| Home | Log-in | Admin | Sitemap |
Home | Program | Detailed Program
Detailed Program
Paper Number : EL-P03
Time Frame : 12:00~13:30
Presentation Date : Friday, 28, November
Session Name : Electronic Ceramics
Session Chair 1# : -
Session Chair 2# : -
Phase transition temperature control of thermochromic
Mr. Takuya Okuda
Shizuoka University
[Introduction] Vanadium dioxide, VO2, undergoes the phase transition from monoclinic to tetragonal with property change from semiconductor to metal 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, however it can be lowered by tungsten or the other metal cation doping. Furthermore, 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 phase transition temperature of VO2 nanoparticles by the microemulsion method using molecular-designed precursors. [Experimental] Tungsten pentaethoxide(W(OC2H5)5) and acetic acid were mixed in cyclohexane, and added vanadium oxyisopropoxide(VO(O-i-Pr)3) into the solution. Microemulsion was prepared by mixing Triton X-100, cyclohexane and water as surfactant, oil phase and aqueous phase, respectively. Precursor solution was added into the microemulsion, and stirred for 24 hr. Precursor sols were washed with acetone, centrifuged, and dried at 150¡§¬C. Dried gel were annealed at 400¡§¬C for 1hr under the reducing atmosphere of Ar:H2=9:1, then annealed again at 600¡§¬C for 1hr under the inert atmosphere of N2. Doping amount of tungsten was fixed at 2at.% for all samples and the ratio of acetic acid, RA(=[Acetic acid]/[W]) was fixed at 3. The resultant VO2 particle was characterized by XRD, DSC, SEM and TEM. [Result & Discussion] 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 of W doped VO2 was lowered to 28 to 40¢®¨¡C by the W-doping. Therefore, microemulsion method from the molecular-designed precursors was expected to control the phase transition temperature to around room temperature and application of VO2 to the thermochromic smart window.
Acknowledgements :