Partial Discharge Signal Detection by Piezoelectric Ceramic Sensor and The Signal Processing

Partial discharge (PD) in an insulator or on surface of defective conductor emits acoustic wave transmitting through an air or an insulator. The acoustic wave between 20 kHz and several hundred of kHz can be detected by piezoelectric ceramic sensor that converts the acoustic wave into an electrical signal. Piezoelectric ceramic sensor has either the wide resonant band or the local resonant band depending on the ceramic material or the various combinations of each different component in the manufacturing process. This paper presents the piezoelectric ceramic sensor with 0.95 PZT–0.05 PMNS that yields the piezoelectric properties of high k_p, high Q_m. It has the frequency characteristics of local resonant band, such that it can be applied to PD detection. We have demonstrated the properties of the proposed piezoelectric ceramic sensor by comparing with the conventional electrical PD detector. Quantitative analysis is accomplished by comparing the -q_max from a PD detector and the -v_max from the proposed sensor while -n distributions are the same for both the conventional phase-resolved PD analysis method and the proposed one.     

Magnetoelectric Effect in Composites of Magnetostrictive and Piezoelectric Materials

In the past few decades, extensive research has been conducted on the magnetoelectric (ME) effect in single phase and composite materials. Dielectric polarization of a material under a magnetic field or an induced magnetization under an electric field requires the simultaneous presence of long-range ordering of magnetic moments and electric dipoles. Single phase materials suffer from the drawback that the ME effect is considerably weak even at low temperatures, limiting their applicability in practical devices. Better alternatives are ME composites that have large magnitudes of the ME voltage coefficient. The composites exploit the product property of the materials. The ME effect can be realized using composites consisting of individual piezomagnetic and piezoelectric phases or individual magnetostrictive and piezoelectric phases. In the past few years, our group has done extensive research on ME materials for magnetic field sensing applications and current measurement probes for high-power electric transmission systems. In this review article, we mainly emphasize our investigations of ME particulate composites and laminate composites and summarize the important results. The data reported in the literature are also compared for clarity. Based on these results, we establish the fact that magnetoelectric laminate composites (MLCs) made from the giant magnetostrictive material, Terfenol-D, and relaxor-based piezocrystals are far superior to the other contenders. The large ME voltage coefficient in MLCs was obtained because of the high piezoelectric voltage coefficient of the piezocrystals and large elastic compliances. In addition, an optimized thickness ratio between the piezoelectric and magnetostrictive phases and the direction of the magnetostriction also influence the magnitude of the ME coefficient.     

无铅压电陶瓷的研究现状与发展趋势

随着人们环保意识的增强,无铅压电陶瓷的研究和开发成为当前压电材料领域研究的热点。本文综述了无铅压电陶瓷研究开发的相关进展,重点介绍了BaTiO3基、Bi1/2Na1/2TiO3基、铋层状结构、(K,Na,Li)NbO3基及钨青铜结构无铅压电陶瓷等体系的研究现状,同时对制备方法也进行了简要的评述,对无铅压电陶瓷的发展趋势作了展望。     

用于压电和铁电性能测量的纳秒级脉冲信号发生器

研制成功输出峰值电压从5～80 V连续可调的脉冲信号发生器,信号上升沿小于10 ns.利用该信号源,可将压电和铁电陶瓷材料中的快和慢效应完全分开.介绍该仪器的工作原理及特性,并给出了测量结果.     

Hydrostatic Piezoelectric Coefficient d h of PZT Ceramics and PZN-PT and PYN-PT Single Crystals

The hydrostatic piezoelectric coefficient d_h of Pb(Zr_xTi_{1 – x})O₃ ceramics (PZT), and of Pb(Zn_1/3Nb_{2/ 3})O₃-PbTiO₃ and Pb(Yb_1/2Nb_1/2)O₃-PbTiO₃ (PZN-PT, PYN-PT, respectively) single crystals with compositions near to the morphotropic phase boundary (MPB) have been measured using a dynamic hydrostatic method. The effects of DC electric field and static component of hydrostatic stress on d_h of PZT ceramics, PZN-PT and PYN-PT single crystals were studied. Changes of the piezoelectric hydrostatic coefficients d_h caused by an electric field (DC bias) were observed along with pressure and temperature dependencies. The measurement of the hydrostatic piezoelectric coefficient d_h seems to be promising for investigation of intrinsic (single domain) and extrinsic (domain-walls) contributions to piezoelectric behavior of single crystals and ceramic materials.     

