Langasite based high-temperature bulk acoustic wave sensors

Abstract

The objective of the work is to review the high-temperature properties, the operation limits and the sensor principles related to high-temperature stable langasite (La 3Ga 5SiO 14, LGS) resonators. The electromechanical properties of such resonators including mechanical stiffness, piezoelectric and dielectric constant, effective viscosity and electrical conductivity are determined up to 900°C and described using a one-dimensional physical model. Insights from defect chemical models are correlated with the electromechanical properties of the resonators. Further, application examples are given which demonstrate the capabilities of high-temperature stable piezoelectric resonators. For example, the simultaneous determination of mechanical and electrical properties of thin sensor films by resonant sensors enables the detection of CO in hydrogen-containing atmospheres. Further, the ability of langasite resonators to detect soot at elevated temperatures is demonstrated. © 2011 IEEE.