Dynamics of glass-forming liquids. II. Detailed comparison of dielectric relaxation, de-conductivity, and viscosity data

F. Stickel, E. W. Fischer, R. Richert

Research output: Contribution to journalArticle

490 Scopus citations

Abstract

We have studied the temperature dependence of dielectric relaxation times in terms of the peak frequency fmax(T) of dielectric loss ε″(ω) and the de-conductivity σdc(T). of several glass-forming liquids, covering 12 decades in the peak frequency fmax and 9 decades in σac. Although de-conductivity samples the mobility of ionic tracers, its variation with temperature is similar to that of fmax(T). The fmax(T) and σdc(T) are analyzed using the temperature-derivative method and compared to the viscosity data η-1 (T). While most liquids reveal a common Vogel-Fulcher-Tammann (VFT) behavior for fmax, σdc and η-1 in an extended temperature range T≥Tm, some liquids deviate from this behavior by displaying a crossover at T=TA to an Arrhenius regime. In these cases the quantity fmax(T) decouples from the common curves for σdc(T) and η-1(T) and attains activation energies in excess (∼40% for alcohols) of those related to translational processes. For many samples a departure from the VFT behavior occurs at lower temperatures TB<Tm which tends to retard the glass transition. The onset of this qualitative change in the temperature dependence at TB turns out to be a characteristic temperature also in other experiments.

Original languageEnglish (US)
Pages (from-to)2043-2055
Number of pages13
JournalJournal of Chemical Physics
Volume104
Issue number5
DOIs
StatePublished - Jan 1 1996
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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