scholarly journals Study of Dielectric Relaxation Behavior of Liquid Crystal Copolyester Vectra-A by Thermally Stimulated Discharge Current Technique

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Sapna Kalia ◽  
J. K. Sharma ◽  
Vandana Sharma
Keyword(s):  
Activation Energy ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Preexponential Factor ◽  
Relaxation Behavior ◽  
Depolarization Current ◽  
Temperature Range ◽  
Natural Logarithm ◽  
Relaxation Parameters ◽  
Dielectric Relaxation Behavior

The dielectric relaxation behavior of thermotropic liquid crystal copolyester of 73% of p-hydroxy-benzoic acid (HBA) and 27% of 2-hydroxy-6-naphthoic acid (HNA) (Vectra-A) at poling temperature 80°C has been studied using thermally stimulated depolarization current (TSDC) technique in the temperature range from 15°C to 250°C. The TSD currents were obtained for different polarizing fields ranging from 3.8 kV/cm to 19.2 kV/cm. TSD current spectra in the temperature range from 15°C to 250°C show three current maxima around 25°C, 110°C, and 220°C. The maxima around 25°C and 110°C correspond to characteristic dipolar relaxations β and α, respectively. The peak around 220°C is due to space charge effects named as δ-relaxation. The various relaxation parameters like activation energy (U), relaxation strength , preexponential factor , the quantity of charge released (Q) and concentration of trap for β- and α-relaxations at polarizing temperature 80°C for different polarizing fields were evaluated using Bucci-Fieschi fit. The linear variation between activation energy and natural logarithm of preexponential factor indicates the presence of compensation effect for dipolar relaxations of Vectra-A under present poling conditions.

scholarly journals Dielectric relaxation behavior in antiferroelectric metal organic framework [(CH3)2NH2][FeIIIFeII(HCOO)6] single crystals

2016 ◽  
Vol 18 (12) ◽  
pp. 8462-8467 ◽  
Author(s):  
A. Sieradzki ◽  
S. Pawlus ◽  
S. N. Tripathy ◽  
A. Gągor ◽  
A. Ciupa ◽  
...  
Keyword(s):  
Dielectric Relaxation ◽  
Single Crystals ◽  
Metal Organic Framework ◽  
Mixed Valence ◽  
Relaxation Behavior ◽  
Relaxation Dynamics ◽  
Temperature Range ◽  
Metal Organic ◽  
Dielectric Relaxation Behavior ◽  
Organic Framework

The fundamental aspects of the relaxation dynamics in niccolite-type, mixed valence metal–organic framework, multiferroic [(CH3)2NH2][Fe3+Fe2+(HCOO)6] single crystals have been reported, covering eight decades in frequency (10−2 ≤ f ≤ 106) in the temperature range 120 K ≤ T ≤ 250 K.

Dielectric Relaxation Studies of Silver Nanoparticles dispersed Liquid Crystal

2015 ◽  
Vol 8 (3) ◽  
pp. 2176-2188 ◽  
Author(s):  
Keisham Nanao Singh
Keyword(s):  
Activation Energy ◽  
Silver Nanoparticles ◽  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Relaxation Times ◽  
Low Frequency ◽  
Bulk Liquid ◽  
Molecular Rearrangement ◽  
Relaxation Studies

This article reports on the Dielectric Relaxation Studies of two Liquid Crystalline compounds - 7O.4 and 7O.6 - doped with dodecanethiol capped Silver Nanoparticles. The liquid crystal molecules are aligned homeotropically using CTAB. The low frequency relaxation process occurring above 1 MHz is fitted to Cole-Cole formula using the software Dielectric Spectra fit. The effect of the Silver Nanoparticles on the molecular dipole dynamics are discussed in terms of the fitted relaxation times, Cole-Cole distribution parameter and activation energy. The study indicate a local molecular rearrangement of the liquid crystal molecules without affecting the order of the bulk liquid crystal molecules but these local molecules surrounding the Silver Nanoparticles do not contribute to the relaxation process in the studied frequency range. The observed effect on activation energy suggests a change in interaction between the nanoparticles/liquid crystal molecules.

Nonmonotonic dielectric relaxation behavior of thermochromic epoxy composite

2022 ◽  
pp. 131678
Author(s):  
Jian Gao ◽  
Yiwei Long ◽  
Kangning Wu ◽  
Jianying Li ◽  
Guilai Yin
Keyword(s):  
Dielectric Relaxation ◽  
Epoxy Composite ◽  
Relaxation Behavior ◽  
Dielectric Relaxation Behavior
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