# Stoichiometric Lithium Niobate Crystals: Towards Identifiable Wireless Surface Acoustic Wave Sensors Operable up to 600$^\circ$C

## TL;DR

This paper explores the use of stoichiometric lithium niobate crystals for high-temperature wireless surface acoustic wave sensors, demonstrating their stability and high electromechanical coupling up to 600°C, enabling potential sensor identification at elevated temperatures.

## Contribution

It introduces stoichiometric lithium niobate crystals as a stable, high-coupling substrate for high-temperature wireless SAW sensors, extending operational temperature limits and enabling sensor identification.

## Key findings

- sLN crystals withstand temperatures up to 800°C for days
- K2 remains high and stable up to 600°C in sLN-based SAW resonators
- Potential for high-temperature identifiable wireless sensors is demonstrated

## Abstract

Wireless surface acoustic wave (SAW) sensors constitute a promising solution to some unsolved industrial sensing issues taking place at high temperatures. Currently, this technology enables wireless measurements up to 600-700$^\circ$C at best. However, the applicability of such sensors remains incomplete since they do not allow identification above 400$^\circ$C. The latter would require the use of a piezoelectric substrate providing a large electromechanical coupling coefficient K 2 , while being stable at high temperature. In this letter, we investigate the potentiality of stoichiometric lithium niobate (sLN) crystals for such purpose. Raman spectroscopy and X-ray diffraction attest that sLN crystals withstand high temperatures up to 800$^\circ$C, at least for several days. In situ measurements of sLN-based SAW resonators conducted up to 600$^\circ$C show that the K 2 of these crystals remains high and stable throughout the whole experiment, which is very promising for the future achievement of identifiable wireless high-temperature SAW sensors.

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Source: https://tomesphere.com/paper/1907.09998