Elastic and dielectric dispersion in the dipole glass K _1-xLi_xTaO₃

Measurements of the elastic properties of Li-doped KTaO3 by the resonance technique and by the pulse-echo method show a softening of 1/s 11 and c11, respectively, at temperatures below 120K. The strong dispersions observed between the respective measuring frequencies (300 kHz and 15 MHz) and the ultrasonic attenuation point to strain relaxation in which reorientation of Li by thermal activation is the rate-limiting process. A comparison of these data with nuclear spin relaxation and dielectric relaxation provides evidence for a condensed state at low T, and yet evidence against long-range order.