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驰豫型铁电体是很重要的功能材料,其介电性能和极化机制一直是研究的热点。作者通过对掺钛铌镁酸铅系列铁电陶瓷介电、铁电、热电等宏观性能和微观结构详细、系统的实验研究,提出铁电微畴为三方相畸变结构散布于立方钙钛矿母相中,通过类马氏体预相变的位移型形核过程,实现顺电—驰豫型铁电态的弥散相变,进一步通过类马氏体相变,完成驰豫型铁电态无序态分布的微畴向正常铁电态长程序铁电宏畴转变;提出T_1可调整A(B′B″)O_3型复合钙钛矿铁电体B′和B″离子价态和离子半径等不同所产生的内电场和弹性场,使立方母相所承受切应力发生变化,诱发极性微区、铁电微畴随组成变化表现不同活性。对弛豫型铁电体介电谱分析与计算表明,其在介电常数峰值温度Tm附近的介电弛豫过程连续变化,不对应结构突变的相变过程,较接近偶极介质。通过铌锌酸铅基系列铁电陶瓷在准同型相界附近异常特性的研究,进一步揭示弛豫型铁电体中结构特征决定宏观行为的必要性,反映出铁电材料由微观到介观、再到宏观的有趣规律性。在此基础上,对复合钙钛矿弛豫型铁电体偏压介电行为、电致伸缩特性、介电老化行为等进行了系统研究,合理解释了一系列新的实验现象和结果;并对钨青铜结构铌酸锶钡弛豫型铁电陶瓷复介电响应进行了详细的对比分析和讨 相似文献
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本文通过铌锌酸铅基复合钙钛矿结构铁电陶瓷的电畴观察、强场极化反转行为以及直流偏压下介电行为和X射线衍射峰等的详细测量,对铁电微畴、宏畴在外场诱导下的反转规律进行了分析,探讨了与铁电陶瓷介电行为相对应的微观极化机制。 相似文献
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复合钙钛矿铁电陶瓷的电场诱导畴反转特征研究 总被引:1,自引:0,他引:1
本文通过铌锌酸铅基复合钙钛矿结构铁电陶瓷的的电畴观察,强场极化反转行为以及直流偏压下介电行为和X射线射衍射峰等的详细测量,对铁电微畴,宏畴在外场诱导下的反转规律进行了分析,探讨了与铁电陶瓷介电行为相对应的微观极化机制。 相似文献
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研究了(Na0.8K0.2)0.5Bi0.5TiO3陶瓷的介电和压电性能,发现陶瓷从室温到500℃温度范围的介电谱中存在两个介电峰,电滞回线显示第一个介电峰由铁电-反铁电相变引起的,温度继续升高,反铁电相由宏畴变为微畴,微畴向顺电相转变导致了第二个介电峰,该峰对应的相变为弥散型相变.室温下陶瓷具有较高的剩余极化强度Pr=29.4μC/cm2和相对低的矫顽电场Ec=2.8kV/mm,极化后的陶瓷显示出较高的压电常数d33=120pC/N和机电耦合系数Kp=28.5%,以及高的频率常数Nφ=2916Hz.m,120℃具有最小的谐振频率温度系数. 相似文献
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具有铁电性且厚度在数十纳米至数微米的铁电薄膜具有良好的压电性、介电性及热释电性等特性,在微电子、光电子和微电子机械系统等领域有着广阔的应用前景.随着铁电薄膜制备技术的发展,使现代微电子技术与铁电薄膜的多种功能相结合,必将开发出众多新型功能器件,促进新兴技术的发展,因此对铁电薄膜的研究已成为国内、国际上新材料研究中的一个十分活跃的领域.在铁电薄膜的许多应用中,铁电存储器尤其引人注目.如何制备性能良好的铁电薄膜,满足集成铁电器件的要求成为制约铁电薄膜应用的关键环节,薄膜制备技术的进步可以提高铁电薄膜的质量,目前人们已经能够使用多种方法制备优良的铁电薄膜.总体来说,制备铁电薄膜按其制膜机理大体上可分为化学沉积法和物理沉积法两大类.化学沉积法制备微纳铁电薄膜,通过对薄膜成分、元素掺杂及薄膜取向等方面的研究提高铁电薄膜的性能,从而制备出高质量的薄膜.物理沉积法一般是在较高的真空度下进行,采用不同的基片和调节基片的温度可制得不同取向的薄膜,甚至外延薄膜,这种方法对自发极化呈现高度各向异性的薄膜制备显得尤为重要.热喷涂方法制备厚涂层通过从元素掺杂、热处理、工艺参数优化等方面来改善铁电涂层的性能.铁电薄膜制备技术的进步可以提高薄膜的质量,而薄膜质量的提高又可以促进功能器件制备技术的进步、使用性能的提升,从而使其得到更广泛的应用.本文综述了近年来铁电薄膜制备技术及其应用研究的新进展,主要针对化学方法、物理方法及热喷涂方法制备铁电薄膜的技术难点讨论了铁电薄膜成形的物理化学机理、优缺点及其应用情况. 相似文献
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Summary Crack kinking induced by domain switching in a ferroelectric material under purely electric loading is investigated. Boundaries
of domain switching zones for the asymptotic problem of a semi-infinite crack under the small scale conditions are determined
based on the nonlinear electric theory. Stress intensity factors induced by the domain switching are numerically evaluated
using the solution of the switching zone. Numerical results of the kink angle are obtained as a function of the ratio of the
coercive electric field to the yield electric field for various polarization angles. Crack kinking in ferroelectric materials
subjected to a cyclic electric field is also examined. The crack in the fully poled materials branches with different directions
at application of the positive and negative electric fields, respectively. The electric fatigue crack is shown to have a forked
crack pattern in the fully poled materials. 相似文献
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Zhao T Scholl A Zavaliche F Lee K Barry M Doran A Cruz MP Chu YH Ederer C Spaldin NA Das RR Kim DM Baek SH Eom CB Ramesh R 《Nature materials》2006,5(10):823-829
Multiferroic materials, which offer the possibility of manipulating the magnetic state by an electric field or vice versa, are of great current interest. In this work, we demonstrate the first observation of electrical control of antiferromagnetic domain structure in a single-phase multiferroic material at room temperature. High-resolution images of both antiferromagnetic and ferroelectric domain structures of (001)-oriented multiferroic BiFeO3 films revealed a clear domain correlation, indicating a strong coupling between the two types of order. The ferroelectric structure was measured using piezo force microscopy, whereas X-ray photoemission electron microscopy as well as its temperature dependence was used to detect the antiferromagnetic configuration. Antiferromagnetic domain switching induced by ferroelectric polarization switching was observed, in agreement with theoretical predictions. 相似文献
