Elastic, anelastic and nonlinear acoustic properties of (ZnCl2)x(P2O5)1-x glasses

The effects of hydrostatic pressure and temperature on the velocities of longitudinal and shear ultrasonic waves propagated in (ZnCl2)(x)(P2O5)(1-x) glasses (x= 0.2, 0.3, 0.5) have been measured. The hydrostatic pressure derivatives (partial derivative C-11(s)/partial derivative P)(T.P=0) and (partial derivative C-44(s)/partial derivative P) (T,P=0) of the longitudinal C-11(s) and shear C-44(s) elastic stiffnesses are negative, both longitudinal and shear acoustic mode Gruneisen parameters are small and negative: the application of hydrostatic pressure results in softening of the long wavelength acoustic phonon modes. The temperature dependence of the ultrasonic attenuation shows the broad loss peak characteristic of oxine glasses which is analysed in terms of thermally activated relaxation processes. After subtraction of the relaxation and anharmonic contributions, another contribution remains to the velocity of ultrasonic waves, which has a linear temperature dependence, as predicted by the soft potential model (SPM) of soft harmonic oscillators (HO). This soft HO relaxation contribution to the temperature dependence of ultrasonic velocity has a similar magnitude to that found for other glasses. Agreement with the SPM theoretical prediction suggests that the proposed universality of this model extends to this group of pseudo-binary phosphate glasses.