Selective Synthesis of Vanadium Oxides and Investigation of the Thermochromic Properties of VO2 by Infrared Spectroscopy

This paper reports a facile and low‐cost routine for the selective synthesis of vanadium oxides by hydrothermal treatment of V2O5 sol. Our experiments found a defined phase evolution sequence [V2O5 → V3O7·H2O → VO2 (B) → VO2 (A) → VO2 (M)] that is strongly dependent on the hydrothermal temperature, pressure, and reaction time. A mechanism for the formation of the vanadium oxides based on the oriented attachment (OA) growth model is proposed and discussed. The VO2 (A + M) phase and the pure VO2 (M) phase each show an abrupt change in infrared transmittance with temperature, which demonstrates their potential for applications in the field of energy conservation, and the modulation in the infrared properties of the VO2 (M) phase, thanks to its high purity, is far more prominent than that of the mixture phase VO2 (A + M). An approach combing sol–gel and hydrothermal methods is described for the selective synthesis of vanadium oxides based on the phase evolution sequence V2O5 → V3O7·H2O → VO2 (B) → VO2 (A) → VO2 (M). A mechanism for the formation of the vanadium oxides based on the oriented attachment (OA) growth model is proposed. The highly pure VO2 (M) phase shows prominent infrared modulation properties.