Dynamics of glass-forming liquids. IV. True activated behavior above 2 GHz in the dielectric α-relaxation of organic liquids

Publisher Website
Google Scholar
Abstract
We have measured the dielectric relaxation of butylbenzene and of the glass-former propylbenzene in the frequency range 10 −2 Hz to 2×10 10 Hz in order to characterize the variation of relaxation times with temperature for these low loss liquids. Additionally, salol has been remeasured above 1 GHz with improved resolution. Using the sensitive data representation [−d log 10 (f max Hz)/ d(1/T)] −1/2 vs 1/ T we find demarcation temperatures T A , at which the temperature dependence changes from a Vogel–Fulcher type law within the limits T B ⩽T⩽T A to Arrhenius behavior for T>T A , corresponding to a position of the loss peak f max >2 GHz . The activation energies derived from dielectric relaxation data for T>T A are associated with the energy of vaporization, E η ∝ΔE vap . A comparison of dielectric relaxation times τ D to viscosity data in this wide range of temperatures suggests the relation τ D ∝η/T rather than τ D ∝η.

This publication has 26 references indexed in Scilit: