A nonlinear model of piezoelectric polycrystalline ceramics under quasi-static electromechanical loading

Nonlinear characteristics of tetragonal perovskite type polycrystalline piezoelectric ceramics under electromechanical loading are theoretically simulated using a threedimensional micromechanical model. The model consists of many differently oriented grains which form the bulk material. Uni-axial, quasi-static loading is applied in the simulations. The calculations which are based on a linear constitutive and nonlinear domain switching model are performed at each grain. All grains are assumed to be statistically random oriented at the virgin state.The behavior of piezoelectric ceramics under constant compressive stress which is applied in the same direction of the cyclic electric field is investigated. The macroscopic response of the bulk ceramics to the applied loading is predicted by averaging the response of individual grains. It is assumed that a domain or a microstructure switches if the reduction in potential energy of the polycrystal exceeds a threshold of critical energy per unit volume of the material. Due to intergranular effects domain switching may occur in reality even for those grains, for which the critical energy level is not reached. This effect is modeled by introducing a probability for domain switching as a function of the actual energy level related to the critical energy level. By use of the probability functions, it is possible to model the nonlinearity even in a small electromechanical loading range. The effect of different probability functions, and material parameters are also analysed. The results of simulations have been compared with experimental data from literature.     

Ultrahigh Piezoelectric Properties in Textured (K,Na)NbO3‐Based Lead‐Free Ceramics

High‐performance lead‐free piezoelectric materials are in great demand for next‐generation electronic devices to meet the requirement of environmentally sustainable society. Here, ultrahigh piezoelectric properties with piezoelectric coefficients (d₃₃ ≈700 pC N^?1, d₃₃* ≈980 pm V^?1) and planar electromechanical coupling factor (k_p ≈76%) are achieved in highly textured (K,Na)NbO₃ (KNN)‐based ceramics. The excellent piezoelectric properties can be explained by the strong anisotropic feature, optimized engineered domain configuration in the textured ceramics, and facilitated polarization rotation induced by the intermediate phase. In addition, the nanodomain structures with decreased domain wall energy and increased domain wall mobility also contribute to the ultrahigh piezoelectric properties. This work not only demonstrates the tremendous potential of KNN‐based ceramics to replace lead‐based piezoelectrics but also provides a good strategy to design high‐performance piezoelectrics by controlling appropriate phase and crystallographic orientation.     

BiAlO3掺杂PZT陶瓷的高压电性能和低电场应变滞后

铅基压电陶瓷因其优异的压电性能, 被广泛应用于压电器件。其中, 压电驱动器要求压电陶瓷具有较高压电性能并且在电场下具有较高的电致应变和较小的应变滞后。本研究通过施主-受主共掺, 得到高压电性能和低电场应变滞后的PZT陶瓷。采用传统固相反应法制备了(1-x)(Pb_0.95Sr_0.05)(Zr₅₃Ti₄₇)O₃-xBiAlO₃+0.2%MnO₂陶瓷(掺杂量为质量百分数), 并对其微观结构和压电性能进行了研究。结果表明：BiAlO₃掺杂量较少时, 陶瓷中缺陷偶极子的“钉扎”效应使得陶瓷畴壁转动困难, 陶瓷压电性能较弱, 应变滞后也较小。随BiAlO₃掺杂量增加, 缺陷偶极子“钉扎”效应减弱, 陶瓷的压电性能和应变滞后随之提高。本实验得到的性能最优组分为x=1.75%, 该组份陶瓷的压电系数d₃₃=504 pC/N, 机电耦合系数k_p=0.71, 机械品质因数Q_m=281, 居里温度T_C=312 ℃, 在10 kV/cm电场下的应变滞后仅为15%, 并且还具有较好的温度稳定性, 是一种具有应用价值的压电驱动器用压电陶瓷材料。     

压电压磁双层材料界面二维裂纹分析

该文利用积分变换和奇异积分方程技术研究压电压磁双材料界面裂纹二维断裂问题.假设界面上压电材料电势和压磁材料磁势为零:压电层表面受机械载荷和电位移作用,压磁层表面受机械载荷和磁导作用.导出了相应问题的应力强度因子和机械能量释放率的表达式,给出了机械能量释放率的数值结果.结果表明:在同样机械载荷作用下,压电压磁双材料界面裂...     

