Abstract
The longitudinal ultrasonic attenuation in 20Li(2)O-(80-x) B2O3-xWO(3) (0 <= x <= 12.5) glass system, was measured using pulse echo technique at ultrasonic frequencies 2, 4, 6 and 14 MHz in the temperature range from 150 to 300 K. The absorption curves showed the presence of well-defined broad peaks at various temperatures depending upon the glass composition and operating frequency. The maximum peaks move to higher temperatures with the increase of operating frequency indicating the presence of some kind of relaxation process. This process has been described as a thermally activated relaxation process which occurs when ultrasonic waves disturb the equilibrium of an atom vibrating in a double-well potential in the glass network structure. Results proved that the average activation energy of the process is mainly depending on the modifier content. This dependence was analyzed in terms of the loss of standard linear solid type, with low dispersion and a broad distribution of Arrhenius type relaxation with temperature independent relaxation strength. The experimental acoustic activation energy has been quantitatively analyzed in terms of the number of loss centers (number of oxygen atoms that vibrate in the double well potential). (C) 2015 Elsevier B.V. All rights reserved.