zinc sulphide properties
ZnS is an important semiconductor with the unique ability to exhibit strong phosphorescence, an unusual property that makes it attractive for use in glow in the dark products and electroluminescent panels. In its pure form, ZnS has a large (3.6 eV) direct band gap and large exciton binding energy1 that make it ideally suited for doping with copper, silver or manganese2,3,4 to introduce an intermediate level in the forbidden band, which can then be used to emit luminescence.
The crystalline structure of ZnS is polymorphic, with two main forms, cubic sphalerite and hexagonal wurtzite. These crystalline forms are both naturally occurring and synthetically feasible, with sphalerite being the more stable of the two allotropes.
In both crystalline forms, the coordination geometry at Zn and S is tetrahedral; however, in the sphalerite form the Zn atom is bonded to the S atom with an octahedron angle of about 1020 degC. In the wurtzite form, on the other hand, Zn is bonded to the S atom with a trigonal angle of about 590 degC.
Zinc sulphide can be found in a variety of applications, including paints, rubber, plastics and glass-fiber reinforced plastics. In addition, it is a pigment for printing inks, UV-hardened systems, powder coatings, adhesives and insulating & sealing compounds.
The material is often used as a coating on glass-fiber-reinforced thermoplastics to help protect them against moisture damage during the extrusion process. It is also an effective lubricant for metal production machines.
