Abstract
Langasite surface acoustic wave devices can be used to implement harsh-environment wireless sensing of gas concentration and temperature. This paper reviews prior work on the development of langasite surface acoustic wave devices, followed by a report of recent progress toward the implementation of oxygen gas sensors. Resistive metal oxide films can be used as the oxygen sensing film, although development of an adherent barrier layer will be necessary with the sensing layers studied here to prevent interaction with the langasite substrate. Experimental results are presented for the performance of a langasite surface acoustic wave oxygen sensor with tin oxide sensing layer, and these experimental results are correlated with direct measurements of the sensing layer resistivity.
Highlights
Harsh environment sensing has received increased attention in recent years
We will report our recent work on the development of oxygen gas and temperature sensors using langasite substrates
Surface acoustic waves can be launched on the piezoelectric substrate by exciting an interdigitated transducer with a sinusoid or a windowed sinusoid (Figure 2)
Summary
Harsh environment sensing has received increased attention in recent years. Harsh environment applications require sensors that can survive high temperature, high vibration, and chemically aggressive environments. This paper addresses the development of temperature and gas sensors for combusion exhaust environments. In principle refractory semiconductors such as aluminum gallium nitride, silicon carbide, or diamond could be used to build sensors and the associated electronics This may well be possible in the near term for operation at moderately high temperatures (up to 350 °C or so). Surface acoustic wave devices have been demonstrated to operate at elevated temperatures. Surface acoustic wave sensors can address all of the requirements for harsh-environment applications. We will report our recent work on the development of oxygen gas and temperature sensors using langasite substrates. We outline some remaining barriers to the development of harsh-environment SAW sensors and the prospects for further development
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