Piezoelectric Layered Structure Research Articles

Piezoelectric Layered Structure with Conductive Polymer Composites as a Waveguide Layer: Swelling Monitoring Based on the Propagation of Love-Type Wave

Piezoelectric Layered Structure with Conductive Polymer Composites as a Waveguide Layer: Swelling Monitoring Based on the Propagation of Love-Type Wave

Acoustic Waves in Piezoelectric Layered Structure for Selective Detection of Liquid Viscosity.

The acoustic waves of higher orders propagating in a layered structure consisting of a silicon plate coated with piezoelectric ZnO and/or AlN films were used for the development of a sensor with selective sensitivity to liquid viscosity η in the range of 1-1500 cP. In that range, this sensor possessed low sensitivity to liquid conductivity σ and temperature T in the ranges of 0-2 S/m and 0-55 °C, respectively. The amplitude responses insensitive to the temperature instead of the phase were used to provide the necessary selectivity. The sensor was based on a weak piezoactive acoustic wave of higher order. The volume of the probes sufficient for the measurements was about 100 μL. The characteristics of the sensors were optimized by varying the thicknesses of the structure layers, number of layers, wavelength, wave propagation direction, and the order of the acoustic waves. It was shown that in the case of the layered structure, it is possible to obtain practically the same selective sensitivity toward viscosity as for acoustic waves in pure ST, X quartz. The most appropriate waves for this purpose are quasi-longitudinal and Lamb waves of higher order with in-plane polarization. It was found that for various ranges of viscosity η = 1-20 cP, 20-100 cP, and 100-1500 cP, the maximum sensitivity of the appropriate wave is equal to 0.26 dB/cP, 0.087 dB/cP, and 0.013 dB/cP, respectively. The sensitivity of the waves under study toward the electric conductivity of the liquid is much less than the sensitivity to liquid viscosity. These two responses become comparable only for very small η < 2 cP. The waves investigated have shown no temperature responses in contact with air, but in the presence of liquid, they increase depending on liquid properties. The temperature dependence of liquid viscosity is measurable by the same sensors. The results obtained have shown the possibility of designing acoustic liquid viscosity sensors based on multilayered structures. The set of possible acoustic waves in layered structures possesses modified propagation characteristics (various polarization, phase velocities, electromechanical coupling coefficients, and attenuations). It allows choosing an optimal acoustic wave to detect liquid viscosity only.

Vibrations analysis of propagation of SH-type wave influenced by a point source in a porous piezoelectric layered structure by Green’s function approach

Vibrations analysis of propagation of SH-type wave influenced by a point source in a porous piezoelectric layered structure by Green’s function approach

Layered piezoelectric structures with arbitrary acoustic termination impedances.

Multilayer piezoelectric transducers and resonators are widely used for generating propagating and standing acoustic waves as well as for sensor devices. More recently, layered piezoelectric structures based on thin film technology became increasingly important for electromechanical filters used in mobile phones. As a consequence, analytical mathematical modeling of such structures is of high interest. In this paper, a general rigorous transfer matrix description for one-dimensional (1D) layered structures consisting of piezoelectric, visco-elastic, and dielectric layers of arbitrary number is introduced to characterize the electrical and mechanical behavior of a general piezoelectric transducer or resonator with two electrodes and arbitrary acoustic termination impedances (Rig-1D-model). This model is the most general 1D analytical description of layered piezoelectric structures available and can be used for the characterization of various composite transducer and resonant sensor applications. Considered in detail are layered structures with the technically important cases of only one electromechanically coupled mode, and the structure at one or both outer surfaces is in contact with semi-infinite media. For such devices, it is shown how the frequency dependence of the total electrical admittance and spatial dependence of the displacements can be calculated.

