Sensitive Elements for Wirelessly Interrogated High Temperature SAW Deformation Sensors

The surface acoustic waves (SAW) delay sensitivity to different types of deformation was calculated for different orientations of langasite (LGS) substrate. Besides LGS properties recent experimental data from several sources related to high-temperature SAW sensors are discussed that also show useful properties of other materials. Notably catangasite (CTGS) is a promising candidate for replacing LGS. The applicability of devices based on lithium niobate (LN) was obtained up to 600°C paving the way to wide-bandwidth devices. For mounting the deformation sensors onto DUT testing of different high-temperature adhesives was carried out. Another way to high-temperature deformation sensor development makes use of piezoelectric thin film directly deposited on a metallic object whose deformation is measured. Successful testing of ZnO/metal-based devices is appealing, because the direct deposition of piezoelectric layer on metal can allow to directly measure the strain of the monitored object and thus to eliminate the hysteresis and unreliable strain transfer in a wide range of temperatures.