Micro-Raman spectroscopic characterization of nanosized TiO₂ powders prepared by vapor hydrolysis

Micro-Raman analysis was used to study the structure of TiO₂ powders produced at low (260°C) and high (600-900°C) temperatures by vapor hydrolysis of titanium tetraisopropoxide (TTIP). Spatial inhomogeneity was discovered after the amorphous TiO₂ powders produced at low temperature were calcined at 700, 800, and 900°C for 3 h. The TiO₂ powders produced at high temperatures (from 600 to 900°C) were found to be spatially homogeneous and predominately anatase in structure. Small amounts of rutile and brookite are found for powders produced at 700, 800, and 900°C after calcination at 600°C for 3 h. The rutile and brookite impurities are believed to be concentrated on the surface of anatase based on a comparison of results of Raman and x-ray diffraction studies.