A Double Layer Sensing Electrode "Bati(1-X)Rhxo3/Al-Doped Tio2" For No2 Detection Above 600 Degrees C

NO2 emission is mostly related to combustion processes, where gas temperatures exceed far beyond 500 degrees C. The detection of NO2 in combustion and exhaust gases at elevated temperatures requires sensors with high NO2 selectivity. The thermodynamic equilibrium for NO2/NO 500 degrees C lies on the NO side. High temperature stability of TiO2 makes it a promising material for elevated temperature towards CO, H-2, and NO2. The doping of TiO2 with Al3+ (Al:TiO2) increases the sensitivity and selectivity of sensors to NO2 and results in a relatively low cross-sensitivity towards CO. The results indicate that NO2 exposure results in a resistance decrease of the sensors with the single Al:TiO2 layers at 600 degrees C, with a resistance increase at 800 degrees C. This alteration in the sensor response in the temperature range of 600 degrees C and 800 degrees C may be due to the mentioned thermodynamic equilibrium changes between NO and NO2. This work investigates the NO2-sensing behavior of duplex layers consisting of Al:TiO2 and BaTi(1-x)RhxO3 catalysts in the temperature range of 600 degrees C and 900 degrees C. Al:TiO2 layers were deposited by reactive magnetron sputtering on interdigitated sensor platforms, while a catalytic layer, which was synthesized by wet chemistry in the form of BaTi(1-x)RhxO3 powders, were screen-printed as thick layers on the Al:TiO2-layers. The use of Rh-incorporated BaTiO3 perovskite (BaTi(1-x)RhxO3) as a catalytic filter stabilizes the sensor response of Al-doped TiO2 layers yielding more reliable sensor signal throughout the temperature range.