压电陶瓷/聚合物基新型阻尼复合材料的研究进展

压电陶瓷/聚合物基复合材料兼具了聚合物和压电陶瓷两相的优点,是新型的智能阻尼材料.叙述了压电陶瓷/聚合物基复合材料的阻尼性能表征、阻尼原理以及影响阻尼性能的主要因素,并展望了研究前景.指出从压电阻尼材料的基础理论、制备工艺和性能表征、结构与性能关系上寻找突破,可以获得可控的高阻尼压电复合材料.     

高性能压电材料制备技术及其应用

本项目在研究压电材料各向异性和微结构相图基础上,针对钙钛矿结构压电陶瓷和有机压电聚合物,采用独特工艺,制备了高性能低成本压电陶瓷,实现了新型陶瓷成分设计、微结构表征和性能优化;结合第一性原理密度泛函方法,建立了高性能有机压电聚合物的组织设计、结构调控、性     

超声电机用压电材料的研究进展

压电材料是超声电机的核心,压电材料性能的优劣在很大程度上影响和制约着超声电机的发展.从几个方面对超声电机用压电材料的应用及研究进展进行了评述和探讨.在总结超声电机对压电陶瓷性能的要求以及目前压电陶瓷的使用现状之后,从配方、工艺、质量3方面提出了可能的改进方法,针对超声电机在特殊环境下的服役条件,介绍了弛豫铁电体单晶和高居里温度压电陶瓷等新型压电材料在超声电机上应用的新进展,提出了未来超声电机对压电材料的要求.     

压电材料的K正则方程及其层合板的显式辛算法

显式辛数值算法有一个重要的特性,即在长时间内保存Hamilton函数的指数幂,用这种方法求解可分的微分方程所得到的解逼近精确解.该文基于压电材料修正后的H-R混合变分原理,首先推导了Hamiltonian四节点有限元列式,然后通过对该列式进行行列变换,得到了K正则方程.最后将显式辛数值算法用于求解压电材料层合板的静力学...     

减小磁滞损耗的偏转磁芯设计

本通过对偏转磁芯用的铁氧体材料的磁滞损耗特性的分析，提出了通过改变偏转磁芯外表面形状以减小磁滞损耗的方法。优化计算结果表明，对于Philips 17″CMT的3C2材料5mm壁厚的磁芯，改用椭圆外表面的磁芯后，磁滞损耗降低了27.5％。     

压电功能梯度材料中的SH表面波

为了提高声表面波器件的性能,压电功能梯度材料(FGPM)被广泛应用在声表面波(SAW)技术上,因此,压电功能梯度材料中表面波的传播特性研究变得十分重要.研究了压电功能梯度材料中SH(Shear Horizontal)波的传播特性.对于材料特性沿厚度方向为线性函数、二次函数和三次函数变化的三种形式,基于压电-弹性理论,得...     

低Qm压电振子机电耦合系数的标准计算方法的原理误差分析

压电材料的机电耦合系数通常由谐振及反谐振频率之间的相对间隔确定。常用的ＩＥＥＥ标准计算公式,是由描述理想无损压电振子的电行为方程推导得出的。本文结出了压电材料的固有损耗产生的谐振及反谐振频率的偏移及由此引起的标准公式的误差。代替以往分析时常用的等效电路方法,本文采用把损耗考虑在内的严格的压电振子导纳或阻抗模型。分析结果表明：由测得的谐振子及反谐振频率用标准公式得出的耦合系数小于材料的固有耦合系数;     

压电材料修正后的H-R混合变分原理及其层合板的精确法

将三维弹性体的Hellinger-Reissner(H-R)混合变分原理引入到具有机-电耦合效应的压电材料静力学问题中,建立了压电材料修正后的H-R混合变分原理,通过变分运算和分部积分得到了压电材料的状态向量方程。给出了四边简支的压电材料层合板静力学状态向量方程的精确求解方法,数值实例的结果证明了方法是正确性的。这里的理论和求解方法同样适应于纯弹性材料板和压电材料板混合的层合板静力学问题的分析。变分原理将有利于压电材料问题相应的半解析法或有限元法的推导。     

