Temperature-dependent attenuation of surface acoustic waves in proton-exchanged 128°-rotated Y-cut LiNbO3

3 has been experimentally studied in the frequency range 100 to 460 MHz and in the temperature range 90 to 300 K. At room temperature, the proton exchange leads to the considerable enhancement of acoustic attenuation as compared to the pure samples. Annealing in air, in general, reduces the attenuation. However, an anomalous enhancement of the attenuation at several frequencies for particular conditions of annealing is observed. When the temperature is reduced, the attenuation decreases practically to zero in as-exchanged samples. In the annealed ones, the attenuation attains a minimum in the vicinity of 160 K, and begins to grow at lower temperatures. A sharp peak in the attenuation is observed at 210 K. Several different physical mechanisms including acousto-protonic interaction and structural phase transition seem to be responsible for the observed acoustic attenuation behaviour. Received: 17 July 1996/Accepted: 2 December 1996