基于能量转换原理的磁电层合材料低频磁电响应分析

提出了一种基于能量转换原理的磁致伸缩/压电层合材料低频磁电响应模型,并对不同层合结构的磁电响应特性进行了对比研究.该模型假定层合材料层间能量传递通过层间剪切力来实现,利用应力函数法分析了磁致伸缩层和压电层的应力与应变,求出了磁致伸缩层的应变能和存储磁场能以及压电层的应变能和电场能;利用Hamilton最小能量原理求出了层间剪切力的大小,获得了开路状态下层合材料的低频磁电响应模型.发现磁电电压系数与磁致伸缩材料的磁导率、泊松比、磁机耦合系数以及压电材料的泊松比、机电耦合系数等有关,并对这些参数的影响进行了分析.同时对两层和三层结构的层合材料磁电特性进行了对比研究,发现层合结构不同则获得的磁电系数公式不同,用相应的公式计算得到的误差才会最小.研究结果表明,本文的理论误差小于6.5%,与其他方法相比,本文的理论模型能更好地描述磁电层合材料的低频磁电响应特性.     

Optimal magnetoelectric coupling performance of Terfenol-D/PZT composites in resonance state under bias magnetic field

Laminated magnetoelectric (ME) composites with various thickness ratios were optimized, fabricated and experimentally investigated in this work. The Terfenal-D/PZT specimens with optimal thickness ratio between the magnetostrictive phase and piezoelectric phase, and two other values were tested for their ME coupling performance. The coupling voltage output increases linearly with the increase of DC bias magnetic field. The ME voltage coefficient increases more than 100 times in the resonance state for the optimal laminate. The DC bias magnetic field affects the ME voltage coefficient significantly, and also has little effect on the resonant frequency. The strength of AC magnetic field also slightly affects the ME voltage coefficient in resonance state, but does not affect the resonant state under which the same DC magnetic field is required. The experimental results can help understand the coupling performance of ME composite under bias magnetic field and prompt the application of ME devices.     

Frequency response of magnetoelectric effect in piezoelectric-magnetostrictive disk-ring composite structures

A theoretical model is presented for frequency dependence of magnetoelectric (ME) effect in piezoelectric-magnetostrictive disk-ring composite structures. Expressions for ME voltage coefficients in piezoelectric-magnetostrictive (PE-MS) disk-ring and MS-PE disk-ring are obtained by solving elastodynamic equations. The calculated resonance frequency and frequency dependence of ME voltage coefficients are in good agreement with the experimental results. This model indicates better mechanical coupling in disk-ring structure than that in traditional layered structure, and this may be responsible for the enhancing ME effect. The analysis suggests the disk-ring composites structures are promising for magnetoelectric applications.     

偏置磁场对磁致伸缩/弹性/压电层合材料磁电效应的影响

根据磁致伸缩材料的非线性本构关系得到其动态杨氏弹性模量和动态压磁系数,结合等效电路法得到磁致伸缩/弹性/压电层合材料的磁电效应与磁致伸缩材料的动态杨氏弹性模量和动态压磁系数的关系,讨论了偏置磁场对这种层合材料的谐振频率和谐振磁电电压转换系数的影响.理论推导和实验结果均表明,存在最佳偏置磁场使磁致伸缩/弹性/压电层合材料的谐振磁电电压转换系数最大. 关键词： 磁致伸缩/弹性/压电层合材料 磁电效应 偏置磁场 非线性本构关系     

Bath temperature effect on magnetoelectric performance of Ni-lead zirconate titanate-Ni laminated composites synthesized by electroless deposition

Magnetoelectric (ME) Ni-lead zirconate titanate-Ni laminated composites have been prepared by electroless deposition at various bath temperatures. The structure of the Ni layers deposited at various bath temperatures was characterized by X-ray diffraction, and microstructures were investigated by transmission electron microscopy. The magnetostrictive coefficients were measured by means of a resistance strain gauge. The transverse ME voltage coefficient α_E,31 was measured with the magnetic field applied parallel to the sample plane. The deposition rate of Ni increases with bath temperature. Ni layer with smaller grain size is obtained at higher bath temperature and shows higher piezomagnetic coefficient, promoting the ME effect of corresponding laminated composites. It is advantageous to increase the bath temperature, while trying to avoid the breaking of bath constituents.     

