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As an emerging sensor technology, the flexible piezoelectric sensor has a very wide range of applications. Therefore, in order to achieve better output performance of flexible piezoelectric sensors, it is particularly important to choose piezoelectric materials with good piezoelectric performance. In this study, polyvinylidene difluoride (PVDF)/polyvinyl chloride (PVC)/graphene oxide (GO) composite fibers were fabricated by the electrospinning technique. FTIR and XRD studies showed that the β-phase content of the composite fibers reached 94.6% with the addition of PVC and GO. The mechanical properties of the composite films doped with PVC and GO were also significantly improved. The sensitivity of the sensor made of composite fibers doped with 0.2 % GO reached 16.2 V/N in the range of 1 N. Compared to other systems, the PVDF/PVC/GO system showed excellent piezoelectric output performance with output voltages of up to 6 V and 3 μA by the action of palm tapping. And after 2000 cycles, the sensor system showed good stability. The resulting flexible piezoelectric sensor can monitor actions such as impacts and bending and has great potential for motion monitoring. [ABSTRACT FROM AUTHOR]

The applications of piezoelectric materials in the field of smart structures have received significant attention from both the communities of science and engineering. Numerous experimental studies have been carried out to endow smart structures with good flexibility. The flexible/stretchable piezoelectric materials are developed to fit this emerging trend. Generally, these materials undergo significant deformation before reaching fracture failure, and they often exhibit a stress-softening phenomenon during the deformation process. However, the traditional linear constitutive model, typically used for rigid piezoelectric ceramics, continues to dominate theoretical and modeling processes in many scenarios. Existing nonlinear constitutive models usually introduce additional coefficients besides elastic, piezoelectric, and dielectric coefficients. Determining these coefficients requires a substantial number of experiments. In this work, based on a Neo-Hookean material model and electromechanical theory, a novel model for flexible piezoelectric material considering large deformation has been established. In contrast with existing models, the present model describes the nonlinear behavior of flexible piezoelectric material without the need for introducing additional parameters. Furthermore, this model exhibits a quadratic dependence of stress on the electric field. To facilitate practical applications, the constitutive model has been implemented using the commercial simulation software ABAQUS through a user subroutine. The accuracy of the subroutine is validated by comparing simulations with analytical solutions for uniaxial stretching of a flexible piezoelectric ribbon. Several numerical examples are followed to demonstrate the robustness of the elements. The proposed model offers a valuable tool for the analysis and design of flexible piezoelectric material. [ABSTRACT FROM AUTHOR]

Piezoelectric materials have been proposed as embedded power source, which are capable of converting mechanical energy into electrical energy. However, power generated from a piezoelectric material usually comes with poor characteristics such as high voltage, low current and high impedance. In order to drive the embedded sensor circuit, piezoelectric power needs to be characterized and regulated. In this paper, we present an analysis on the power generation characteristics of the stiff lead zirconate titanate (PZT) ceramics and its equivalent circuit. It is then verified by simulation and experimental results. Since a single PZT element may not meet the needs of real-world embedded applications, we present experiments and analysis using four identical PZTs. Finally, we outline an application where PZT elements are used for power generation in a Total Knee Replacement (TKR) implant. [ABSTRACT FROM AUTHOR]

This research explored the impact of four different electrolytes on the orientation of cellulose nanocrystals (CNCs) in shear-cast films prepared from aqueous CNC gels. Changes in the aqueous CNC gels' rheological properties with electrolyte addition were correlated to the orientation and optical properties of dried CNC films. Film alignment was qualitatively assessed using cross-polarized optical microscopy and quantified by order parameters computed by UV–Vis transmission spectroscopy. Electrolyte addition resulted in an increased alignment in dried CNC films. For pure CNCs, the film order parameters remained constant at approximately 0.3 for shear rates from 20 s−1 to 100 s−1. However, higher order parameters were achieved in the presence of electrolytes. Notably, an order parameter of 0.88 was achieved at a shear rate of only 20 s−1. In addition, films produced from dispersions containing electrolytes exhibited improved clarity and haze. The results of this work highlight that electrolyte addition can enable higher order parameters at lower shear rates and facilitate the development of aligned CNC films for applications such as polarizers, clear coatings, and piezoelectric materials. [ABSTRACT FROM AUTHOR]

Digital light processing (DLP) is a projection-based vat photopolymerization 3D printing technique that attracts increasing attention due to its high resolution and accuracy. The projection-based layer-by-layer deposition in DLP uses precise light control to cure photopolymer resin quickly, providing a smooth surface finish due to the uniform layer curing process. Additionally, the extensive material selection in DLP 3D printing, notably including existing photopolymerizable materials, presents a significant advantage compared with other 3D printing techniques with limited material choices. Studies in DLP can be categorized into two main domains: material-level and system-level innovation. Regarding material-level innovations, the development of photocurable resins with tailored rheological, photocuring, mechanical, and functional properties is crucial for expanding the application prospects of DLP technology. In this review, we comprehensively review the state-of-the-art advancements in DLP 3D printing, focusing on material innovations centered on functional materials, particularly various smart materials for 4D printing, in addition to piezoelectric ceramics and their composites with their applications in DLP. Additionally, we discuss the development of recyclable DLP resins to promote sustainable manufacturing practices. The state-of-the-art system-level innovations are also delineated, including recent progress in multi-materials DLP, grayscale DLP, AI-assisted DLP, and other related developments. We also highlight the current challenges and propose potential directions for future development. Exciting areas such as the creation of photocurable materials with stimuli-responsive functionality, ceramic DLP, recyclable DLP, and AI-enhanced DLP are still in their nascent stages. By exploring concepts like AI-assisted DLP recycling technology, the integration of these aspects can unlock significant opportunities for applications driven by DLP technology. Through this review, we aim to stimulate further interest and encourage active collaborations in advancing DLP resin materials and systems, fostering innovations in this dynamic field. [ABSTRACT FROM AUTHOR]

