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 degrees C) and high (600-900 degrees 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 degrees C for 3 h. The TiO2 powders produced at high temperatures (from 600 to 900 degrees 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 degrees C after calcination at 600 degrees 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