Dielectric study of nematic (4-Cyano- 4’-Pentylbiphenyl) liquid crystal
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Date
2019-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Dielectric studies of the liquid crystals are important as they provide useful information about molecular structure, molecular dynamics, phase transition and display performance of liquid crystals. Present thesis work deals with the investigation of dielectric parameters of nematic (4-cyano-4’-pentylbiphenyl) liquid crystal over a wide range of frequency (100Hz- 10MHz) at different temperatures ranging from -100C to 500C. The fabrication of liquid crystal cell was done by using the photolithography technique. For the measurement of dielectric properties parallel plate capacitor cell was used. The area and separation between the plates were taken 35.54mm2 and 14.3μm respectively. The resistance of electrode wires was very low and was soldered with the help of USS 9200 ultrasonic soldering unit. All the dielectric measurements were performed using an HP 4192A impedance analyzer. The cells with the material under the study were placed with in a Linkam hot stage (THMS 600) controlled by a Linkam temperature for insuring the desired temperature for the measurements. As a result, at low frequency, the magnitude of dielectric permittivity was found to be increased with an increase in the temperature but at the higher frequency, it was decreased. At low frequency region, the magnitude of dielectric loss increases with increase in the temperature, after attaining maxima it is decreases. It was also observed that the transition temperature from nematic to isotropic phase was 320C.
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