磁致伸缩/压电叠层复合材料磁-机-电耦合系数分析

分析和推导了磁致伸缩/压电叠层复合材料的机-电耦合系数、磁-机耦合系数及磁-电耦合系数与磁致伸缩层和压电层性能参数及几何参数之间的关系.进一步分析表明,叠层复合材料低频时的磁电电压系数正比于磁-电耦合系数,谐振时的磁电电压系数正比于磁-电耦合系数与机械品质因素的乘积;磁电电压系数还与复合结构的本征阻抗有关,本征阻抗越大磁电电压系数越大.通过性能差异较大的Terfenol-D和FeNi基弹性合金分别与压电材料PZT5-H和PZT8相互组合构成复合材料的比较分析,进一步阐明了磁电复合材料磁-电耦合系数和机械品 关键词： 磁电效应 磁-机-电耦合系数 磁致伸缩材料 压电材料     

对称磁电层合板磁电转换效应理论研究

磁致伸缩和压电层合材料通过磁致伸缩和压电效应的乘积可以获得大的磁电效应.通过材料的力学本构方程，建立了对称磁电层合板磁电耦合的静态力学模型；采用ANSYS 80多物理场有限元分析软件，对层合结构的磁电转化效应进行了数值计算，并与理论计算值进行了对比.研究结果表明：磁致伸缩/压电的厚度比增加使磁电电压系数增大；所推导的磁电电压系数公式的计算值与等效电路模型推导的公式计算值符合很好；有限元数值计算结果介于两种模型的计算结果之间. 关键词： 磁电效应 层合板 本构方程 有限元分析     

The physics of magnetoelectric composites

This paper gives an overview about the basic ideas of magnetoelectric materials. Up to now single-phase materials show the magnetoelectric effect only below room temperature. Mixing a magnetostrictive with a piezoelectric component is a way to overcome this limitation. This delivers a composite which can exhibit a magnetoelectric effect even at room temperature and higher. Possible candidates for these composites (piezoelectric as well as magnetostrictive) are shown, examples from literature and own results are given. The most important coupling mechanism (magnetization, magnetostriction, local stress, charge) between the magnetostrictive and the piezoelectric phase are discussed. Hints for a direct coupling between the electric polarization and the magnetization are also presented. Different measurement methods for determining the magnetoelectric coefficient are discussed. Representative results as obtained on a technical useful composite between 50% Co-Ferrite+50% BaTiO₃ are given. The behavior of a simple “mixed” structure with that of a “core-shell” structure is compared. The later gives a 20-times larger magnetoelectric coefficient.     

磁电异质结及器件应用

磁电异质结是由铁磁和铁电材料通过连接层耦合而成,其磁电效应来源于铁电相的压电效应和铁磁相的磁致伸缩效应.相对于颗粒混相磁电复合材料,层状磁电异质结材料具有更高的磁电耦合系数和更低的介电损耗,使得其在磁场传感器、能量收集器、天线以及存储器等领域都有着巨大的应用前景.本综述重点总结了磁电异质结材料的发展历程以及相关应用领域的最新进展,最后评述了磁电异质结材料发展的挑战和前景展望.     

Magnetoelectric laminate based DC magnetic field sensor

We report on a DC magnetic field sensor that utilizes magnetoelectric (ME) laminate composites. It consists of a ring‐dot piezoelectric transformer laminated to a magnetostrictive disc. When a constant voltage is applied to the ring section of the piezoelectric layer at resonance, a stress is induced in the dot section. Then, if an external magnetic object is introduced in the vicinity of the dot section, the effective elastic stiffness is increased, altering the resonance frequency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Magnetoelectric properties of particulate and bi-layer PMN-PT/CoFe2O4 composites

Our studies comprise electrical dielectric and magnetoelectric properties of CoFe₂O₄ (CFO) and Pb(Mg_1/3Nb_2/3)_0.67Ti_0.33O₃ [PMN-PT] magnetoelectric composites. The individual phases were prepared by conventional ceramic method. The particulate composites of ferrite and ferroelectric phases were prepared in ferroelectric rich region. Presence of both the phases in the composites was confirmed using X-ray diffraction techniques. The scanning electron microscopic images recorded in backscattered mode were used to study the microstructure of composites. Lattice constant, dielectric constant, electrical resistivity, ferroelectric, and magnetic properties of individual as well as particulate composites were studied. Further the bi-layer composites were made using the discs obtained from the powders of individual phases where hot press technique was employed to obtain disc of individual phases. CFO phase used in bi-layer composites was obtained using chemical co-precipitation technique. Magnetoelectric (ME) measurements were carried out on both, particulate and layered magnetoelectric composites. Comparison of ME signal obtained from particulate and layered composites revealed that the layered composites gives superior magnetoelectric signal. ME data obtained for layered composites show good agreement with the theoretical model.     

