Surface and flexoelectric polarization in a nematic liquid crystal 5CB |
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Authors: | LM Blinov MI Barnik H Ohoka M Ozaki NM Shtykov K Yoshino |
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Institution: | (1) Institute of Crystallography, Russian Academy of Sciences, 117333, Leninsky prosp. 59, Moscow, Russia, RU;(2) Department of Electronic Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-Oka, Suita, Osaka 565-0871, Japan, JP |
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Abstract: | The temperature dependence of the surface polarization has been measured for both the planar and homeotropic orientation of
a nematic liquid crystal at a solid substrate. A conventional liquid crystal 5CB, pure and doped with an azo-dye, was used
in cells with controlled asymmetry for light absorption. The measurements have been made by a pyroelectric technique using
short pulses of a YAG laser to create a temperature increment. The latter, in turn, was measured independently by a novel
time-resolved “optical thermometer” technique monitoring temperature-dependent birefringence by a He- Ne laser beam. In accordance
with the symmetry of the order parameter, the surface polarization has different sign for the two orientations, its magnitude
ranges from -4 to +2pC/m. The same technique has been used for the measurement of the flexoelectric polarization in hybrid
cells. The sum of the flexoelectric coefficients is e
1 + e
3 = - 13pC/m at 25°C.
Received 28 February 2000 and Received in final form 5 September 2000 |
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Keywords: | PACS 61 30 -v Liquid crystals – 77 70 +a Pyroelectric and electrocaloric effects – 77 84 Nh Liquids emulsions and suspensions liquid crystals |
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