2011 年 119 巻 1390 号 p. 464-469
The metastable anatase phase of YXTi1−2XNbXO2 (X = 0–0.15) was formed as nanosized-particles from precursor solutions of TiOSO4, NbCl5, and YCl3 under mild hydrothermal conditions using the hydrolysis of urea. The aeschynite phase YTiNbO6 coexisted with anatase-type titania in the precipitate that was formed at the composition of X = 0.20. The crystallite sizes of anatase formed under hydrothermal conditions at 240°C for 5 h were approximately 15 nm. The diffuse reflectance spectra continuously varied and optical band gap gradually increased with increased yttrium and niobium content in the samples. The anatase formed at the composition of Y0.05Ti0.90Nb0.05O2 showed the same level of photocatalytic activity as that of pure TiO2. The precipitation of YTiNbO6 phase out of the anatase above 850°C was observed before the formation of rutile through the anatase-to-rutile phase transformation. The crystallite growth of anatase in the course of heating was delayed and the phase transformation shifted into higher temperature more than 150–200°C via the co-presence of yttrium and niobium.
