The study of thermochromic and thermo-optical properties of sol–gel V1−x−y WxSiyO2 films by response surface method

Abstract

Vanadium dioxide (VO2) is an attractive thermochromic material for smart windows attributed to its reversible phase transition between semiconductors to metal phase at its phase transition temperature. In this paper, various quantities of tungsten and SiO2 were mixed into VO2 sols to fabricate V1−x−y WxSiyO2 gels. The gels were spin coated on a sodium-free glass slide and subsequently calcined at 500 °C in an atmospheric control furnace under reducing gas flow (H2–Ar, 5%–95%). The comprehensive investigation was conducted on the corresponding thermochromic and thermo-optical characteristics of VO2 composite films by response surface methodology and ANOVA analysis. Results show that the addition of SiO2 has greatly inhibited the agglomeration of particles. Additionally, the thermal induced infrared filtering effect is found to be strongly dependent on the mixing ratios of SiO2/W. However, the optical parameters such as refractive index and extinction coefficient were temperature-dependent and less influenced by the doping contents of SiO2 and W. The phase transition temperature of the doped VO2 films containing both SiO2 and W was dropped to the room temperature (31 °C). Furthermore, the temperature dependent electrical–optical properties of VO2 of the as-prepared films were strongly correlated with the dopant concentrations of W and SiO2.