Electrical, Electromechanical and Piezoelectric Properties of Ca₃TaGa₃Si₂O₁₄ Resonators at Elevated Temperatures

The electrical conductivity, resonance frequency and piezoelectric strain constants are determined for ordered piezoelectric Ca₃TaGa₃Si₂O₁₄ (CTGS) single crystals from room temperature to 900°C. The latter result from three independent methods, namely resonant, ultrasonic pulse-echo, and laser Doppler vibrometry techniques, which allows validating the results. Further, the long-term behaviour of fundamental materials properties including electrical conductivity and resonance frequency are examined at 1000°C for CTGS crystals, grown by different manufacturers. After an initial period of about 500 h, the conductivity is found to remain nearly constant for at least 1500 h. In a period of 2000-5000 h a decrease of conductivity by only 20% is observed. The resonance frequency is found to decrease almost linearly in a period of 500-5000 h for all investigated samples.