Extensive research has focused on green and renewable energies to address the increasing demand for flexible, reliable, and self-sustaining advanced technology and electrical supplies. Piezoelectric nanogenerators (PENGs) have garnered significant interest as a pioneering energy-harvesting technology, due to their notable advancements and capacity to effectively capture and convert mechanical energy from the environment into electrical power. This review article seeks to cover the latest developments and innovations in piezoelectric materials for PENG applications. It explores key topics, such as the strategic selection of piezoelectric materials to optimize energy-harvesting efficiency, advancements in fabrication techniques, and the evaluation of PENGs performance. Throughout this manuscript, critical points are highlighted that require further investigation in the field of high-performance piezoelectric material fabrication. Ongoing research is crucial for improving the flexibility and durability of functional materials, thus advancing the development of superior electronic devices with enhanced piezoelectric properties. Furthermore, addressing enhancements in the electromechanical properties of current piezoelectric materials is imperative. This review article aims to support researchers in their quest for a comprehensive understanding of piezoelectric mechanisms and offers valuable insights for the progression and refinement of PENGs, which have broad potential applications. An overview of the PENGs applications, piezoelectric materials selection, fabrication methods and PENGs performance discussed in this review paper. [ABSTRACT FROM AUTHOR]

Piezoelectric devices exhibit unique properties that vary with different vibration modes, closely influenced by their polarization direction. This paper presents an analysis on the free vibration of laminated piezoelectric beams with varying polarization directions, using a state-space-based differential quadrature method. First, based on the electro-elasticity theory, the state-space method is extended to anisotropic piezoelectric materials, establishing state-space equations for arbitrary polarized piezoelectric beams. A semi-analytical solution for the natural frequency is then obtained via the differential quadrature method. The study commences by examining the impact of a uniform polarization direction, and then proceeds to analyze six polarization schemes relevant to the current research and applications. Additionally, the effects of geometric dimensions and gradient index on the natural frequencies are explored. The numerical results demonstrate that varying the polarization direction can significantly influence the natural frequencies, offering distinct advantages for piezoelectric elements with different polarizations. This research provides both theoretical insights and numerical methods for the structural design of piezoelectric devices. [ABSTRACT FROM AUTHOR]

The mechanic-electro coupling overlapping finite element method (OFEM) is proposed to improve the accuracy in solving the mechanical characteristics of piezoelectric structures. Based on the basic equations and boundary conditions of piezoelectric materials, overlapping triangle elements are used to discretize the solution domain of piezoelectric structures, and the displacement function and potential function of the mechanic-electro coupling OFEM are constructed through local interpolation. The control equation of the mechanic-electro coupling OFEM is derived using the variation principle. The accuracy and validity of this method are verified by comparing with the reference solution and analytical solution in patch test and piezoelectric patch bending test. The static characteristics of the cantilever-typed piezoelectric sensor model, the rectangular plate with one-sided piezoelectric patch configuration, and the hole-containing piezoelectric energy harvester model are analyzed. The mechanic-electro coupling OFEM has high engineering value and broad application prospects in analyzing the structural mechanical properties of intelligent piezoelectric components. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric materials have gained considerable attention due to their remarkable properties, including electromechanical coupling and high stretchability. These characteristics make them valuable in the realm of flexible electronic devices. However, the issue of fracture in these materials cannot be ignored. In general, these flexible/stretchable materials experience fractures when subjected to significant deformation, unlike brittle piezoelectric materials with low failure strain which have been extensively studied. There is a pressing need to investigate the fracture behavior of flexible piezoelectrics under finite deformation conditions. Within the framework of the phase field method, this work addresses the fracture of flexible piezoelectrics utilizing a nonlinear electromechanical material model. To investigate the influence of electrical boundary conditions on fracture behavior, a function related to the electric permittivity ratio and phase field variable is employed to degrade the electric energy density. By adjusting the electric permittivity ratio, the analysis encompasses the fracture behavior of flexible piezoelectric materials under the assumptions of electrically impermeable, semi-permeable, and permeable conditions, respectively. In order to solve the coupled governing equations, a residual controlled staggered algorithm (RCSA) is employed in the user element subroutine of commercial software ABAQUS. The simulation results indicate that fracture behavior in flexible piezoelectric materials is influenced by several factors, including material parameters, geometry, polarization direction, and the external electric field. Notably, when the poling direction is perpendicular to the electric field direction, variations in the external electric field have a minimal impact on fracture behavior. In contrast, when the poling direction is parallel to the electric field direction, the influence on fracture behavior is pronounced. These findings provide valuable insights for developing strategies to enhance the fracture resistance and durability of flexible piezoelectric materials in practical applications. [ABSTRACT FROM AUTHOR]

The conversion of ambient mechanical vibrations into electricity using piezoelectric nanogenerators (PENGs) has garnered significant attention from researchers over the past few years, in light of its potential in wearable applications. The high flexibility and significant ferroelectricity of poly(vinylidene fluoride) (PVDF) make them the most promising candidates for PENG applications among polymer piezoelectric materials. In the present work, NiO nanoparticles were incorporated in different ratios into a PVDF matrix, and their potential for use in piezoelectric nanogenerators was investigated. The PVDF/NiO (5 wt.%) nanocomposite PENG exhibited the highest electrical output, with a 2.8-fold increase in open-circuit voltage and short-circuit current observed as compared to a bare PVDF-based PENG. However, a further increase in the compositional ratio of NiO led to a decrease in PENG output. The improved piezoelectricity in the PVDF/NiO (5 wt.%) nanocomposite is attributed to the enhanced polar phases and improved ferroelectricity of PVDF. Further confirmation of the improved piezoresponse was explored by measurement of the piezoelectric coefficient (d33) and dielectric study of the nanocomposites. The PENG electrical output was further simulated using the finite elemental method in COMSOL Multiphysics 5.5. The simulated results matched well with the experimental output, which confirmed the improved electrical performance of the PVDF/NiO nanocomposite-based PENGs. The enhanced performance of the nanocomposite PVDF film is attributed to the higher β phase in the PVDF. The efficiency of the PENG devices in motion-sensing applications was also explored. Different output voltage signals corresponding to different movements of the nanocomposite-based PENGs make the device compatible with sensor applications. [ABSTRACT FROM AUTHOR]

