Solid State Gas Sensor Research in Germany – a Status Report

Abstract

This status report overviews activities of the German gas sensor research community. It highlights recent progress in the field of potentiometric, amperometric, conductometric, impedimetric, and field effect-based gas sensors. It is shown that besides step-by-step improvements of conventional principles, e.g. by the application of novel materials, novel principles turned out to enable new markets. In the field of mixed potential gas sensors, novel materials allow for selective detection of combustion exhaust components. The same goal can be reached by using zeolites for impedimetric gas sensors. Operando spectroscopy is a powerful tool to learn about the mechanisms in n-type and in p-type conductometric sensors and to design knowledge-based improved sensor devices. Novel deposition methods are applied to gain direct access to the material morphology as well as to obtain dense thick metal oxide films without high temperature steps. Since conductometric and impedimetric sensors have the disadvantage that a current has to pass the gas sensitive film, film morphology, electrode materials, and geometrical issues affect the sensor signal. Therefore, one tries to measure directly the Fermi level position either by measuring the gas-dependent Seebeck coefficient at high temperatures or at room temperature by applying a modified miniaturized Kelvin probe method, where surface adsorption-based work function changes drive the drain-source current of a field effect transistor.

SiC–FET based SO2 sensor for power plant emission applications

“…Saturation of the sensor surface was faster during exposure to higher concentrations of SO 2 . This might be caused by the increased rate of SO 2 oxidation to SO 3 or SO 4 , which enhance the uptake of the sulfur containing gas by the oxide surface [29] and the difficulty to release the molecules. …”

“…Metal oxide sensors usually are not the best choice in environments with low and changing concentration of oxygen [2,3]. Optical detection such as FTIR is relatively more expensive than chemical sensors [4]. This line of reasoning reduces the options to SiC-FET and solid electrolyte sensors.…”

High-temperature CO / HC gas sensors to optimize firewood combustion in low-power fireplaces

“…All molecules involved in the MP formation process, together with adsorbed oxygen, contribute to the sensor signal U (Moos et al, 2009). This means that the sensor signal depends in a complicated way on all reactive gas components with different sensitivities, which is further influenced by temperature and electrode material (Miura et al, 2014).…”

Platform to develop exhaust gas sensors manufactured by glass-solder-supported joining of sintered yttria-stabilized zirconia

“…In mixed-potential applications, complex alloys, metal-oxide cermets, etc., are of interest (Moos et al, 2009;Miura et al, 2014;Zosel et al, 2004;Zhuiykov and Miura, 2007). Such materials may be long-term stable in exhaust atmospheres.…”