Showing papers on "Piezoelectricity published in 2002"
TL;DR: A new class of all-organic field-type EAP composites is reported, which can exhibit high elastic energy densities induced by an electric field of only 13 V µm-1, and could find applications as artificial muscles, ‘smart skins’ for drag reduction, and in microfluidic systems for drug delivery.
Abstract: Electroactive polymers (EAPs) can behave as actuators, changing their shape in response to electrical stimulation. EAPs that are controlled by external electric fields--referred to here as field-type EAPs--include ferroelectric polymers, electrostrictive polymers, dielectric elastomers and liquid crystal polymers. Field-type EAPs can exhibit fast response speeds, low hysteresis and strain levels far above those of traditional piezoelectric materials, with elastic energy densities even higher than those of piezoceramics. However, these polymers also require a high field (>70 V micro m(-1)) to generate such high elastic energy densities (>0.1 J cm(-3); refs 4, 5, 9, 10). Here we report a new class of all-organic field-type EAP composites, which can exhibit high elastic energy densities induced by an electric field of only 13 V micro m(-1). The composites are fabricated from an organic filler material possessing very high dielectric constant dispersed in an electrostrictive polymer matrix. The composites can exhibit high net dielectric constants while retaining the flexibility of the matrix. These all-organic actuators could find applications as artificial muscles, 'smart skins' for drag reduction, and in microfluidic systems for drug delivery.
992 citations
TL;DR: In this paper, a review of the magnetoelectric (ME) effect in single phase and composite materials is presented, where the authors mainly emphasize their investigations of ME particulate composites and laminate composites, and summarize the important results.
Abstract: 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.
647 citations
TL;DR: The dielectric and piezoelectric properties of the new perovskite solid solution system (1-x)BiScO3-xPbTiO3 were investigated in this paper.
Abstract: The dielectric and piezoelectric properties of the new perovskite solid solution system (1-x)BiScO3–xPbTiO3 were investigated. This system is representative of a new group of high temperature piezoelectrics that includes Bi(Me)O3–PbTiO3, where Me+3 is a relatively large cation, Sc, Y, Yb, In, etc., and combinations thereof. In the (1-x)BiScO3–xPbTiO3 series, perovskite stability was achieved for x>50 mol% PbTiO3 being ferroelectric rhombohedral and transforming to ferroelectric tetragonal in the region x=64 mol% PbTiO3, designated as the morphotropic phase boundary (MPB). Analogous to (1-x)PbZrO3–xPbTiO3 (PZT), the dielectric and piezoelectric properties were enhanced for compositions near the MPB. Piezoelectric coefficient d33 values reached 450 pC/N, comparable to soft PZT's with a transition temperature of 450°C, more than 100°C higher than commercial PZT. The combination of high TC and excellent piezoelectric activity make (1-x)BiScO3–xPbTiO3 materials candidates for high temperature, and temperature stable actuators and transducers.
480 citations
TL;DR: A review of the recent advances in the understanding of piezoelectricity in lead oxide solid solutions is presented in this paper, giving special attention to the structural aspects, and it has now become clear that the very high electromechanical response in these materials is directly related to the existence of low symmetry monoclinic phases.
Abstract: A review of the recent advances in the understanding of piezoelectricity in lead oxide solid solutions is presented, giving special attention to the structural aspects. It has now become clear that the very high electromechanical response in these materials is directly related to the existence of low symmetry monoclinic phases.
391 citations
TL;DR: In this article, the fracture behavior of piezoelectric ceramics under combined electrical and mechanical loading has been among the most prevalent research topics, and four types of nonlinear approaches considered are: electrostriction, domain switching, domain wall kinetics, and polarization saturation at a crack tip.
