| Summary: | Monoclinic vanadium dioxide VO<sub>2</sub>(M) is a well-known thermochromic material, with its critical transition temperature (68 °C) being the closest to room temperature (RT). Among the variety of grown methods, hydrothermal synthesis is a simple and cost-effective technique to grow thermochromic VO<sub>2</sub> in the form of powder. In the present work, VO<sub>2</sub> nanoparticles were prepared by hydrothermal synthesis in mild conditions, followed by a thermal annealing process at 700 °C under nitrogen flow for two hours. Vanadium pentoxide (V<sub>2</sub>O<sub>5</sub>) was used as the vanadium precursor, while two different reducing agents, namely oxalic and succinic acid, were employed for the reduction of V<sub>2</sub>O<sub>5</sub> to VO<sub>2</sub>. Additionally, urea as well as thiourea were used as additives, in order to investigate their effects on the thermochromic performance of VO<sub>2</sub>. As a result, the VO<sub>2</sub> (M) phase was obtained after annealing the crystalline powder, grown hydrothermally using oxalic acid and thiourea as a reducing agent and additive, respectively. This synthesis had a high yield of 90%, and led to a VO<sub>2</sub>(M) powder of high purity and crystallinity. In particular, the VO2 (M) nanoparticles had an average crystallite size of approximately 45 nm, a critical transition temperature of approximately 68 °C and a hysteresis width of 11 °C.
|
|---|