Effect of co-dopant on the formation and properties of anatase-type titania solid solutions doped with niobium Original Research Article

The effect of co-dopant M (M=gallium (Ga), aluminum (Al), and scandium (Sc)) on the formation, crystallite growth, optical band gap, photocatalytic activity, and phase stability of anatase-type titanium dioxide solid solutions (Ti1−2XNbXMXO2) containing the same amount of dopant niobium (Nb) that were directly formed as nanoparticles under mild hydrothermal conditions at 180 °C for 5 h was investigated. The composition range X of the anatase-type solid solutions (Ti1−2XNbXMXO2) depended on the co-dopant M, i.e., X=0.15–0.20 for M=Ga and Al, and X=0.33 for M=Sc. A remarkable increase in the lattice parameter c0 was detected in the solid solutions co-doped with M=Sc. The increase in the amount of co-dopant M=Ga and Al enhanced the crystallite growth of the anatase-type solid solutions under the hydrothermal conditions. The photocatalytic activity of the solid solutions (Ti0.80Nb0.10M0.10O2) co-doped with M=Sc, Ga, and Al increased in that order. The co-dopant M=Ga promoted the anatase-to-rutile phase transformation of the solid solutions at lower temperature.