The role of additives in SnO/sub 2/ semiconductor gas sensors

The effects of additives on the gas sensitivity to CH/sub 3/CN and CO are examined. The overall trends are similar in both gases. The Al-loaded SnO/sub 2/ sensor shows a slight increase in the sensitivity as compared with SnO/sub 2/. The Nb-loaded SnO/sub 2/ sensor decreases the sensitivity except in the low-temperature region. For CH/sub 3/, Pd does not appreciably improve the sensitivity in the low-temperature region in the sensors considered. However, the Pd-loaded SnO/sub 2/ enhances the sensitivity to CO in the low-temperature region. XPS studies suggest that the oxidation states of Pd are 4+ and 2+ with a relative ratio of 3:1.<
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