STUDY ON THE MICROSTRUCTURE AND PROPERTIES OF NANOSIZED STANNIC OXIDEPOWDERS

Stannic oxide xerogel was prepared by a forced hydrolysis method using SnCl4 as the precursor. The average grain sizes of the nanosized stan nic oxide powders varied with the sintering temperatures. The powders were characterized by several different physico-chemical techniques. T EM was employed for the direct observation on grain sizes, shape and s tate of aggregation of the particles. XRD technique was used for the d etermination of the crystalline structure. Microstructural parameters of average crystallite size (<D>) and mean-square root microstrain (ep silon(2)>(1/2)) for the samples were calculated from the broadened val ues of the half-peak intensity of XRD. The atomic ratio between oxygen and tin in the surface region of the particles was estimated through the analysis of XPS. Attributing to lots of oxygen vacancies in the su rface region of the nanoparticulates and the 'trapped electrons' in th e vacancies, an ESR signal was observed in the sample sintered at 300 degrees C for 2 h. FTIR of the powders showed that intensity of the tr ansverse optical mode of Sn-O stretching vibration increased with the sintering temperature while the bending vibration of O-Sn-O showed a b lue shift. For Raman spectra, very important spectral characteristics such as variations of intensity and width of the bands were observed. A new Raman vibrational band located at 572 cm(-1) was identified in t he samples of nanosized stannic oxide powders. Variation of these spec troscopic properties were strongly affected by grain size, shape and s tate of aggregation of the nanosized particulates.