Insights into the regulation mechanism of ring-shaped magnetoelectric energy harvesters via mechanical and magnetic conditions

This paper presents a theoretical model for predicting and tuning magnetoelectric(ME) effect of ring-shaped composites, in which stress boundary conditions are empoyed and the multi-field coupling property of giant magnetostrictive materials are taken into account. A linear analytical solutions for the closed-and open-circuit ME voltages are derived simultaneously using mechanical differential equations, interface and boundary conditions, and electrical equations. For nonlinear ME coupling effect, the nonlinear multi-field coupling constitutive equation is reduced to an equivalent form by expanding the strains as a Taylor series in the vicinity of bias magnetic field. Sequentially, the linear model is generalized to a nonlinear one involving the field-dependent material parameters. The results show that setting a stress-free condition is beneficial for reducing resonance frequency while applying clamped conditions on the inner and outer boundaries may improve the maximum output power density. In addition, performing stress conditions on one of the boundaries may enhance ME coupling significantly, without changing the corresponding resonance frequency and optimal resistance. When external stimuli like bias magnetic field and pre-stress are applied to the ring-shaped composites, a novel dual peak phenomenon in the ME voltage curve around resonance frequencies is revealed theoretically, indicating that strong ME coupling may be achieved within a wider bias field region. Eventually, the mutual coordination of the bias field and pre-stress may enhance ME coupling as well as tuning the resonance frequency, and thus is pivotal for tunable control of ME energy harvesters. The proposed model can be applied to design high-performance energy harvesters by manipulating the mechanical conditions and external stimuli.     

采用磁电换能器的振动能量采集器

采用磁致伸缩/压电层合磁电换能器设计了一个振动能量采集器,该能量采集器采用悬臂梁作为振动敏感机构,并用四个NdFeB磁铁组成磁路放在悬臂梁末端.该磁路在空气隙中产生梯度较大的非均匀磁场,使得磁电换能器在较小的振动下感应到较大的磁场变化量,输出较高的功率.利用等效磁荷理论,分析了空气隙磁场分布以及振动时磁路受到的磁力,并用林斯泰特-庞加莱法研究了能量采集器的非线性振动特性,同时将能量采集器的振动方程和换能器的磁电特性结合,分析了能量采集器谐振时的机-磁-电转换特性.通过实验表明：理论与实验符合得较好,且在加 关键词： 振动能量采集 磁致伸缩/压电层合材料 机磁电转换 非线性振动     

Direct and inverse magnetoelectric effect in layered composites in electromechanical resonance range: A review

A model is presented for the increase in magnetoelectric (ME) coupling in magnetostrictive-piezoelectric bilayers in the electromechanical resonance region. The ME voltage coefficients α_E have been estimated for transverse field orientations corresponding to minimum demagnetizing fields and maximum α_E. We solved the equation of medium motion taking into account the magnetostatic and elastostatic equations, constitutive equations, Hooke's law, and boundary conditions. The resonance enhancement of ME voltage coefficient for the bilayer is obtained at antiresonance frequency. To obtain the inverse ME effect, a pick up coil wound around the sample is used to measure the ME voltage due to the change in the magnetic induction in magnetostrictive phase. The measured static magnetic field dependence of ME voltage has been attributed to the variation in the piezomagnetic coefficient for magnetic layer. The frequency dependence of the ME voltage shows a resonance character due to the longitudinal acoustic modes in piezoelectric layer. The model is applied to specific cases of cobalt ferrite–lead zirconate titanate and nickel–lead zirconate titanate bilayers. Theoretical ME voltage coefficients versus frequency profiles are in agreement with data.     

Studies on lead-free multiferroic magnetoelectric composites

Lead-free multiferroic magnetoelectric composites consisting of ferrimagnetic Ni_0.93Co_0.02Mn_0.05Fe_1.95O₄ (NMF) and ferroelectric Na_0.5Bi_0.5TiO₃ (NBT) phases were synthesized by the solid-state sintering method. The presence of constituent phases in composites was confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A systematic study of dc conductivity as a function of temperature (RT −450 °C) revealed that the conduction is due to small polarons. The effect of constituent phase variation on the dielectric constant and piezoelectric strength (d₃₃) was examined. The composites exhibited typical magnetic hysteresis (M–H) loops at room temperature. Furthermore, magnetoelectric (ME) output was evaluated as a function of applied magnetic field, which is a product property of the constituent phases. The compound 50% NMF–50%NBT is a new lead-free magnetoelectric composite with 155 μV/cm ME output, which may have potential applications.     

