Stability and applications of high-temperature piezoelectric crystals

High-temperature piezoelectric crystals such as gallium phosphate (GaPO
₄
) and langasite (La
₃
Ga
₅
SiO
₁₄
) have been demonstrated to show piezoelectric properties at fairly high temperatures. For example, langasite can be exited piezoelectrically up to temperatures close to its melting point at about 1470 °C. The resonance behavior including damping and temperature dependent frequency of resonators made of these crystals are investigated and reviewed to evaluate the applicability of such devices as high-temperature gas sensors or film deposition monitors.