Investigation of zero temperature compensated cuts in langasite-type piezocrystals for high temperature applications

Langasite-type crystals, including La 3 Ga 5.5 Nb 0.5 O 14 (LGN), and La 3 Ga 5.5 Ta 0.5 O 14 (LGT) with disordered structure, and Ca 3 TaGa 3 Si 2 O 14 (CTGS) and Ca 3 NbGa 3 Si 2 O 14 (CNGS) with ordered structure, were grown using the Czochralski method. Resistivity was studied as a function of temperature. Temperature coefficients of frequency (TCFs) for different cuts were investigated in the above crystals at elevated temperatures, which were found to be ±11 ppm K −1 and ±6.0 ppm K −1 up to 400 °C for LGN ( YXl )1.5° and LGT ( YXl ) − 20° cuts, respectively, in thickness shear mode, while the TCF was found to be 21 ppm K −1 up to 800 °C for CTGS ( YXl ) − 20° and CNGS ( YXl ) − 20°. Furthermore, the dielectric and electromechanical behaviour of the above crystals with low TCF cuts as a function of temperature were studied. It was observed that CTGS and CNGS crystals with an ordered structure possessed temperature independent dielectric and electromechanical behaviour up to 800 °C, making CTGS and CNGS potential candidates for high temperature sensor applications.