Abstract: Publisher Summary Piezoelectric ceramics can sense and actuate by rapidly converting mechanical and thermal signals into electrical ones, the reverse also being true. The piezoelectric properties and quick response characteristics have made piezoelectric ceramics one of the most commonly used smart materials. The intrinsic brittleness of piezoelectric ceramics and damageability of the materials under electric field — making the materials prone to fracture — are of major concern for product reliability. The fracture of piezoelectric ceramics under combined electrical and mechanical loading has been among the most prevalent research topics. The chapter describes piezoelectricity, ferroelectrics, spontaneous polarization, and electric domains; and discusses the poling process, the hysteresis loop of polarization versus the electric field strength, and the butterfly loop of strain versus the electric field. The chapter focuses on the basic equations commonly used in the study of the fracture behavior of piezoelectric ceramics within the thermodynamics framework, the general solution based on Stroh's formalism (a powerful tool for solving two-dimensional electroelastic problems), analysis of Green's functions for insulating elliptical cavities and cracks, study of conductive elliptical cavities and cracks, study of piezoelectric interface cracks, and three-dimensional electroelastic problems. The four types of nonlinear approaches considered are: electrostriction, domain switching, domain wall kinetics, and polarization saturation at a crack tip. The polarization saturation model that treats piezoelectric ceramics as mechanically brittle and electrically ductile materials is also discussed. The chapter provides an overview of experimental observations whose results show that microstructure and temperature have a profound influence on the fracture behaviors of piezoelectric ceramics under purely mechanical loads, and also discusses the commonly used failure criteria, the electric saturation model, the stress intensity factor criterion and the stress criterion.
330 citations
Book•
01 Jan 2002
TL;DR: A background of piezoelectric sensors can be found in this paper, where the authors discuss the role of force and torque sensors, strain sensors, acceleration sensors, and acceleration sensors.
Abstract: 1 Introduction.- 2 Background of Piezoelectric Sensors.- 3 Piezoelectric Materials for Sensors.- 4 Piezoelectric Sensor Terminology.- 5 Piezoelectric Sensors.- 6 Force and Torque Sensors.- 7 Strain Sensors.- 8 Pressure Sensors.- 9 Acceleration Sensors.- 10 Acoustic Emission Sensors.- 11 Amplifiers for Piezoelectric Sensors.- References.- List of Manufacturers.
262 citations
TL;DR: In this article, a general form for multiaxial constitutive laws for ferroelectric ceramics is constructed, where switching surfaces and associated flow rules are postulated in a modified stress and electric field space such that a positive dissipation rate during switching is guaranteed.
Abstract: In this paper, a general form for multi-axial constitutive laws for ferroelectric ceramics is constructed. The foundation of the theory is an assumed form for the Helmholtz free energy of the material. Switching surfaces and associated flow rules are postulated in a modified stress and electric field space such that a positive dissipation rate during switching is guaranteed. The resulting tangent moduli relating increments of stress and electric field to increments of strain and electric displacement are symmetric since changes in the linear elastic, dielectric and piezoelectric properties of the material are included in the switching surface. Finally, parameters of the model are determined for two uncoupled cases, namely non-remanent straining ferroelectrics and purely ferroelastic switching, and then for the fully coupled ferroelectric case.
247 citations
TL;DR: An epitaxial 200 nm thick film of Pb(Zr0.40Ti0.60)O3 has been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3 (100) (STO).
Abstract: An epitaxial 200 nm thick film of Pb(Zr0.40Ti0.60)O3 (PZT) has been deposited by reactive rf magnetron sputtering on conductive Nb-doped SrTiO3 (100) (STO). The patterning process involved electron-beam lithography of polymethylmethacrylate, fabrication of a 75 nm thick Cr hard mask layer by means of a lift-off process, and dry etching of PZT. The smallest PZT features obtained were 100 nm in lateral dimensions. Piezoelectric sensitive scanning force microscopy in the contact mode revealed a strong increase of the piezoelectric response for feature sizes with lateral dimensions below 300 nm. It is proposed that this behavior is mainly due to vanishing a domains.
227 citations
TL;DR: In this paper, a theoretical model for low-frequency magnetoelectric (ME) effects in bilayers of magnetostrictive and piezoelectoric phases is presented for the consideration of actual boundary conditions at the interface.
Abstract: A theoretical model is presented for low-frequency magnetoelectric (ME) effects in bilayers of magnetostrictive and piezoelectric phases. An approach is proposed for the consideration of actual boundary conditions at the interface. An averaging method is used to estimate effective material parameters. The model predicts the strongest ME effect in cobalt ferrite-lead zirconate titanate (PZT) among ferrite based composites. The ME voltage coefficient for transverse field orientation is estimated to be 25–50% higher than for the longitudinal case. Comparison with data for multilayer samples reveals poor interface coupling in cobalt ferrite-PZT and ideal coupling in nickel ferrite-PZT.
215 citations
TL;DR: In this paper, the elastic buckling of column structures with a pair of piezoelectric layers surface bonded on both sides of the columns was investigated and an eigenvalue problem was solved using the direct difference method.
