A New Set of LGT Constants and Temperature Coefficients Extracted Through Resonant and Pulse Echo Techniques

The langasite family of crystals (LGX) has received significant attention in the past ten years for acoustic wave (AW) applications due to their higher piezoelectric coefficients than quartz, the existence of temperature compensated orientations confirmed experimentally, the absence of crystalline phase transitions below their melting points, and consistency in the crystals' growth and processing for device fabrication. In this paper, langatate (LGT) acoustic wave phase velocities have been measured using combined thickness and lateral field excitation (TFE, LFE) resonant techniques along with pulse echo measurements. The measured phase velocities are used for the extraction of room temperature elastic and piezoelectric constants along with their temperature coefficients measured in this work from 5deg and 120degC. The techniques and methodology employed, the LGT extracted constants and temperature coefficients, and comparisons with existing data in the literature are discussed.