Size effect on the lattice parameters of nanocrystalline anatase

Crystallite size dependence on the lattice parameters of nanocrystalline anatase was examined by x-ray diffraction pattern analysis, x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The lattice parameter a increased while the parameter c decreased with reducing crystallite sizes. However, the cell volume increased with decreasing crystallite size indicating an overall expansion due to confinement effect. The observed shift in E-g Raman mode (at 144 cm(-1)) was in accordance with an empirical phonon confinement model while no substoichiometric titania Could be detected by XPS. It was concluded that the lattice. expansion was purely due to electrostatic relaxation as a result of size confinement. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3261754]