Fabrication of lead-free piezoelectric (Bi<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)TiO<Subscript>3</Subscript>–BaTiO<Subscript>3</Subscript> ceramics using electrophoretic deposition

Electrophoretic deposition (EPD) process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi_0.5Na_0.5)TiO₃–15BaTiO₃ (85BNT–15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. Various conditions were optimized such as suspension media, applied electrical field, and deposition time in order to yield dense green ceramics of 85BNT–15BT composition using EPD process. 85BNT–15BT ceramics prepared using EPD process revealed the Curie temperature of about 250 °C, coercive field of about 30 kV/cm, and piezoelectric constant (d ₃₃) of 75 pC/N. The EPD-processed samples exhibited structural and electrical properties similar to that of the conventionally processed one suggesting the successful fabrication of 85BNT–15BT piezoelectric ceramics by EPD method without composition deviation. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.     

Love wave propagation in layered magneto-electro-elastic structures with initial stress

Summary An analytical approach is taken to investigate Love wave propagation in layered magneto-electro-elastic structures with initial stress, where a piezomagnetic (piezoelectric) material thin layer is bonded to a semi-infinite piezoelectric (piezomagnetic) substrate. The magneto-electrically open and short conditions are applied to solve the problem. The phase velocity of the Love wave is numerically calculated for the magneto-electrically open and short cases, respectively. The effect of the initial stress on the phase velocity and the magneto-electromechanical coupling factor are studied in detail for piezomagnetic ceramics CoFe₂O₄ and piezoelectric ceramics BaTiO₃. We find that the initial stress has an important effect on the Love wave propagation in layered piezomagnetic/piezoelectric structures.     

Review Nonlinearity in piezoelectric ceramics

The paper presents an overview of experimental evidence and present understanding of nonlinear dielectric, elastic and piezoelectric relationships in piezoelectric ceramics. This topic has gained an increasing recognition in recent years due to the use of such materials under extreme operating conditions, for example in electromechanical actuators and high power acoustic transducers. Linear behaviour is generally confined to relatively low levels of applied electric field and stress, under which the dielectric, elastic and piezoelectric relationships are described well by the standard piezoelectric constitutive equations. Nonlinear relationships are observed above certain threshold values of electric field strength and mechanical stress, giving rise to field and stress-dependent dielectric (), elastic (s) and piezoelectric (d) coefficients. Eventually, strong hysteresis and saturation become evident above the coercive field/stress due to ferroelectric/ferroelastic domain switching. The thermodynamic method provides one approach to describing nonlinear behaviour in the intermediate field region, prior to large scale domain switching, by extending the piezoelectric constitutive equations to include nonlinear terms. However, this method seems to fail in its prediction of the amplitude and phase of high frequency harmonic components in the field-induced polarisation and strain waveforms, which arise directly from the nonlinear dielectric and piezoelectric relationships. A better fit to experimental data is given by the empirical Rayleigh relations, which were first developed to describe nonlinear behaviour in soft magnetic materials. This approach also provides an indication of the origins of nonlinearity in piezoelectric ceramics, in terms of ferroelectric domain wall translation (at intermediate field/stress levels) and domain switching (at high field/stress levels). The analogy with magnetic behaviour is also reflected in the use of Preisach-type models, which have been successfully employed to describe the hysteretic path-dependent strain-field relationships in piezoelectric actuators. The relative merits and limitations of the different modelling methods are compared and possible areas of application are identified.An erratum to this article can be found at     

Piezoelectric properties and thermal stabilities of cobalt-modified potassium bismuth titanate

The cobalt-modified potassium bismuth titanate (K_0.5Bi_4.5Ti₄O₁₅, KBT) piezoelectric ceramics have been prepared using conventional solid–state reaction. X-ray diffraction analysis revealed that the cobalt-modified KBT ceramics have a pure four-layer (m = 4) Aurivillius-type structure. The dielectric, ferroelectric, and piezoelectric properties of cobalt-modified KBT ceramics were investigated in detail. The piezoelectric activities of KBT ceramics were significantly improved by the cobalt modification. The reasons for piezoelectric activities enhancement with cobalt modification were given. The piezoelectric coefficient d₃₃ and Curie temperature T_c for the 5 mol% cobalt-modified KBT ceramics (KBT-Co5) were found to be 28 pC/N and 575 °C, respectively. The DC resistivity, frequency constants (N_p and N_t), and electromechanical properties at elevated temperature were investigated, indicating the cobalt-modified KBT piezoelectric ceramics possess stable piezoelectric properties up to 500 °C. The results show the cobalt-modified KBT ceramics are potential materials for high temperature piezoelectric applications.     

