Nanostructured vanadium dioxide films

Abstract

Vanadium (IV) oxide (VO2) is the most widely researched thermochromic (TC) material. Owing to its fully reversible metal-insulator transition (MIT) at the critical temperature (τc) of 68 ˚C, which is the closest to the room temperature and adjustable through doping, it has the potential application as the energy-saving coating for smart windows. Recent researches revealed that introducing porosity and fabrication of nanoparticles (NPs)/matrix composite foils could produce VO2 coatings at the best TC performance. This research employs lyophilisation (freeze drying) technique to fabricate nanoporous VO2 thin films and agglomeration-free NPs. The best combination of TC properties for the former achieved Tlum ≈ 50% and ΔTsol = 14.7%, while that for the latter achieved average Tlum = 35%, ΔTsol = 6.8%, τc = 64.5 ˚C and Δτc = 4.5 ˚C, with small particle size and narrow distribution (37-53 nm) as well as high crystallinity (LC = 36.76 J/g, close to the commercial VO2 powder).