High-temperature electromechanical properties of strontium-doped langasite

Abstract

Langasite (La 3Ga 5SiO 14) is a suitable piezoelectric material for high-temperature bulk acoustic wave applications such as resonant microbalances and gas sensors using specific surface affinity layers. Langasite has been shown to exhibit bulk oscillations at temperatures of up to 1400 °C. Factors limiting its use as piezoelectric transducer at elevated temperatures such as excessive conductive and viscous damping are presented and discussed. The paper focuses on the investigation of the defect chemistry and transport mechanisms in strontium-doped langasite single crystals. It is found that strontium suppresses point defect relaxations observed in langasite up to about 400 °C. Thereby viscous damping could be lowered up to this temperature. Between about 400 and 600 °C strontium-doping does not impact the damping. Further, strontium dopants enhance the movement of oxygen ions via creation of oxygen vacancies above about 600 °C leading to a slight increase in damping. One concludes, that the relatively strong impact on damping exhibited by ionic defects can be utilized by the application of acceptor doping at elevated temperatures.