Converse Piezoelectric Effect Research Articles

Challenges and opportunities in piezoelectric polymers: Effect of oriented amorphous fraction in ferroelectric semicrystalline polymers

AbstractDespite extensive research on piezoelectric polymers since the discovery of piezoelectric poly(vinylidene fluoride) (PVDF) in 1969, the fundamental physics of polymer piezoelectricity has remained elusive. Based on the classic principle of piezoelectricity, polymer piezoelectricity should originate from the polar crystalline phase. Surprisingly, the crystal contribution to the piezoelectric strain coefficient d31 is determined to be less than 10%, primarily owing to the difficulty in changing the molecular bond lengths and bond angles. Instead, >85% contribution is from Poisson's ratio, which is closely related to the oriented amorphous fraction (OAF) in uniaxially stretched films of semicrystalline ferroelectric (FE) polymers. In this perspective, the semicrystalline structure–piezoelectric property relationship is revealed using PVDF‐based FE polymers as a model system. In melt‐processed FE polymers, the OAF is often present and links the crystalline lamellae to the isotropic amorphous fraction. Molecular dynamics simulations demonstrate that the electrostrictive conformation transformation of the OAF chains induces a polarization change upon the application of either a stress (the direct piezoelectric effect) or an electric field (the converse piezoelectric effect). Meanwhile, relaxor‐like secondary crystals in OAF (SCOAF), which are favored to grow in the extended‐chain crystal (ECC) structure, can further enhance the piezoelectricity. However, the ECC structure is difficult to achieve in PVDF homopolymers without high‐pressure crystallization. We have discovered that high‐power ultrasonication can effectively induce SCOAF in PVDF homopolymers to improve its piezoelectric performance. Finally, we envision that the electrostrictive OAF mechanism should also be applicable for other FE polymers such as odd‐numbered nylons and piezoelectric biopolymers.

Direct and converse piezoelectricity of thickness tuned BCZT ceramics: toward efficient bilayered magnetoelectric devices

Here we report the effect of thickness reduction of bulk 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Ti0.8Zr0.2)O3 (BCZT) pellet on its direct and indirect piezoelectric properties. Upon reducing the thickness to 0.3 mm, the pellet shows a very high electrostrain of ∼0.7% and piezoelectric coefficient of ∼353 pC/N which were ∼0.14% and 258 pC/N for the 1 mm thick sample. These results have been correlated with the reduction in hardness and mutual mechanical clamping between the grains due to the reduced thickness of BCZT. Due to this improved strain sensitivity, the bilayered magnetoelectric (ME) devices of BCZT with magnetostrictive CoFe1.9Bi0.1O4 (CFBO) pellet have also shown gradually improved ME coupling coefficient ( αME ) with reduced BCZT thickness ( αME = 27 and 66 mV·cm−1·Oe−1 for 1 and 0.3 mm BCZT thickness, respectively). This demonstrates the possible applicability of thickness tuned BCZT pellets for various technological purposes.

Controllable and reversible electric field tuning of photoluminescence response in lanthanide ions doped ferroelectric films

The rare-earth doped ferroelectric photoluminescence (PL) phosphors are attracting considerable interest because of their flexible structure, wide band gap and high-quality fluorescence signal emission. Although the change of PL performance in different samples have been solved to a certain extent, how to achieve the tuning of PL intensity in one sample sensitively and reversibly is still an issue. In this work, we present an "electric-elastic-optical" coupled structure of 0.94Bi0.5Na0.5TiO3–0.06BaTiO3:1 mol%Eu3+ (BNTBT:Eu)/ 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 (PMN-PT) heterostructures, which transfers strain from the PMN-PT to the BNTBT:Eu film via the converse piezoelectric effect and dynamically modulates the PL response of the epitaxial thin film. Our findings demonstrate that the PL response of the thin film can be effectively and linearly tuned under the influence of an external electric field. The relative change in the PL intensity (ΔI/I) of the BNTBT:Eu film was found to be linearly correlated with the lateral strain of the substrate. We also propose a novel design strategy for detecting strain, with significant implications for using BNTBT:Eu/PMN-PT heterostructures as sensors for integrating piezophotonic devices. This work provides valuable insights into the feasibility of electric field tuning of PL performance, which could inspire future research endeavors in the fields of nanophotonics, optical storage technology and photovoltaics.