(K,Na)NbO3(KNN)-based ceramics are a promising lead-free piezoelectric material that could replace Pb(Zr1−xTix)O3-based materials due to their higher Curie temperature and superior electrical properties. However, the volatilization of sodium and potassium during conventional high-temperature sintering makes it difficult to obtain KNN ceramics with a dense structure and excellent electrical properties. Herein, a conventional solid-phase method combined with microwave sintering is applied for the preparation of KNN ceramics. The influence of the microwave sintering process on the microstructure and electrical properties of KNN ceramics were studied. The optimal microwave sintering conditions for KNN ceramics were determined to be 1100°C for 50 min. Under these conditions, the ceramic samples exhibited excellent ferroelectric properties, with the maximum polarization (Pmax) of 20.4 μC/cm2 and a remanent polarization (Pr) of 18.1 μC/cm2. Additionally, the samples demonstrated impressive piezoelectric properties, including the maximum electric field-induced strain (Smax) of 0.0251%, a dynamic piezoelectric coefficient (d33*) of 125.5 pm/V, and a piezoelectric coefficient (d33) of 109.8 pC/N. The study has important implications for the use of microwave sintering to achieve the densification of the ceramic with volatile elements such as KNN-based ceramics at lower sintering temperature and short sintering time. [ABSTRACT FROM AUTHOR]

In recent years, driven by the pressing demand for sustainable energy solutions, polyvinylidene fluoride (PVDF), a promising piezoelectric material, has garnered considerable attention for its application in energy-harvesting devices. PVDF stands out as the material of choice in piezoelectric generator technology owing to its remarkable flexibility, superior processability, long-term stability, and biocompatibility. Nevertheless, PVDF-based generators exhibit inferior piezoelectric responses compared to traditional piezoelectric ceramic materials, thereby constraining their performance in large-scale deployments. To address this limitation, researchers have been exploring innovative strategies to enhance the piezoelectric properties of PVDF. Among these, electrospinning technology emerges as a pivotal approach due to its ability to impart mechanical stretching and in situ polarization to the polymer during fabrication. This paper comprehensively reviews recent advancements in optimizing the output performance of PVDF-based piezoelectric nanofiber membranes through the integration of filler doping technology with electrospinning. We delve into the effects of various filler types on the properties of electrospun PVDF-based piezoelectric nanofiber membranes and explore their underlying mechanisms. These fillers significantly bolster the output performance of PVDF-based piezoelectric devices by augmenting PVDF's piezoelectric activity, fostering dipole orientation, and elevating the dielectric constant. Notably, the incorporation of fillers not only elevates the piezoelectric coefficient but also optimizes the microstructure, facilitating an efficient conversion between mechanical and electrical energy. Furthermore, we envision the promising application prospects of PVDF piezoelectric nanofibers in cutting-edge fields, such as health monitoring, environmental monitoring, and energy-harvesting systems. These domains urgently require piezoelectric materials that combine high sensitivity, stability, and cost-effectiveness, where PVDF-based piezoelectric nanofibers, with their distinctive advantages, are poised to demonstrate significant application potential and societal value. [ABSTRACT FROM AUTHOR]

Flexible sensors are in great demand in the field of wearable electronics because of their good softness, stretchability, breathability and structural elasticity. Besides, polyvinylidene fluoride (PVDF) and its copolymers have been considered as promising piezoelectric materials for advanced sensing and excellent biocompatibility. Electrospinning is simple, low cost, and scalable technology that can be used to fabricate PVDF-based nanofibers applied in long-term monitoring or human–computer interaction. In this paper, we initially presented the basic process for preparing PVDF nanofibers, followed by a systematic elaboration on extended electrospinning techniques to facilitate more in-depth research on PVDF-based nanofibers. Then, the enhancements methods were summarized, complemented by some reinforcing mechanisms, novel structures and some solutions for filler agglomeration. Furthermore, the latest applications as wearable sensors were introduced. Potential difficulties, problems and perspectives are also discussed. We hope that this article can help researchers better understand this field and push it to a higher level. [ABSTRACT FROM AUTHOR]

Studies on the piezoelectric materials capable of efficiently outputting high electrostrains at low electric fields are driven by the demand for precise actuation in a wide range of applications. Large electrostrains of piezoceramics in operation require high driving fields, which limits their practical application due to undesirable nonlinearities and high energy consumption. Herein, a strategy is developed to enhance the electrostrains of piezoceramics while maintaining low hysteresis by incorporating lead magnesium niobate relaxors into lead zirconate titanium at the morphotropic phase boundary. An ultrahigh inverse piezoelectric coefficient d 33 * of 1380 pm/V with a reduced hysteresis of 11.5% is achieved under a low electric field of 1 kV/mm, outperforming the major lead-based piezoelectric materials. In situ synchrotron X-ray diffraction and domain wall dynamics characterization with sub-microsecond temporal resolution reveal that the outstanding performances originate from facilitated domain wall movement, which in turn is due to reduced lattice distortion and miniaturized domain structures. These findings not only address the pending challenges of effective actuation under reduced driving conditions but also lay the foundation for a more systematic approach to exploring the origin of large electrostrains. The authors develop an application-oriented low-field actuating piezoceramic via relaxor substitution. Their in situ synchrotron XRD analysis along with domain wall dynamics characterization reveals the mechanisms of outstanding performance. [ABSTRACT FROM AUTHOR]

