Low-temperature thermal synthesis of pure phase VO2(M) nanopowder for smart windows application

Abstract Monoclinic vanadium dioxide (VO 2 (M)) is a promising material for thermochromic smart window applications due to its semiconductor–metal phase transition near 65 °C. In order to utilize the full potential of this application, the fabrication process of VO 2 smart windows should be optimized to produce the best quality VO 2 films with reasonable resource usage. This study comparethe efficiency of the VO 2 production process in terms of time, temperature, and cost by exploring three thermal synthesis methods in an air atmosphere: Solution Combustion (SC), Thermolysis on a Hot Plate (THP), and Rapid Thermal Annealing (RTA) for producing VO 2 (M) nanopowder. X-ray diffraction (XRD) and Raman analysis confirm high-purity VO 2 , with RTA producing the best results at just 200 °C annealing temperature for 3 minutes. However, prolonged annealing in RTA causes oxidation to V 7 O 16 and V 2 O 5 in someregions. Scanning Electron Microscopy (SEM) reveals nanobelt morphology with embedded nanoparticles. VO 2 -based composite films exhibit favorable optical performance, with dual band gaps (0.28 eV for infrared switching and 2.44 eV for visible transparency). Furthermore, after 240 days, the sample retained 97.94% of its performance after 100 cycles. These findings highlight a fast and energy-efficient approach to produce high-quality VO 2 (M), facilitating its practical application in energy-saving smart window technologies.