Linear electro-optic effect in strontium barium niobate: A first principles study

We report a first-principles study of the linear electro-optic or Pockels effect in SrxBa1-xNb2O6 (SBN). SBN is an attractive material for building electro-optic modulators in silicon photonics as it has one of the highest known Pockels coefficients and can be integrated on Si. We investigate the microscopic mechanism behind the giant Pockels effect and find that the optical phonon contribution dominates the electro-optic response. We identify the phonon modes that have a significant contribution to the Pockels response and discuss the microscopic origin of the response. In addition, we analyze the contribution of the converse piezoelectric effect to the Pockels response. We find good agreement when comparing our results to available experiment.

Liquid Piezoelectric Materials: Linear Electromechanical Effect in Fluid Ferroelectric Nematic Liquid Crystals

AbstractThe first demonstration of converse piezoelectricity in 3D fluids is presented by measuring a linear electromechanical effect in ferroelectric nematic liquid crystals. The observed piezoelectric coupling constant below 6 kHz electric field is larger than 1 nC/N, comparable to, or better than, values for the strongest solid piezoelectric materials. Symmetry considerations indicate that the alignment of the ferroelectric nematic liquid crystal in the experimental study is not optimized, so the observed signal is likely only a fraction of the theoretically achievable signal. Understanding the electromechanical response of ferroelectric nematics will enable mechanical energy harvesting and open up a new avenue for developing fluid actuators, micro positioners, and electrically tunable optical lenses.

New [formula omitted]-type localization sets for [formula omitted]-eigenvalues of a piezoelectric-type tensor

The C-eigenvalues of piezoelectric-type tensors play an important role in piezoelectric effect and converse piezoelectric effect. By breaking N={1,2,…,n} into disjoint subsets S and S¯, He et al. (2021) provided an S-type inclusion set to locate all C-eigenvalues of a piezoelectric-type tensor. In this paper, we give two new S-type localization sets for C-eigenvalues of a piezoelectric-type tensor. Moreover, the theoretical comparisons of these localization sets are established. Finally, numerical experiments are performed to show the effectiveness of the main results.

NON-LINEAR MODEL OF A RECUPERATIVE SHOCK ABSORBER

This article examines the rationale for using a shock absorber with the function of recuperating mechanical energy into electrical energy. Current trends in the transport industry, regarding the need to use autonomous power sources in the transport infrastructure, are considered. This direction is promising due to the replacement of vehicles with internal combustion engines by electric transport, as well as the need for autonomous power supply of individual nodes and aggregates. The need for autonomy emerges acutely in the conditions of the energy crisis, and at the same time, the lack of energy resources. Special attention is paid to energy recovery using the direct and conversepiezoelectric effect. The structure, chemical and physical properties, principle of operation and practical application of piezoceramic transducers, and the possibility of their use as energy harvesters (generators) are considered. The considered scientific and technical problem, which consists in determining the nature of the negative impact of various types of external oscillations on the functioning of structural elements of vehicles, to reduce which various shock absorbers or dampers are used. This work considers the use of a recuperative shock absorber of vibration loads with the use of a piezoelectricenergy harvester as a converter of mechanical energy of vibrations into electrical energy. Piezoceramic inserts are used as an energy collector in the design of an automobile hydraulic shock absorber. An assessment of the efficiency of recuperation and conclusions regarding the feasibility of use and implementation are provided. The shock absorbers which are installed to absorb vibrations consume a large amount of mechanical energy, converting it into heat which is dissipated into the atmosphere. This energy, without reducing the efficiency of functioning, can be beneficially used by using a piezoelectric generator with piezoelectric ceramics to convert mechanical energy into electrical energy.

Compositional Modification of Epitaxial Pb(Zr,Ti)O3 Thin Films for High‐Performance Piezoelectric Energy Harvesters

