Synthesis of anatase nanoparticles with extremely wide solid solution range and ScTiNbO6 with α-PbO2 structure

Anatase-type nanoparticles ScXTi1−2XNbXO2 with wide solid solution range (X=0–0.35) were hydrothermally formed at 180 °C for 5 h. The lattice parameters a0 and c0, and the optical band gap of anatase gradually and linearly increased with the increase of the content of niobium and scandium from X=0 to 0.35. Their photocatalytic activity and adsorptivity by the measurement of the concentration of methylene blue (MB) that remained in the solution in the dark or under UV-light irradiation were evaluated. The anatase phase existed stably up to 900 °C for the samples with X=0.25–0.30 and 750 °C for that with X=0.35 during heat treatment in air. The phase with α-PbO2 structure and the rutile phases coexisted in the samples with X=0.25–0.30 after heated at temperatures above 900–950 °C. The α-PbO2 structure having composition ScTiNbO6 with possibly some cation order similar to that seen in wolframite existed as almost completely single phase after heat treatment at temperatures 900–1500 °C through phase transformation from anatase-type ScTiNbO6.