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

• Published in: Journal of alloys and compounds 2017-07, Vol.711, p.222-228
• Main Authors: Wang, Ning, Goh, Qing Sheng, Lee, Pei Lin, Magdassi, Shlomo, Long, Yi
• Format: Article
• Language: English
• Subjects: Chemical compounds; Crystallinity; Doping; Grain size; High temperature; Hydrothermal synthesis; Nanomaterials; Nanoparticles; Phase transitions; Rare earth elements; Solar modulation; Thermochromic smart window; Transition temperature; Vanadium dioxide; Vanadium oxides
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2017.04.012

As a reversible thermochromic material, vanadium dioxide (VO2) is a promising candidate for smart window applications. The trade-off between the integrated visible transmission (Tlum) and the solar modulating ability (ΔTsol), as well as the high phase transition temperature (τc∼68 °C) are regarded as the main obstacle for practical applications of pure VO2 nanomaterials. The combination of both high τc reducing efficiency of W and improving Tlum/ΔTsol properties of RE (rare earth: Eu, Tb), herein lies the purpose of RE/W-codoping to enhance the thermochromic performance. The RE/W-codoped VO2 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 VO2 nanoparticles onto glass, exhibits a thermochromic performance with a combination Tlum = 40%, ΔTsol = 6.3%, τc = 40.8 °C or Tlum = 63%, ΔTsol = 3.6%, τc = 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 RE3+ cations controlled the crystallinity of the VO2 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 τc of the VO2 products. The findings should be meaningful for investigating the codoping mechanisms for VO2 nanomaterials. [Display omitted] •First case to investigate the RE/W-codoping effects.•The crystallinity could be controlled by the ionic radius of the RE dopants.•Tc was reduced by h+/e−carrier counteraction and strain/h + competition.