Structural and optical properties of ZnS:Mn micro-powders, synthesized from the charge with a different Zn/S ratio

The influence of Zn/S ratio in the charge on structural and optical properties of ZnS: Mn powders produced by high-temperature self-propagated synthesis was investigated. The samples was shown to consist of mixed-polytypes ZnS crystallites with hexagonal (2H) and cubic (3C) phases, the contribution of the latter increases with the sulfur content in the charge. The most homogeneous size distribution were found at stoichiometric Zn/S ratio. The Zn/S relation affects the Mn incorporation into ZnS lattice. The highest quantity of incorporated Mn is observed at stoichiometric Zn/S relation while lowest one is realized at Zn excess. Besides, the distribution of manganese ions in the blocks, which compose the crystallites, was found to be inhomogeneous, their concentration decreases from crystallites surface to the depth. Mn ions are nearer to the surface in ZnS: Mn synthesized with Zn excess. At Mn concentration in the charge of 1 wt% the shift of ZnS band edge to low energy side is observed, that is ascribed to formation of solid solution ZnS-MnS with lower band gap value.