Thermochromic Properties of Double-Doped VO2 Thin Films Prepared by a Wet Coating Method Using Polyvanadate-Based Sols Containing W and Mo or W and Ti

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A mixture of metallic vanadium, tungsten and molybdenum powder was dissolved in a hydrogen peroxide solution, to yield a polyvanadate sol containing W and Mo. A thin film of V1-x-yWxMoyO2 was fabricated on a fused silica substrate by spin-coating using such a sol followed by reduction in hydrogen and successive annealing in a nitrogen atmosphere. Thin films in the system V1-x-zWxTizO2 were similarly prepared using a sol containing W and Ti. All the films obtained in this study showed a clear thermochromic switching performance with a large transmittance change in the infrared region. For V1-x-yWxMoyO2, the switching temperature ($T_{\text{t}}$) was lowered by doping at approximately $T_{\text{t}}=T_{\text{t}0}$ ($=67$°C)-$\textit{ax}$-$\textit{by}$, where $a$ and $b$ are the decrease rates of each individual dopant (about 1920 and 870°C, respectively, for $0\leqq x$, $y\leqq 0.03$). Doping of Ti had little effect on $T_{\text{t}}$, but markedly reduced hysteresis of the transition. We demonstrated that a double-doped film of V1-x-zWxTizO2 ($x=0.018$ and $y=0.10$) showed thermochromic switching almost without any hysteresis at a temperature as low as 45°C.
Publication Office, Japanese Journal of Applied Physics, Faculty of Science, University of Tokyoの論文
2001-03-15