【作者】 张文辉；

【导师】 曹江伟；

【作者基本信息】 兰州大学 ， 凝聚态物理， 2012， 硕士

【摘要】 磁电压层复合材料由于其蕴含的丰富的物理现象成为近几年来物理学和材料学科中的研究热点。其独特的物理特性以及它在多功能电子器件方面的应用前景受到科研工作者的广泛关注。随着人们对这种材料的研究越来越多,它在高灵敏度磁场传感器、换能器、滤波器、谐振器、换相器和信息存储设备等方面的应用潜力逐步被发掘。利用它制作的高性能电子器件和其他的材料相比具有很多优越性。因而,围绕磁电压层复合材料新的物理特性的研究将会有一定的实际意义。本文则主要是研究磁电压层材料的一些特殊输出信号和外加磁场条件的关系。具体的研究工作和结论如下：(1)基于已搭建的测试平台,我们对metglas/PZT L-T型磁电双层复合材料的输出信号随外加直流场的变化进行了研究。输出信号幅值随着直流场的增大先增大后减小,这和磁致伸缩材料metglas的磁导率变化趋势相符。关于输出信号的频率得到的结果是：在交流磁场幅值不高的情况下,输出信号的频率为输入的2倍。随着直流磁场的增大,输出信号波形发生变化,其频率逐渐转向和输入频率相同。对输出信号的快速傅里叶变换结果表明,输出是由一系列谐波信号组成。这些谐波信号的幅值随外加直流场的变化而变化。(2)在没有直流场的情况下,随着交流磁场幅值的增大,在不同结构尺寸样品中发现了4种不同的输出倍频关系,并且.研究了单个样品的输出信号和交流磁场幅值的关系。结果表明：输出的谐波信号幅值随着交流磁场幅值的增加而增加,谐波数目随交流场幅值的增大而增大。(3)当交流场幅值增大到34.30e后,同样品的输出中观察到了一系列的倍频现象。这些倍频信号的频率都在同一个频率附近,从样品阻抗和相角得出的机械共振频率和这些倍频信号的频率相同。在只有交流输入时,倍频输出是输入频率的偶次倍；随着直流场的引入,奇次偶次倍频输出均出现。这些输出信号的快速傅里叶变换表明：在只有交流输入时,输出是由偶倍于输入频率的谐波组成。当加入直流磁场时,输出信号中既包含奇次谐波,也包含偶次谐波。(4)从样品在大交流场幅值下的测量结果得到了它的磁电系数曲线。4个不同的测试条件下得到的磁电系数曲线均出现了多于一个机械共振峰的现象。这些峰出现的位置和观察到输出倍频现象的地方一致,均处于l/n于样品机械共振频率的地方。(5)对以上样品的倍频输出和磁电系数多峰现象综合分析后得到如下结论：制备的L-T型磁电双层结构样品在大幅值的交流磁场作用下,由于metglas层磁致伸缩的非线性特性而产生高次谐波信号,当某一谐波信号的频率在样品的机械共振频率附近时则会引起样品的机电共振,使得该谐波信号主导了样品的输出信号,从而输出出现明显的倍频现象。同时机电共振也导致在该频率下的磁电系数增大,出现了磁电系数的峰值。更多还原

【Abstract】 Magnetoelectric(ME) laminate material has recently became an extremely hot and competitive field in physics and materials science because it contains a wealth of physical phenomena. Its unique characteristics and prospects of multi-functional electronic devices application have drawn considerable interests from scientists. As more and more research on this materials being done, its applications potential, like high sensitivity magnetic field sensors, transducers, filters, resonators, commutations,and information storage devices, is gradually being discovered. High-performance electronic devices made of this material has many advantages compared to other materials. Thus, research about novel physical characteristics of ME laminate composites will have some practical significance. This article is mainly about some special output signal of ME laminate composites and its relationship with external magnetic field conditions. Specific research work and conclusions as follows;(1) Based on a ME measurement system, we investigated output signal of metglas/PZT L-T ME unimorph under different direct current (DC) magnetic field.The amplitude of Output signal increases at first and then decreases with the increase of DC magnetic field, which is consistent with the magnetostrictive material-metglas’permeabiiity trends. The result on the frequency of the output signal obtained is:the output frequency is two times of the input when the amplitude of alternative current (AC) magnetic field is not high; with the increase of DC magnetic field, the output signal waveform changes, and its frequency gradually shifted to the input frequency. The fast Fourier transform of output signal shows that the output of the ME unimorph consists of a series of harmonic signals, and amplitude of these harmonics change when the external DC magnetic field increases.(2) when the AC magnetic field amplitude increases, in the case of no DC field, four different output multiplying relationship were found in the samples with different dimension. Then we investigated the relationship between output signal and AC magnetic field amplitude in a chosen sample. Fast Fourier transform shows that the amplitude of harmonic signals increase with increasing AC magnetic field amplitude, and so the number of harmonics.(3) A series of output frequency multiplying phenomenon were observed in a ME laminate sample, as the amplitude of the AC field was increased up to34.3Oe. These multiplying signal are all around a same frequency, which is consisting with the mechanical resonance frequency fr.And fr was obtained from the impedance and phase angle of sample. The multiplying output phenomenon is only odd times of the input frequency when there is only AC field input. With the superimposition of DC field, odd and even-order multiplying output are both observed. Fast Fourier transform of output signal shows; as AC field inputs, output of ME unimorph contain only odd harmonics of input; when there is DC field applied,both odd and even harmonics of input present in output signal.(4) ME coefficient curves were obtained from the measurement result as sample were exposed to high-amplitude AC magnetic field. With different measurement condition, four ME coefficient curve all demonstrate a phenomenon that there are more than one mechanic resonance peak in four curves. Positions of these peaks Coincide with places we observed frequency multiply phenomenons before, all of these peaks’frequency are all around1/n of fr.(5) By analyzing the multiplying output behavior and multi-peaks phenomenon in ME coefficient above,we get following conclusions; under high-amplitude AC magnetic field, magnetostrictive layer in L-T ME unimorph presents AC magnetostriction, its AC magnetostrictive signal and nonlinear harmonics result in the the electromechanical resonance of sample. Magnetostrictive signal or harmonics with frequency around the fr, caused the resonance of sample. Electromechanical resonance make these signal occupy the entire output of sample. It also make the ME coefficient increase as input frequency is around1/n of fr, and there are also peaks presented in ME coefficient curves Correspondingly.更多还原