Temperature dependence of dielectric properties of the liquid crystal 6CB with the embedded Ag7GeS5I nanoparticles

Abstract

Within the frequency range 10–1–105 Hz under the temperatures 293–295 K, the dielectric properties of a planar-oriented nematic liquid crystal 6CB with the embedded of 0.1% superionic conductor Ag7GeS5I nanoparticles have been investigated. It has been shown that for the whole temperature range, the obtained frequency dependences of the components ε' and ε" composing the complex dielectric function can be separated into 3 sections. The dispersion of ε' and ε" for the lowest frequencies (less than 102 Hz) is described by the Debye equation and is caused by the rotation of the dipole moments of LC molecules under the action of electric field within the angles corresponding to the fluctuations of the order parameter in a thin near-electrode layer. It has been shown that the temperature dependence of the value of inverse relaxation time for such a process is described by straight lines in the Arrhenius coordinates within each mesophase. The activation energies for these dependences have been estimated for each mesophase. It should be noted that within the middle range of frequencies (102–104 Hz), for each temperature, one can separate a section where the magnitude of the conductivity does not depend on the frequency. The conductivity in these sections is equal to the conductivity of LC with the nanoparticles. It has been found that both the value of inverse relaxation time and the value of conductivity change according to the Arrhenius law on the temperature. The activation energies for the temperature dependence of conductivity and the temperature dependence of inverse relaxation time have been estimated, and it has been shown that they are close (for the nematic phase) and equal (for the isotropic phase). In the highest frequency section of the dielectric spectrum (104–105 Hz), the conductivity of the mixture 6CB + 0.1 wt.% Ag7GeS5I changes according to the power law of the frequency. It has been suggested that a sharp increase in the conductivity of 6CB with nanoparticles of the superionic conductor Ag7GeS5I at the concentration 0.1 wt.% was caused by the sharp increase in the electronic component of conductivity through Ag7GeS5I nanoparticles.

Keywords

• keydielectric properties
• superionic conductor
• frequency dependence
• temperature dependence
• debye dispersion
• relaxation time
• activation energy