Selective Synthesis of γ-WO3 and β-WO3⋅H2O by the Hydrothermal Treatment of Peroxotungstic Acid

A selective method has been suggested for the synthesis of highly dispersed powders of γ-WO3 (monoclinic) and β-WO3⋅H2O (orthorhombic) by the hydrothermal treatment of aqueous suspensions of peroxotungstic acid in temperature range 70–250°С. The hydrothermal treatment of suspensions of peroxotungstic acid leads to formation of monophase β-WO3⋅H2O at temperature up to 100°С and monophase γ-WO3 at 250°С. The hydrothermal treatment in the temperature range 120–200°С gives two-phase samples of γ-WO3 and β-WO3⋅0.33H2O (orthorhombic syngony). The obtained monophase and two-phase powders have been studied by X-ray powder diffraction, scanning electron microscopy, IR spectroscopy, thermal analysis, and diffuse reflectance spectroscopy.