磁致伸缩、压电层状复合磁电传感器非线性动态有限元模型

基于磁致伸缩材料标准平方模型和压电材料线性本构关系,应用Hamilton变分原理建立了磁电传感器的磁-机-电耦合特性的动力学方程。建立的动力学方程考虑了磁致伸缩材料的磁滞现象和E效应的影响。应用所建立的模型求解了LT型磁致伸缩/压电磁电传感器的输出特性,与实验结果进行对比发现模型可较准确地预测磁电传感器在不同偏置磁场和交流驱动磁场激励下其输出电压随时间的变化关系。当偏置磁场为22.1kA/m,正弦交流驱动磁场为7.4kA/m、频率为100Hz时,计算结果和实验结果误差为0.9%。同时,应用该模型还可以确定磁电传感器的最大交流驱动磁场。     

Gas Sensors Based on Piezoelectric Micro-Diaphragm Transducer

ABSTRACT

We have fabricated high sensitive gas sensor based on piezoelectrically driven micro-diaphragm transducers. The micro-diaphragm transducer was fabricated using micro-electro-mechanical-system (MEMS) technique. The diol based sol-gel derived Pb(Zr_0.52,Ti_0.48)O₃(PZT) film was used as a piezoelectric actuating layer. We have used the resonant frequency change of micro-diaphragm transducer upon mass increase as a sensing signal. The resonant frequency values were measured by analysis of electrical signals from the micro-diaphragm transducer. The fundamental resonant frequency of the micro-diaphragm was in the range of 250 to 360 kHz, depending on their physical boundary conditions. The mass sensitivity of bare micro-diaphragm transducer was 66.5 Hz/ng. Two polymer sensing layers such as the polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS) films were used to estimate the gas sensing behavior of microtransducers for various vapors of organic compounds. PMMA was used to detect primary alcohols while PDMS was used for toluene and benzene. The resonant frequency of micro-diaphragm transducer was shifted toward lower frequency range as the vapor concentration increased. With PMMA gas sensing layer, the micro-diaphragm showed a gas sensitivity of 0.456 Hz/ppm for ethanol vapor. When the PDMS gas sensing layer was used, the micro-diaphragm showed a gas sensitivity of 0.143 Hz/ppm for toluene vapor. When the test vapors were removed from the reaction chamber, the resonant frequencies of micro-diaphragm sensors were completely recovered to their initial state.     

Theoretical Study on the Tip-Deflection of Multilayer Piezoelectric Cantilever Structures

Tip-deflection is one of the most important characters of the piezoelectric cantilever vibration. In this paper, a new piezoelectric model of multilayer piezoelectric cantilever is obtained, and the analytic expressions for the curvature, displacement and tip-deflection of the multilayer structure are derived. On the base of this solution, the curvature and tip-deflection of five different elementary structures are considered. Compared with others' model, the analytic expressions for the curvature, displacement and tip-deflection are also suitable for more complex structures with more layers based on these elementary structures. Above-mentioned methods and conclusions can be used for optimized design of PZT cantilever structure.     

