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

Sapna Kalia | Zendy; Sanjay Sharma | Zendy; Vandana Sharma | Zendy

Open Access

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

Author(s) -

Sapna Kalia,

Sanjay Sharma,

Vandana Sharma

Publication year - 2013

Publication title -

isrn polymer science

Language(s) - English

Resource type - Journals

ISSN - 2090-8733

DOI - 10.1155/2013/590682

Subject(s) - liquid crystal , materials science , thermotropic crystal , activation energy , poling , relaxation (psychology) , analytical chemistry (journal) , dielectric , copolyester , atmospheric temperature range , dipole , space charge , thermodynamics , ferroelectricity , chemistry , organic chemistry , psychology , social psychology , liquid crystalline , physics , optoelectronics , quantum mechanics , polyester , electron , composite material

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.

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