压电体的混合变分原理及叠层板的自由振动分析

建立了具有机一电耦合效应的压电材料修正后的Hellinger—Reissner(H—R)混合变分原理，并推导了压电材料的Hamilton正则方程，即压电材料自由振动的控制微分方程；根据矩阵分析理论给出了带有压电材料层的叠层矩形板自由振动的精确求解方法，文中没有引入任何位移模式或应力模式假设，实例分析得到了压电混合叠层板正逆效应两种情况自由振动的低阶频率，并与已有文献结果进行了比较。本文提出的压电材料修正后的H—R混合变分原理将有利于压电材料动力问题的有限元法或半解析法的推导。     

材料固有损耗对压电振子谐振特性及参数测量的影响

本从考虑损耗时压电振子的阻抗（或导纳）议程出发,详细分析了材料固有损耗对压电振子的频率特性及参数测量的影响。分析结果表明：谐振（或反谐振）频率与理想无损时的相应值的偏差随损耗的增大而增大、随谐序的增大而减小。中还进一步分析了机械损耗对压电振子几种常用参数测量结果的影响。     

基于系统相似方法的叠堆型压电驱动器非线性动力学建模及实验研究

根据机械系统与电气系统的相似方法,将叠堆型压电驱动器的非线性电-机械耦合模型完全转换到电气域内,建立了其非线性相似电路模型;给出了非线性相似电路模型中迟滞因子的辨识方法,并对某款商用叠堆型压电驱动器进行了迟滞因子的辨识试验;基于非线性相似电路模型和迟滞因子的辨识结果,对该款叠堆型压电驱动器的非线性特性进行了仿真分析,得到了其非线性位移迟滞回线;仿真结果与试验结果吻合,证明了该建模过程与辨识方法的正确性。该建模方法在电气域内对叠堆型压电驱动器电-机械耦合特性及非线性迟滞特性进行描述,建模过程物理意义清晰且简单实用,对于研究压电驱动器的动态特性及控制算法具有实际意义。     

1-3-2型压电陶瓷/聚合物复合材料的理论模型

根据Chan的1-3型复合材料理论模型和Newnham的复合材料串并联理论,提出了一种用于计算新型1-3-2型压电陶瓷/聚合物复合材料的介电常数和压电常数的理论模型.并制备了一批1-3-2型压电复合材料样品,把理论模型的计算值与实际测量的材料参数进行了比较,结果表明两者符合较好,误差小于10%.     

Polar glass ceramics — A new family of electroceramic materials: Tailoring the piezoelectric and pyroelectric properties

Grain oriented multicomponent polar glass-ceramics have been prepared by crystallizing the glasses in a temperature gradient. Inexpensive, large area piezoelectric and pyroelectric devices can be fabricated by this method, and by adjusting the composition of the glasses and crystallization conditions, it is possible to tailor the properties to meet device requirements. Based on the growth characteristics and the connectivity pattern of the crystallites, the piezoelectric, pyroelectric and dielectric properties of glass-ceramic composites can be predicted. Two examples discussed in this paper are piezoelectric glass-ceramics which are not pyroelectric, and pyroelectric glass-ceramics which are not piezoelectric.     

Identification of material constants for piezoelectric transformers by three-dimensional,finite-element method and a design-sensitivity method

In this paper, an inversion scheme for piezoelectric constants of piezoelectric transformers is proposed. The impedance of piezoelectric transducers is calculated using a three-dimensional finite element method. The validity of this is confirmed experimentally. The effects of material coefficients on piezoelectric transformers are investigated numerically. Six material coefficient variables for piezoelectric transformers were selected, and a design sensitivity method was adopted as an inversion scheme. The validity of the proposed method was confirmed by step-up ratio calculations. The proposed method is applied to the analysis of a sample piezoelectric transformer, and its resonance characteristics are obtained by numerically combined equivalent circuit method.     

High-frequency resonant characteristics of triple-layered piezoceramic bimorphs determined using experimental measurements and theoretical analysis

This is an experimental, theoretical, and numerical investigation of vibration characteristics in high-frequency resonance, which are studied for parallel- and series-type piezoelectric bimorphs. In the experimental measurements, the full-field optical technique known as electronic speckle pattern interferometry (ESPI) is used to measure the transverse (out-of-plane) and planar (in-plane) resonant frequencies and corresponding mode shapes for piezoelectric bimorphs. In addition, in-plane resonant frequencies are obtained from impedance analysis and the response curves of the frequency spectra show different vibration characteristics of the piezoelectric bimorphs with different electrical connections. Piezoelectric bimorphs with normal connections have three-dimensional coupled vibration characteristics and the out-of-plane vibration dominates the motion. However, only in-plane vibration motions can be excited in the high-frequency range for abnormal connections, and the resonant characteristics are similar to the single-layered piezoelectric plate. The triple-layered piezoelectric bimorphs with abnormal connection are also analyzed using theoretical analysis. The resonant frequencies, mode shapes, and normalized displacements are calculated based on the analytical solution. The experimental results and the theoretical analysis are in good agreement with the numerical calculations using the finite element method. From the discussion of the results for the parallel- and series-type piezoelectric bimorphs with normal and abnormal connections, the vibration characteristics at high frequencies are completely analyzed in this study.     

