Zinc sulfide Crystal

Zinc sulfide is only a little water-soluble. It has a solubility of 6.46×10^-5g/100 g H2O (18℃) for zinc-blend, and 6.88×10^-4g/100 g H2O (18℃) for wurtzite. Zinc sulfide is used as a source material for the evaporation to make the interference filter. This is due to the transparency of the material in the wide wavelength region and also its large refractive index. Irtran-2 is used for windows and lenses.

Crystal System

It takes two types of structures: zinc blend and wurtzite structures. Cubic system and zinc-blend structure with a lattice constant of a=0.5412 nm and Zn–S=0.236 nm. It is called b-ZnS. 

Hexagonal system and wurtzite structure with lattice constants of a=0.3892 nm, c=0.6260 nm, and u=3c/8, Zn–S=0.233 nm. It is called a-ZnS.

Production

Zinc sulfide produces naturally as zinc blend or Sphalerite and rarely as wurtzite. It contains impurities, such as Fe, Mn, Cd, Hg, Pb, Sn, Au, Ag, etc. A single crystal can be grown using the vapor phase method. It is also grown by encapsuling the quartz boat coated with carbon on its inner surface into the quartz tube with Ar gas and moving in the tube in a horizontal direction slowly in the Stockbarger furnace. The pressure of Ar gas reaches about 120 atm. at zinc sulfide’s melting point.

 When the powder is pressed, it makes a material called Irtran-2. Thin films are deposited using vacuum evaporation in a conical basket of Ta, or the boat and a crucible of Mo. It decomposes slightly during the evaporation. The flim deposited on a glass substrate is not so strong.