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

Langasite-type crystals, including La3Ga5.5Nb0.5O14 (LGN), and La3Ga5.5Ta0.5O14(LGT) with disordered structure, and Ca3TaGa3Si2O14 (CTGS) and Ca3NbGa3Si2O14 (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 degrees C for LGN (YXl) 1.5 degrees and LGT (YXl) - 20 degrees cuts, respectively, in thickness shear mode, while the TCF was found to be 21 ppm K-1 up to 800 degrees C for CTGS (YXl) - 20 degrees and CNGS (YXl) - 20 degrees. 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 degrees C, making CTGS and CNGS potential candidates for high temperature sensor applications.