Effect of sintered temperature on structural and piezoelectric properties of barium titanate ceramic prepared by nano-scale precursors

Lead-free piezoelectric ceramics barium titanate has been successfully fabricated by a facile modified (nano-scale precursors) solid phase method. The sintered temperature was employed as the main regulatory factor to control the growth of the grain size and crystallinity of the sample. When the sintered temperature was set as 1350?°C, the pure phase barium titanate ceramics could be prepared with the grain size of about 1 μm. In addition, piezoelectric tests showed that, the samples sintered at this temperature possessed the maximum ?_r, P_r and d₃₃ values, 3533, 16.24 μC/cm² and 420 pC/N, respectively. These characteristics make them promising candidates as lead-free piezoelectric ceramic materials.     

Manufacturing of prestressed piezoelectric unimorphs using a postfired biasing layer

A novel manufacturing method for prestressed piezoelectric unimorphs is introduced and the actuator properties are examined. Prestressed PZT 5A and PZT 5H unimorphs with piezo material thickness of 250 microm and 375 microm were manufactured by using sintering and thermal shrinkage of the prestressing material. The process was carried out by screen printing a layer of AgPd paste on one side of the sintered bulk ceramic. As an alternative method, dielectric low temperature co-fired ceramic (LTCC) tape was used as the prestressing material. Different configurations were tested to obtain high displacements and to make a comparison between materials. After firing, the samples were poled, and the displacement versus load characteristics of the resulting actuators were investigated. A maximum displacement of 118 microm was obtained from a 250 microm thick, prestressed PZT 5H actuator with a diameter of 25 mm, in which LTCC tape was used as the prestressing layer. Similarly, the PZT 5H material provided a maximum displacement of 63 microm with a screen-printed AgPd prestressing layer. The manufacturing method described offers a novel approach for the production of a wide range of integrated active structures on, for instance, an LTCC circuit board. This is especially important because piezoelectric bulk materials with high piezoelectric coefficients can be used to produce high displacements.     

The Shrinkage Characteristic of a Spherical Cavity in Three-Dimensional Piezoelectric Grain

In this article, an analytical method is presented to solve the shrinkage rate and the healing history of a spherical cavity in three-dimensional piezoelectric grains under electric field, interface pressure, and internal gas pressure. From example calculations, it is seen that because of the influence of piezoelectric characteristics and electric fields, a spherical cavity in three-dimensional piezoelectric grain subjected to hydrostatic interface pressures does not completely eliminate, which is obviously consistent with some experimental observations from the micro-hole healing process. The result is useful to reveal the healing mechanism of defects in piezoelectric materials under electric and mechanical loads.     

Features of photoacoustic transformation in microporous nanocrystalline silicon

Results of a study of the photoacoustic transformation in microporous nanocrystalline silicon are described. The amplitude-frequency and phase-frequency characteristics of the photoacoustic signal from microporous silicon samples on a monocrystalline substrate exposed to illumination at various wavelengths are experimentally determined. Informative response was measured by the gas-microphone and piezoelectric detection methods. In terms of the proposed mathematical model, it is shown that the difference in the parameters of the photoacoustic signal for different wavelengths of exciting radiation is attributed to a shift of the fundamental absorption edge in nanocrystalline silicon. It is pointed out that the piezoelectric detection method is more sensitive to changes in the thermophysical and optical parameters of the porous layer.     

Thermal hysteresis of electromechanical characteristics of <Emphasis Type="Italic">Y</Emphasis> + 42° cut LiTaO<Subscript>3</Subscript> single crystals

The temperature stability of electromechanical characteristics of Y + 42° cut LiTaO₃ crystals has been studied using dielectric spectroscopy and static and dynamic piezoelectric effect measurements. It has been shown that, during thermal cycling, the piezoelectric properties of crystalline LiTaO₃ samples exhibit a thermal hysteresis and that the thermal history of samples influences their resonance and antiresonance frequencies.