Langasite surface acoustic wave sensors for high temperatures

Langasite (La/sub 3/Ga/sub 5/SiO/sub 14/) has been used successfully as a piezoelectric substrate for surface acoustic wave (SAW) devices operating up to 1000/spl deg/C. New investigations of material properties concerning the quality as well as the stability at high temperatures are presented. Apart from high temperature measurements on SAW devices and thermal analyses, optical absorption properties and the electric conductivity have been investigated. The crystal quality has been examined by various methods such as X-ray topography and chemical etching combined with optical microscopy for many LGS wafers from different growers.