逆压电效应的压电常数和压电陶瓷微位移驱动器

本文介绍了由过压电效应的应变-电场曲线测得弱场和强场下的压电常数d₃₃、d₃₁．测量发现S～E曲线上呈现应变和压电系数突增的阈值场强E_b,用铁电陶瓷固有的90°畴转向对应变的贡献进行了分析和讨论．该方法与以往常用的正压电效应的压电常数测试相比,方便、简单,尤其对过压电效应的压电微位移驱动器应用更具有实际意义．     

(Ba0.85Ca0.15)(Ti0.9Zr0.1-xSnx)O3无铅压电陶瓷的相结构与压电性能

钙锆共掺钛酸钡陶瓷(BCZT)具有优异的介电性能和压电性能, 是一类具有发展潜力的无铅压电陶瓷, 但其压电性能仍无法与铅基陶瓷媲美。为提高压电性能, 本研究对陶瓷材料进行Sn元素掺杂改性((Ba_0.85Ca_0.15)- (Ti_0.9Zr_0.1-xSn_x)O₃, x=0.02~0.07))。晶体结构分析证实所有组分的陶瓷无杂相, 处于正交相与四方相两相共存状态, 并具有较大的c/a; 显微结构分析发现所有陶瓷都很致密, 且平均晶粒尺寸随着Sn含量的增加而增大。当x=0.04时, 陶瓷最致密, 且室温处于准同型相界附近, 因此拥有最佳的电学性能: d₃₃=590 pC•N ^-1, k_p=52.2%, tanδ=0.016, ε ^T₃₃=5372, d ^*₃₃=734 pm•V ^-1, IR=57.8 GΩ•cm。本研究表明: Sn掺杂的BCZT基无铅压电陶瓷具有优异的压电性能, 有望在换能器、机电传感器和驱动器等方面得到应用。     

压电陶瓷场致疲劳特性与机理研究进展

压电陶瓷的场致疲劳是材料性能在外加循环载荷作用下逐步退化的现象, 是导致其失效的主要因素, 近年来一直是国内外的研究热点. 本文综合分析了压电陶瓷在电场, 多场耦合(力-电-温度)作用下的疲劳机理和影响因素, 并对压电陶瓷场致疲劳的未来研究方向进行了展望.     

高Tc铋层状压电陶瓷结构与性能

综述了铋层状压电陶瓷的结构特点及性能研究．铋层状压电陶瓷的结构由（Ｂｉ_２Ｏ_２）^２＋层和钙钛矿层（Ａ_ｍ－１Ｂ_ｍＯ_３ｍ＋１）^２－按一定规则共生排列而成．此处 Ａ为适合干 １２配位的离子;Ｂ为适合于八面体配位的离子,ｍ为一整数,其值一般为１～５．与钛酸钡（ＢａＴｉＯ_３）或锆钛酸铅（ＰＺＴ）陶瓷相比,铋层状压电陶瓷具有以下特点：低介电常数、高Ｔ_ｃ、机电耦合系数各向异性明显、低老化率、高电阻率等． 先前研究证明,居里温度不仅与极化原子位移、自发极化强度、Ａ位Ｂｉ含量有关,而且还与取代离子的特性诸如离子半径、电负性、核外电子排布有关．压电活性低是铋层状陶瓷的本质缺点,通常发展该材料的途径为化学取代或晶粒取向技术．研究材料结构与性能之间的关系有助于发展铋层状压电陶瓷材料．     

Chemical processing and microstructure of piezoelectric lead titanate ceramics

Lead titanate-based ceramics with different microstructures were prepared from PbO-TiO₂ gels with equimolar and non-equimolar mixtures of the oxides. Deviations from the initial compositions were found in the sintered materials. As a consequence, microstructures with different grain sizes and secondary phases were developed in the resultant ceramics. These microstructures had a strong influence on the piezoelectric behaviour of the materials obtained.     

SFM in acoustic mode and its applications to observation of ferroelectric domain

Ferroelectric domain structures as well as other surface topologies such as grain boundaries and scratches in transparent (PbLa)(ZrTi)O₃ (PLZT) ceramics and BaTiO₃ ceramics have been respectively investigated by scanning probe acoustic microscopy (SPAM). A periodic striation-like domain pattern has been imaged. The observed SPAM domain contrast is related to acoustic signals generated through a local piezoelectric coupling mechanism. The submicron domain structure was confirmed by scanning force microscopy (SFM) in the piezoresponse mode.     

(Bi0.5Na0.5)TiO3(BNT)基无铅压电陶瓷研究进展

(Bi0.5Na0.5)TiO3(BNT)基无铅压电陶瓷体系是目前研究最广泛的功能陶瓷材料之一.综述了BNT基无铅压电陶瓷的研究现状,讨论了相关体系的设计方法、铁电性、压电性以及BNT体系的制备方法.分析比较了BNT系压电陶瓷与Pb(Zr,Ti)O3(PZT)压电陶瓷的性能差异以及存在的问题,对BNT基无铅压电陶瓷进行了展望.     

