Solid-state-reaction synthesis of VO2 nanoparticles with low phase transition temperature, enhanced chemical stability and excellent thermochromic properties

Abstract

The synthesis of VO₂ has been a fundamental topic in the study of VO₂-based materials for energy-saving applications. Methods including hydrothermal, sol–gel and chemical vapor deposition can be used to synthesize VO₂ (M1/R). However, these techniques may usually involve some problems such as expensive raw materials, complex steps, and difficulties in controlling appropriate ratios of precursor amounts. In this study, a solid-state-reaction route was developed to prepare well-crystallized VO₂ (M1/R) nanoparticles with low, variable phase transition temperature, enhanced chemical stability and excellent thermochromic properties. The phase transition temperatures ranged from 43.5 °C to 59.3 °C by regulating reaction conditions, and it could be inferred from the study of the preparation process that the amorphous phases around the crystalline VO₂ phases played an important role in the decrease of phase transition temperatures compared with the reported values for bulk VO₂ (68 °C). Moreover, the obtained VO₂ (M1/R) nanoparticles exhibited enhanced anti-oxidation and acid-resistance abilities compared with particles prepared by hydrothermal process, and the derived flexible foils on polymer from the prepared VO₂ (M1/R) nanoparticles showed excellent thermochromic properties (T_lum = 54.2%, ΔT_sol = 9.2%).