TL;DR: In this article, the authors studied the problem of a finite crack in a strip of functionally graded piezoelectric material (FGPM) and showed that the singular stresses and electric displacements at the tip of the crack in the FGPM carry the same forms as those in a homogeneous piezolectric materials but that the magnitudes of the intensity factors are dependent upon the gradient of the FG PM properties.
Abstract: In this paper the problem of a finite crack in a strip of functionally graded piezoelectric material (FGPM) is studied. It is assumed that the elastic stiffness, piezoelectric constant, and dielectric permitivity of the FGPM vary continuously along the thickness of the strip, and that the strip is under an antiplane mechanical loading and in-plane electric loading. By using the Fourier transform, the problem is first reduced to two pairs of dual integral equations and then into Fredholm integral equations of the second kind. The near-tip singular stress and electric fields are obtained from the asymptotic expansion of the stresses and electric fields around the crack tip. It is found that the singular stresses and electric displacements at the tip of the crack in the functionally graded piezoelectric material carry the same forms as those in a homogeneous piezoelectric material but that the magnitudes of the intensity factors are dependent upon the gradient of the FGPM properties. The investigation on the influences of the FGPM graded properties shows that an increase in the gradient of the material properties can reduce the magnitude of the stress intensity factor. ©2002 ASME
TL;DR: In this article, a debonding model was developed for composite patches using infinitesimal-length springs to model the joint between a composite patch and its base structure, which directly influences the structural mechanical impedance as well as the piezoelectric electric admittance.
Abstract: A modified electro-mechanical impedance model of piezoelectric actuator-sensors is presented in this study. The presented model treats the bonding layer between a piezoelectric patch and a host structure as a spring-mass-damper system in the coupled electro-mechanical analysis. The effect of bonding layers on the dynamic interaction between piezoelectric actuator-sensors and host structures is thus taken into account. The model is then used for debonding detection of composite patches. A debonding model is accordingly developed. The debonding model uses infinitesimal-length springs to model the joint between a composite patch and its base structure. The spring stiffness varies with the joint rigidity and directly influences the structural mechanical impedance as well as the piezoelectric electric admittance. A numerical example is provided to reveal the effect of bonding layers and demonstrate the feasibility of the proposed detection method.
TL;DR: In this paper, the local elastic properties and the ferroelectric domain configuration of piezoelectric ceramics have been examined by atomic force acoustic microscopy and by ultrasonic PEM microscopy.
Abstract: The local elastic properties and the ferroelectric domain configuration of piezoelectric ceramics have been examined by atomic force acoustic microscopy and by ultrasonic piezoelectric force microscopy The contrast mechanisms of the two techniques are discussed From the local contact stiffness which is obtained by evaluation of the contact resonance spectra, the elastic constants of the sample surface can be calculated In the case of anisotropic materials these elastic constants correspond to the indentation moduli Indentation moduli for barium titanate and for a lead zirconate-titanate ceramics were calculated theoretically and are in reasonable agreement with experiments The non-linearity of the tip–sample interaction becomes noticeable at large vibration amplitudes or large mechanical tip loads
TL;DR: In this article, the complete set of self-consistent parameters of nominally undoped LiNbO3 crystals of congruent composition that describe the electro-optic, piezoelectric, elasto-optics, elastic, and dielectric response has been determined by numerically evaluating available measurements.
Abstract: The complete set of self-consistent parameters of nominally undoped LiNbO3 crystals of congruent composition that describe the electro-optic, piezoelectric, elasto-optic, elastic, and dielectric response has been determined by numerically evaluating available measurements. The parameters were determined at room temperature and consist of the low-frequency clamped dielectric constants eS
ij, elastic stiffness constants at constant electric field CE
ijkl, piezoelectric stress coefficients eijk, elasto-optic constants at constant electric field pE
ijkl, and clamped electro-optic coefficients rS
ijk. It is shown that the complete set is required for calculating the effective electro-optic coefficients and dielectric constants in photorefractive applications of LiNbO3.
TL;DR: In this paper, closed-cell polymer foams have been found to be highly sensitive piezoelectric materials, which can be switched by applying dc-voltage pulses of alternating polarity above the breakdown threshold.