Ultra-wide band and improved quality factor SH-type SAW devices by employing Mn-doped Pb(In1/2Nb1/2)O3– Pb(Mg1/3Nb2/3)O3–PbTiO3 thin film/diamond layered structure

This paper presents a piezoelectric layered structure composed of Mn-doped PIN-PMN-PT thin film combined with diamond for high electromechanical coupling factor (K2) and improved quality factor (Q) SAW devices. Comprehensive theoretical analysis of SAW resonator on the proposed structure is performed to calculate its SAW characteristics including K2, V (phase velocity) and Q. The influence of the Euler angle, Mn-doped PIN-PMN-PT layer's thickness and the electrode's thickness as well as electrode's materials on the SAW properties are investigated. It is shown that the maximum electromechanical coupling factor of the proposed structure has been theoretically shown up to be 79.5 % for the main mode called shear-horizontal (SH)-type SAW. The FOM(K2·Q) is enhanced to 868.5, which is more than two times larger than that of the previously reported work using pure PIN-PMN-PT. Such enhancement of FOM makes such structure has great potential application in ultra-wide band and high Q SAW filters operating at 1GHz–3GHz.

Perfectly matched layer and infinite element coupled with finite elements for SH waves in an imperfect piezoelectric viscoelastic structure

Discontinuities of dielectric/mechanical properties at the interfaces in piezoelectric actuators or sensors reduce the efficiency of the system. This may arise due to the uneven transfer of stress or potential across the surface. The present study encapsulates the dispersion phenomenon of SH waves in an imperfectly bonded piezoelectric viscoelastic layered structure. Besides the basic analytical study, two different numerical methodologies have been adopted to obtain the frequency curves; first, semi-analytical finite element and perfectly matched layer and second, semi analytical infinite element with reciprocal of distance decay. The solution treatment utilizes the electro-visco-mechanical field equations and the Rayleigh–Ritz method to derive the mass and stiffness matrices of the perfectly matched layer or infinite element. The assembly process of discretized elements at the mechanical/dielectric imperfect interface is a major theme of this study. Frequency curves obtained by all three aforementioned methodologies have been portrayed graphically with special emphasis on interface imperfection on them. Comparing with the analytical results, it is reported that the method of perfectly matched layer or infinite element coupled with finite element fairly emulates SH wave propagation in piezoelectric viscoelastic (layer and half-space) structure.

Transference of SH waves in a piezoelectric fiber-reinforced composite layered structure employing perfectly matched layer and infinite element techniques coupled with finite elements

Most commercially used piezoelectric materials suffer from certain drawbacks like low piezoelectric output, brittle nature, etc. Thus, they cannot be utilized to their fullest extent in dynamic applications involving actuators, transducers, Surface Acoustic Wave (SAW) devices, and Love wave sensors, among others. The present work focuses on the transference attributes of anti-plane SH wave in a layered structure composed of a piezoelectric fiber-reinforced composite (PFRC) layer lying over a piezoelectric half-space. The PFRC composed of PZT-5A-epoxy is micro-mechanically modeled using Strength of Materials and Rule of Mixtures, and some of its electro-mechanical advantages over monolithic PZT-5A are discussed. The dispersion relation is obtained by analytical means, as well as two numerical techniques, viz., Semi-Analytical Finite Element - Perfectly Matched Layer (SAFE-PML) technique and Semi Analytical Infinite Element (SAIFE) technique with (1/r) type decay. The Rayleigh–Ritz method and Gauss 3-point quadrature formula are employed to derive the dispersion relation numerically. The effects of the existing parameters, viz. fiber volume fraction, PML length, PML function, etc., on the dispersion curves are graphically demonstrated and discussed. The present work is validated by matching the obtained results with the ones found in the extant literature.

Asymmetric non-slipping adhesion behavior of layered piezoelectric structures

Layered piezoelectric structures have found wide applications in micro-electro-mechanical systems (MEMS) due to their intrinsic electro-mechanical coupling effect. The adhesion effect resulting from various surface forces (e.g., the electrostatic force, capillary force, and Van der Waals force) has become one dominant factor in determining the reliability and service life of the MEMS devices. In this study, the asymmetric non-slipping adhesion behavior of layered piezoelectric structures under the action of different external loadings is investigated. A system of coupled singular integral equations are obtained for the stated problem in the framework of the generalized JKR theory, where the coupling effect between the normal and tangential contact stresses is taken into consideration. The closed-form analytical solutions of the electric displacement and stress fields within the contact zone are derived. The relations between the contact size and applied loadings are set up with the Griffith energy balance criterion. The effect of the mechanical and electric loads and the mismatch strain on the adhesion behavior of layered piezoelectric structures is discussed in detail. It is found that applying the electric load can only strengthen the adhesion effect for different types of layered piezoelectric structures. Both the inclined angle of the mechanical force and the geometric parameter of the contacting objects have significant effects on the adhesion behavior. The results obtained from present paper should be very useful for understanding the adhesion failure mechanism of the MEMS devices composed of layered piezoelectric structures.

