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Phenomenological Calculation of the Domain-size-dependent Ferroelectric Domain-wall Velocity
송태권,양상모 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
The ferroelectric domain-wall velocity was calculated using a modified Landau-Khalatnikov equation by considering the electrostatic energy for the growth of cylindrical 180˚ domains. The parameters for the calculation were measured from piezoresponse force microscope images of epitaxial Pb(Zr,Ti)O3 thin films. The calculated domain-wall velocity was inversely proportional to the domain radius and agreed well with the measured velocity. The electrostatic energy was found to be the most important factor governing ferroelectric domain growth kinetics in the initial stage. The ferroelectric domain-wall velocity was calculated using a modified Landau-Khalatnikov equation by considering the electrostatic energy for the growth of cylindrical 180˚ domains. The parameters for the calculation were measured from piezoresponse force microscope images of epitaxial Pb(Zr,Ti)O3 thin films. The calculated domain-wall velocity was inversely proportional to the domain radius and agreed well with the measured velocity. The electrostatic energy was found to be the most important factor governing ferroelectric domain growth kinetics in the initial stage.
송태권 한국물리학회 2017 New Physics: Sae Mulli Vol.67 No.7
항전기장을 중심으로 강유전 분극-전기장 이력곡선과 압전 변형-전기장 이력곡선을 비교 연구하였다. 외부 전기장에 따른 선형 유전 반응과 비선형 스위칭 특성을 고려하여 쌍곡선 함수를 이용하여 강유전 이력곡선을 시늉내었다. 그리고 압전 이력곡선은 강유전 이력곡선에서 구한 강유전 분역의 비율을 고려하여 압전 반응으로부터 유도하였다. 시늉낸 이력곡선을 BiFeO$_{3}$-BaTiO$_{3}$ 압전 세라믹의 실제 측정 이력곡선들과 비교하였다. 강유전 이력곡선에서 측정된 항전기장은 압전 변형-전기장 이력곡선에서 측정된 변형이 없어지는 전기장에 비하여 약간 작게 나타났다. 이 결과를 분역의 비율을 이용하여 설명할 수 있었다. 이로부터 전기장의 변화에 따른 압전 계수 $d(E)$ 값의 변화를 유도하고 다른 실험 결과와 잘 일치함을 알 수 있었다. Ferroelectric polarization-electric field hysteresis loops and piezoelectric strain-electric field hysteresis loops of ferroelectric materials are systematically compared, especially from the viewpoint of coercive fields. The ferroelectric hysteresis loops were simulated with simple hyperbolic functions by considering linear dielectric responses and non-linear switching responses; the piezoelectric hysteresis loops were simulated with the piezoelectric responses of ferroelectric domains. Then, the simulated hysteresis loops were compared with the experimental hysteresis loops of piezoelectric BiFeO$_{3}$-BaTiO$_{3}$ ceramics. Based on these results, the electric-field-dependent piezoelectric constants $d(E)$ of the samples were calculated.
Landau-Khalatnikov 방정식을 이용한 강유전 이력곡선과 펄스 스위칭 특성과의 비교
송태권,김명호 國立 昌原大學校 產業技術硏究院 2004 産技硏論文集 Vol.18 No.-
A phenomenological thermodynamics theory of Landau-Khalatnikov equation was used to study the relation between ferroelectric hysteresis loops and pulse switching current responses for the application of ferroelectric random access memory devices. Independent of hysteresis loop shape whether square or S-shape, the polarizations were switched within one-decade time interval but the characteristic switching times were much different. S-shaped hysteresis loop has longer switching time than square-shaped loop. These results confirm the Kolmogorov-Avrami-Ishibashi model in ferroelectric switching.
에너지 저장 응용을 위한 반강유전체 Landau-Khalatnikov 시늉내기
송태권 한국물리학회 2023 새물리 Vol.73 No.2
For energy storage applications, various antiferroelectric properties were modeled via Landau–Khalatnikov (LK) simulations. LK simulation methods for switching sublattice polarizations of antiferroelectrics were developed through the control of coercive fields and frequency. The methods were compared with those developed in previous phenomenological studies. Through the coupling of antiferroelectrics and relaxor ferroelectrics, superior energy storage properties were obtained. Under optimal conditions, the recoverable energy storage density reached 9.66 J/m3 and the energy storage efficiency was 98%. These results showed that antiferroelectrics can be useful for environment-friendly energy storage applications. 에너지 저장 응용을 위하여 다양한 반강유전 특성에 대하여 Landau-Khalatnikov (LK) 시늉내기를 이용하여 반강유전체의 활용 가능성을 살펴보았다. LK 시늉내기가 반강유전체의 하부 격자 분극의 스위칭 특성을 설명하는 데 활용하는 방법을 주파수의 변화와 항전기장의 변화를 이용하여 개발하고 알려진 반강유전 현상론과 비교하였다. 반강유전과 완화형 강유전 특성을 결합하여 매우 우수한 에너지 저장 특성을 얻을 수 있음을 확인하였다. 이를 통하여 우수한 회수 에너지 밀도 9.66 J/m3와 저장 효율 98%를 얻을 수 있었고 반강유전체가 친환경 에너지 저장 응용에 널리 활용될 수 있음을 보였다.