To improve the efficiency of topology optimization for piezoelectric energy harvesters (PEHs), this paper proposes a discrete level set method enhanced by conformal mapping. By mapping the PEH onto a 2D regular domain, the original 3D topology optimization problem is simplified as a 2D problem by using a scalar function. Then re-meshing and barycentric interpolation theory are used to simplify the solution of the driving equation and resolve the issue of inconsistent discretization between the level set function and the finite element model. Moreover, based on the proposed method, the finite element expression of the piezoelectric shell element is derived, taking into account the piezoelectric material coupling effect and polarization direction. This leads to an accurate numerical solution for the optimization process. Resultantly, numerical examples demonstrate that proposed method enables the optimization using a simple discretization, while effectively preserving surface characteristics of PEHs. Hence, this method offers a new approach for the structural optimization of PEHs. [ABSTRACT FROM AUTHOR]

Broadband vibration attenuation is a challenging task in engineering since it is difficult to achieve low-frequency and broadband vibration control simultaneously. To solve this problem, this paper designs a piezoelectric meta-beam with unidirectional electric circuits, exhibiting promising broadband attenuation capabilities. An analytical model in a closed form for achieving the solution of unidirectional vibration transmission of the designed meta-beam is developed based on the state-space transfer function method. The method can analyze the forward and backward vibration transmission of the piezoelectric meta-beam in a unified manner, providing reliable dynamics solutions of the beam. The analytical results indicate that the meta-beam effectively reduces the unidirectional vibration across a broad low-frequency range, which is also verified by the solutions obtained from finite element analyses. The designed meta-beam and the proposed analytical method facilitate a comprehensive investigation into the distinctive unidirectional transmission behavior and superb broadband vibration attenuation performance. [ABSTRACT FROM AUTHOR]

At present, rigid-flexible coupling systems have been used in various engineering fields extensively, due to task demands, the systems have become complex increasingly, and thus, it is crucial to study the dynamic problems and active control of rigid-flexible coupling systems. Piezoelectric materials with electromechanical coupling phenomenon have great applications in active control of rigid-flexible coupling systems. In the current study, the active control of rigid-flexible coupling rectangular thin plate is investigated based on piezoelectric effect. The dynamic model of rigid-flexible coupling piezoelectric rectangular thin plate is established first using the Hamilton's principle, and its discrete form is obtained using the superposition method. The dynamic equations of the system are numerically solved using the Newmark-β method. The active control of the rigid-flexible coupling system has been carried out. Case studies show that, for rigid-flexible coupling rectangular thin plate, the rigid motion will drive the vibration of flexible thin plate, and the vibration of the flexible thin plate can cause rigid body motion. The piezoelectric patch can achieve active control of rigid body motion and flexible plate vibration simultaneously. The active control effect is related to the distribution position and thickness of the piezoelectric patch, as well as the excitation voltage. The closer the piezoelectric patch is to the edges of the rectangular thin plate, the better the active control effect on the rigid body motion. The closer the piezoelectric patch is to the center of the rectangular thin plate, the better the active control effect on the flexible plate vibration. Furthermore, the thicker the piezoelectric patch, the greater the excitation voltage, and the better the active control effect. The conclusion of the current work has direct and important engineering applications. [ABSTRACT FROM AUTHOR]

In this work, the sound transmission loss (STL) of a simply supported doubly curved shallow aluminum shell covered by two layers of piezoelectric material, PZT-5H is presented. The study takes into account the presence of uncertain ambient temperature which is shown to significantly affect piezoelectric control of sound transmission. To derive the equations of motion, the assumed mode method combined with the first-order shear deformation theory and Hamilton's principles are employed. The modeling process incorporates the ambient temperature and thoroughly investigates its effects on STL, vibrational displacement, and piezoelectric voltage in terms of thermal strain, piezoelectric constants, and the pyroelectric coefficient uncertainties. Results show that uncertainty in environmental temperature significantly affects STL uncertainty up to 10% and vibrational displacement of the shell to the 15 times of its lowest value. The piezoelectric voltage also fluctuates with the variation in the temperature in a maximum range of 0.12–5.2 Volt. Further, the piezoelectric sensing voltage which accounts for the piezoelectric sensor thickness is observed to be highly sensitive to the temperature uncertainty with a maximum range of 0.65–7.6 Volt, causing depolarization and hysteresis nonlinearity. Thus, environmental temperature variation is considered as one of the main uncertain aspects for robust sound transmission controller. The proposed study provides an insightful investigation for robust piezoelectric control of STL in the presence of thermal uncertainty. [ABSTRACT FROM AUTHOR]

Hierarchical Bi2Fe4O9/BiOI S-scheme nanoflower heterostructures are prepared by hydrothermal method, which exhibit exceptional photo-piezoelectric catalytic performance. The tight binding between the sheets ensures the efficient electron transport, and provides a large interface area and adequate reaction sites for photo-piezoelectric catalytic reactions. At the same time, because the water flow in the water body produces hydraulic shear force on the material, the material produces piezoelectric effect. Bi2Fe4O9/BiOI exhibit a remarkable degradation efficiency of 99.4% for tetracycline and a hydrogen production rate of 4089.36 µmol h−1 g−1. The observed behavior can be explained by the combined influence of the formation of S-scheme structure and the process of photo-piezoelectric catalysis, confirmed by in-situ XPS, transient/steady-state fluorescence and piezoelectric response force test. The excellent stability of the material suggests its possible use in the sectors of energy and environment. This work introduces novel concepts for the future advancement of photo-piezoelectric synergistic catalysis. [ABSTRACT FROM AUTHOR]

The study reviews the current progress in the sol-gel method for the synthesis of ferroelectric powders, thin films, and rods in the lead zirconate-titanate system. In addition, it examines methods for obtaining controlled particle morphology, primarily rod-like. The synthetic approaches in the sol-gel process and heat treatment conditions for obtaining lead zirconate-titanate ceramics of pre-defined morphology are the primary focus of the present review. [ABSTRACT FROM AUTHOR]