Study of Propagation of Microwave Lamb Waves in a Piezoelectric Layered Structure

Study of Propagation of Microwave Lamb Waves in a Piezoelectric Layered Structure

The Effect of Micro-Inertia and Flexoelectricity on Love Wave Propagation in Layered Piezoelectric Structures.

The non-classical linear governing equations of strain gradient piezoelectricity with micro-inertia effect are used to investigate Love wave propagation in a layered piezoelectric structure. The influence of flexoelectricity and micro-inertia effect on the phase wave velocity in a thin homogeneous flexoelectric layer deposited on a piezoelectric substrate is investigated. The dispersion relation for Love waves is obtained. The phase velocity is numerically calculated and graphically illustrated for the electric open-circuit and short-circuit conditions and for distinct material properties of the layer and substrate. The influence of direct flexoelectricity, micro-inertia effect, as well as the layer thickness on Love wave propagation is studied individually. It is found that flexoelectricity increases the Love-wave phase velocity, while the micro-inertia effect reduces its value. These effects become more significant for Love waves with shorter wavelengths and small guiding layer thicknesses.

Love wave propagation in piezoelectric structures bonded with conductive polymer films

In this study, we investigate analytically Love wave propagation in layered piezoelectric structures, where a thin conductive polymer layer is bonded to an unbounded piezoelectric substrate. The dispersive relation is derived and the effects of viscosity and conductivity on the phase velocity and attenuation of Love wave are analyzed and discussed. The results reveal that the effects of the viscosity and conductivity on the properties of Love wave are obvious. The phase velocity is affected by the viscosity and conductivity slightly, while the attenuation is remarkably changed with the varying frequency of the waves, viscosity and conductivity, respectively. The relationship between attenuation and frequency are not monotone increasing. The analytical solutions results are well-matched with the finite element results. The results in this work is useful for the design of acoustic wave device.

Excitation of Surface Acoustic Waves and Lamb Waves at Superhigh Frequencies in a Diamond-Based Piezoelectric Layered Structure

The authors have carried out an experimental and theoretical study of the propagation of surface acoustic waves (SAW)—Rayleigh, Sezawa and SH-modes, as well as Lamb waves in Me-IDT/AlN/(100) diamond (Me = Pt, Al) piezoelectric layered structures with a SAW resonator configuration. The types of modes are identified and the dispersion curves of the phase velocities and electromechanical coupling coefficients for SAW and Lamb waves are obtained. The excitation of Lamb waves up to a frequency of 7.3 GHz was observed experimentally. The resonance curves for Lamb waves have a higher quality factor Q compared to surface acoustic waves propagating on the same substrates. At a frequency of about 7 GHz, the loaded Q-factor reaches 3400, while the quality parameter Q × f = 2.4 × 1013 Hz. An unusual effect of a significant increase in the Q-factor of Lamb waves with the frequency increasing from 760 at 1.5 GHz to 3400 at 7 GHz is noted.

Bleustein–Gulyaev wave in a nonlocal piezoelectric layered structure

Manifesting the piezoelectric and nonlocal effects on the propagation of surface waves in nanoscale smart structures can provide some new insights for the designs and applications of the nanoscale wave devices. Taking the nanoscale size effect into consideration based on the nonlocal theory, the propagation of Bleustein–Gulyaev (BG) wave in a nonlocal piezoelectric (PE) layer overlying a nonlocal piezoelectric (PE) half-space, is investigated. The dispersion relations and particular cases are derived for the open and short circuit conditions. The results show that wave propagation is highly affected by nanoscale size effects due to the nonlocality present in the media.

