Dual functions of thiourea for solution combustion synthesis of ZnO/ZnS composite powders: fuel and sulphur source

In the present study, ZnO/ZnS composite powders were synthesized by one-step solution combustion method. Thiourea was used both as the combustion fuel and sulphur source. Oxidizer-to-fuel (O:F) ratios between 0.5 and 1 were chosen as the main synthesis parameter. Structure, microstructure, chemical composition, and photoluminescence properties of the powders were also investigated. X-ray diffraction patterns showed simultaneous functions of thiourea as combustion fuel and sulphur source. The relative concentration of ZnS to ZnO increased by O:F ratio. Fourier-transform infra-red spectroscopy spectra demonstrated some bands associated with the unwanted organic compounds in the final product in addition to Zn-O and Zn-S bonds. Furthermore, scanning electron microscope micrographs showed the presence of some gel-like regions located around highly agglomerated particles. Photoluminescence spectra also indicated strong emission peaks for O:F ratio of 0.5 due to significant crystal defects and lower crystallinity.