Iron oxide-based semiconductor gas sensors were exploited for detecting dimethyldisulfide (DMDS) gas, an important flavor component of consomme soup. Among the various metals and metal oxides tested, Pr
6O
11 was the most effective additive to Fe
2O
3 for promoting the sensitivity to DMDS vapor (20 ppm) in air at 300°C, giving the highest sensitivity at a Pr
6o
11 content of 5wt%. The sensor using 5wt%Pr
6O
11-added Fe
2O
3 was also fairly good in selectivity to DMDS among various flavor components of consomme soup. As characterized by XRD, 5wt%Pr
6O
11-added Fe
2O
3 system contained no crystalline phases other than Fe
2O
3, while PrFeO
3 was observed at Pr
6O
11 contents of 1Owt% and above. The Pr
4+/Pr
3+ ratio as revealed from XPS analysis remained far higher for Pr
6O
11-added systems than that for pure Pr
6O
11, though it tended to decrease with increasing Pr
6O
11 content. These results suggest that, at low Pr
6O
11 contents, a major part of Pr components added exist as finely dispersed Pr
4+ species on the surface of Fe
2O
3 particles and that such surface Pr
4+ species are responsible for the observed enhancement of gas sensitivity to DMDS.
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