Chemical Deposition Method for Preparing VO2@AlF3 Core–Shell-Structured Nanospheres for Smart Temperature-Control Coating

Vanadium dioxide (VO2) has become one of the most promising smart temperature-controlled thin-film materials due to its reversible phase transition between a metallic and an insulating state at approximately 68 °C, accompanied by negligible volume change and excellent optical modulation properties. However, the practical application of VO2 is still limited by its relatively high phase transition temperature and susceptibility to oxidation. To address these two major shortcomings, this study employed a one-step hydrothermal method to prepare a VO2 nanopowder, followed by a chemical precipitation method to form a VO2@AlF3 core–shell structure. The coated nanoparticles were then dispersed in a PVP ethanol solution, coated onto a glass substrate, and evaluated for performance. The experimental results indicate that when the molar ratio of VO2 to AlF3 reached 1:1, the phase transition temperature of VO2@AlF3 was effectively reduced to 50.3 °C, significantly lower than the original temperature of 68 °C. Additionally, the material exhibited favorable optical properties, with a solar modulation ability (ΔTsol) of 17.2% and a luminous transmittance (Tlum) of 36.3%. After calcination in air at 300 °C for 3–6 h, the VO2 core remained oxidation-resistant and maintained excellent phase-change thermal insulation properties.