New Type Piezoelectric Gas Sensor Using Temperature Characteristics of Quartz Crystal

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Abstract
A new type quartz piezoelectric sensor coated with a sputtered Pt film was proposed for the detection of inflammable gases, i.e., H2, CO, and iso-butane diluted with air. The sensing signal of the new sensor is provided by an increase in resonance frequency of the crystal (ΔF) due to a temperature increase upon contact with sample gases in the temperature range 100°-400°C. The frequency change of the sensor was found to be opposite in direction to that of a conventional adsorptiontype piezoelectric gas sensor operating at ambient temperature. The temperature change of the present sensor resulted from the oxidation of the inflammable gas on the surface of the catalyst film. A linear relationship between ΔF and H2 concentration (0-0.4vol%) was observed at the temperatures examined. The 90% response time of the present sensor to 0.3vol% H2 was about 20s at 200°C. The sensitivity of the sensor to H2 in air increased sharply with increasing temperature above 100°C. Furthermore, the gas selectivity to H2 was very high especially at 100°-200°C.

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