Dielectric and conductivity relaxation in mixtures of glycerol with LiCl

TL;DR

This study provides a detailed dielectric analysis of glycerol with LiCl, revealing how ion concentration influences the coupling between translational and reorientational dynamics, with implications for understanding the glass transition.

Contribution

It offers new insights into ion-induced coupling of translational and reorientational dynamics in glass formers through dielectric spectroscopy.

Findings

Increased ion concentration shifts behavior from reorientational to translational dominance.

Coupling between ion and dipolar dynamics increases with salt concentration.

Dielectric spectroscopy can probe translational degrees of freedom near the glass transition.

Abstract

We report a thorough dielectric characterization of the alpha relaxation of glass forming glycerol with varying additions of LiCl. Nine salt concentrations from 0.1 - 20 mol% are investigated in a frequency range of 20 Hz - 3 GHz and analyzed in the dielectric loss and modulus representation. Information on the dc conductivity, the dielectric relaxation time (from the loss) and the conductivity relaxation time (from the modulus) is provided. Overall, with increasing ion concentration, a transition from reorientationally to translationally dominated behavior is observed and the translational ion dynamics and the dipolar reorientational dynamics become successively coupled. This gives rise to the prospect that by adding ions to dipolar glass formers, dielectric spectroscopy may directly couple to the translational degrees of freedom determining the glass transition, even in frequency regimes where usually strong decoupling is observed.