This work presents the development of a two-way coupled flexoelectric plate theory starting from a 3D gradient electromechanical theory. The gradient electromechanical theory considers three mechanical length scale parameters and two electric length scale parameters to account for both mechanical and electrical size effects. Variational formulation is used to derive the plate governing equations and boundary conditions considering Kirchhoff's assumptions. A computationally efficient C 2 continuous non-conforming finite element is developed to solve the resulting plate equations. To assess the accuracy of the non-conforming finite element framework, the results are compared with Navier-type analytical solution for a simply supported flexoelectric plate. The finite element framework is also validated with experimental results in the existing literature for a passive micro-plate. The results show excellent agreement with both analytical and experimental results. Furthermore, computational efficiency of the non-conforming element is compared with the standard conforming element, which contains greater degrees of freedom and continuity across all elemental edges. It was observed that the non-conforming element is almost twice as fast as the conforming element without a significant loss of accuracy. The 2D finite element formulation is subsequently used to analyze the size-dependent response of flexoelectric composite plates operating in both sensor and actuator modes. Various parametric studies are performed to analyze the effect of boundary conditions, length scale parameters, size of the plate, flexoelectric layer thickness ratio, etc., on the response of flexoelectric plate-type sensors and actuators. It is found that the effective electromechanical coupling increases in a flexoelectric plate at microscale (due to the size effects), and it is higher than standard piezoelectric materials for plate thickness h ≤ 8 μ m. [ABSTRACT FROM AUTHOR]

Over time, industrialization, population expansion, building, and other human-related activities have made water contamination a major problem. As a result, steps towards waste water treatment must be taken. By using piezoelectric materials in the purifying process, a new area of waste water treatment known as piezo-photocatalysis has emerged. To improve the material's water purification effectiveness, the piezoelectric action is paired with sun irradiation in this case. Up until this point, photocatalysis has served as a sophisticated method for purification. Thus, the piezoelectric materials became the center of attention in the quest for cutting-edge technologies for water purification. Piezoelectric materials have other potential applications outside of water treatment, including hydrogen production and carbon dioxide adsorption. The lead, barium, KNN, and bismuth perovskite compounds that have seen extensive usage in wastewater treatment are covered in this paper. These materials have the potential to achieve an efficiency of almost 100% when they combine the effects of piezoelectricity with photocatalysis. Consequently, the function of piezoelectric materials in wastewater treatment and the mechanism of piezo-photocatalysis are covered extensively in this paper. [ABSTRACT FROM AUTHOR]

Ferroelectrics are essential in memory devices for multi-bit storage and high-density integration. Ferroelectricity mainly exists in compounds but rare in single-element materials due to their lack of spontaneous polarization in the latter. However, we report a room-temperature ferroelectricity in quasi-one-dimensional Te nanowires. Piezoelectric characteristics, ferroelectric loops and domain reversals are clearly observed. We attribute the ferroelectricity to the ion displacement created by the interlayer interaction between lone-pair electrons. Ferroelectric polarization can induce a strong field effect on the transport along the Te chain, giving rise to a self-gated ferroelectric field-effect transistor. By utilizing ferroelectric Te nanowire as channel, the device exhibits high mobility (~220 cm2·V−1·s−1), continuous-variable resistive states can be observed with long-term retention (>105 s), fast speed (<20 ns) and high-density storage (>1.92 TB/cm2). Our work provides opportunities for single-element ferroelectrics and advances practical applications such as ultrahigh-density data storage and computing-in-memory devices. Authors find room-temperature ferroelectricity in single element Te nanowires, highlighting that reducing dimensions to 1D in low-dimensional piezoelectric materials with chain structures is an effective strategy to induce ferroelectricity absent in their 2D form. [ABSTRACT FROM AUTHOR]

The piezotronics effect utilizes a piezopotential to modulate and control current in piezo-semiconductors. Ferroelectric materials, as a type of piezoelectric materials, possess piezoelectric coefficients that are significantly larger than those found in conventional piezoelectric materials. Here, we propose a strain modulated ferroelectric field-effect transistor (St-FeFET) utilizing external strain instead of gate voltage to achieve ferroelectric modulation, which eliminates the need for gate voltage. By applying a very small strain (0.01%), the St-FeFET can achieve a maximum on-off current ratio of 1250% and realizes a gauge factor (GF) of 1.19 × 106, which is much higher than that of conventional strain sensors. This work proposes a new method for realizing highly sensitive strain sensors and presents innovative approaches to the operation methods of ferroelectric field-effect transistors as well as potential applications for coupling of strain sensors and various devices across different fields. [ABSTRACT FROM AUTHOR]

Piezoelectric actuator (PEA) is widely applied in the field of micro/nano high precision positioning. However PEA has the phenomenon of hysteresis non-linearity between input voltage and output displacement, owing to the natural property of piezoelectric materials. The PEA hysteresis can be compensated by the hysteresis models and control methods, which make the input voltage and output displacement more linearity. The research work on tracking control of PEA trajectories by using various feedforward-feedback controller has been being a hot topic. This paper presents a feedforward-feedback controller based on the modified Prandtl–Ishlinskii (PI) (MPI) model and submodel and the incremental proportional-integral–differential(IPID) controller for tracking control the trajectories of PEA. The polynomial model is adopted as submodel, and parameters of MPI model and submodel are calculated by matlab optimization tool box. The proposed hybrid controller is compiled by C language in VC + + environment. A series of comparative experiments are validated on a platform of commercial PEA. Comparing with the classical PI model, Bouc-Wen model, and other MPI models based IPID controller, the proposed hybrid controller has better control performance. According to the experimental results of the sinusoidal and triangular trajectories of different peaks and the mix sinusoidal and triangular trajectories, the proposed hybrid control method is feasible and effective in improving the tracking control accuracy of PEA trajectories. [ABSTRACT FROM AUTHOR]

