Infrared thermochromic properties of VO₂ thin films prepared through aqueous sol-gel process

Abstract

The stoichiometric vanadium(IV) oxide thin films were obtained by controlling the temperature, time and pressure of annealing. The thermochromic phase transition and the IR thermochromic property of 400 nm and 900 nm VO₂ thin films in the 7.5 μm-14 μm region were discussed. The derived VO₂ thin film samples were characterized by Raman, XRD, XPS, AFM, SEM, and DSC. The resistance and infrared emissivity of VO₂ thin films under different temperature were measured, and the thermal images of films were obtained using infrared imager. The results show that the VO₂ thin film annealed at 550 °C for 10 hours through aqueous sol-gel process is pure and uniform. The 900 nm VO₂ thin film exhibits better IR thermochromic property than the 400 nm VO₂ thin film. The resistance of 900 nm VO₂ film can change by 4 orders of magnitude and the emissivity can change by 0.6 during the phase transition, suggesting the outstanding IR thermochromic property. The derived VO₂ thin film can control its infrared radiation intensity and lower its apparent temperature actively when the real temperature increases, which may be applied in the field of energy saving, thermal control and camouflage.