Temperature independent resistive oxygen sensor for the control of combustion processes
Final Report Abstract
In this DFG-funded project, resistive oxygen sensors based on BaFe(1−x)−0.01Al0.01TaxO3−δ were investigated for combustion processes with excess oxygen. It had been known from the previous project MO 1060/22 that a tantalum content of about 25% (BFAT25) yields to an almost temperature-independent resistivity of the gas sensing material. On this basis, BFATxbased oxygen sensors were extensively characterized and optimized for potential technical applications. The objectives of the project were to evaluate the suitability of screen printing and powder aerosol deposition (PAD) for producing the sensitive films and their influence on the sensor properties, to investigate poisoning mechanisms and long-term stability, and to manufacture demonstrators and test them in real exhaust gas. The project focused on the PAD layers due to their greater sensitivity to O 2 compared to the thicker, porous screen-printed films, as well as their better sensor kinetics and signal stability. Pulsed laser deposition was found to be inadequate. Additionally, only the PAD films exhibited temperature-independent sensor behavior. Additionally, the poisoning impact of sulphur dioxide (SO2) and hydrogen chloride (HCl) on the sensor layers was investigated. The findings indicate that HCl had a negligible effect on the sensor behavior, whereas sulfurization increased the resistance of the sensor layer by approximately ten times and adversely affected both its sensitivity and selectivity. The formation of barium sulphate (BaSO4) on the film surface was detected using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The suitability of a PAD-BFATx layer as a sensitive material for self-heated, housed oxygen sensors was demonstrated in real exhaust gas: On the one hand, the oxygen concentration of a wood-burning stove was reliably monitored. Secondly, a BFAT25 coating in the exhaust of a diesel engine (test bench) proved its worth as an O2-sensitive component of a combined nitrogen oxide/oxygen sensor (multi-gas sensor). In these tests, the oxygen stoichiometry during a NEDC (New European Driving Cycle) was successfully determined.
Publications
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Impedance based NO x sensor for exhaust applications, 18th FAD-Conference, 15.16.-16.09.2021, Dresden
J. Herrmann, M. Steiner, T. Wöhrl, G. Hagen, J. Kita, R. Moos, F. Noack & D. Bleicker
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Kombinierter Stickoxid- und Sauerstoffsensor in Planartechnik, Sensoren und Messsysteme 2022, 10.05.-11.05.2022, Nürnberg
T. Wöhrl, M. Steiner, G. Hagen, J. Kita & R. Moos
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Resistive Multi-Gas Sensor for Simultaneously Measuring the Oxygen Stoichiometry (λ) and the NOx Concentration in Exhausts: Engine Tests under Dynamic Conditions. Sensors, 23(12), 5612.
Steiner, Carsten; Wöhrl, Thomas; Steiner, Monika; Kita, Jaroslaw; Müller, Andreas; Eisazadeh, Hessam; Moos, Ralf & Hagen, Gunter
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Resistive, Temperature-Independent Metal Oxide Gas Sensor for Detecting the Oxygen Stoichiometry (Air-Fuel Ratio) of Lean Engine Exhaust Gases. Sensors, 23(8), 3914.
Steiner, Carsten; Püls, Simon; Bektas, Murat; Müller, Andreas; Hagen, Gunter & Moos, Ralf
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Sulfur poisoning of powder aerosol deposited films of BaFe0.74Al0.01Ta0.25O3−: A material for resistive temperature independent oxygen sensors. Sensors and Actuators B: Chemical, 425, 136984.
Steiner, Carsten; Hagen, Gunter & Moos, Ralf