Peculiarities of energy trapping of the UHF elastic waves in diamond-based piezoelectric layered structure. II. Lateral energy flow

Features of an acoustic energy trapping and outflow in a High-overtone Bulk Acoustic Resonator (HBAR) were considered. On the example of a specified resonator based on a piezoelectric layered structure (PLS) as “Al/AlN/Mo/(100) diamond”, the simulation of the propagation of microwave acoustic waves in the range of 10–6000 MHz by Finite Element Method (FEM) in COMSOL Multiphysics has been carried out. It was found that the magnitude of acoustic energy retained in the substrate under the bottom electrode depends substantially on the relation between the HBAR’s antiresonance frequency fa,n and the cut-off frequencies fs,n-k and fs,n-k+1 of the substrate. The term “cut-off frequency” has the meaning of the frequency point when integer value of half-waves fits along the thickness of substrate. Parameter gk,n estimating the degree of the HBAR’s energy trapping has been proposed. If 0.5 < gk,n < 1, then a retention of acoustic energy in the HBAR’s center as a maximal ET-effect at the overtone frequency fa,n should be fulfilled. Increasing the width of the top electrode as well as the HBAR’s aperture should expand the frequency interval in which the retained elastic energy in the vicinity of the HBAR’s center will be greater than the similar outside. It was shown that the area-averaged Umov-Poynting’s power energy flow vector from the HBAR’s center in the lateral directions increases when approaching the Thin Film Piezoelectric Transducer half-wave resonance frequency from below, and then decreases sharply in the point of complete energy trapping. This can be explained by the outflow of acoustic wave energy from the center to the periphery as a consequence of the transformation of an operational longitudinal acoustic mode into waves of Lamb type mainly. Results on the peculiarities of an energy trapping effect will be useful developing the HBARs and HBAR-based acoustic sensors operating at microwave frequencies.

Electromechanical coupling and mass loading sensitivity of SH waves in a dielectrically imperfect piezoelectric structure

Imperfect mechanical or dielectric interfaces in piezoelectric sensors/actuators reduce the electromechanical efficiency of the system. The major drawback of an imperfect interface in a system is its disability to transfer stress or potential across the surface effectively. This leads to imperfect signal communication and thereby affecting its performance. The present study encapsulates the shear wave (Love wave in low velocity layer and B-G wave) propagation characteristics in an imperfectly bonded piezoelectric layered structure, also subjected to material gradients. The imperfect bonding interface is considered to be mechanically compliant and dielectrically weak (or high) conducting. With help of admissible, but non-traditional, boundary conditions at the interface, the dispersion equations of waves are derived by method of infinite determinants for both electrically open and shorted conditions at the free surface. Phase velocity, electromechanical coupling factor and mass loading sensitivity of shear waves are sketched graphically with special concern on the influence of interface imperfection on them. The results reported can serve to overcome the deficit in the performance of Love wave sensors due to mechanically/dielectrically imperfect interfacial surface.

Influence of a piezoelectric ZnO intermediate layer on Rayleigh waves propagating in Sc43%AlN57%/ZnO/diamond hetero-structures subjected to uniaxial stress

Surface acoustic waves (SAWs) are of practical importance across several fields. Particularly, a wide range of SAW devices is available, which are based on the stacking piezoelectric layered hetero-structures. As such, efficient and stable algorithm of analyzing electromechanical coupling factor (K2) should be of specific interest, inspiring a variety of piezoelectric layered structures. Motivated by the above considerations, this paper exploits the performance of Sc43% AlN57%/ZnO/diamond piezoelectric hetero-structures using matrix and polynomial methods. Consequently, dispersion curves, the electromechanical coupling factor and profiles of Rayleigh waves are calculated, in which the properties of hexagonal intermediate ZnO layer are varied. Here, $$ (0001) - [10\bar{1}0]{\text{ZnO}} $$ or $$ (11\bar{2}0) - [0001]{\text{ZnO}} $$ directions of the middle layer were integrated with Sc43% AlN57%/diamond to be a composite hetero-structure with a larger K2 of SAW. Accordingly, a commercial ZnO specimen was characterized by scanning electron microscopy (SEM) as well as Raman and XRD spectroscopy to determine its available crystallographic directions and the C-axis hexagonal character. Comparing with conventional AlN/diamond hetero-structures, the inclusion of ZnO as the intermediate layer provides with an excellent electromechanical coupling factor which significantly improves the $$ (11\bar{2}0) - [0001] $$ structure. However, comparing with the ZnO/diamond hetero-structure, a high phase velocity (Vph) was observed. Therefore, the development of a well-balanced structure that maximizes the values of Vph and K2 is systematically challenging. Moreover, it was found that initial stresses have a significant effect on the Rayleigh wave velocities. Fundamental A0 Lamb mode can be generated in piezoelectric hetero-structures when the properties of substrate remain very low relative to the film. Numerical results obtained in this paper can provide a deeper insight into the nature of the Rayleigh wave behaviors in piezoelectric hetero-structures, involving a ZnO intermediate layer.

