Abstract: Nanosized stannic oxide powders were prepared by sol-gel method.The microstructure change of the ultrafine particles after heat-treatment at 300～800℃ has been investigated by XRD,TEM,TG-DTA,and FT-IR techniques. It is found that the intensity ofthe transverse optical mode of Sn-O streching vibration increased with the calcining tempcrature and the bonding vibration of O-Sn-O showed a blue shift.The changes are strongly affected by the size, shape, and the state of aggregation of the ultrafine particles.

Key words: stannic oxide, nanosized particle, heat-treatment, microstructure, IR