Phase switching phenomenon in magnetoelectric laminate polymer composites: Experiments and modeling

This article reports on the magnetoelectric (ME) effect observed in bi- and trilayered polymers consisting of polyvinylidene fluoride (PVDF) and polyurethane (PU) filled with magnetically hard magnetite Fe₃O₄ or Terfenol-D(TeD) magnetostrictive material. The samples had the following compositions: (PU+2 wt% Fe₃O₄/PVDF), (PU+2 wt% Fe₃O₄/PVDF/PU+2 wt% Fe₃O₄), (PU+50 wt% TeD/PVDF) and (PU+50 wt% TeD/PVDF/PU+50 wt% TeD). A model, based on a driven damped oscillation system, has been developed to evaluate and study the influence of the first and second-order ME coefficients on the dc magnetic field-induced phase switching phenomenon between dynamic ME current and the applied ac magnetic field. A good agreement between the simulated results and experimental data was obtained and it was found that phase switching characteristics are mainly influenced by the ME losses induced by magnetostriction losses.     

基于Metglas/PFC磁电层状复合材料的电能无线传输系统

本文完整推导了无直流偏磁条件下, 磁致伸缩材料和压电材料黏接而得的磁电层状复合材料输出电压、电流、磁电系数表达式, 制备了多个样品并实现了电能无线传输系统. 对样品的测试结果验证了理论分析的正确性. 进一步试验结果表明: 磁电层状复合材料的输出具有倍频特性, 材料长度与谐振频率成反比, 谐振状态下样品可在20 Oe的磁场中输出接近100 V (有效值)开路电压, 样品最大传输功率为520 mW (此为该传输方式下公开报道的最大功率), 功率密度为1.21 W/cm³, 样品最大传输效率达35%, 30°以内的偏转角度对材料的输出无显著影响. 试验结果表明, 基于Metglas/PFC磁电层状复合材料是小体积、 小功率、 对传输效率不甚敏感的电能无线传输应用的一种非常有前景的实现方式. 关键词： 磁电复合材料 无线能量传输     

Recent development and status of magnetoelectric materials and devices

The magnetoelectric (ME) materials and related devices have been attracting increasing research attention over the last few years. They exhibit strong ME coupling effect at room temperature, and electric field control of magnetization or magnetic field control of ferroelectric polarization can be achieved. The ME coupling effect brings novel functionalities to develop ultra-fast, low-power, and miniaturized electronics. Recent progress shows the performance of ME materials is further improved and the materials are used to develop many new types of electronics such as high-speed memory, radio frequency resonator, compact ME antenna, and weak magnetic field sensor. In this review, we present the overview in those fields with emphasis on both the opportunities and challenges for the application of ME materials and devices in the cutting-edge technologies.     

考虑损耗的磁致/压电层合材料谐振磁电响应分析

运用等效电路法，对磁致/压电层合材料谐振状态下的磁电响应进行分析，得到了材料在谐振状态下的磁电电压转换系数理论计算公式. 详细地分析了磁致/压电层合材料在谐振点附近的磁损耗、机械损耗、电损耗，并给出了各种损耗相应的计算方法和大小，发现谐振状态下，材料的主要损耗来源于机械损耗. 分析结论较好地解释了磁电层合材料在不同偏置磁场下磁电响应的实验结果. 关键词： 磁致/压电层合材料 磁电效应 谐振 损耗分析     

Enhancement of the magnetoelectric coupling in an A-line shape magnetostrictive/piezoelectric structure

In this study, a new kind of magnetoelectric (ME) structure is designed with Terfenol-D, PZT-5A and nonmagnetic and nonelectric trestle. The configuration of this ME structure presents “A-line” type, PZT-5A and Terfenol-D are respectively bonded with the trestles, which adopt the knuckle joint assembly. Differently from the conventional ME layered structure, in the new structure, the deformation of the PZT-5A of larger size is driven by a Terfenol-D layer of smaller size at an external magnetic field. Since the driven force is applied at the ends of piezoelectric layer through the trestles, the whole piezoelectric layer can be completely stretched or compressed, and the larger voltage should be induced. For the new ME structure with mica trestle, the maximum value of ${\alpha }_E$ is twice higher than that for the conventional laminated ME structure. Furthermore, a wider range of response frequency is also observed in this structure. For the new ME structure with ABS trestle, the experimental results indicate that the maximum ME voltage coefficient is measured as high as 31.85 V/cm?Oe at 405 Oe.