Effects of pH on the microstructures and optical property of FeWO4 nanocrystallites prepared via hydrothermal method

FeWO4 nanocrystallites were prepared via a hydrothermal process using ferrous ammonium sulfate [(NH4)2Fe(SO4)2·6H2O] and sodium tungstate [Na2WO4·2H2O] as raw materials. The as-prepared nanocrystallites were characterized by X-ray diffraction(XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and UV–vis analyses. Results show that pH values significantly influence the phase and morphology of the as-prepared FeWO4 nanocrystallites. It is easy to obtain pure FeWO4 nanocrystallites in a wide range of the pH=2–11. The powders display a hexagonal flakes morphology under acidic conditions of pH=2. With the increase of pH, the morphology change from hexagonal flakes into rods. By UV–vis analysis, the optical band gap of the FeWO4 powders is calculated to be about 2.40 eV.