Abstract: Charged closed-cell polymer foams have been found to be highly sensitive piezoelectric materials. Charging is shown to arise from dielectric barrier microdischarges within the voids of the cellular polymer. Above the threshold voltage for breakdown in the voids, the microdischarges are evidenced by light emission from the polymer, as well as by displacement-voltage hysteresis loops. Monitoring light emission during breakdown is shown to provide a quick check for the suitability of foams for piezoelectric applications. Additionally it allows for the visualization of micropores in foams in a nondestructive way. The piezoelectric response of the foam can be switched by applying dc-voltage pulses of alternating polarity above the breakdown threshold, thereby showing the feasibility of patterning the piezoelectric properties within the film plane. Although piezoelectric foams are nonferroelectric, the experiments prove similarities to ferroelectric materials with respect to hysteresis behavior, as well as a threshold (coercive) field for switching of the polarization and piezoelectricity.
TL;DR: In this article, a high performance piezoelectric solution using the spark-plasma-sintering method has been prepared using the (1-y)(Na0.5K 0.5k 0.50) NbO3-PbTiO3 (y≤0.50).
Abstract: In the search for high-performance piezoelectrics, (1-y)(Na0.5K0.5)NbO3–yPbTiO3 (y≤0.50) solid solution has been prepared using the spark-plasma-sintering method. Dielectric investigation reveals that both the ferroelectric phase transition temperatures and the peak value of the dielectric constant are strongly suppressed in the low y range. However, improved electromechanical coupling constants are observed at the same y range. These properties are explained by considering factors such as composition, crystal structure, ferroelectric domain microstructure, and poling conditions.
Patent•
26 Jun 2002TL;DR: A piezoelectric electroacoustic transducer as mentioned in this paper eliminates the need for the interconnection between main surface electrodes and internal electrodes, and is capable of constructing a bimorph diaphragm using a simple connection structure.
Abstract: A piezoelectric electroacoustic transducer eliminates the need for the interconnection between main surface electrodes and internal electrodes, and is capable of constructing a bimorph diaphragm using a simple connection structure. The piezoelectric electroacoustic transducer includes a laminated body formed by laminating two or three piezoelectric ceramic layers, main surface electrodes each provided on the top and bottom main surfaces, and an internal electrode provided between any adjacent two piezoelectric ceramic layers. In the piezoelectric electroacoustic transducer, all ceramic layers are polarized in the same direction with respect to the thickness direction, and by applying an alternating voltage across the main surface electrodes and the internal electrode, the laminated body generates a bending vibration in its entirety.
TL;DR: Both press-focusing and application of a lens proved to be useful beam focusing methods for high frequency transducers and under equal gain schemes, the LiNbO/sub 3/ and PbTiO/ sub 3/ transducers provided better image contrast than the other materials.
Abstract: The performance of high frequency, single-element transducers depends greatly on the mechanical and electrical properties of the piezoelectric materials used. This study compares the design and performance of transducers incorporating different materials. The materials investigated include 1-3 lead zirconate titanate (PZT) fiber composite, lead titanate (PbTiO/sub 3/) ceramic, poly(vinylidene fluoride) (PVDF) film, and lithium niobate (LiNbO/sub 3/) single crystal. All transducers were constructed with a 3-mm aperture size and an f-number between 2 and 3. Backing and matching materials were selected based on design goals and fabrication limitations. A simplified coaxial cable tuning method was employed to match the transducer impedance to 50 /spl Omega/ for the PZT fiber composite and PbTiO/sub 3/ ceramic transducers. Transducers were tested for two-way loss and -6 dB bandwidth using the pulse/echo response from a flat quartz target. Two-way loss varied from 21 to 46 dB, and bandwidths measured were in the range from 47 to 118%. In vitro ultrasonic backscatter microscope (UBM) images of an excised human eye were obtained for each device and used to compare imaging performance. Both press-focusing and application of a lens proved to be useful beam focusing methods for high frequency. Under equal gain schemes, the LiNbO/sub 3/ and PbTiO/sub 3/ transducers provided better image contrast than the other materials.
TL;DR: In this paper, the authors reported direct first-principles density-functional calculations of the piezoelectric tensor d⇊ relating polarization to applied stress for the binary compounds AlN, GaN, and InN.
Abstract: We report direct first-principles density-functional calculations of the piezoelectric tensor d⇊ relating polarization to applied stress for the binary compounds AlN, GaN, and InN. The values of d⇊ are rather sensitive to the choice of the exchange-correlation functional, and results are presented for both the local-density and gradient approximations. A comparison with experiment and with values predicted indirectly from the elastic C⇊ and piezoconstant e⇊ tensors is also presented.
TL;DR: In this article, a diamond atomic force microscopy (AFM) probe with a piezoelectric sensor and actuator was developed based on the free vibration theory of cantilever beams.
