共查询到20条相似文献,搜索用时 218 毫秒
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采用外加电场法制备了LiNbO3单晶周期畴结构. 在对不同尺寸周期畴的反转电流进行比较研究的基础上,提出了一种确定反转畴成核时间和纵向贯穿速率的方法. 根据这一方法,得到在电场强度为25.1kV/mm,脉冲宽度为50 ms的脉冲方波作用下,LiNbO3单晶反转畴的成核时间约为80ns,纵向贯穿速率约为0.1667m/s.
关键词:
3单晶周期极化')" href="#">LiNbO3单晶周期极化
反转电流
反转畴成核时间
反转畴纵向贯穿速率 相似文献
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在前期的研究中曾通过Ag掺杂降低Sm123/Sm211体系熔点,利用Nd123冷籽晶技术成功制备出具有理想织构的SmBCO/Ag单畴块材.但在实验结果中发现相比于未掺杂坯体,掺入Ag后的SmBCO坯体生长速率下降,在所考察的慢冷温区里,生长速率呈不断减小趋势,最终因自发成核而无法继续生长,使得SmBCO单畴区域局限于15×15mm2范围内.为了抑制单畴生长中的自发成核现象,本文研究了降温速率对SmBCO/Ag单畴自发成核的影响.在两组不同条件下的降温速率实验中发现,不同的降温速率对体系自发成核的抑制效果是不同的.利用降低降温速率,成功地将掺Ag SmBCO单畴面积从15×15mm2增大至26×26mm2. 相似文献
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紫外激光诱导近化学计量比钽酸锂晶体铁电畴反转 总被引:1,自引:0,他引:1
对紫外激光诱导近化学计量比钽酸锂晶体铁电畴反转进行了实验研究。波长为351 nm的连续紫外激光被聚焦在近化学计量比钽酸锂晶体的-z表面,同时沿与晶体自发极化相反的方向施加均匀外电场。实验证实紫外激光辐照可以有效地降低晶体畴反转所需的矫顽电场,采用数字全息干涉测量技术检测证实在激光辐照区域实现局域畴反转。研究表明采用紫外激光诱导可以实现对近化学计量比钽酸锂晶体铁电畴反转的局域控制。提出了物理机理的理论分析,认为外电场和激光辐照场的共同作用在晶体内部产生高浓度、大尺寸的缺陷结构,缺陷一定程度上降低畴体成核和畴壁运动所需要克服的退极化能和畴壁能,实现激光诱导畴反转。 相似文献
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利用扫描力显微术中压电响应模式原位研究了(111)择优取向的PZT60/40铁电薄膜的纳米尺度畴结构及其极化反转行为.铁电畴图像复杂的畴衬度与晶粒中的畴排列和晶粒的取向密切相关.直接观察到极化反转期间所形成的小至30nm宽的台阶结构,该台阶结构揭示了(111)取向的PZT60/40铁电薄膜在极化反转期间其畴成核与生长机理主要表现为铁电畴的纵向生长机理.
关键词:
畴结构
反转机理
PZT薄膜
扫描力显微术 相似文献
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采用K2O作助熔剂直接拉晶法和气相输运平衡技术制备出了高质量近化学计量比铌酸锂晶体,研究了铌酸锂晶体中的[Li][Nb]比含量对其畴反转结构和极化电场的影响.实验结果表明:随着晶体中[Li][Nb]比的提高,畴极化反转电场呈明显下降趋势,使用近化学计量比铌酸锂晶体,在4.0±0.5kVmm大小极化电场条件下,成功地实现了1.0mm厚度的周期极化畴反转.并用铌酸锂晶体的Li空位缺陷模型对上述实验结果给出了合理的解释.
关键词:
近化学计量比铌酸锂晶体
周期极化
畴反转 相似文献
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Xingjiao Li Jianshe Liu Jianhong Zhao Dexin Lu Jiangde Xuan Haoshuang Gu 《Physics letters. A》1995,200(6):445-452
Fatigue in thin-film ferroelectrics has been simulated by using a two-dimensional modified diffusion-limited aggregation model with drift representing the applied alternating electric field. It is shown that the fatigue process follows a power law at early times and speeds up dramatically at later times. Besides, it was found revealed that the fatigue rate can be lower when the drift strength becomes higher. This curious result, which has some experimental evidences, has been explained by noting that the fatigued units pattern for a higher drift strength has a larger fractal dimension. 相似文献
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Switching kinetics of uniaxial ferroelastic ferroelectrics (FFs) in external electric and stress fields is studied using classical theory of nucleation and growth. The stage in which the polarization and deformation reversal involves the main body of the FF and the final stage (Ostwald ripening) of the FF switching are studied with allowance for the change in the repolarization and redeformation during the phase transition. The time dependences of the repolarization and redeformation are found, and equations are derived from which the polarization current and the deformation flux, as well as their time dependence, can be calculated. The calculated main characteristics of the FF switching are compared with the experimental data for switching of Rochelle salt single crystals. 相似文献
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We simulate field-induced nucleation and switching of domains in a three-dimensional model of ferroelectrics with quenched
disorder and varying domain sizes. We study (1) bursts of the switching current at slow driving along the hysteresis loop
(electrical Barkhausen noise) and (2) the polarization reversal when a strong electric field was applied and back-switching
after the field was removed. We show how these processes are related to the underlying structure of domain walls, which in
turn is controlled by the pinning at quenched local electric fields. When the depolarization fields of bound charges are properly
screened we find that the fractal switching current noise may appear with two distinct universal behaviors. The critical depinning
of plane domain walls determines the universality class in the case of weak random fields, whereas for large randomness the
massive nucleation of domains in the bulk leads to different scaling properties. In both cases the scaling exponents decay
logarithmically when the driving frequency is increased. The polarization reverses in the applied field as a power-law, while
its relaxation in zero field is a stretch exponential function of time. The stretching exponent depends on the strength of
pinning. The results may be applicable for uniaxial relaxor ferroelectrics, such as doped SBN:Ce.
