Tailoring the Size and Shape-New Path for Ammonium Metavanadate Synthesis

Ammonium metavanadate, NH₄VO₃, plays an important role in the preparation of vanadium oxides and other ammonium compounds, such as NH₄V₃O₈, (NH₄)₂V₃O₈, and NH₄V₄O₁₀, which were found to possess interesting electrochemical properties. In this work, a new route for the synthesis of NH₄VO₃ is proposed by mixing an organic ammonium salt and V₂O₅ in a suitable solvent. The one-step procedure is carried out at room temperature. Additionally, the need for pH control and use of oxidants necessary in known methods is eliminated. The mechanism of the NH₄VO₃ formation is explained. It is presented that it is possible to tailor the morphology and size of the obtained NH₄VO₃ crystals, depending on the combination of reagents. Nano- and microcrystals of NH₄VO₃ are obtained and used as precursors in the hydrothermal synthesis of higher ammonium vanadates. It is proven that the size of the precursor particles can significantly affect the physical and chemical properties of the resulting products.