Development of SnO2-based gas sensor sensitive to dilute ethylene oxide in air

In order to enhance sensitivity to C2H4O for the medical safety purpose, foreign additives (e.g. La2O3, SrO and CaO) were loaded on SnO2 powder. Among the additives tested, La2O3 proved itself to be a promising promoter for the sensitivity. On the other hand, the response and recovery rates were found to be deteriorated with La2O3. The rates were accelerated considerably when the La2O3-loaded SnO2 was further added with Pd or Pt. The device using Pt (0.5 wt.%)–La2O3 (0.5 wt.%)–SnO2 thus prepared showed sensor response exceeding 10 to 1 ppm C2H4O as well as fairly good response rates under dry condition at 300 °C, where response was defined as the resistance ratio (Rair/Rgas).