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

Three types of SnO2 based sensors developed at Swansea have been teste d in NO(x) containing environments. Polycrystalline Bi2O3 doped device s exhibit a reverse sensitivity to NO(x) both in air and in nitrogen a t temperatures of 300-degrees-C or less. In this case sensor resistanc e falls markedly upon exposure to the oxidising gas. In contrast, sens ors prepared from undoped SnO2 which had been precalcined at 1500-degr ees-C behave in a conventional manner, where marked resistance increas es are observed in the presence of NO(x). Gas sensitive thin films fab ricated via the oxidation of a metallic Sn layer display high sensitiv ity to NO(x) while remaining unresponsive to common interfering gases such as carbon monoxide or methane.