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We have demonstrated an effective electrical control of polarization in the individual crystalline nanomesas of the ferroelectric polymer, poly(vinylidene fluoride)-trifluoroethylene (PVDF-TrFE) and its relation to the polymer structure. The mechanism of polarization reversal has been investigated via sub-10 nm real space imaging of domain pattern evolution under an applied electric field. The domain switching behavior revealed in PVDF-TrFE nanomesas is drastically different from that observed in inorganic solid-state crystalline ferroelectrics. The nanoscale features of the switching process include remote domain nucleation and spatially nonuniform wall velocity. Local switching spectroscopy and domain dynamics studies relate the observed switching features to a random-bond type disorder associated with defects in conformation and molecular packing. 相似文献
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Meinhard Kuna 《Engineering Fracture Mechanics》2010,77(2):309-326
Piezoelectric and ferroelectric materials have gained extensive applications in electromechanical devices, microelectromechanical systems and smart composite materials. In order to assess the strength and durability of those materials and components, exhaustive theoretical and experimental investigations have been performed over the past three decades. The aim of the paper is to give a short overview and a critical discussion about the present state in the field of piezoelectric fracture mechanics. After an introduction, linear piezoelectric fracture theory is explained with emphasis to special features like anisotropy, mode mixture and electric properties of cracks. Next, suggested fracture criteria are presented and contrasted with experimental observations in fracture testing. Cracks under static, cyclic and dynamic loading by electrical and mechanical fields are taken into account. A great challenge is to tackle the non-linear phenomena and ferroelectric domain switching in the fracture process zone. Finally, conclusions are drawn with respect to open problems and desirable future research areas. To limit the scope of the paper, fracture behavior of interface cracks will not be addressed. 相似文献
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In this article, a set of equivalent variational formulations for computing the driving forces for domain switching in ferroelectric materials is presented. It is proven that these formulations allow the free adoption of any couple of mechanical and electric fields as independent variables while obtaining consistent results. In addition, explicit expressions are provided for each formulation which allows for the study of the phase transformation process under different constraints. 相似文献
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Khodayari A Mohammadi S 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(3):503-508
