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Liquid Crystals
Year: 2008  |  Volume: 35  |  Issue: 9  |  Page No.: 1101 - 1108

Switching and electrical properties of ferro- and antiferroelectric phases of MOPB(H)PBC

Anoop Kumar Srivastava, Ravindra Dhar, Vinai Krishna Agrawal, Seung Hee Leeb and Roman Dabrowski    

Abstract: Switching and dielectric relaxation phenomena were investigated for an antiferroelectric liquid crystal, 4,4-(1-methyloctyloxycarbonyl)phenyl]-4`-[3-(butanoyloxy)prop-1-oxy]biphenyl carboxylate, exhibiting chiral smectic A (SmA*), smectic C (SmC*) and antiferroelectric (SmCA*) phases. Spontaneous polarisations, rotational viscosities, relaxation frequencies, dielectric strengths and distribution parameters were determined as a function of temperature. The electric field required for saturation of the spontaneous polarisation increased with a decrease in temperature. In the SmA* phase, only one relaxation mechanism was observed that behaves as soft mode. Two relaxation processes were detected in the SmC* phase. A high-frequency relaxation process invariant at 2.2 kHz was due to a Goldstone mode, but the origin of low-frequency relaxation process (1-20 Hz) is unclear; however, it may belong to an X-mode. The dielectric spectrum of the SmCA* phase exhibits two absorption peaks separated by two decades of frequency. The low-frequency peak is related to the antiferroelectric Goldstone mode, whereas the high-frequency peak originates from the anti-phase fluctuation of the directors in the anti-tilt pairs of the SmCA* phase.

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