RAMAN-STUDY OF NANOSIZED TITANIA PREPARED BY SOL-GEL ROUTE

TiO2 polycrystalline powders have been prepared by different sol-gel r outes and have been investigated by Raman spectroscopy and transmissio n electron microscopy. The influence of different catalysts on the cry stalline phases obtained by thermal annealing is studied. The mechanis ms that determine the Raman line shapes are discussed, including phono n confinement and pressure effects. The analysis of the Raman spectra, after thermal treatments in air and N-2, indicates the importance of the non-stoichiometry due to oxygen vacancies. (C) 1998 Elsevier Scien ce B.V. All rights reserved.