Synthesis and investigation of blue and green emissions of ZnS ceramics

ZnS ceramics were successfully synthesized by the solid-state reaction method under different conditions. The structural transformation of ZnS ceramics from zinc-blende to hexagonal wurtzite was observed with the help of X-ray diffraction (XRD). The hexagonal wurtzite ZnS ceramics with much better quality were obtained at a sintering temperature of 1100 °C and for 100 min sintering time, meanwhile the relative density reaches 94%. Room temperature photoluminescence measurements with 325 nm excitation showed four emission bands, that is, the near band edge (NBE) emission band at ∼342 nm, the emission band of ∼407 nm from the sulfur vacancies, the emission peak at 488 nm which was explained as the radioactive transition from the conduction band to the energy level of zinc vacancies, and the green emission band at 525 nm which was attributed to the recombination of electrons from the energy level of sulfur vacancies with the holes from the line or surface defects. The observed green PL emission of the wurtzite-type ZnS ceramics could provide an interesting application in the development of novel luminescent devices.