서지주요정보
반강유전성 Ceramic $Pb(Yb_{1/2}Ta_{1/2})O_3$ 와 반강유전성 액정 CS4001의 이완 특성에 관한 연구 = A study on dielectric relaxations in ceramic $Pb(Yb_{1/2}Ta_{1/2})O_3$ and antiferroelectric liquid crystal CS4001 near phase transition
서명 / 저자 반강유전성 Ceramic $Pb(Yb_{1/2}Ta_{1/2})O_3$ 와 반강유전성 액정 CS4001의 이완 특성에 관한 연구 = A study on dielectric relaxations in ceramic $Pb(Yb_{1/2}Ta_{1/2})O_3$ and antiferroelectric liquid crystal CS4001 near phase transition / 이승우.
저자명 이승우 ; Yi, Seung-Woo
발행사항 [대전 : 한국과학기술원, 2005].
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등록번호

8016736

소장위치/청구기호

학술문화관(문화관) 보존서고

DPH 05027

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초록정보

Antiferroelectic materials of Pb(Yb$_{1/2}$Ta$_{1/2}$)O$_{3}$ ceramics and liquid crystal CS4001 are studied for comparison of their rexation behaviors near the respective phase transitions. Raman spectra of Pb(Yb$_{1/2}$Ta$_{1/2}$)O$_3$ reveals a phase transition from paraelectric to antiferroelectric phase at 300℃, and a diffuse phase transtion from antiferroelectric to ferroelectric phase at about 150℃. Raman spectra of Pb(Yb$_{1/2}$Ta$_{1/2}$)O$_3$ depicts $A_{1g}$, $E_g$, and 2 $F_g$ modes in ferroelectric phase, where the $A_{1g}$ mode is observed to decrease in frequency with decreasing temperature. The frequency shift of ω from $ω_0$, the hard core Einstein-mode frequency, is found to show a big jump at 300℃ in a similar form as seen with inverse real part dielectric constant. The $F_g$ mode associated at the displacement of Pb ions split from one peak structure in high temperature phase to three peaks in low temperature phase. And the splitting between peaks is observed to be increasing in the temperature region from 200℃ (antiferroelectric) to 100℃ (ferroelectric phase). Liquid crystal CS4001 appears in a stripped pattern in antiferroelectric phase because of the modulation of smectic layer, when electro-optic double hysteresis loop can be observed. Switching current dependence on temeprature and external field can be analyzed to follow the relaxational characteristics. In antiferroelectric phase, two peaks, P1 and P2, are observed with P1 peak showing a strong dependence on the frequency and amplitude of external field but P2 peak with a weak dependence. P1 peak corresponds to the field-induced transition from antiferroelectric to ferroelectric but P2 peak a spontaneous relaxation from ferroelectric to antiferroelectric state. The relaxation time, controlling the switching time, is found to be a function of R, an effective rate constant determined as a peak to peak amplitude multiplied by frequency of the applied field.

서지기타정보

서지기타정보
청구기호 {DPH 05027
형태사항 vii, 93 p. : 삽도 ; 26 cm
언어 한국어
일반주기 저자명의 영문표기 : Seung-Woo Yi
지도교수의 한글표기 : 김종진
지도교수의 영문표기 : Jong-Jean Kim
수록잡지명 : "Low frequency dielectric response of antiferroelectric liquid crystal CS-4001". Ferroelectrics, 315, 1(2005)
학위논문 학위논문(박사) - 한국과학기술원 : 물리학과,
서지주기 참고문헌 : p. 90-93
주제 반강유전성
라만 산란
상전이현상
Antiferroelectricity
Raman Scattering
Phase Transition
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