【作者】 张源；

【导师】 李美亚；

【作者基本信息】 武汉大学 ， 凝聚态物理， 2016， 博士

【摘要】 多铁性材料同时具有铁电、铁磁或者铁弹性以及这些电、磁及弹性参量之间的耦合,使其在磁传感、多态存储、电控微波器件等领域具有极大的潜在应用价值,因此被广泛研究。磁电效应作为多铁材料的一个重要特性,它所具有的理论和实际意义促使其成为科研工作者密切关注的热点。磁电效应包括正磁电效应和逆磁电效应,正磁电效应是指电极化对外加磁场的响应,而逆磁电效应是指磁化对外电场的响应。。两相磁电复合材料的磁电耦合系数要比单相磁电材料大得多,而且易制备,因此得到了越来越多的研究。两相磁电复合材料是由压电相和铁磁相复合而成,常见的复合体系有0-3型、1-3型、2-1型以及2-2型等。近年来研发的新的磁扭电耦合模式因具有极大的磁电耦合效应亦受到很大关注。本文着重研究2-2型磁电复合材料的正逆磁电性能,磁-弹-电复合材料的磁扭电效应,并在器件应用方面进行一些探索。主要研究内容和结果如下：1、制备了厚度方向极化的无铅陶瓷材料0.95(K0.5Na0.5)Nb0.96Sb0.02Ta0.02O3 0.05(Bi0.5K0.5)ZrO3 (KNNST-BKZ)与长度方向磁化的磁致伸缩材料Metglas构成的无铅磁电复合材料,利用本组自主构建的全自动磁电耦合系数测试系统对其磁电耦合性能进行了表征。在谐振频率下的磁电耦合系数达到7.85V/cm·Oe。结果表明这一无铅KNNST-BKZ/Metglas层状复合材料具备器件应用的前景。2、制备了不包含磁致伸缩材料的铁磁体-弹性材料-压电材料的磁扭电复合材料,实现了强磁电耦合效应。研究了不同长度梁结构磁电耦合系数随频率的变化关系,及谐振条件下磁电电压随磁场大小的线性关系。其中8cm长悬臂梁在5.524Hz谐振频率下磁电耦合系数达到3800V/cm·Oe。从理论上解释了准静态下不同梁长度磁电耦合系数相同(皆为10V/cm·Oe)的现象。这种长梁的结构设计显示出低频下非常高的磁传感灵敏度。本研究为优化设计高磁电耦合性能的磁扭电复合材料提供了指导意义3、研究了两种不同模式的逆磁电复合材料,一种是基于Pb(Zr,Ti)O3-bimorph/Metglas弯曲模式的复合材料,另一种是叉指电极Pb(Zr,Ti)O3/Metglas纵向模式的复合材料。相同电场下的逆磁电耦合系数分别是是传统的unimorph/Metglas结构的1.4倍和1.97倍。实验结果与理论预测相一致。这两种逆磁电复合材料对于弯曲模式和纵向模式的逆磁电耦合器件的优化设计提供了指导。4、分析了可调电感的可能性,制备了环形压电/铁氧体复合材料的可调电感器件。实验验证了电感的线性可调,在4kV/cm的电场作用下,电感的可调量达到56.7%。更多还原

【Abstract】 Multiferroic materials that simultaneously display ferroelectricity, ferromagnetism, and ferroelasticity as well as coupling among them, have been widely investigated due to their potential applications in magnetic sensors, multi-state storage and electrically controllable microwave devices. Magnetoelectric (ME) effect, as one of the important features of multiferroic materials, have recently become a research subject of intense interest due to their theoretical and practical significance. The direct magnetoelectric (DME) effect is defined as a variation of polarization in response to an applied magnetic field, and the converse magnetoelectric(CME) effect is defined as a variation of magnetization in response to an applied electric field.Two-phase ME composite has much higher ME coupling coefficient than single-phase ME material and is of simple fabricating process, which make it attract extensive research interests. Two-phase ME composite usually consists of ferromagnetic and ferroelectric ceramics with various connective architectures. The common connective architectures are zero to three dimensions (0-3), two to one dimensions (2-1), two to two dimensions (2-2) and so on. In addition, some new coupling modes have been developed in recent years, such as magneto-torque-electric composites, which has attracted much attention due to its colossal magnetoelectric effect.This article focus on the research of direct and converse magnetoelectric effect of 2-2 type magnetoelectric composite, magneto-torque-electric effect of ferromagnetic-elastic-piezoelectric (FEP) composite, and make some exploration in device applications. The main contents are as follows:1. A lead free magnetoelectric (ME) laminate composite consisting of polarized piezoelectric ceramic of 0.95(K0.5Na0.5)Nb0.96Sb0.02Ta0.02O3-0.05(Bi0.5K0.5)ZrO3 (KNNST-BKZ) and magnetized magnetostrictive Metglas have been fabricated and its ME properties have been evaluated. Under the resonant frequency, the magnetoelectric coupling coefficient reaches up to 7.85 V/cm·Oe. This result suggests the lead-free KNNST/BKZ/Metglas layered composite has the promising prospect in application of devices.2. The non-magnetostrictive ME effect was realized in a simple ferromagnetic-elastic-piezoelectric (FEP) composite. The FEP composite comprised two piezoceramic Pb(Zr,Ti)O3 (PZT) plates and NdFeB magnets elastically coupled by a cantilever beam made of phosphor copper-sheet. The effects of the beam length on the ME coefficient as a function of frequency and the linear relationship between the ME voltage output and the applied magnetic field at the resonant frequency were experimentally investigated. A notably superior ME coefficient of 3800 V/cm-Oe at extremely low resonant frequency of 5.524 Hz was obtained for the FEP composite with the beam length of 8 cm. The quasi-static ME coefficients for the FEP composites with different beam lengths are all of the same value of 10 V/cm-Oe, which was also theoretically explained. Such a composite structure shows the possibility to obtain a magnetic sensor element with ultrahigh sensitivity in low frequency range. The results provide a comprehensive understanding for the optimal design of FEP composite with high ME coefficient.3.Two different models of CME composites based on Pb(Zr,Ti)O3-bimorph/Metglas(bending model) and screen-printed interdigitated electrodes (IDE) Pb(Zr,Ti)O3/Metglas(Longitudinal-longitudinal model) laminate were studied, which all show enhanced CME effect compared to the homomorphic unimorph/Metglas laminate. Under the same electric field, the converse magnetoelectric coupling coefficient of the Pb(Zr,Ti)O3-bimorph/Metglas and IDE PZT/Metglas laminates are 1.4 and 1.97 times compared with that of the homomorphic unimorph/Metglas one. The experiment results are consistent with the theoretical predictions. This work provide a guiding for the optimal design of CME devices working in low voltage drived bending and longitudinal work mode.4. The possibility of the tunability of inductance was analyzed, and a circular ferrite/piezoelectric.composite inductor was prepared. The results revealed that the inductance has linear response with the electric field. Under 4 kV/cm of the electric field, the inductance tunability reached a value up to 56.7%更多还原