Abbreviated Journal Title
J. Appl. Phys.
TEMPERATURE PIEZOELECTRIC MATERIALS; INDUCED FREQUENCY-SHIFTS; INTERNAL-FRICTION; ELECTROMECHANICAL PROPERTIES; ELEVATED-TEMPERATURES; DIELECTRIC-PROPERTIES; DEFECT CHEMISTRY; SINGLE-CRYSTALS; CUT; RESONATORS; KINK MOTION; Physics, Applied
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 Q(-1) as a function of ultrasonic frequency and temperature of undoped LGS (100 K to 750 K) and LGT (300 K to 760 K) 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 interpreted as arising from a relaxation process with a distribution of activation energies. This distributed relaxation is suggested to be a result of anelastic kink migration. No evidence for a significant background of this form is found in the LGT specimen, consistent with the lower measured dislocation etch-pit density of this crystal. The analysis of the dependence of Q(-1) of LGT on frequency and temperature 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 found not to be a significant contribution to Q(-1), relative to defect-related contributions, in either LGS or LGT in the measured range of temperatures.
Journal of Applied Physics
Johnson, Ward L.; Kim, Sudook A.; Uda, Satoshi; and Rivenbark, Christine F., "Contributions to anelasticity in langasite and langatate" (2011). Faculty Bibliography 2010s. 1442.