One-step hydrothermal synthesis of rare earth/W-codoped VO2 nanoparticles: Reduced phase transition temperature and improved thermochromic properties

Abstract

Abstract As a reversible thermochromic material, vanadium dioxide (VO 2 ) is a promising candidate for smart window applications. The trade-off between the integrated visible transmission ( T lum ) and the solar modulating ability (Δ T sol ), as well as the high phase transition temperature ( τ c ∼68 °C) are regarded as the main obstacle for practical applications of pure VO 2 nanomaterials. The combination of both high τ c reducing efficiency of W and improving T lum /Δ T sol properties of RE (rare earth: Eu, Tb), herein lies the purpose of RE/W-codoping to enhance the thermochromic performance. The RE/W-codoped VO 2 nanoparticles were synthesized under hydrothermal conditions, and exhibited grain size of less than 100 nm. The smart window which was fabricated by coating RE/W-codoped VO 2 nanoparticles onto glass, exhibits a thermochromic performance with a combination T lum = 40%, Δ T sol = 6.3%, τ c = 40.8 °C or T lum = 63%, Δ T sol = 3.6%, τ c = 31.9 °C, indicating the largely reduced absorption compared with the single W doping. Under the RE/W-codoping conditions, it was found that the ionic radius of the RE 3+ cations controlled the crystallinity of the VO 2 particles and the electron/hole carrier counteraction as well as the competition between the strain and the hole carrier played a vital role in modulating the τ c of the VO 2 products. The findings should be meaningful for investigating the codoping mechanisms for VO 2 nanomaterials.