NOx response of tin dioxide based gas sensors

Abstract

Three types of SnO2 based sensors developed at Swansea have been tested in NOx containing environments. Polycrystalline Bi2O3 doped devices exhibit a reverse sensitivity to NOx both in air and in nitrogen at temperatures of 300 °C or less. In this case sensor resistance falls markedly upon exposure to the oxidising gas. In contrast sensors prepared from undoped SnO2 which had been precalcined at 1500 °C behave in a conventional manner, where marked resistance increases are observed in the presence of NOx. Gas sensitive thin films fabricated via the oxidation of a metallic Sn layer display high sensitivity to NOx while remaining unresponsive to common interfering gases such as carbon monoxide or methane. © 1993.