This study examines the use of piezoelectric materials/patches for passive, active, and hybrid repairs of a double-edged cracked plate. The study considers the stiffness effect of the piezoelectric patch for passive repair, the actuation effect of piezoelectric materials for active repair, and their combination as hybrid repair. The analytical model for cracked structures is developed using linear elastic fracture mechanics, which calculates the stress intensity factor (SIF) for various repair techniques under constant tensile load. The passive effect of the piezoelectric patch is determined using Rose's equations, while the stress produced by the piezoelectric material is computed using the weight function method. The fatigue life cycle for various repair configurations is determined under cyclic tensile loading using the Paris law with a stress ratio (R) of 0.1 and different voltage ratios (VR). The model is verified with experimental results and analytical fatigue life with FE solutions using ABAQUS software. It is to be noted that an analytical model is developed for the first time to account for both passive and active repairs, i.e., hybrid repair, and to verify the efficacy of the model using published experimental and FE solutions using ABAQUS. A parametric study is conducted to choose the best-sized piezoelectric actuator/patch, voltage, and voltage ratio. The results show a significant reduction in Mode-I SIF for all repair cases, with hybrid repair achieving the greatest reduction and extending fatigue life by 174.88, 116.23, and 37.92% as compared to without repair, active, and passive repairs, respectively, under 500 V with zero VR application. [ABSTRACT FROM AUTHOR]

The goal of this research article is to investigate the effects of using two-dimensional functionally graded materials on the performance of piezoelectric sensors/actuators when subjected to simultaneous complex loading conditions. The considered disc-shaped sensors/actuators have nonuniform thicknesses and undergo asymmetric hygro-thermo-electro-mechanical loading. A power-law model is used to grade the materials radially, whereas the cosine function, which includes two independent parameters, describes the pattern along the circumferential direction. Comparing the results obtained by using the finite element method with those of one-dimensional graded structures leads to promising outcomes. For example, the radial displacement exhibits vital changes that varied between - 13 and 31 % . This is beneficial for such structures in terms of enhancing their sensing/actuating abilities. Also, the tangential stress can be reduced substantially by about 39.5 % through the proper selection of the corresponding material parameters. In addition, this reduction of the tangential stress has a positive effect on the von Mises stress that can be decreased by nearly 33 % . Accordingly, the structure would have improved durability and sustain higher loads. These findings would revolutionize the manufacturing of smart structures and enhance their behaviors under severe conditions. [ABSTRACT FROM AUTHOR]

In recent years, the demand for sustainable and degradable materials and electronic devices has increased significantly. Among a range of biodegradable polymers, poly(lactic acid) (PLA) is a good alternative to conventional petrol-based polymers because of its attractive mechanical properties and its easy processability. Recently, PLA has also been described as a promising dielectric material with piezoelectric and electret properties. We expect that PLA—after further optimization—will play an important role as a material for environmentally friendly sensors in the future, where first applications such as air filters and pressure sensors have already been proposed. However, degradation under normal ambient conditions is very slow, and an accelerated and controllable degradation process is highly desirable for any type of PLA-based sensors. Enzymatic hydrolysis with embedded enzymes has been proposed as an approach to accelerate and control degradation. In this work, we investigate the properties of PLA in terms of dielectric and mechanical properties with a focus on its ability to store charges after the enzyme proteinase K (Trit. album) has been incorporated. Results reveal that proteinase K has a positive effect on the charge stability of solvent-cast PLA electrets after complete evaporation of the solvent. Furthermore, we observed a concentration-dependent acceleration of mass loss in a Tris-HCl buffer. A fast degradation within only one day occurred at a concentration of 6 wt% proteinase K. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive exploration of the role of smart materials, specifically triboelectric and piezoelectric materials, in the context of human-integrated healthcare systems. The study begins by elucidating the fundamentals of smart materials in healthcare, providing a detailed definition and characteristics of these materials and underscoring their paramount importance in advancing healthcare technologies. The research approach employed in this study involves a combination of literature review, experimental investigation, and computational modeling to analyze the potential of smart materials in healthcare applications. The subsequent sections delve into the individual contributions of triboelectric and piezoelectric materials in healthcare systems, outlining their unique attributes and potential applications. Eventually, real-world implementation challenges, such as scaling p production, ensuring stability, and establishing ethical deployment protocols, are meticulously examined. [ABSTRACT FROM AUTHOR]

Re-poling of unexpected partially depoled piezoelectric materials conventionally needs to be first fully depoled through annealing above their Curie temperature to revive piezoelectric performances. Here, we investigated de-poling and re-poling of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals under electric fields at room temperature. We found that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to successfully depolarize poled crystals at room temperature. We also demonstrated a reversible polarization switching process with a relaxor-PbTiO3 single crystal ultrasound transducer without device performance degradations. This experimental observation is supported by phase-field simulation, showing that alternating current electric fields can readily induce de-poling at room temperature, while direct current electric fields induce a transient depoled state only within an uncontrollable short period of time. The findings suggest new strategies for unprecedented in-device tailoring of the polarization states of ferroelectric materials. The authors find that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to depolarize poled relaxor-PbTiO3 single crystals at room temperature, without conventional heat treatment. [ABSTRACT FROM AUTHOR]

