[19p-E214-1~12] 22.1 Joint Session M "Phonon Engineering"

△ [19p-E214-6] Structure and Properties of WO_3-x Thin Films (2): Dependence of Thermal Conductivity on Reduced State

〇(M1)Koichi Sakata¹, Kai Otani¹, Takashi Yagi^1,2, Yuichiro Yamashita^1,2, Makoto Kashiwagi¹, Junjun Jia³, Naoyuki Taketoshi^1,2, Yuzo Shigesato¹ (1.Aoyama Gakuin Univ., 2.AIST, 3.GCSE, Waseda Univ.)

Keywords:electrochromic materials, tungsten oxide, thermal conductivity

Amorphous tungsten oxide is one of the electrochromic materials that can change their optical properties reversibly between colored and transparent states by electrochemical oxidation-reduction. Tungsten oxide have attached large interest as the thermal switching materials because phase transition to metal takes place at x>0.32 in H_xWO₃. In this study, we prepared WO_3-x films reduced by controlled an O₂ flow ratio in the deposition and H_xWO₃ films reduced by electrochemical reaction, where x was smaller than 0.32. The thermal conductivity was analyzed using a pulsed light heating thermoreflectance apparatus. Thermal conductivities of the WO_3-x films controlled to the transmittance of 32%-100% and H_xWO₃ films applied +0.2V or -0.2V, where the x was smaller than 0.32, showed almost no-changes.