Received 7 February 2002 / Received in final form 10 April 2002 Published online 9 July 2002 相似文献
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Potts-Ising model for simulation of polarization switching in polycrystalline ferroelectrics 下载免费PDF全文
This paper proposes a scheme based on the Potts and Ising models for
simulating polarization switching of polycrystalline ferroelectrics
using the Monte Carlo method. The polycrystalline texture with
different average grain size is produced from the Potts model. Then
Ising model is implemented in the polycrystalline texture to produce
the domain pattern and hysteresis loop. The domain patterns and
hysteresis loops have been obtained for polycrystalline texture with
different average grain size. From the results of domain pattern
evolution process under an applied electric field using this scheme,
an extended domain, which covers more than one grain with
polarization aligned roughly in the same direction, has been
observed during the polarization reversal. This scheme can well
reproduce the basic properties of polycrystalline ferroelectrics and
is a valuable tool for exploring the physical properties of
polycrystalline ferroelectrics. 相似文献
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Jie Wang Zheng Chen Takahiro Shimada Takayuki Kitamura 《Physics letters. A》2013,377(25-27):1643-1648
The effect of electrical conductivity on the domain evolution of semiconducting ferroelectrics is investigated using a phase field model which includes the drift of space charges. Phase field simulations show that the tail-to-tail 90° charged domain wall appears during the domain formation in the semiconducting ferroelectrics at zero field, which is prohibited in common insulating ferroelectrics. Due to the screening of polarization charges, the domain switching takes place through the motion of head-to-head 180° charged domain wall in the semiconducting single-domain ferroelectrics subjected to an electric field. Comparing to the insulating ferroelectrics, the semiconducting ferroelectrics have a lower speed of domain evolution due to the decrease of mobility of charged domain walls. The response of semiconducting ferroelectrics to a mechanical load is also found different from that of insulating ferroelectrics. 相似文献
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Highland MJ Fister TT Richard MI Fong DD Fuoss PH Thompson C Eastman JA Streiffer SK Stephenson GB 《Physical review letters》2010,105(16):167601
Polarization switching in ferroelectrics has been thought to occur only through the nucleation and growth of new domains. Here we use in situ synchrotron x-ray scattering to monitor switching controlled by applied chemical potential. In sufficiently thin PbTiO? films, nucleation is suppressed and switching occurs by a continuous mechanism, i.e., by uniform decrease and inversion of the polarization without domain formation. The observed lattice parameter shows that the electric field in the film during switching reaches the theoretical intrinsic coercive field. 相似文献
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Considering external electric field as well as third- and fourth-order phonon anharmonic interaction terms in the pseudospin-lattice
coupled mode (PLCM) model Hamiltonian for KDP-type ferroelectrics, expressions for field-dependent shift, width, renormalized
soft mode frequency, Curie temperature, dielectric constant and dielectric loss are evaluated. For the calculation, method
of statistical double-time temperature-dependent Green’s function has been used. By fitting model values of physical quantities,
temperature and electric field dependences of soft mode frequency, dielectric constant and loss have been calculated which
compare well with experimental results of Baumgartner [8] and Choi and Lockwood [9]. Both dielectric constant and loss decrease
with electric field. 相似文献
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基于随机场Ising模型描述的有序无序相变中偶极子在电场作用下的反转运动, 研究了有序无序相变过程中电场与极化强度的关系. 认为tanh(x) 的函数关系与位移型二阶铁电相变极化强度随电场变化的实验结果完全相同. 由此得出基本结论: 偶极子的集体转向造成了极化强度的增大并等同于内电场的增加. 通过区分光学模和偶极子对介电隔离率的贡献, 考虑偶极子极化对介电常数复数形式的频率色散关系, 发现从高斯分布的居里温度可以导出二阶铁电相变过程中介电常数与温度和频率的色散关系.
关键词:
铁电相变
极化强度
随机场 相似文献
20.
A. S. Starkov O. V. Pakhomov I. A. Starkov 《Journal of Experimental and Theoretical Physics》2013,116(6):987-994
A modified Weiss mean-field theory is used to study the dependence of the properties of a thin ferroelectric film on its thickness. The possibility of introducing gradient terms into the thermodynamic potential is analyzed using the calculus of variations. An integral equation is introduced to generalize the well-known Langevin equation to the case of the boundaries of a ferroelectric. An analysis of this equation leads to the existence of a transition layer at the interface between ferroelectrics or a ferroelectric and a dielectric. The permittivity of this layer is shown to depend on the electric field direction even if the ferroelectrics in contact are homogeneous. The results obtained in terms of the Weiss model are compared with the results of the models based on the correlation effect and the presence of a dielectric layer at the boundary of a ferroelectric and with experimental data. 相似文献