Measurement of the Second-Order Material Constants of Lanthanum-Gallium Tantalate (LGT) through Ultrasound.

Lanthanum Gallium Tantalate (LGT) is a member of the LGX crystal family (Langasite, Langanite and Langatate) known for high quality factor and stability at higher temperatures. These characteristics enable filters and sensors for use in harsh environments. Accurate values for the second-order material constants are required for electromechanical modeling of such devices. A sufficient set of BAW propagation velocities have been measured in cube-shaped samples to obtain the full set of second-order elastic and piezoelectric material constants along with the experimental uncertainties. The cross-correlation method was used to accurately measure the time-of-flight values between the first two back-wall echoes under a constant room-temperature environment. The calculated BAW velocities and extracted material constants show good agreement with earlier work.