压电式传感器及其在火电厂中的应用

介绍了压电式传感器的原理和特点,并预示了压电式传感器在火电厂的应用前景。     

Lead Free Piezoelectric Materials

Lead oxide based ferroelectrics, represented by lead zirconate titanate (Pb(Zr, Ti)O₃) or PZT) are the most widely used materials for piezoelectric actuators, sensors and transducers due to their excellent piezoelectric properties. Considering lead toxicity, there is interest in developing piezoelectric materials that are biocompatible and environmentally friendlier. The low density of non-lead based materials can also be an advantage in transducers for underwater and medical imaging due to expected lower acoustical impedance. Another impetus for seeking alternative to lead based compositions is the need for piezoelectric materials for operation at high temperatures. Several classes of materials are now being reconsidered as potentially attractive alternatives to PZT for special applications. The potassium niobate family, KNbO₃, exhibits low dielectric constants, large thickness coupling coefficient along certain non-polar directions, and low density, all of which have advantages for high frequency transducer applications. Several compositions belonging to bismuth titanate family, Bi₄Ti₃O₁₂, such as SrTi₄Bi₄O₁₅, are promising candidates for high temperature applications. Lead free materials alone (eg. (Na_0.5Bi_0.5)TiO₃) or in solution with PT (BiScO₃ – PbTiO₃) are also potentially interesting as they combine high piezoelectric activity and, in some cases, relatively high T_c. For these families of piezoelectric materials, the processing and piezoelectric response under different conditions of pressure, frequency, and temperature are presently much less understood than for the classical lead containing systems. In this presentation we review and discuss piezoelectric properties of selected lead free compositions (principally for members of the potassium niobate family and bismuth titanate layered compounds) in relation to structural and microstructural features as well as extrinsic contributions (domain walls displacement, conductivity) to their electromechanical properties. It is shown that it is possible to obtain remarkably stable piezoelectric response in some compositions, while others exhibit strong dependence of piezoelectric properties on driving field and frequency. Origins of these different behaviours are discussed.     

AF9M1对KNN基陶瓷的结构与压电性能的影响

采用传统固相烧结法制备了K0.5Na0.5Nb O3-x Al(Fe0.9Mn0.1)O3(KNN-AF9M1)无铅压电陶瓷,着重研究了AF9M1的不同掺杂量(x分别为0,0.02,0.04,0.06,0.08)对陶瓷显微结构和压电性能的影响。结果表明,室温下,少量AF9M1的掺杂并未改变KNN基陶瓷正交相钙钛矿结构,但有助于陶瓷晶粒的生长及致密化。随着AF9M1含量的增加,陶瓷的压电常数(d33)、机电耦合系数(kp)、机械品质因数(Qm)和居里点(Tc)均先增大后减小,当x=0.04时,均达到最大值,分别为121 p C/N、0.35、179和392℃。     

Effects of Sintering Temperature on the Dielectric and Piezoelectric Properties of Nb-Doped PZT Ceramics and Their Applications

The PZT-based ceramics with a composition of Pb_{1 ? 0.5x} (Zr_0.52Ti_0.48)_{1 ? x} Nb _x O₃; x = 0.04–0.06 were prepared by conventional mixed-oxide method, with sintering temperature at 1200°–1300° for 2 hours. Microstructural and compositional analyses of the PZT-based ceramics have been carried out using XRD and SEM. The dielectric constant measured at 1 kHz is about 1500 and the loss factor is small than 2%. The maximum planar electromechanical coupling coefficient, k _p , is 0.59. It showed that the Nb additives were helpful improve both of the dielectric and piezoelectric properties. Surface acoustic wave (SAW) filters were fabricated and the property, phase velocity, were measured.     

面向电力设备检测与诊断的压电材料及器件

随着中国智能电网建设不断推进及电网规模的扩大,以压电材料为核心的传感器和能量采集器在电力系统在线监测、故障检修、无线传感器网络等方面扮演着越来越重要的角色。从电力检测和传感器自取能出发,回顾近年来基于压电效应的电压电场传感器、声检测和环境能量采集装置的研究进展并介绍了压电陶瓷、压电驻极体、压电复合材料等传统和新兴的压电材料。在现有研究基础上,指出在智能电力系统建设中各类压电器件所面临的挑战,包括频率匹配、环境适应性和集成化等,需要新的微纳加工技术、探索压电效应与其他物理效应耦合、设计新型压电材料和能量收集电路来助力新型压电器件的实际应用。     

烧结保温时间对KNN-LS-BF-0.15%Cu压电陶瓷性能的影响

采用传统的陶瓷制备工艺,在1 060℃下分别保温2 h、4 h和6 h,制备了{0.996[0.95(Na0.5K0.5)-NbO3-0.05LiSbO3]-0.004FeBiO3}+0.15mol%CuO(简称KNN-LS-BF-0.15%Cu)压电陶瓷,研究了烧结保温时间对陶瓷性能的影响。结果表明,过短的烧结保温时间并不能促成陶瓷晶粒的长成,但超过4 h后继续延长烧结保温时间对晶粒尺寸的影响不大;随着烧结保温时间的延长,KNN-LS-BF-0.15%Cu陶瓷的压电常数d33、机电耦合系数kp和介电常数εr先升高后降低,而介电损耗tanδ和机械品质因数Qm则随之下降;当烧结保温时间为4 h时,样品具有最佳的综合性能:d33=185 pC/N,kp=0.28,εr=1054.25,tanδ=2.1%,Qm=53.39。     

