An Initial Physics-Based Model for the Impedance Spectrum of a Hydrocarbon Sensor with a Zeolite/Cr&lt;SUB&gt;2&lt;/SUB&gt;O&lt;SUB&gt;3&lt;/SUB&gt; Interface

Fischerauer, Alice; Gollwitzer, A.; Thalmayr, Florian; Hagen, Gunter; Moos, Ralf; Fischerauer, Gerhard

doi:10.1166/sl.2008.553

Cited by 9 publications

(6 citation statements)

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“…A very selective sensor element was prepared, which was almost insensitive toward H 2 , CO, NO, CO 2 and O 2 (if oxygen is available in excess). In recent work, Fischerauer et al discussed a mechanistic model of the sensing mechanism [ 127 ] taking into account the ionic conductivity of the zeolite and the p-type semiconductor properties of Cr 2 O 3 . In addition, the blocking electrode characteristics of the zeolite/Cr 2 O 3 interface were included.…”

Section: Conductometric Sensorsmentioning

confidence: 99%

Solid State Gas Sensor Research in Germany – a Status Report

Moos

Sahner

Fleischer

et al. 2009

Sensors

136

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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.

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Section: Conductometric Sensorsmentioning

confidence: 99%

Solid State Gas Sensor Research in Germany – a Status Report

Moos

Sahner

Fleischer

et al. 2009

Sensors

136

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“…9 and the theory of Ref. 38 does not provide a sufficient explanation for the observed impedance spectra, especially the occurrence of diffusion‐type impedances.…”

Section: Discussionmentioning

confidence: 83%

“…This explanation was falsified by the observation that solely impedance changes of the zeolite/chromia interface are responsible for the sensor effect 8, 9. Another theory assumed that changes of the space charge boundary layers in the chromia film due to adsorption or reaction of hydrocarbon molecules at the Cr 2 O 3 surface are responsible for the sensor effect 38. Such capacitive effects are common at contacts of liquid electrolytes with semiconductors 39, where sharp interfaces are metastable.…”

Section: Discussionmentioning

confidence: 99%

Integrated impedance based hydrocarbon gas sensors with Na‐zeolite/Cr₂O₃ thin film interfaces: Electrochemical mechanism of the impedance changes

Dubbe

2010

Physica Status Solidi (a)

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This study aims to clarify the mechanism of a hydrocarbon gas sensor effect, which involves impedance changes of a Na+ ion conducting Pt‐doped zeolite layer in contact with chromia (Cr2O3) films as electrodes. Based on our previous studies on sensing characteristics and model experiments with asymmetrical cells, a coherent picture of the sensing mechanism is derived: The impedance change is attributed to the process of Na+ ion insertion from the zeolite into the chromia film. The impedance of this interface process is a function of the electrical potential at the interface. Combined with the observation that gas sorption in the zeolite micropores causes changes of the electrochemical potential at the zeolite surface, these two effects explain the observed sensor effect. The sensor response as predicted from this theory agrees well with the experimental data of the original sensor. Implications for the development of integrated devices are discussed.

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“…Initial calculations confirm that under these assumptions a changing hydrocarbon concentration does strongly affect the impedance spectra, mainly at low frequencies. A good correlation between measured and calculated data is found [19], [20]. …”

Section: Electrical Results and Discussionmentioning

confidence: 93%

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

Hagen

Schulz

Knörr

et al. 2007

Sensors

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Impedometric zeolite hydrocarbon sensors with a chromium oxide intermediate layer show a very promising behavior with respect to sensitivity and selectivity. The underlying physico-chemical mechanism is under investigation at the moment. In order to verify that the effect occurs at the electrode and that zeolite bulk properties remain almost unaffected by hydrocarbons, a special planar setup was designed, which is very close to real sensor 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 the sensing 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 the volume impedance can be suppressed and an easy signal evaluation is possible, without taking impedance data at different frequencies.

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An Initial Physics-Based Model for the Impedance Spectrum of a Hydrocarbon Sensor with a Zeolite/Cr<SUB>2</SUB>O<SUB>3</SUB> Interface

Cited by 9 publications

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Solid State Gas Sensor Research in Germany – a Status Report

Solid State Gas Sensor Research in Germany – a Status Report

Integrated impedance based hydrocarbon gas sensors with Na‐zeolite/Cr₂O₃ thin film interfaces: Electrochemical mechanism of the impedance changes

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

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An Initial Physics-Based Model for the Impedance Spectrum of a Hydrocarbon Sensor with a Zeolite/Cr<SUB>2</SUB>O<SUB>3</SUB> Interface

Cited by 9 publications

References 0 publications

Solid State Gas Sensor Research in Germany – a Status Report

Solid State Gas Sensor Research in Germany – a Status Report

Integrated impedance based hydrocarbon gas sensors with Na‐zeolite/Cr2O3 thin film interfaces: Electrochemical mechanism of the impedance changes

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

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Integrated impedance based hydrocarbon gas sensors with Na‐zeolite/Cr₂O₃ thin film interfaces: Electrochemical mechanism of the impedance changes