A VIBRATIONAL STUDY OF UNIFORM SNO2 POWDERS OF VARIOUS MORPHOLOGIES

The vibrational characteristics of uniform SnO2 powders consisting of particles of various shapes (spherical, prismatic, rod-like) and of di fferent size distributions were studied by infrared and Raman spectros copy. The infrared spectra of the samples displayed variations in the position, relative intensity and width of the absorption bands, which were attributed to particle shape effects. The Raman spectra showed a weakening of the intensities of the single-crystal SnO2 modes as the c rystallite size decreased. In addition, the spectra of all studied sam ples also exhibited some bands not predicted by group-theory considera tions, the origin of which was related to the particle surface. A deta iled vibrational study provides information on the particle shape and size and the crystallinity of powdered materials.