Abstract: In order to develop a diamond atomic force microscopy (AFM) probe with a piezoelectric sensor and actuator, we fabricated piezoelectric zinc oxide (ZnO) thin film and measured its piezoelectric constant. First, we developed a simple measurement method for the piezoelectric constant of the thin film, d 31 . This was based on the free vibration theory of cantilever beams. The values of d 31 were determined by measuring an electric charge induced in the piezoelectric thin film on the vibrating cantilever beam and its displacement. Using this method, we evaluated d 31 for ZnO thin film sputtered at various substrate temperatures. The ZnO thin film deposited at temperatures of less than 350 °C was highly c -axis oriented and showed a high piezoelectric constant d 31 of −3.5 pC/N. Using this value, we calculated properties of the diamond cantilever AFM probes of various dimensions and of 5 μm in thickness with a ZnO sensor and actuator of 1 μm in thickness. The resolution of displacement and actuation force for a probe of 150 μm in length and 50 μm in width were estimated to be about 1.5 nm at a resolution of charge measurement of 1×10 −15 C and 7 μN at an applied voltage of 10 V, respectively.
TL;DR: In this article, the authors presented the experimental confirmation of the high coupling factor and elucidates the relationship between the domain structure and the piezoelectric properties in the pseudocubic (001)pc cut.
Abstract: The electromechanical coupling factor for the thickness-extensional mode, kt, in KNbO3 crystals has been predicted to be as high as 69% for the 49.5° rotated X-cut about the Y-axis, which is the highest among known piezoelectrics. This paper presents the experimental confirmation of the high coupling factor and elucidates the relationship between the domain structure and the piezoelectric properties in the pseudocubic (001)pc cut, which is close to the maximum kt cut and has a piezoelectric strain constant about 2.9 times that of the Z-cut. Etching of crystals is found to have an outstanding effect on the piezoelectric characteristics. That is, in the case of “as-cut” crystals, the strain versus electric field curves have a large hysteresis and instability due to the occurrence of 60° domains in a high electric field region, whereas etched crystals remain the single domain state and exhibit linear piezoelectric properties even in the high electric field region. It is also demonstrated that the (001)pc cut...
TL;DR: The plane-wave-expansion approach dedicated to the simulation of periodic devices has been extended to 1-3 connectivity piezoelectric composite structures and the model is reported and compared to previously published analyses of this problem.
Abstract: The plane-wave-expansion (PWE) approach dedicated to the simulation of periodic devices has been extended to 1-3 connectivity piezoelectric composite structures. The case of simple but actual piezoelectric composite structures is addressed, taking piezoelectricity, acoustic losses, and electrical excitation conditions rigorously into account. The material distribution is represented by using a bidimensional Fourier series and the electromechanical response is simulated using a Bloch-Floquet expansion together with the Fahmy-Adler formulation of the Christoffel problem. Application of the model to 1-3 connectivity piezoelectric composites is reported and compared to previously published analyses of this problem.
TL;DR: In this paper, a detailed characterization of piezoelectric shear mode inkjet actuators micromachined into bulk Pb(Zr0.53Ti0.47)O3 (PZT) ceramics is presented.
Abstract: We report on comprehensive characterization of piezoelectric shear mode inkjet actuators micromachined into bulk Pb(Zr0.53Ti0.47)O3 (PZT) ceramics. The paper starts with an overview of different drop-on-demand inkjet systems, whereas the main attention is then turned on particular Xaar-type piezoelectric shear mode inkjet printheads. They are an example of complex microelectromechanical system (MEMS) and comprise a ferroelectric array of 128 active ink channels (75 μm wide and 360 μm deep). Detailed information about fabrication process and principles of operation are given. Since each actuating wall of 128 channels is a piezoelectric capacitor metallized from both sides to be animated by electric pulse, electrical properties of channel walls (CWs) are easy to test and serve as a fingerprint of actuator performance in the virgin state as well as after high voltage/elevated temperature heavy duties. We present several techniques to control manufacturing process and fatigue effects. So, continuous wave and pulsed spectroscopy and hysteresis P–E loop tracing showed that compared to a virgin PZT ceramics state, dielectric permittivity (e′) was reduced three times, the loss factor (tan δ) increased from initial 4.8 to 6.6%, remnant polarization decreased by 43%, coercive field increased by 38%, whereas Curie temperature increased from 508 to 560 K after 90,000 cycles of ferroelectric hysteresis P–E loop tracing at 50 Hz at electric field of 88.5 kV/cm. Heat treatment also results in PZT ceramics degradation: appreciable reduction of the coupling coefficient (k15) and the degradation of inkjet performance were revealed by optical stroboscope technique: 8.7 and 14% reduction of drop velocity and volume in electrically fatigued actuator, 2.5% reduction of drop velocity and unchanged drop volume in temperature-treated actuators.