Propagation characteristic of Love-type wave in different types of functionally graded piezoelectric layered structure

A mathematical model has been proposed for the analytical study of the propagation of Love-type wave in an initially stressed functionally graded piezoelectric material (FGPM) layer overlying an orthotropic fluid-saturated porous half-space. The expression of dispersion equation is derived in closed form for both electrically open and electrically short conditions. The impact of various affecting parameters viz. wave number, gradient parameter, tensile initial stress on the dispersion curve of Love-type wave has been revealed by means of graphical illustrations. Some remarkable observation has been made through numerical computation for different piezoelectric ceramics of BaTiO, PZT-4 and PZT-5A, respectively. The outcomes of the present study are momentous for both theoretical and practical implication for the surface acoustic wave (SAW) devices.

Dispersion characteristics of wave propagation in layered piezoelectric structures: Exact and simplified models

This article presents a study of the dispersion characteristics of wave propagation in layered piezoelectric structures under plane strain and open-loop conditions. The exact dispersion relation is first determined based on an electro-elastodynamic analysis. The dispersion equation is complicated and can be solved only by numerical methods. Since the piezoelectric layer is very thin and can be modeled as an electro-elastic film, a simplified model of the piezoelectric layer reduces this complex problem to a non-trivial solution of a series of quadratic equations of wave numbers. The model is simple, yet captures the main phenomena of wave propagation. This model determines the dispersion curves of PZT4-Aluminum layered structures and identifies the two lowest modes of waves: the generalized longitudinal mode and the generalized Rayleigh mode. The model is validated by comparing with exact solutions, indicating that the results are accurate when the thickness of the layer is smaller or comparable to the typical wavelength. The effect of the piezoelectricity is examined, showing a significant influence on the generalized longitudinal wave but a very limited effect on the generalized Rayleigh wave. Typical examples are provided to illustrate the wave modes and the effects of layer thickness in the simplified model and the effects of the material combinations.

On the characteristics of shear acoustic waves propagating in an imperfectly bonded functionally graded piezoelectric layer over a piezoelectric cylinder

A theoretical approach is taken into consideration to investigate the propagation behaviour of shear acoustic waves in a piezoelectric cylindrical layered structure composed of a piezoelectric material cylinder imperfectly bonded to a concentric functionally graded piezoelectric material (FGPM) cylindrical layer of finite width. The functional gradient in the FGPM cylindrical layer is considered to vary continuously along the radial direction (function of radial coordinate), and the imperfection of the interface of the cylindrical structure is taken into account which may practically exist due to some mechanical and/or electrical damage. By means of mathematical transformation, the governing electromechanical coupled field differential equations are reduced to Bessel’s equations. An analytical treatment has been employed to determine the dispersion relations of propagating shear acoustic waves for both electrically short and electrically open conditions, which are further validated by reducing the obtained results to the pre-established standard results and classical Love wave equation as a special case of the problem. The effects of functional gradient parameter, radii ratio, wave number, order of Bessel’s function appearing in the dispersion relations and mechanical/electrical imperfection parameters associated with the imperfect bonding of a piezoelectric material cylinder and FGPM layer on the phase velocity of shear acoustic waves have been reported through numerical simulation and graphical demonstration. For the sake of numerical computation, the data of PZT-5H for the FGPM cylindrical layer and AlN for a piezoelectric material cylinder have been considered.

Effect of Initial Stress on the Electromechanical Coupling and the Bleustein-Gulyaev Wave in a Transversely Isotropic Piezoelectric Layered Structure

Effect of Initial Stress on the Electromechanical Coupling and the Bleustein-Gulyaev Wave in a Transversely Isotropic Piezoelectric Layered Structure