Inhibition of tungsten particle growth during reduction of V-doped WO3 nanoparticles prepared by co-precipitation method

The effect of vanadium on the tungsten particle growth during hydrogen reduction has been discussed. The nanostructured V-doped WO3 powder was synthesized by co-precipitation method with ammonium tungstate and ammonium metavanadate as its starting materials and was then reduced in hydrogen atmosphere. The products were characterized by X-ray diffractometry, scanning electron microscopy, thermogravimetric analysis and small angle X-ray scattering. It was observed that the vanadium added to tungsten oxide formed tungsta-vanadate solid solution and was then reduced to V–O–W bronze, VxWO3−y, during the early stage of hydrogen reduction and decomposed continuously to α-W and V2O3 during the entire WO2 → W transition. The results of particle size measurement and morphological analysis showed that the addition of vanadium could effectively inhibit the particle growth of tungsten powder during the reduction process. The addition of vanadium mainly effects on nucleation of tungsten at the lower temperatures below 850 °C because the slow decomposition of V–O–W bronze continuously provides the nucleation sites on the surface of WO2 particles during reduction via impeding the formation of WO2(OH)2 and providing of nucleation aids for W deposition from the surrounding WO2.