ゾル-ゲル法によるバナジウム-チタン系酸化物薄膜の作製とそのエレクトロクロミック特性

抄録

Vanadium-titanium oxide thin films were prepared by sol-gel method. Spin-coating solutions containing VO(O-i-C₃H₇)₃ and Ti(O-i-C₃H₇)₄ in isopropanol could be stabilized properly with the addition of acetylacetone and excess acetic acid. Electrochromic properties of the coated films were strongly dependent both on the atomic ratio of titanium and vanadium, i.e., Ti/(V+Ti) (x) in the coating solutions of alkoxides and on the calcination temperatures. In the case of calcination at 400°C, the films having x=0-0.17 gave the two-step electrochromism, that is, blue↔green↔yellow, while the titanium-rich films, especially those having x=0.60-0.67, exhibited new coloration of reddish-brown at a cathodic potential of -0.8V vs. SCE. On the other hand, the electrochromism of the films calcined at 500°C was similar to that of a pure V₂O₅ film. No crystalline phases but poorly crystalline TiO₂ (anatase) were detected in the 400°C-calcined films having x≥0.60 by XRD, indicating that vanadium oxide should be amorphous. The formation of V³⁺ in the cathodically polarized films was observed by XPS measurement, which seems to cause the reddish-brown coloration.