similar to ZnSe procurement lead times are somewhat longer
  3. Good spectral range down to 600cm-1 for windows and 700 cm-1 for beamsplitters.

 

Physical Data

Melting point: 1526 °C

Density: 4.1 g/cm3

Solubility in H2O: insoluble

Hardness: 240 kg/mm2

Appearance: Clear crystalline (for CVD material}

2 mm ZnS IR Spectrum

 

Refractive Index

WAVELENGTH (Microns) INDEX
0.35 2.727
0.36 2.670
0.38 2.577
0.40 2.523
0.42 2.451
0.46 2.408
0.50 2.370
0.54 2.349
0.58 2.336
0.62 2.320
0.66 2.311
0.70 2.301
0.74 2.293
0.78 2.286
0.82 2.284
0.86 2.281
0.90 2.280
0.94 2.276
0.98 2.273
1.00 2.270
1.40 2.268
1.80 2.263
2.20 2.259
2.60 2.256
3.00 2.254
3.40 2.252
WAVELENGTH (Microns) INDEX
3.80 2.249
4.20 2.244
4.60 2.244
5.00 2.243
5.40 2.241
5.80 2.241
6.20 2.238
6.60 2.231
7.00 2.225
7.40 2.224
7.80 2.221
8.20 2.221
8.60 2.217
9.00 2.212
9.40 2.208
9.80 2.203
10.20 2.198
10.60 2.188
11.00 2.186
11.40 2.176
11.80 2.173
12.20 2.167
12.60 2.159
13.00 2.152
13.40 2.139
13.80 2.135
14.20 2.126

Specific index listed; Generic: 2.20@10 microns

Spectral Range

Short Wavelength Limit: 17,000 cm-1 (1 mm)

Long Wavelength Limit: 690 cm-1 (2 mm), 722 cm-1 (4 mm)

Coatings

The infrared throughput of ZnS can be significantly increased with application of specialized BBAR coatings to levels exceeding 95% transmission. It may also be coated to control depth of penetration in ATR applications.

Typical Uses

IR transmission analysis

IR detector windows

ATR elements

Condensing lenses

Imaging lenses

Notes

Short and Long Wavelength Limits defined for which transmissivity is greater than 50% of stated crystal thickness.

  1.  Commercially published data: Chemical Vapor Deposition (CVD) Inc.

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