Preparation And Characterization Of VO₂ Thermochromic Coatings For Smart Window

Vanadium dioxide?VO₂?,as a typical thermochromic material,can be widely applied as smart window coatings.The VO₂ coating is a potential material for smart window in the future building.But VO₂ coating has lower transmittance and higher phase transition temperature,it can not be directly applied to the surface of building glass,which hinders its industrialization.Based on above analyse,in order to improve visible light transmission of VO₂coating,this paper proposed various deposition processes to construct SiO₂/VO₂ double-layer coating.In order to reduce the phase transition temperature of the VO₂coating,it is proposed a variety of deposition processes to construct the W-VO₂ film.On this basis,this paper proposed to constructe SiO₂/W-VO₂multilayer coating.The specific work progress was shown as follows:?1?SiO₂/VO₂thermochromic coatings are prepared via VO₂sintering alone and SiO₂/VO₂ co-sintering respectively.The microstructure and thermochromic properties as well as the optical properties of samples are characterized by Raman Scattering Spectrum,Scanning Electron Microscopy,Atomic Force Microscopy and UV/VIS/NIR Spectrophotometry.The experimental results show that,both the microstructure and the properties of coatings are strongly dependent on the depositon route,whereas the type of SiO₂ precursor sols can only have little effect on the microstrcture and even less effect on the thermochromic and optical properties.When the coatings are prepared by the VO₂ alone-calcinated route,double-layer SiO₂/VO₂ coatings with a clear interface and comparatively high crystalline degree of monoclinic VO₂ could be obtained,endowing the coatings with higher transmittance but a legible decrease in thermochromic properties.The typical sample exhibited a good comprehensive performance,with the near infrared switching rate at 2000 nm value of 39.6%,the solar energy modulation value of 8.4%,the integral visible and the integral solar transmittance at 25°C is 68.4%and 72.0%,respectively.?2?On the basis of the previous work,W-VO₂ coatings with different WPTA dopants were prepared.The microstructure and thermochromic properties as well as the optical properties of samples were characterized by X-ray Photoelectron Spectroscopy,Raman Scattering Spectrum,Transmission Electron Microscope,Scanning Electron Microscopy,Atomic Force Microscopy and UV/VIS/NIR Spectrophotometry.It is found that the+3valent vanadium ion and tetragonal phase appears in the coating with doping proceeds,tungsten ions have been successfully doped into VO₂ coating and the phase transition temperature of W-VO₂ coating decreases with the increase of tungsten doping content,even the lowest phase transition temperature can reach 36.9?.The typical sample exhibited a good comprehensive performance,with phase transition temperatures T_t value of 42.7°C,the near infrared switching ability at 2000 nm?T₂₀₀₀ value of 35.7%,the solar energy modulation?T_sol value of 8.0%,the integral visible and the integral solar transmittance T_vis,_L and T_sol,L at 25? value of 52.0%and 52.1%,respectively.?3?With the self-made W-CA-V?IV?as the precursor of VO₂ layer and SiO_2,obtained from the acid or base catalytic system,as the precursor sol of low refractive index layer,SiO₂/W-VO₂ thermochromic coatings were prepared via W-VO₂sintering alone.The experimental results show that,when the coatings are prepared by the W-VO₂ alone-calcinated,multilayer coating with a clear interface.The typical sample exhibited a good comprehensive performance,with the near infrared switching ability at 2000 nm?T₂₀₀₀ value of 30.1%,the solar energy modulation?T_sol value of 6.1%,the integral visible and the integral solar transmittance T_vis,_L and T_sol,L at 25? value of 71.8%and 73.1%,respectively.