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Dubbe, Andreas ; Hagen, Gunter ; Moos, Ralf:
Micro Sensors for Hydrocarbon Gases Sensors Based on Zeolite / Chromium (III)-Oxide Interfaces.
2005
Veranstaltung: International Workshop on Integrated Electroceramic Functional Structures
, 06.-09.06.2005
, Berchtesgaden, Deutschland.
(Veranstaltungsbeitrag: Workshop
,
Sonstige
Präsentationstyp)
Abstract
In this study, the sodium-ion exchanged aluminosilicate zeolite ZSM-5 is investigated as a sensor material for hydrocarbon gas detection. It combines fairly high ionic conductivity and well-defined gas adsorption/permeation capability inside its pore channels with nearly circular aperture (diameter 0.51-0.56 nm). Platinum doping of the zeolites was used to modify the catalytic activity for oxidation of hydrocarbons. The zeolite was applied as a ceramic thick-film on micropatterned gold interdigital electrodes (e.g. 15 µm line / 15 µm space) on alumina substrates. The sensors were characterized by impedance spectroscopy in atmospheres of various test gases in nitrogen/oxygen/water carrier gas at 570-670 K. The impedance at a fixed frequency (20 Hz) served as the sensor signal for transient and sensitivity measurements with step changes in gas concentrations. A very small dependence of the bulk ionic conductivity on changes in hydrocarbon gas concentrations was detectable at 570 K, but was not considered as an intrinsic sensor effect, because its main cause were temperature changes due to catalytic reactions. The gold/zeolite systems showed a very high electrode impedance, which means that the exchange and charge transfer of sodium ions is nearly blocked. For systems with a chromium(III)-oxide layer between gold and zeolite, this interface impedance showed a strong and well-reproducible response to changes in hydrocarbon concentration. This effect was not observed for gold/zeolite without the chromium(III)-oxide interlayer. A similar effect was observed for zeolite films on gold electrodes covered with a chromium(III)-oxide layer. Resistive gas sensor effects of the p-type semiconductor chromium(III)-oxide are well known, but were ruled out as an explanation for the present sensor effect. Thus, we conclude that the sensor mechanism is based on changes of the impedance of the chromium(III)-oxide/zeolite interface. The sensors are promising for application in on-board diagnostics of hydrocarbons downstream catalytic converters in automotive engines. They show low or negligible crosssensitivity to hydrogen, carbon monoxide, and carbon dioxide.
Weitere Angaben
| Publikationsform: | Veranstaltungsbeitrag (Sonstige) |
|---|---|
| Begutachteter Beitrag: | Ja |
| Institutionen der Universität: | Fakultäten > Fakultät für Ingenieurwissenschaften Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien > Lehrstuhl Funktionsmaterialien - Univ.-Prof. Dr.-Ing. Ralf Moos Fakultäten Fakultäten > Fakultät für Ingenieurwissenschaften > Lehrstuhl Funktionsmaterialien Profilfelder > Advanced Fields > Neue Materialien Forschungseinrichtungen > Forschungszentren > Bayreuther Materialzentrum - BayMAT Profilfelder Profilfelder > Advanced Fields Forschungseinrichtungen Forschungseinrichtungen > Forschungszentren |
| Titel an der UBT entstanden: | Ja |
| Themengebiete aus DDC: | 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften |
| Eingestellt am: | 16 Jun 2015 08:59 |
| Letzte Änderung: | 05 Apr 2016 07:06 |
| URI: | https://eref.uni-bayreuth.de/id/eprint/15003 |