Patent•
29 Oct 2002
TL;DR: A micromechanical device is composed of a single crystal micromachined micro-structural structure and a piezoelectric epitaxial layer that is capable of performing a mechanical motion as discussed by the authors.
Abstract: A micromechanical device includes a single crystal micromachined micromechanical structure. At least a portion of the micromechanical structure is capable of performing a mechanical motion. A piezoelectric epitaxial layer covers at least a part of said portion of the micromechanical structure that is capable of performing a mechanical motion. The micromechanical structure and piezoelectric epitaxial layer are composed of different materials. At least one electrically conducting layer is formed to cover at least part of the piezoelectric epitaxial layer.
TL;DR: In this paper, a finite element formulation capable of modeling two different kinds of piezoelastically induced actuation in an adaptive composite sandwich beam is derived to couple certain piezoelectric constants to a transverse electric field to develop extension-bending actuation and shear-induced actuation.
Abstract: We have used quasi-static equations of piezoelectricity to derive a finite element formulation capable of modelling two different kinds of piezoelastically induced actuation in an adaptive composite sandwich beam. This formulation is made to couple certain piezoelectric constants to a transverse electric field to develop extension-bending actuation and shear-induced actuation. As an illustration, we present a sandwich model of three sublaminates: face/core/face. We develop a control scheme based on the linear quadratic regulator/independent modal space control (LQR/IMSC) method and use this to estimate the active stiffness and the active damping introduced by shear and extension-bending actuators. To assess the performance of each type of actuator, a dynamic response study is carried out in the modal domain. We observe that the shear actuator is more efficient in actively controlling the vibration than the extension-bending actuator for the same control effort.
TL;DR: In this article, a damage identification approach was developed for carbon fiber/epoxy composite laminates with localized internal delamination, which uses distributed piezoelectric transducers to generate and monitor the ultrasonic Lamb wave with narrowband frequency.
TL;DR: A film bulk acoustic resonator as discussed by the authors consists of a substrate (12) of a single silicon crystal, a base film (13) consisting of a dielectric film mainly containing silicon oxide, and a piezoelectric multilayer structure (14) formed on the base film.
Abstract: A film bulk acoustic resonator comprises a substrate (12) of a single silicon crystal, a base film (13) formed on the substrate (12) and composed of a dielectric film mainly containing silicon oxide, and a piezoelectric multilayer structure (14) formed on the base film (13) A vibratory section (21) composed of a part of the base film (13) and a part of the piezoelectric multilayer structure (14) The piezoelectric multilayer structure (14) includes a lower electrode (15), a piezoelectric film (16), and an upper electrode (17) in this order from below The substrate (12) has a via hole in the region corresponding to the vibratory section (21) The via hole forms a space for allowing vibration of the vibratory section (21) The piezoelectric film (16) is an aluminum nitride thin film containing 02 to 30 atom% of alkaline earth metal and/or a rare earth metal Thus, the film bulk acoustic resonator has a large electromechanical coupling coefficient, an excellent acoustic quality factor (Q), an excellent frequency-temperature characteristic, high characteristics, and a high performance
TL;DR: In this article, a high-order theory is presented to examine the electromechanical behavior of piezoelectric generic shells with graded material properties in the thickness direction, which can be readily reduced to typical structures, such as beams, plates and circular cylindrical shells.
01 Jan 2002
TL;DR: In this paper, a model considering the compensation of piezoelectric effect and the dislocation theory of fault was developed to investigate theoretically the generation of co-seismic electric signals.
Abstract: A model considering the compensation of piezoelectric effect and the dislocation theory of fault is developed to investigate theoretically the generation of co-seismic electric signals. Charges are assumed to be induced by the stress changes associated with earthquakes. The stressinduced charges are quantified by the charge density as a function of the polarization, which can be calculated using a piezoelectric model and an analytical solution of seismic stress. The theoretical charge distribution around the Nojima fault, which moved at the 1995 Kobe earthquake (M=7.2), was obtained. The co-seismic electric field consistent with that observed at the Kobe earthquake was estimated as the field due to the charges, which compensated the piezoelectric charges.