AbstractIn this study, Piezoelectric energy harvesters (PEHs) are fabricated based on epitaxial Pb(Zr,Ti)O3 (PZT) thin films deposited by an RF magnetron sputtering with varied Zr/[Zr+Ti] ratio. For a compatibility with micro‐electromechanical systems, the epitaxial PZT thin films are deposited on Si substrates (PZT/Si). The morphotropic phase boundary (MPB) are formed in the compositional range of 0.44 ≤ Zr/[Zr+Ti] ≤ 0.51 of the epitaxial PZT/Si, which is far broader than that of the bulk PZT. Meanwhile, effective transverse piezoelectric coefficient (|e31,f|) values are evaluated by the direct and converse piezoelectric effects using the unimorph cantilever method. Among the compositions, the rhombohedral‐dominant MPB (MPB‐R) of Zr/[Zr+Ti] = 0.51 exhibits a direct |e31,f| of 10.1 C m−2 and a relative permittivity (εr) of 285, leading to the maximum figure of merit of 40 GPa in this study. On the other hand, the maximum converse |e31,f| of 14.0 C m−2 is measured from the tetragonal‐dominant MPB (MPB‐T) of Zr/[Zr+Ti] = 0.44. At a resonance frequency, the MPB‐T presents a high output power density of 301.5 µW−1/(cm2 g2) under an acceleration of 3 m−1 s−2, which is very promising for the high‐performance PEH applications.

A Biomimetic Piezoelectric Composite‐Driven Undulation Underwater Robotic Structure: Characteristic Analysis and Experimental Investigation

Numerous proposals and recommendations have been made in the development of underwater undulation robots, but very few studies have focused on the undulation characteristics of undulation robots. The undulating mode of the clearnose skate utilizing the activation of the pectoral fins in undulatory bursts is particularly suitable for slow and efficient swimming. Inspired by the working principle of the clearnose skate, herein, an undulation robotic structure is presented. Considering the hydrodynamic skeleton and propulsion mechanism of the clearnose skate, the solution is based on a piezoelectric composite for realizing undulatory propulsion. This approach leverages the converse piezoelectric effect and modal coupling to produce the desired undulating motion, thereby achieving the undulation design of the robot. The proposed robotic structure can realize the propulsion mode using piezoelectric composites to undulate in the same direction and can use the clockwise or counterclockwise undulation of piezoelectric composites to achieve the steering mode. In addition, finite element analysis is employed as an approach to investigate the undulation characteristics and transient vibration characteristics of the robot. The operational efficiency of the robotic structure is assessed through experiments. The results show that the propulsion mode achieves the speed of 3.33 body‐length s−1. The steering mode exhibits the steering velocities of 17.4 deg s−1.

Tunable dynamic microwave properties of a magnetic skyrmion manipulated by strains

In this paper, we theoretically studied the tunable dynamic microwave properties of a magnetic skyrmion manipulated by strains through micromagnetic simulations. The strains are induced by voltage due to the converse piezoelectric effect and then applied to modulate the dynamic characteristics through the magneto-elastic coupling effect. The tunable dynamic microwave characteristics of a breathing mode and gyration modes are investigated. The resonant frequency of the breathing mode increases abruptly and then decreases slowly with the strain changing from compressive to tensile. A clockwise gyrotropic mode has been obtained, and the resonant frequency keeps increasing with the strain changing from compressive to tensile. In particular, strains can induce different gyrotropic trajectories of the skyrmion driven by an in-plane microwave field. Our results may contribute to the understanding of dynamic properties of skyrmions manipulated by voltage-induced strains and provide a method to realize tunable spintronic microwave devices based on skyrmion.

The influence of Bi nonstoichiometry on the depolarization temperature in lead-free piezoelectric Na0.5Bi0.5+xTiO3+1.5x

The influence of Bi-nonstoichiometry of Na0.5Bi0.5+xTiO3+1.5x (NBT) on the depolarization temperature Td was investigated by in-situ direct piezoelectric measurements (d33) and Resonant Piezoelectric Spectroscopy (RPS). For the latter measurements, the converse piezoelectric effect was used to determine the temperature dependence of the piezoelectric effect and elastic modulus. The composition x = 0.01 shows Td = 137 °C, whereas in x = 0 and x = 0.015 Td = 177 °C. The composition with x = 0 has defects, such as oxygen/bismuth vacancies, related to the loss of Bi2O3 that occurs during high temperature sintering, such as oxygen/bismuth vacancies. At x = 0.01, these defects are minimized via the compensation of Bi2O3 loss, whereas x = 0.015 contains excess Bi2O3. This indicates that minimization of defects decreases Td, while higher Td values are attributed to the shift of the transition temperature between the rhombohedral and the intermediate phases.

