Acoustic damping in langatate as a function of temperature, frequency, and mechanical contact

Resonant acoustic damping in planoconvex (trapped-mode) langatate (La₃Ga_5.5Ta_0.5O₁₄) disks was measured at frequencies from 2 MHz to 18 MHz and temperatures from 130 K to 450 K. A broad anelastic relaxation peak was observed in the temperature dependence of the damping, and this peak extends into the ambient temperature range. Measurements and theoretical calculations of the vibrational trapping efficiency indicate that external damping was not significant for measured overtones above the fundamental. For some modes, relatively narrow peaks in the temperature dependence of the loss were observed, and these are attributed to coupling with other modes.