Structure and phase composition of zinc sulfide produced by self-propagating high-temperature synthesis

The structure of polycrystalline ZnS produced by self-propagating high-temperature synthesis is investigated. The monolithic specimens produced are a mixture of wurtzite and sphalerite. In the cross section of the specimens there are three distinct zones: an outer zone of fine crystals and zones of acicular and equiaxial crystals. Changing heat-exchange conditions, one can affect the dimensions of the second and third zones. Introduction of the disperser NH$_4$Cl into the starting mixture changes the crystallization mechanism and produces powder ZnS of a hexagonal modification with a varying grain size. Experimental results are explained within the framework of a two-phase model of crystallization and Ostwald’s phase rule.