In this paper, the feasibility of using ferroelectric materials as a cooling device or solid-state refrigerator based on the electrocaloric effect has been considered. The electrocaloric responses of two different ferroelectric capacitors (PMN-25PT, PZN-4.5PT) are studied. In this study, the dynamics of temperature variation at the edges of a layered structure comprised of an electrocaloric material with heatconducting elements on its sides to an applied periodic electric field have been studied. Electrocaloric elements can generate directed heat flux as a thermal pump by alternative switching. A temperature reduction of 6° is obtained in an electric field of 1 KV/mm at a frequency of 1 Hz for PMN-25PT material after applying 80 cycles. It is shown that the type of applied electric pulses and ferroelectric material affect the results. 相似文献
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Summary A crack with growth in ferroelectric ceramics under purely electric loading is analyzed. The crack tip stress intensity factor for the growing crack under small scale conditions is evaluated by employing the model of nonlinear domain switching. The electrical fracture toughness is obtained from the result of the stress intensity factor. It is shown that the ferroelectric material can be either toughened or weakened as the crack grows. Fatigue crack growth in a ferroelectric material under cyclic electric loading is also examined. The incremental fatigue crack growth under cyclic electric loading is obtained numerically. The fatigue crack growth rate is affected strongly by the electrical nonlinear behavior. It is found that the curve of fatigue crack growth rate versus electric field intensity factor is linear on the log-log plot at intermediate values of the electric field intensity factor. 相似文献
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Some piezoelectric ceramic materials do behave in a nonlinear way when they are subjected to large electric or mechanical stress fields. This macroscopic nonlinearity comes from microscopic domain switchings during which one type of variant switches to other types of variants under large electromechanical fields. This switchable piezoelectric ceramic materials are called ferroelectric ceramics. In the present paper, a typical ferroelectric material particle is represented by a regular dodecahedron representative volume element (RVE) which includes twenty distinct types of variants, and a finite element analysis is carried out on a cubic specimen subjected to both a constant compressive stress and an electric field cycling. The calculation results are compared with experimental observations and isotropy of the responses is discussed.The authors gratefully acknowledge the support of the Agency for Defense Development through Grant ADD 01-05-01. 相似文献
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K. Jayabal 《International Journal of Engineering Science》2009,47(10):1014-1024
A thermodynamically consistent uniaxial model combining the benefits of both phenomenological and micromechanical models is proposed. The driving forces derived from irreversible thermodynamics induce domain switching on reaching certain critical values. The back stress and electric fields, assumed as linear functions of remanent strain and polarization, developed by the domain switching process are introduced to assist or resist further changes in microscopic state of the crystal depending on the loading history. In this model, volume fractions of three distinct uniaxial variants act as internal variables describing the microscopic state of the crystal. Domain switching process for general cases involving two variants and for simultaneous evolution cases where three distinct variants participate the switching process are dealt with. The model is found to reproduce the characteristics of the responses of ferroelectric polycrystals under uniaxial complex electro-mechanical loading cases that are consistent with the experimental observations. 相似文献