Langasite for high-temperature bulk acoustic wave applications

Langasite (La3Ga5SiO14) and related compounds are promising candidates for high-temperature piezoelectric applications. To determine the stable operation of langasite as a high-temperature bulk acoustic wave (BAW) resonator, we characterized electrical conductivity [σel=1.56×exp(−1.07 eV/kT)S/cm] and oxygen diffusivity [DoxT=5×10−5 exp(−1.45 eV/kT)cm2/s] up to elevated temperatures. Langasite was successfully operated up to 900 °C as a BAW resonator with an average mass sensitivity of about 0.17 μg Hz−1 cm−2. This enables, in principle, high-temperature monitoring of deposition rates and thermogravimetry with high sensitivity.