Most piezoelectric materials exhibit a positive longitudinal piezoelectric effect (PLPE), while a negative longitudinal piezoelectric effect (NLPE) is rarely reported or paid much attention. Here, utilizing first-principles calculations, we unveil the origin of negative longitudinal piezoelectricity in ferroelectric hafnia by introducing the concept of weighted projected bond strength around cation in the c direction (WPBc), which is proposed to quantitatively characterize the asymmetric bonding stiffness along the strain direction. When the WPBc is anti-parallel to the direction of bulk spontaneous polarization, the polarization decreases with respect to tensile strain and leads to a negative piezoelectricity. Furthermore, to confirm the influence of WPBc on the piezoelectric effect and understand how the value of WPBc influences the piezoelectric coefficient e33, we acquire both the piezoelectric coefficient of doped hafnia and the corresponding bonding environment around each cation. The finding reveals that the more negative piezoelectric coefficient can be achieved through a concurrent achievement of the more negative average WPBc and the lower standard deviation (STD) of WPBc. In addition, the Sn-doped hafnia with the lowest average WPBc and smaller STD-WPBc is identified to have the highest piezoelectric coefficient (−2.04 C/m2) compared to other dopants, showing great potential in next-generation electromechanical devices. [ABSTRACT FROM AUTHOR]

Piezocatalysis is considered as an evolving technology based on the piezoelectric properties of catalysts, has shown great potential in the field of environmental remediation, water splitting, and biotechnology. In this work, the catalytic performance of (Ba0.95Ca0.05) (Ti1-xSnx)O3 (BCT1-xSx, 0.04 ≤ x ≤ 0.12) piezoelectric ceramics was studied systematically. The relationship between piezoelectric performance and piezo-photocatalytic performance was investigated. As the Sn content increased, the crystalline structure gradually changed from the orthorhombic (O) phase (x = 0.04) to O-pseudocubic (PC) two-phase coexistence (x = 0.08 and x = 0.10), and finally to the PC phase (x = 0.12). The piezoelectric constant d33 exhibited an initial increases followed by a decreases with rising Sn content, reaching peak of 509pC/N at x = 0.10. The enhanced d33 was due to multiphase coexistence and a Curie temperature near room temperature. The piezocatalytic efficacy of BCT1-xSx was linked to d33, with the maximum degradation rate achieved at x = 0.10. However, the optimal piezo-photocatalytic performance was obtained at x = 0.08 instead of x = 0.10 with the highest degradation rate of 69%. The photo-piezocatalytic performance was discovered to be intricately linked not only to the band gap of piezocatalysts but also influenced by their piezoelectric properties. These results will provide guidance for designing new lead-free piezoelectric materials with excellent catalytic properties. [ABSTRACT FROM AUTHOR]

The piezoelectric property was found by Curie brothers in quartz and Rachel salt (1881). This property is a complicated phenomenon that makes it challenging to study. In 1935, the piezoelectric properties of potassium-dehydrogenated phosphate, the first famous piezoelectric material, were determined. Study about these properties of materials was developed by USA, Russia, and Japan during the Second World War, resulting in some piezoelectric materials such as barium titanate (BT) and lead zirconate titanate (PZT) in 1940 and 1950, respectively. Pure and doped PZT families have been widely studied in ceramics and nanostructured forms to enhance their piezoelectric properties. Because of the lead, the PZT materials are harmful to the environment. Therefore, it has been tried to replace it with suitable lead-free materials for practical purposes. The first lead-free piezoelectric material investigated in this respect is BT. However, the piezoelectric properties of BT are not as good as PZT, so a new generation of lead-free piezoelectric materials has been developed. These new lead-free piezoelectric materials are divided into two categories: (1) the lead-free piezoelectric material based on BNT (bismuth niobium titanate) and (2) the lead-free piezoelectric material based on KNN (potassium sodium niobite). The most significant advantage of these materials is that they are environmentally friendly, but their piezoelectric properties are less than PZT. In this chapter review, lead-based and lead-free piezoelectric materials such as PZT, BT, BZT, KNN, BNT, and ZnO are studied. The synthesized methods of piezoelectric materials in ceramic and nanostructure forms are presented. The applications of piezoelectric ceramics and nanostructures are discussed. [ABSTRACT FROM AUTHOR]

The present work presents the investigation of the dynamics and influence of chaotic behavior on energy capture for a U-shaped structure (portal frame) that contains shape memory alloy (SMA), piezoelectric material (PZT), a nonlinear energy sink (NES) and a non-ideal excitation source represented by an unbalanced electric motor coupled to the U-structure. The mathematical model presents nonlinearities arising from the nonlinear stiffness of the U-structure, the NES system, the SMA, and the PZT material. Chaotic behavior is assessed through time history, bifurcation diagrams, phase diagrams, and the 0–1 test. Energy capture is carried out through a piezoelectric material (PZT), represented by a non-linear electromechanical coupling model, and electromagnetic induction generated by the non-linear electromagnetic energy sink coupled to the structure (NES). Dynamic analysis is performed through parametric analysis of parameters related to piezoelectric coupling and NES parameters. Numerical simulations demonstrate that the system has chaotic behavior for specific parameters and that its energy capture is influenced by parametric variation. It is shown numerically that the parameters of the SMA material, the PZT material, and the NES significantly influence the chaotic behavior and energy capture of the investigated electromechanical system. [ABSTRACT FROM AUTHOR]

The paper investigates the possibilities of purposefully changing the properties and lowering the sintering temperatures of piezoelectric materials used in multilayer converters. The aim of the work was to correct the basic properties of piezoelectric ceramics at the stage of its manufacture, due to changes in technological modes with unchanged chemical composition. At the most important technological stage—the sintering of piezoelectric ceramics, a ceramic frame is formed, as well as mechanical properties—density, hardness, strength, affecting electrophysical properties. Consequently, by correcting the conditions for the formation of the microstructure of piezoelectric ceramics, it is possible to purposefully change its functional parameters. Consolidated sintering of piezoelectric ceramics by methods of hot pressing and spark plasma sintering, provides an opportunity to effectively control the process of microstructure formation. The objective of the study was to practically test these sintering methods in the manufacture of piezoelectric ceramics of various functional groups and variations of their parameters. The model objects of the study were: a relaxation piezoelectric material based on the lead zirconate-titanate system, a ferroalloy material of the PMN-PT system and a multicomponent piezoelectric material with a sintering temperature of less than 1000°C. In the course of the study it was found that the sintering of piezoelectric ceramics by hot pressing and spark plasma sintering contributes to the formation of a homogeneous defect–free microstructure that provides an increase in the basic mechanical and electrophysical properties by 10–16%. Also, these methods help to reduce sintering temperatures by 150–300°C. The spark plasma sintering method, characterized by its high speed, reduces the duration of isothermal exposure by 36 times, which has a positive effect on energy saving. As part of the study, batch multilayer converters were manufactured using consolidated sintering methods. The efficiency of consolidated sintering has been experimentally established and confirmed for purposefully changing the functional parameters of piezoelectric ceramics with the possibility of lowering the sintering temperature. [ABSTRACT FROM AUTHOR]

