High-temperature electromechanical loss in piezoelectric langasite and catangasite crystals

摘要

Temperature-dependent acoustic loss Q~(-1) is studied in partially disordered langasite (LGS, La_3Ga_5SiO_(14)) and ordered catangasite (CTGS, Ca_3TaGa_3Si_2O_(14)) crystals and compared with previously reported CTGS and langatate (LGT, La_3Ga_(5.5)Ta_(0.5)O_(14)) data. Two independent techniques, a contactless tone-burst excitation technique and contacting resonant piezoelectric spectroscopy, are used in this study. Contributions to the measured Q~(-1)(T) are determined through fitting to physics-based functions, and the extracted fit parameters, including the activation energies of the processes, are discussed. It is shown that losses in LGS and CTGS are caused by a superposition of several mechanisms, including intrinsic phonon-phonon loss, point-defect relaxations, and conductivity-related relaxations.