NO(X) RESPONSE OF TIN DIOXIDE-BASED GAS SENSORS

Three types of SnO2 based sensors developed at Swansea have been tested in NO(x) containing environments. Polycrystalline Bi2O3 doped devices exhibit a reverse sensitivity to NO(x) both in air and in nitrogen at temperatures of 300-degrees-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-degrees-C behave in a conventional manner, where marked resistance increases are observed in the presence of NO(x). Gas sensitive thin films fabricated via the oxidation of a metallic Sn layer display high sensitivity to NO(x) while remaining unresponsive to common interfering gases such as carbon monoxide or methane.