The effects of crystal size on the Raman spectra of nanophase TiO2

Raman scattering was applied as a probe for the evolution of the crystalline size and distribution of nanosized TiO2, Small physical dimensions of TiO2 crystals lead to a shift and broadening of the first-order Raman lines through a relaxation of the q = 0 selection rule and affects on to the position of a low-frequency Raman (LFR) band. The details of the evolution of the 144 cm(-1) Raman line shape (frequency, broadening and asymmetry) on the size and distributions of the nanocrystals are presented. The methodologies for the size determination of nanocrystals using the LFR mode together with a deconvolution treatment to obtain the size distribution were analyzed. Both the Raman results were compared with the grain size distribution obtained by high-resolution electron microscopy. (C) 1999 Elsevier Science B.V. All rights reserved.