Measurements of Acoustical Physical Constants of La 3 Ta 0.5 Ga 5.3 Al 0.2 O 14 Single Crystals at High Temperatures

The dielectric, elastic, and piezoelectric constants of langasite family single-crystal La 3 Ta 0.5 Ga 5.3 Al 0.2 O 14 (LTGA) were measured by combing plane-wave ultrasonic microspectroscopy (PW-UMS) technology with the resonance–antiresonance method in a range from room temperature to 1000 °C. The influence of dielectric loss at high temperatures on resonance and antiresonance frequencies was discussed. At room temperature, the piezoelectric constants d 11 and d 14 were 6.62 and -4.65 pC/N, respectively. d 11 increased to 7.5 pC/N at 1000 °C. The electromechanical coupling factor k 12 was about 16.8% in the entire temperature range. All the necessary parameters of the LTGA crystal for acoustic wave applications at high temperatures were determined in this research.