Metal oxide semiconductor N2O sensor for medical use

In order to develop a semiconductor type gas sensor applicable to the monitoring of N2O in air, a search for the semiconducting oxides sensitive to N2O was carried out. Among the 23 kinds of single oxides tested, SnO2 turned out to give the highest sensitivity to N2O, although the sensitivity was not high enough. The N2O sensitivity was found to be promoted effectively when SnO2 was loaded with a small amount of a basic oxide such as SrO, CaO, BaO, Bi2O3 and Sm2O3. The promotion was particularly conspicuous with SrO loading. For example, 0.5 wt.% SrO-loaded SnO2, exhibited the N2O sensitivity about three times as high as that of pure SnO2, and could detect N2O in air fairly well in the concentration range of 10–300 ppm at 500°C.