Synthesis of Vanadium dioxide VO₂ nanoparticles for thermochromic applications

Abstract

Vanadium dioxide (VO₂) has a metal-semiconductor phase transition at 68°C. This transition associates with the change of crystallographic structure from the monoclinic (M, P21/c, semiconductor) to the rutile (R, P42/mnm, metal). Abrupt changes in transmittance and reflectance in the Infrared region and electrical resistance also occur during the transition. This optical property can be used in energy-saving smart windows (automatically block heat). In this study, VO₂ nanoparticles have been fabricated by combusting the low-cost precursor solution consisting of NH₄VO₃, C₂H₆O₂ and C₂H₅OH. Structural analysis of VO₂ was studied by X-ray diffraction (XRD) and Raman spectroscopy. Though XRD pattern are well corresponding to VO₂ (M), Raman results (grinded vs. non-grinded powder) demonstrate the same response as V₆O₁₃. After spin coating with polymer PMMA, the optical properties of VO₂-based composited film was measured to be 70-90% of transmittance and = 16% of reflectance of 300-2,400 nm wavelength at the room temperature. The variation of transmittance are observed when the particle density is varied. However, there is no change or very little change of reflectance when sample are heated up to 90°C. This could lead to focus on synthesis process and Raman analysis that affect the optical properties at room temperature (semiconductor) and at 90°C (metal).