双面激振矩形复合压电振子的有限元分析

基于Ansys的压电耦合场,对复合压电振子进行模态,谐响应分析。通过模态分析了解振子的动态力学特性,得到振子的固有频率和振型;通过谐响应分析得到振子在简谐激励下的稳态响应,并得到振幅对频率的变化曲线,实现了矩形复合式压电振子的电压加载分析并利用瞬态分析模拟了振子的椭圆运动轨迹,对双面激振和单面激振效果进行了对比,结果表明双面激振更具优势。     

Fabrication of PZT Thick Films on Silicon Substrates for Piezoelectric Actuator

In recent years, there has been an increased interest in ferroelectric lead zirconate titanate (PZT) films for applications in piezoelectric devices. Many potential applications require a film thickness of about 10 m for higher force, better sensitivity and stability. In this study we fabricate lead zirconate titanate (PZT) thick films by screen printing on silicon substrates with a platinum bottom electrode. Various substrates were studied. The longitudinal piezoelectric coefficient, d₃₃, was measured by the normal load testing method. Breakdown voltage, tan , P-E hysteresis loop and permittivity were measured on the PZT thick films. The results are promising for the use of PZT thick films in various applications, for example, in silicon micromachined micro-pump.     

High Power Characterization of Piezoelectric Materials

Three techniques for measuring high voltage/power piezoelectric properties, which have been developed recently, are compared: a voltage-constant piezoelectric resonance method, a current-constant piezoelectric resonance method, and a pulse drive method. The conventional resonance method with a constant voltage circuit exhibits significant distortion (or a hysteresis) in the resonance frequency spectrum under a high vibration level due to large elastic non-linearity, which limits precise determination of the electromechanical coupling parameters. To the contrary, the resonance method with a constant current circuit (i.e., constant velocity) can determine the coupling parameters more precisely from a perfectly-symmetrical resonance spectrum. The general problem in both resonance methods is heat generation in the sample during the measurement. In order to separate the temperature characteristic from the non-linearity, it is recommended that the pulse method be used in parallel, even though the accuracy is not very high.     

一种低成本解调系统的双光栅电压传感器

设计了一种由2×2和3×3耦合器构成的M-Z干涉仪,并成功应用到所设计的光纤光栅电压传感器解调中。与其他电子式、光学电压传感器相比较,基于2×2和3×3耦合器构成的M-Z干涉仪解调的光纤光栅电压传感器系统结构简单、价格优廉。此系统通过2根不同波长的光纤光栅分别对温度和电压进行测量。测量结果表明,此系统在50 V到450 V之间线性度比较好,消除了光纤光栅温度交叉敏感的问题,使得测量的结果更加准确,能够满足电力系统测量的要求。     

Thickness Dependence of Piezoelectric Properties for PZT Thin Films with Regard to MEMS Applications

In this work we report on the investigation of the piezoelectric and ferroelectric properties of Pb(Zr,Ti)O₃ (PZT) thin films with a composition of 45% zirconium and 55% titanium prepared by chemical solution deposition (CSD) regarding the major properties required in MEMS applications. Therefore we have measured the polarization and the piezoelectric coefficient d ₃₃ and strain using a high-resolution double beam laser interferometer. We found that d ₃₃ alike the strain is nearly independent of the sample thickness. To estimate the lifetime of MEMS we stressed the samples by applying switching and non-switching voltage pulses. In the non-switching case, no change of the material properties was observed whereas the use of switching voltage pulses resulted in a strong decrease of the piezoelectric properties and the polarization. Here we found a linear behavior between the material properties in the fatigued state and the sample thickness.     

压电模型参数辨识仿真实验

在对压电材料电气性能参数分析的基础之上,确立了以等效电路的电容、电感等参数作为压电材料性能指标的主要参数,离散化处理得到相应的差分数学模型,并对其进行了模型参数在线识别与最小二乘法MATLAB参数辨识仿真实验。实验结果表明:压电材料电气参数的辨识可以满足综合性能优化0.5%的设计要求。