Hydrothermal synthesis of tungsten molybdenum mixed oxides

The phase composition, particle size, and morphology of ultrafine products recovered as a result of hydrothermal treatment of precursor solutions were studied. The precursor solutions were prepared by ion exchange and contained various proportions of tungsten and molybdenum. When tungsten percentages in the precursor solution were 20–95 mol %, the major synthesis product was a mixed oxide (substitutional solid solution (W, Mo)O₃ · 1/3H₂O based on the structure of crystal hydrate WO₃ · 1/3H₂O). When the tungsten percentage was 5 mol %, the product was (W, Mo)O₃ solid solution with the structure of orthorhombic MoO₃. Particle shapes and sizes (ranging from 20 to 8 000 nm) were dictated by the proportion between tungsten and molybdenum compounds in the precursor solution and by the method used to prepare the precursor.