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Micro Sensors for Hydrocarbon Gases Sensors Based on Zeolite / Chromium (III)-Oxide Interfaces

Title data

Dubbe, Andreas ; Hagen, Gunter ; Moos, Ralf:
Micro Sensors for Hydrocarbon Gases Sensors Based on Zeolite / Chromium (III)-Oxide Interfaces.
Event: International Workshop on Integrated Electroceramic Functional Structures , 06.-09.06.2005 , Berchtesgaden, Deutschland.
(Conference item: Workshop , Other Presentation type)

Abstract in another language

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.

Further data

Item Type: Conference item (Other)
Refereed: Yes
Institutions of the University: Faculties > Faculty of Engineering Science
Faculties > Faculty of Engineering Science > Chair Functional Materials > Chair Functional Materials - Univ.-Prof. Dr.-Ing. Ralf Moos
Faculties > Faculty of Engineering Science > Chair Functional Materials
Profile Fields > Advanced Fields > Advanced Materials
Research Institutions > Research Centres > Bayreuth Center for Material Science and Engineering - BayMAT
Profile Fields
Profile Fields > Advanced Fields
Research Institutions
Research Institutions > Research Centres
Result of work at the UBT: Yes
DDC Subjects: 600 Technology, medicine, applied sciences > 620 Engineering
Date Deposited: 16 Jun 2015 08:59
Last Modified: 05 Apr 2016 07:06