The Gas Sensing Potential of Nanocrystalline SnO2 and In2O3 Powders Prepared by Mechanical Milling

The use of nanocrystalline metal oxide powders to increase the sensitivity of gas sensors has been the subject of this research. Of particular interest to our application in environmental monitoring is ln₂O₃ and SnO₂, which are known, respectively, to have a high sensitivity to oxidising pollutant gases such as NO₂ and 03, and reducing pollutant gases such as CO and NH₃. Preparation of undoped nanocrystalline SnO₂ and ln₂O₃ powders by mechanical milling via centrifugal action have been conducted. The technique used has allowed the reduction of grain sizes from 3-5 mum to below 100 nm with no contaminating carbon content, as confirmed by SEM and EDS spectra analysis. Furthermore, the FTIR spectra indicated that the SnO₂ nanopowders had a strong band at 671 cm^-1 and ln₂O₃ at 601 cm^-1. The resulting nanopowders were then mixed with alpha-based terpinol to produce a thick film paste as an active material of gas sensors, and applied to an alumina platform consisting of AgPt heater and electrode tracks.