Preparation and structural characterization of nanocrystalline SnO2 powders

Nanocrystalline SnO2 powders have been prepared by solid-liquid reaction and solid-state thermal oxidizing techniques. The microstructures and phase compositions of the product were characterized by thermogravimetry analysis, X-ray diffraction, and the Raman spectrum. It is shown that at least two phases, SnO2 and SnOx, coexist at 450 degrees C. However, only the tetragonal rutile structure SnO2 phase is detected after the Sn powders were annealed at 550 degrees C. The Raman peaks of the nanocrystalline SnO2 powders reveal remarkable red shift and broadening, which could be attributed to the phonon confinement effect, oxygen vacancies, and the stress effect.