Synergy of morphotropic phase boundary and internal bias fields to achieve high d33 and d33* simultaneously in lead-free BNT-based ceramics

It is difficult to obtain high d33 and d33* simultaneously in one piezoelectric ceramic system via a conventional method due to the conflicting structure–properties responding mechanism between the direct piezoelectric and converse piezoelectric effects. In this work, a synergistic approach of constructing morphotropic phase boundary and introducing the internal bias fields in (Bi0.5Na0.5)TiO3 ceramics is proposed through Sr2+ and Li+ doping for mitigating the conflict between d33 and d33*. By this strategy, both high d33 (197 pC/N) and d33* (1500 p.m./V) are realized in Srx(Bi1-xNa0.97-xLi0.03)0.5TiO3 when x = 0.24. The large d33 stems from rhombohedral and tetragonal (R3c and P4bm) phase coexistence. The internal bias field introduced by defect dipoles tends to counteract the effects of depolarization field, thus greatly aiding the external fields with higher actual excitation fields. The superposition of internal bias field, depolarization field and external fields yields strong asymmetry bipolar strain curves, thereby contributing to the large d33*. Thus, this work opens a new door for developing lead-free ceramics with excellent piezoelectric performance.

(Keynote) The Piezoelectric Effect and Ionic Liquids

We have studied the response of room temperature ionic liquids to surface charge and had found the establishment of a free charge density gradient, ρf , in these materials that persists for ca. 50 μm (e-1 depth). We have also applied mechanical force to room temperature ionic liquids with the resulting development of a potential across the ionic liquid when contained in a vessel. These two effects are manifestations the converse and direct piezoelectric effects, respectively. For the converse piezoelectric effect, the induced gradient is seen to be ca. 100 μC/cm3/μm and for the direct piezoelectric effect, the relationship between force applied and potential developed is ca. 16 mV/N. We will discuss the observation of the direct piezoelectric effect in the liquid phase and its possible utility.

Modelling of fatigue damage in granitic rock by piezoelectric effect in quartz phase due to alternating current excitation

This paper considers numerical modelling of hypothetical fatigue damage in granitic rock by alternating current (AC) excitation of piezoelectric properties of Quartz. For this end, a numerical method consisting of a rock mineral mesostructure model, an implicit time stepping scheme to solve the piezoelectro-mechanical problem, and a fatigue damage model was developed. The rock material was assumed to be heterogenous linear elastic and isotropic, save the Quartz piezoelectric properties, which are anisotropic. An evolution equation-based continuum scalar damage model based on an evolving back stress tensor and a moving Drucker–Prager type of endurance surface was applied to compute the damage inflicted by the AC excitation. The damage was computed in a post-processed mode, i.e., un-coupled to the material model, at this stage of investigations. Some preliminary axisymmetric simulations are presented with a rock mesotructure based on electron backscatter diffraction data. These simulations corroborate the hypothesis that fatigue damage can be induced on granitic rock by converse piezoelectric effect in the Quartz phase by sinusoidal alternating current. More specifically, fatigue damage was induced on a disc-shaped numerical rock sample at a voltage of 15 kV with 2.5 kHz of frequency.

Fuzzy logic based active vibration control using novel photostrictive composites

Although conventional actuators like piezoelectric and electrostrictive are efficient, but they required hard wiring, which contaminates the control signal and adds to the weight of the structure. The current study presents a wireless control strategy using photostrictive actuators. Owing to the fortunate combination of photovoltaic effect and converse piezoelectric effect, a photostrictive actuator can generate mechanical strain, when irradiated with light intensity. Limited choices of photostrictive material with high electromechanical coupling coefficient give the motivation to design photostrictive composites. The finite element-based formulation incorporating fuzzy logic controller is employed to study the active vibration control response of cantilever structure when equipped with photostrictive composite actuator. A parametric study has been carried out to study the influence of inclusion’s volume fraction on wireless active vibration control of the structure. Control merits have been defined to compare the control performance of different composites. It is found that particulate composites are the better choice for lightweight structure and fiber composites are better if there is no weight constraint.

Ultrafast Optomechanical Strain in Layered GeS

Strong coupling between light and mechanical strain forms the foundation for next-generation optical micro- and nano-electromechanical systems. Such optomechanical responses in two-dimensional materials present novel types of functionalities arising from the weak van der Waals bond between atomic layers. Here, by using structure-sensitive megaelectronvolt ultrafast electron diffraction, we report the experimental observation of optically driven ultrafast in-plane strain in the layered group IV monochalcogenide germanium sulfide (GeS). Surprisingly, the photoinduced structural deformation exhibits strain amplitudes of order 0.1% with a 10 ps fast response time and a significant in-plane anisotropy between zigzag and armchair crystallographic directions. Rather than arising due to heating, experimental and theoretical investigations suggest deformation potentials caused by electronic density redistribution and converse piezoelectric effects generated by photoinduced electric fields are the dominant contributors to the observed dynamic anisotropic strains. Our observations define new avenues for ultrafast optomechanical control and strain engineering within functional devices.

