The durability study of thermochromic vanadium dioxide films with the addition of barrier coatings

The high-performance thermochromic vanadium dioxide (VO2) films can be applied in many industrial applications such as smart windows, infrared sensors, and infrared imaging (bolometers). The preservation of its highly thermochromic properties of VO2 films is crucial since the oxidation number of vanadium ranges from +2 to +5 under various reducing or oxidizing atmospheres at elevated temperatures and humid environment. In this study, VO2 films were fabricated by thermal oxidation of co-sputtered thin films of vanadium and stainless-steel (SS), followed by the addition of barrier coatings on top of the as-prepared VO2 films for the improvement of long-term stability. The samples with barrier coatings containing zinc oxide (ZnO) and silicon oxide (SiO2) showed significantly better durability in either wet or dry high temperature environment. With an equivalent barrier coating thicknesses, the stability of the samples was ranked in the order of TiO2/ZnO/VO2:SS ∼ ZnO/SiO2/VO2:SS > VO2:SS > TiO2/SiO2/VO2:SS > Plain VO2 at wet condition (95% RH, 80 °C). In addition, the durability order was: TiO2/ZnO/VO2:SS > ZnO/SiO2/VO2:SS ∼ TiO2/SiO2/VO2:SS > VO2:SS > Plain VO2 at dry condition (300 °C). The results suggest that the proposed VO2/TiO2/ZnO barrier coating is a promising material for both durability and thermochromic performance.