Zinc Sulfide (ZnS)

Choose ZnS for domes, windows, lenses and other transmissive optics whenever mechanical strength, hardness, or operation in harsh environments is required.

ZnS is most highly transmissive in the 8 µm to 12 µm spectral range. Its high resistance to rain erosion, high-speed dust, and particulate abrasion, makes it especially suitable for exterior IR windows on aircraft frames.

Zinc Sulfide (ZnS) Characteristics

Coherent routinely supplies ZnS substrates up to 300 mm, and can provide sheet material, core-drilled blanks, edged blanks, generated curved lens blanks, and more.

ZnS Material Properties (at 20°C)

Physical Properties


Cubic zincblende


4.08 g/cm³

Grain Size

2 µm to 8 μm


None > 0.5 mm

Electrical Density

> 1012 ohm-cm

Optical Properties

Bulk Absorption Coefficient @ 10.6 μm

< 0.24 cm-1

Thermo-Optic Coefficient (dn/dT) @ 10.6 μm

4.1 x 10-5/°C

Refractive Index Inhomogeneity @ 0.6328 μm

< 100 x 10-6

Thermal Properties

Thermal Conductivity @ 20° C

0.167 W/cm/°C

Specific Heat

0.469 J/g/°C

Linear Expansion Coefficient @ 20° C

6.8 x 10-6/°C

Mechanical Properties

Young’s Modulus

74.5 GPa (10.8 x 106 psi)

Rupture Modulus

103.4 MPa (15,000 psi)

Knoop Hardness

210-240 kg/mm²


4.08 g/cm³

Poisson’s Ratio


Fracture Toughness

0.8 x 106 N/m1.5