Lowered phase transition temperature and excellent solar heat shielding properties of well-crystallized VO₂ by W...

Monoclinic VO₂ (M) is a key material for energy-efficient smart window applications. Fine crystalline VO₂ particles with an ambient phase transition temperature are urgently required to achieve excellent properties including high luminous transmittance and solar heat shielding ability. Moreover, the anti-oxidation ability is regarded as a significant factor which determines the lifetime of VO₂-based products. In this paper, well-crystallized W-doped VO₂ with low phase transition temperature, excellent solar heat shielding ability and considerable anti-oxidation ability was synthesized by a solid-state reaction process. The phase transition temperature was reduced from 67.3 °C to 10.8 °C at 2.0% W doping with an efficiency of -28.1 °C per at%. Importantly, an excellent balance between the phase transition temperature and the latent heat was obtained at high doping levels (1.5-2.0%). Furthermore, W-doped VO₂ particles exhibited a significantly longer exposure time (more than 5 h) at 300 °C in air than the previously reported 2 h in the literature, and the corresponding derived composite foils showed excellent luminous transmittance and solar heat shielding properties (T_lum = 49.9% and T_sol = 44.8% for 2.0% W doping).