Abstract: Ultra-fine SnO₂ powder with mean size of 2～3 nm was prepared by a sol-gel process.The structure and properties of the powder were studied.It is found that the tetragonal tin dioxide formed essentially during the gel drying at 70℃,and further crystallized on heating at 240～330℃,which was much lower than the temperature reported for the powder prepared with other method.The temperature dependent curue of conductivity for the thick film gas sensors made of this ultrafine powders showed a peak at 130℃,which was obviously lower than that reported in literature.The gas sensing layer of the element exhibited good strength and good resistivity stability as well as high sensitivity to H₂ and C₂H₂ gases.

Key words: nanometer-sized powder, SnO₂, sol-gel process, gas sensing property