Four-Wire Impedance Spectroscopy on Planar Zeolite/Chromium Oxide Based Hydrocarbon Gas Sensors

• Main Authors: Ralf Moos, Matthias Knörr, Anne Schulz, Gunter Hagen
• Format: Article
• Language: English
• Published: MDPI AG 2007-11-01
• Series: Sensors
• Subjects: impedometric gas sensor; electrode effects; zeolite; four-wire impedance spectroscopy
• Online Access: http://www.mdpi.com/1424-8220/7/11/2681/

Impedometric zeolite hydrocarbon sensors with a chromium oxide intermediatelayer show a very promising behavior with respect to sensitivity and selectivity. Theunderlying physico-chemical mechanism is under investigation at the moment. In order toverify that the effect occurs at the electrode and that zeolite bulk properties remain almostunaffected by hydrocarbons, a special planar setup was designed, which is very close to realsensor devices. It allows for conducting four-wire impedance spectroscopy as well as two-wire impedance spectroscopy. Using this setup, it could be clearly demonstrated that thesensing effect can be ascribed to an electrode impedance. Furthermore, by combining two-and four-wire impedance measurements at only one single frequency, the interference of thevolume impedance can be suppressed and an easy signal evaluation is possible, withouttaking impedance data at different frequencies.