Ionic Liquids Exhibit the Piezoelectric Effect.

The piezoelectric effect was discovered over a century ago, and it has found wide application since that time. The direct piezoelectric effect is the production of charge upon application of force to a material, and the converse piezoelectric effect is a change in the material dimension(s) upon the application of a potential. To date, piezoelectric effects have been observed only in solid-phase materials. We report here the observation of the direct piezoelectric effect in room-temperature ionic liquids (RTILs). The RTILs 1-butyl-3-methyl imidazolium bis(trifluoromethyl-sulfonyl)imide (BMIM+TFSI-) and 1-hexyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide (HMIM+TFSI-) produce a potential upon the application of force when confined in a cell, with the magnitude of the potential being directly proportional to the force applied. The effect is one order of magnitude smaller than that seen in quartz. This is the first report to our knowledge of the direct piezoelectric effect in a neat liquid. Its discovery has fundamental implications about the organization and dynamics in ionic liquids and invites theoretical treatment.

Picometer measurements of strain coefficients by quadrature interferometry and lock-in amplification

Modulated strain displacements were measured with a quadrature Michelson–Morley interferometer employing polarization optics and two lock-in amplifiers to filter noise and thermal drift. The advantages of the technique, its limitations, and estimates on the accuracy are discussed, including an algorithm to correct for non-ideal components and non-linear effects. Instructions for the construction and setup of the quadrature interferometer are provided. To test the interferometer, the dynamic converse piezoelectric effect was used, and by modulating the electric field across the sample, the d14 strain coefficient for x-cut quartz was determined to be 0.66±0.04 pC/N, which is within 1.5 standard deviations of the accepted standard. The measurements had a standard deviation of 4.1 pm, resulting in standard errors as low as 5 fm/V after fitting.

Shifted power method for computing the largest C-eigenvalue of a piezoelectric-type tensor

In crystallography, piezoelectric tensors of various crystals play a crucial role in piezoelectric effect and converse piezoelectric effect. The largest C-eigenvalue of a piezoelectric tensor corresponds to the electric displacement vector with the largest 2-norm in the piezoelectric effect under unit uniaxial stress, and the strain tensor with the largest 2-norm in the converse piezoelectric effect under unit electric field vector. In this paper, we propose a shifted power method for computing the largest C-eigenvalue and give its convergence analysis. Numerical examples show that the shifted power method is really efficient in practice.

Fabrication and Characterization of Piezoelectric Polymer Composites and Cytocompatibility with Mesenchymal Stem Cells.

Piezoelectric materials are promising for biomedical applications because they can provide mechanical or electrical stimulations via converse or direct piezoelectric effects. The stimulations have been proven to be beneficial for cell proliferation and tissue regeneration. Recent reports showed that doping different contents of reduced graphene oxide (rGO) or polyaniline (PANi) into biodegradable polyhydroxybutyrate (PHB) enhanced their piezoelectric response, showing potential for biomedical applications. In this study, we aim to determine the correlation between physiochemical properties and the in vitro cell response to the PHB-based composite scaffolds with rGO or PANi. Specifically, we characterized the surface morphology, wetting behavior, electrochemical impedance, and piezoelectric properties of the composites and controls. The addition of rGO and PANi resulted in decreased fiber diameters and hydrophobicity of PHB. The increased surface energy of PHB after doping nanofillers led to a reduced water contact angle (WCA) from 101.84 ± 2.18° (for PHB) to 88.43 ± 0.83° after the addition of 3 wt % PANi, whereas doping 1 wt % rGO decreased the WCA value to 92.56 ± 2.43°. Meanwhile, doping 0.2 wt % rGO into PHB improved the piezoelectric properties compared to the PHB control and other composites. Adding up to 1 wt % rGO or 3 wt % PANi nanofillers in PHB did not affect the adhesion densities of bone marrow-derived mesenchymal stem cells (BMSCs) on the scaffolds. The aspect ratios of attached BMSCs on the composite scaffolds increased compared to the PHB control. The study indicated that the PHB-based composites are promising for potential applications such as regenerative medicine, tissue stimulation, and bio-sensing, which should be further studied.