Microstructure and optical properties of scandium doped TiO₂ nanoparticles

Pure and Sc doped TiO₂ nanoparticles with different molar fractions of Sc were prepared by a sol-gel process, and were characterized by means of XRD, TG-DSC, TEM, UV-Vis and PL spectra. Effects of calcination temperature and Sc content on microstructure and optical properties of as-prepared TiO₂ samples were investigated and the influencing mechanisms were discussed. The results show that Sc dopant greatly inhibits the crystallization from amorphous state to anatase and the phase transformation from anatase to rutile. Retarding effect of Sc on the grain growth of TiO₂ was also observed and the effect becomes significant with the increase of Sc content. Compared with pure TiO₂, the UV-Vis absorption band edge of Sc doped samples shows obvious blue-shift, however, there is no noticeable increase in the shift with increasing Sc content. The ultraviolet absorbing capacity of TiO₂ samples at 200-300 nm is reduced and then enhanced with increasing Sc content. The samples doped with 1.5% and 2% (mole fraction) Sc show stronger ultraviolet absorption than pure one. Photoluminescence peaks at 410 and 460 nm were detected on all the samples, which means that the doping of Sc does not generate new luminescence phenomena, but the luminescence intensity is enhanced with the increase of Sc content.