Morphology-controlled synthesis of tungsten oxide hydrates crystallites via a facile, additive-free hydrothermal process

Tungsten oxide hydrates crystallites with a diversity of morphologies were successfully synthesized by employing peroxo-polytungstic acid as the precursor via a facile and additive-free hydrothermal process. The crystal structure, morphology and orientation relationship were investigated by using X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. Results show that with the increase of the hydrothermal reaction time, the product morphology shows an obvious evolution from hexagonal plates to round angular blocks and to hexagonal gears, through irregular nanosheets and to cuboid rods finally. Furthermore, the driving force of this morphology evolution was found to be correspondent with the interesting change of the orientation growth and the phase transition of tungsten oxide hydrates under the hydrothermal process.