Nd-Doping Induced Lattice Distortion in TiO 2 Nanoparticles

Nd-doping effects are investigated in TiO2 nanoparticles with various annealing temperatures T from 70°C to 1100°C by means of x-ray diffraction (XRD) and Raman scattering spectroscopy. XRD results indicate that the sample shows a rutile phase at 1100°C, which changes to anatase phase at 900°C. With decreasing T down to 300°C, a significant lattice shrink is found, that is, the lattice parameter c is significantly suppressed while the a value shows a gradual decrease. With further decrease of T, the c-value shows an unexpected increase while the α-value keeps a gradual decrease. Thus, a lattice distortion takes place with changing the annealing temperature. In Raman investigation, all the Raman modes for the anatase phase show hardening behaviors with decreasing T in the range 900–300°C, and then the Eg and A1g modes show softening behaviors below 300°C, suggesting the variation of the lattice distortion. The variation of the lattice distortion at different annealing temperatures is ascribed to different depositions of Nd ions on the surface of TiO2 nanoparticles.