マイクロエマルション法による二酸化バナジウムナノ粒子の作製と粒径及び相転移温度の制御

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 phase transition temperature of VO2 nanoparticles by the microemulsion method. The resultant VO2 particles were characterized by XRD, DSC, SEM and TEM. Primary particle size of the resulting VO2 nanoparticles was estimated to be 25 nm with average agglomeration size of about 300 nm. The phase transition temperature for the W doped VO2 was 37 ˚C. As a result, we successfully synthesized the VO2 nanoparticles with controlled particle size and phase transition temperature by microemulsion method.