Contributions to anelasticity in langasite and langatate
Ward L. Johnson, Sudook A. Kim, Christine F. Rivenbark, Satoshi Uda
Maximization of the quality factors Q of langasite (LGS) and langatate (LGT) is necessary for optimal performance of acoustic resonators of these materials in frequency-control and high-temperature sensing applications. In this report, measurements and least-squares analysis of 1/Q as a function of ultrasonic frequency and temperature (up to 750~K) of undoped LGS and LGT reveal a superposition of physical effects, including point defect relaxations and intrinsic phonon-phonon loss. In LGS, these effects are superimposed on a large temperature-dependent background with weak frequency dependence that is understood to arise from a relaxation process with a distribution of activation energies. This distributed relaxation is suggested to be consistent with anelastic kink migration. No evidence for a significant background of this form is found in the more recently fabricated LGT crystal. The analysis of the frequency- and temperature-dependence of 1/Q of LGT indicates that, at near-ambient temperatures, the damping in this specimen is close to the intrinsic limit determined by phonon-phonon interactions. Piezoelectric/carrier relaxation, which must occur at sufficiently elevated temperatures, is not found to be a significant contribution to $1/Q, relative to defect-related contributions, in either LGS or LGT in the measured range of temperatures.
, Kim, S.
, Rivenbark, C.
and Uda, S.
Contributions to anelasticity in langasite and langatate, Physical Review B, [online], https://doi.org/10.1063/1.3672443
(Accessed June 8, 2023)