The effect of chemical reduction conditions on the structural and optical properties of WO3–TeO2 binary compounds by controlled synthesis from oxide precursors

Abstract

Due to the importance of the WO3–TeO2 binary compounds, the characterization of their compounds plays an important role in the study of the properties of these materials. In this paper, WO3–TeO2 nanostructured binary compound was prepared using chemical reduction method with different precursors. In this study, three synthesis processes (A, B, C) of WO3–TeO2 compounds were studied and the chemical reduction conditions were investigated on binary components. Sodium hydroboride (NaBH4) and hydrazine as reduction agents were used in processes. The nano-powders were characterized by XRD analysis, FE-SEM, EDAX elemental analysis, FTIR and UV–vis spectroscopy. The results of X-ray diffraction showed that, before the annealing in the presence of hydrazine, the peaks of diffraction of TeO2 and WO3 binary compounds were independently formed. The first stage of chemical reduction with sodium borohydrate (NaBH4) in synthesis C led to the formation of a WTe2 compound, and the chemical reduction of the second stage with hydrazine significantly reduced the amount of oxygen in various compounds of WO3–TeO2. In addition, after annealing in the presence of hydrazine, tellurium (Te) phase in XRD patterns are increased. The images of the FE-SEM showed that the morphology of the nanoparticles was uniformly spherical. The energy gap of the nanoparticles varied in the range 3.23–3.92 eV with two separated phases of WO3 and TeO2. The bond structure of the nanoparticle is also studied by FT-IR and UV–vis spectroscopy.