Abstract
The longitudinal ultrasonic attenuation in ternary 80TeO(2). (20-x) WO3. xK(2)O tellurite glass systems, was measured using the pulse echo technique at ultrasonic frequencies 2, 4, 6 and 8 MHz in the temperature range from 160 to 300 K The relaxation spectra or the shape of maximum peaks showed the presence of well defined broad peaks at various temperatures depending upon the glass composition and operating frequency. The maximum peak Aft to higher temperatures with increasing frequency suggested some kind of relaxation process. This process has been interpreted as a thermally activated relaxation process which arises when ultrasonic waves disturb the equilibrium of an atom moving in a double well potential in the glass network. Results showed that the mean activation energy of the process is strongly dependent on the modifier content. The dependence of the maximum peaks on composition was analysed in terms of an assumed loss of standard linear solid type, with low dispersion, and a broad distribution of Arrhenius type relaxation with temperature independent relaxation strength. Quantitative analysis of the experimental acoustic activation energy has been discussed in terms of the number of loss centres (number of oxygen atoms that vibrate in the double well potential). The relaxation strength was determined experimentally with the deformation potential which was correlated theoretically with longitudinal and transverse deformation potentials.