Abstract
Vanadium dioxide, VO2, undergoes the phase transition from monoclinic to tetragonal with property change from semiconductor to metal, respectively, at about 68°C. Metallic tetragonal structure reflects infrared light, and semiconducting monoclinic structure transmits it, leading to the thermochromic smart window. On the other hand, the phase transition temperature is slightly higher than the room temperature and can be lowered by tungsten or the other metal cation doping. Furthermore, VO2 nanoparticles with lower transition temperature and particle size less than 100 nm is essential for the smart window because the light scattering can be dramatically suppressed by reducing the particle size to obtain a high transparency. In this study, we tried to control the particle size and the phase transition temperature of VO2 nanoparticles by the microemulsion method from the molecular-designed precursors. The resultant VO2 particles were characterized by XRD, DSC, SEM. Primary particle size of the resulting VO2 nano-particles was estimated to be 37 nm with average aggregation size of about 200 nm. The phase transition temperature for the W doped VO2 was 24°C. As a result, we successfully synthesized the VO2 nanoparticles for smart window with controlled particle size and phase transition temperature by microemulsion method.
