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Numerical and Experimental Analysis of the Response of a SAW Structure with WO3 Layers on Action of Carbon Monoxide

Hejczyk T., Urbańczyk M., Pustelny T., Jakubik W.

Archives of Acoustics

2015

Vol. 40, No. 1

19--24

The paper presents the results of an analysis of gaseous sensors based on a surface acoustic wave (SAW) by means of the equivalent model theory. The applied theory analyzes the response of the SAW sensor in the steady state affected by carbon monoxide (CO) in air. A thin layer of WO3 has been used as a sensor layer. The acoustical replacing impedance of the sensor layer was used, which takes into account the profile of the concentration of gas molecules in the layer. Thanks to implementing the Ingebrigtsen equation, the authors determined analytical expressions for the relative changes of the velocity of the surface acoustic wave in the steady state. The results of the analysis have shown that there is an optimum thickness of the layer of CO sensor at which the acoustoelectric effect (manifested here as a change in the acoustic wave velocity) is at its highest. The theoretical results were verified and confirmed experimentally.

SAW sensor for detection of hydrocarbons. Numerical analysis and experimental results

Hejczyk T., Urbańczyk M., Wituła R., Maciak E.

Bulletin of the Polish Academy of Sciences. Technical Sciences

2012

Vol. 60, nr 3

589-595

The paper presents the results of numerical analyses of the SAW gas sensor in the steady and non-steady state. The effect of SAW velocity changes vs. the surface electrical conductivity of the sensing layer is predicted. The conductivity of the porous sensing layer above the piezoelectric waveguide depends on the profile of the diffused gas molecule concentration inside the layer. Knudsen's model of gas diffusion was used. Numerical results for the gases CH4, C2H4, C3H8, C6H6 in the steady state and CH4 in the non-steady state in the WO3 sensing layer have been shown. The results of numerical analyzes allow to select the sensor design conditions, including the morphology of the sensor layer, its thickness and operating temperature. Some numerical results were verified in experimental studies concerning methane.