Electric and mechanical moduli: comparison between relaxation responses in a superionic glass

Abstract

The modulus formalism has been used in the present study for a direct comparison between mechanical and electric relaxation responses in a superionic glass. The values of complex modulus have been calculated from the results of dielectric and mechanical measurements on the (Ag₂S)_0.3(AgPO₃)_0.7 glass at the same frequency, 10 MHz, as a function of temperature in the range 20–400 K. A peak in the imaginary part of the response function characterizes the dielectric as well as the mechanical relaxation data. The mechanical relaxation peak is larger than the electric relaxation peak. Assuming a phenomenological Cole–Davidson stretched response function, the resulting low value of the stretching exponent indicates a broad distribution of relaxation times. This could indicate that more microscopic processes with typical energies lower than the E _dc, which characterizes ionic long-range diffusion, participate in both macroscopic dynamic responses.

Acknowledgement

We would like to thank Professor K.L. Ngai for valuable discussions.