Hydrothermal synthesis and properties of solid solutions and composite nanoparticles in the TiO2–SnO2 system

Solid solutions and composite nanoparticles in the TiO2–SnO2 system were directly formed via the hydrothermal treatment of precursor solutions of TiCl4 and SnCl4 under weakly basic conditions in the presence of urea. The rutile-type (Ti, Sn)O2 solid solutions were formed in the composition range of Ti 0–70 mol%. The composite nanoparticles consisting of anatase- and rutile-type phases were formed at the composition of Ti 80 and Ti 90 mol%. The change in the lattice parameters a0 and c0 of the rutile-type solid solutions followed the Vegard Law. The crystallite size of the rutile-type solid solutions was in the range of 5–10 nm. The diffuse reflectance spectra varied with changing Ti content in the precipitates. The photocatalytic activity of composite nanoparticles synthesized at 240 °C was higher than that synthesized at 180 °C. The composite nanoparticles consisting of anatase- and rutile-type phases with compositions Ti0.90Sn0.10O2 and Ti0.80Sn0.20O2 showed improved photocatalytic activity.