Relaxor-PT single crystals: observations and developments

Relaxor-PT based ferroelectric single crystals Pb(Zn?/?)Nb(?/?)O?-PbTiO? (PZNT) and Pb(Mg?/?)Nb(?/?)O?-PbTiO? (PMNT) offer high performance with ultra-high electromechanical coupling factors k?? > 0.9 and piezoelectric coefficients d??s > 1500 pC/N. However, the usage temperature range of these perovskite single crystals is limited by T(RT)-the rhombohedral to tetragonal phase transition temperature, which occurs at significantly lower temperatures than the Curie temperature T(C), a consequence of curved morphotropic phase boundaries (MPBs). Furthermore, these <001>-oriented crystals exhibit low mechanical quality Q and coercive fields, restricting their usage in high-power applications. In this survey, recent developments on binary and ternary perovskite relaxor-PT crystal systems are reviewed with respect to their temperature usage range. General trends of dielectric and piezoelectric properties of relaxor-PT crystal systems are discussed in relation to their respective T(C)/T(RT). In addition, two approaches have been implemented to improve mechanical Q, including acceptor dopants, analogous to hard polycrystalline ceramics, and anisotropic domain engineering, enabling low-loss crystals with high coupling for high-power applications.     

Investigation on the composition design and properties study of perovskite lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics can be divided into perovskite, tungsten bronze, and bismuth layered structure ceramics. In recent years, the authors’ group concentrates the researches on the composition design and the properties study of perovskite lead-free piezoelectric ceramics, especially on the (Bi_1/2Na_1/2)TiO₃ (BNT)- and K_1/2Na_1/2NbO₃ (KNN)-based ceramics. All the ceramics were prepared by the conventional ceramic technique. In this paper, the main results obtained are reviewed with emphasis on KNN-based ceramics, including (1) the design on new BNT-based ceramics based on the multiple complex in the A-site of ABO₃ compounds; (2) the design of KNN-based ceramics focused on the effects of Ag ion substitution, K/Na ratio, and LiSbO₃ on KNN-based ceramics; (3) the effects of doping on the properties of BNT- and KNN-based ceramics; and (4) the temperature stability of BNT- and KNN-based ceramics. And some prospects to be resolved in coming years from the viewpoint of the applications of the perovskite lead-free piezoelectric ceramics are also pointed out.     

Improved electrical properties of Co-doped 0.92NBT–0.04KBT–0.04BT lead-free ceramics

The (1???2x)NBT–xKBT–xBT ternary piezoelectric system has been extensively studied in recent years. However, its electrical performance is far inferior to lead-based counterparts, and could not meet the requirements for practical applications. In this contribution, the 0.92NBT–0.04KBT–0.04BT (abbreviated as NKBT4) ceramics were prepared by traditional solid-state method. The effects of doped cobalt content on the structure and electrical performance of NKBT4 ceramics were studied systematically. The content of Co₂O₃ affects the average grain size, maximum dielectric constant, piezoelectric properties and the ferroelectric responses of the ceramics. It was found that the introduction of cobalt did not affect the phase structure of the ceramics, but is beneficial for the improvement of the dielectric and piezoelectric properties. When x?=?0.2, the piezoelectric coefficient (d₃₃) is around 130 pC/N, which is greatly improved compared to pure NKBT4 ceramics. Besides, a relatively high dielectric constant (ε_r?=?1150) was obtained at the same composition. This work paves a new way for the further development of high performance lead-free piezoelectric ceramics.     

Novel modeling technique for the stator of traveling wave ultrasonic motors

Traveling wave ultrasonic motors (TWUM) are a promising type of piezoelectric transducers, which are based on the friction transmission of mechanical propagating waves. These waves are excited on the stator by using high Q piezoelectric ceramics. This article presents a modeling strategy, which allows for a quick and precise modal and forced analysis of the stator of TWUM. First-order shear deformation laminated plate theory is applied to annular subdomains (super-elements) of the stator. In addition to shear deformations, the model takes into account the effect of rotary inertia, the stiffness contribution of the teeth, and the linear varying thickness of the stator. Moreover, the formulation considers a more realistic function for the electric field inside the piezoelectric ceramic, i.e., a linear function, instead of the generally assumed constant electric field. The Ritz method is used to find an approximated solution for the dynamic equations. Finally, the modal response is obtained and compared against the results from classical simplified models and the finite element method. Thus, the high accuracy and short computation times of the novel strategy were demonstrated.