Poisoning of Temperature Independent Resistive Oxygen Sensors by Sulfur Dioxide

Abstract

Sulfur dioxide strongly affects temperature independent resistive oxygen sensors of SrTi 1-x Fe x O 3-δ . Time dependent sensor deterioration was investigated for lanthanum doped SrTi 0.65 Fe 0.35 O 3-δ (STF35). Parameters were sulfur dioxide concentration, oxygen partial pressure, temperature, and sensor morphology. The sensor poisoning consists of two steps. At lower temperatures sulfur dioxide adsorption and sulfate ion formation at the grain surface is suggested. At higher temperatures the material decomposes into SrSO 4 , iron depleted STF35, and Fe 2 TiO 5 .

Selective mixed potential ammonia exhaust gas sensor

“…It has also to be examined whether sensor poisons like SO 2 have the same detrimental effect than they have for resistive oxygen sensors [33]. Tests in engine exhausts under both stationary and transient conditions will provide insight in the sensor system, especially with respect to deficiencies in the sensor control electronics and in the sensor housing.…”

Solid State Gas Sensor Research in Germany – a Status Report

“…As an additional advantage, a temperature independent resistance over this temperature range was reported for the SrTi 0.65 Fe 0.35 O 3-δ -composition in particular [49,93]. Detailed studies were aimed at resolving the observed proneness of the devices to sulfur poisoning [94,95]. In other work by German researchers, p -type members of the system La 2 CuO 4 :LaFeO 3 were identified as alternative candidates for temperature independent oxygen sensors [96-98] and a model of the sensor behavior was proposed [99].…”

Cuprate-ferrate compositions for temperature independent resistive oxygen sensors

“…The devices prepared from LaCu x Fe 1−x O 3 , however, present a sharp, step-like onset at the beginning of sulfur dioxide exposure, followed by a shallow increase. This first step can be attributed to a fast sulfur adsorption and the formation of surface sulfite ions in analogy to the mechanism described in [18] for sulfur dioxide poisoning of SrTi 1−y Fe y O 3−−δ . The following shallow increase of the sensor resistance might be due to a slow decomposition process.…”