Microwave-assisted controlled synthesis of monodisperse pyrite microspherolites

A microwave-assisted polyol method was reported to synthesize uniform and monodisperse pyrite (FeS2) microspherolites. The reaction processes for the synthesis involved the reduction of sulfur and reaction of the intermediate sulphur species with Fe2+. Polyvinyl pyrrolidone (PVP) added to the reaction system exerts an important role in the control of the phase composition and morphology of the products. The sample was characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and selected area electron diffraction (SAED) techniques. A series of TEM/HRTEM and SAED results reveal that the formation of pyrite FeS2 microspherolites is via a nanocrystal aggregation-based mechanism. The time-dependence experiments further demonstrate that primary FeS2 nanocrystals are first formed, and then aggregate into large spherolites, finally Ostwald ripening leads to the uniform and monodisperse microspherolites. The influence of microwave power on the size and morphology of the products and effect of microwave heating in the synthesis were also investigated.