서지주요정보
반강유전성 액정((R)-MHPOBC)에서의 전기장 유도에 의한 상전이 특성 연구 = Field-induced phase transition in antiferroelectric liquid crystal (MHPOBC)
서명 / 저자 반강유전성 액정((R)-MHPOBC)에서의 전기장 유도에 의한 상전이 특성 연구 = Field-induced phase transition in antiferroelectric liquid crystal (MHPOBC) / 유정선.
저자명 유정선 ; Yu, Jeong-Seon
발행사항 [대전 : 한국과학기술원, 1996].
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등록번호

8006865

소장위치/청구기호

학술문화관(문화관) 보존서고

DPH 96026

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초록정보

The phase transitions in an antiferroelectric liquid crystal((R)-MHPOBC) and a ferroelectric liquid crystal(CS1017) were studied by polarization reversal, D--E hysteresis loop and dielectric measurements. Dielectric constant near the $SmA-SmC^*$ phase transition showed the Curie-Weiss behaviour in the ferroelectric liquid crystal CS1017. Slowing down of dielectric relaxation toward the $SmA-SmC^*$ phase transition, associated with the soft mode, was observed in CS1017. Dielectric measurements as a function of both d.c.bias field and a.c.probe frequency were made in the $SmC^*_A$ phase of (R)-MHPOBC compound to study the field induced phase trnsition from the antiferroelectric to the ferroelectric phase. Three dielectric relaxation peaks observed in the concerned region of the field induced transition were analyzed in terms of the Cole-Cole equations and the Landau free energy functional theory of Orihara and Ishibashi to derive the dielectric relaxation frequencies and the threshold electric fields associated with the transition. D-E hysteresis loops were studied at various driving frequencies from 1 Hz to 5 KHz for a 3㎛ thick sample of (R)-MHPOBC at T $\simeg$ 90℃. A double-loop hysteresis curve observed in the antiferroelectric phase was transformed into a single loop hysteresis curve with increasing the driving frequency above 500Hz. A relaxation peak was observed at the same frequency in the dielectric loss measurements under d.c.bias fields. Polarization reversal current was also measured to obtain the field induced polarization as a function of the field strength. All of these measurements confirm that the field induced phase transition undergoes from the antiferroelectric to the ferroelectric phase. A phenomenological model is elaborated for a microscopic understanding of the phase transition from antiferroelectric to ferroelectric phase under an external electric field. The antiferroelectric phase, stabilized by the two layer pairing interactions, was found to become unstable as the electric field is increased above a threshold value $E_c=2JP_o$, where J is the nearest neighbor interaction constant of the molecular dipoles in the adjacent smectic layers and $P_o$ the molecular dipole moment. When the applied electric field brings about the instability of the antiferroelectric phase, the three layer pairing interactions are assumed to stabilize the system in a different configuration possessing ferrielectric ordering. The observed dielectric constant in the antiferroelectric (R)-MHPOBC as a function of the electric field could be understood in the model with the acceptable range of parameters.

서지기타정보

서지기타정보
청구기호 {DPH 96026
형태사항 vii, 115 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Jeong-Seon Yu
지도교수의 한글표기 : 김종진
지도교수의 영문표기 : Jong-Jean Kim
수록잡지명 : "Raman studies on YBa2Cu3O7-d High Tc Superconductors". Ferroelectrics, Vol. 178, pp. 67-72 (1994)
수록잡지명 : "Field Induced Polarization Characteristics of Ferroelectric Ordering in Antiferroelectric (R)-MHPOBC". Ferroelectrics, pp. 205-212 (1996)
수록잡지명 : "Field Induced Phase Transition in Antiferroelectric Liquid Crystal-MHPOBC". Ferroelectrics (1996)
수록잡지명 : "Electric Field Effect on Dielectric Constant of Liquid Crystal (MHPOBC)". Ferroelectrics (1996)
학위논문 학위논문(박사) - 한국과학기술원 : 물리학과,
서지주기 참고문헌 : p. 110-115
주제 반강유전성 액정
강유전성
준강유전성
상전이
Antiferroelectric liquid crystal
Ferroelectric
Ferrielectric
Phase transition
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