Excellent mechanical and electric properties enable the piezoelectric materials to be widely and dynamic aero-mechanical-electric coupling properties of the piezoelectric plate structures can significantly affect performance of aircrafts flying in high speed. This paper is focused on the flutter behaviors of the functionally graded piezoelectric material (FGPM) plate in supersonic airflow. The first-order shear deformation theory (FSDT) is employed to formulate the energy functional of the FGPM plate with general boundary conditions. The supersonic air flow is taken into account using the supersonic piston theory. The governing equations for the aero-mechanical-electric coupling system are deduced on basis of the Hamilton's principle. To address the limitation of intricate boundary conditions to the admissible functions, a modified Fourier series is introduced to yield the unified solutions of the FGPM plate subject to supersonic airflow and with arbitrary boundary conditions. Flutter properties of series of FGPM plates are investigated to demonstrate robust ability of the proposed method to accurately yet consistency include the aero-elastic-electric coupling, inhomogeneous material and arbitrary boundary conditions. The influences of the boundary condition, material constituent, external voltage and yawed flow angle on the vibration, and flutter behaviors of the FGPM plate are examined. Adjusting corresponding parameters accordingly can significantly improve the stability of the plate structures subject to supersonic airflow, which provides physical insights into dynamic optimal design of the plate structures. [ABSTRACT FROM AUTHOR]

In this paper, the free vibration characteristics of stiffened sandwich plates with auxetic core and functionally graded piezoelectric face sheet are investigated. The sandwich plate configuration comprises three distinct layers: a top layer consisting of functionally graded piezoelectric material (FGPie), a core layer composed of auxetic material exhibiting a negative Poisson's ratio, and a bottom layer made of functionally graded material (FGM). The sandwich plate is reinforced by isotropic stiffeners along the x and y directions. A novel model is established based on the four-variable shear deformation refined plate theory and the pb2-Ritz method. This model offers the flexibility to analyze plates with diverse mechanical boundary conditions and supports two types of electrical boundary conditions: closed circuit and open circuit. The accuracy and convergence of the proposed model are validated through comparative analyses against published results, thereby confirming the reliability when analyzing the vibration characteristics of this complex sandwich structure. Furthermore, some new investigations are carried out to explore the influence of various parameters on the vibrational characteristics of the stiffened piezoelectric auxetic sandwich (SA-FGPie) plates. The results suggest that the properties of the reinforcing stiffeners, such as quantity or dimensions, alter the free vibration characteristics of the SA-FGPie plates significantly. In addition, parameters such as the volume fraction indexes of the FGPie and FGM layers, electrical boundary conditions or FGPie layer thickness, as well as geometric parameters of the auxetic unit cell also have a significant influence on the vibration response of SA-FGPie plates. However, the influence of these parameters depends on the specific boundary conditions. [ABSTRACT FROM AUTHOR]

Harvesting electrical energy from mechanical vibrations through piezoelectric-based resonant devices is a suitable form of generating alternative electrical sources for several applications, most dedicated to powering small electronic devices. This technique has attracted considerable attention over the past decades, mainly due to piezoelectric materials' high electrical charge density. However, the amount of harvestable energy is usually small and sensitive to variabilities in design, manufacturing, operation, and environmental conditions. Hence, it is essential to account for predictable and potentially relevant uncertainties during the design of energy harvesting devices. This work presents strategies for the robust design of resonant piezoelectric energy harvesters, considering the presence of uncertainties in design, manufacturing, and mounting conditions, such as the bonding of the piezoelectric materials and the clamping of the resonant device. The work proposes and discusses strategies for finite element modeling, accounting for adhesive bonding of piezoelectric materials and imperfect clamping; harvestable power output mean value and dispersion estimation with Polynomial Chaos Expansion; and robust optimization using multiobjective optimization techniques. Relevant general conclusions concerning harvesting devices include but are not limited to, devices with shorter resonating beams and larger tip masses tend to present performances that are nominally better but also less robust. Additionally, reducing the effective electrical resistance may improve robustness without significantly losing the mean value performance. Also, through an assessment of the most relevant design variables and uncertain parameters, some aspects that should receive special attention when designing, manufacturing, and mounting these devices are discussed, such as the bonding of piezoelectric patches and the clamping of cantilever beams due to their essential effect on the robustness of the device. It is also shown that including well-selected design variables may mitigate the impact of uncertainties and, thus, improve the robustness of the device. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials that combine ferromagnetic, semiconductor, and piezoelectric properties hold significant potential for both fundamental research and spin electronic devices. However, the majority of reported 2D ferromagnetic-semiconductor-piezoelectric materials rely on d-electron systems, which limits their practical applications due to a Curie temperature lower than room temperature (RT). Here, we report a high-crystallinity carbon nitride (CCN) material based on sp-electrons using a chemical vapor deposition strategy. CCN exhibits a band gap of 1.8 eV and has been confirmed to possess substantial in-plane and out-of-plane piezoelectricity. Moreover, we acquired clear evidences of ferromagnetic behavior at room temperature. Extensive structural characterizations combined with theoretical calculations reveal that incorporating structural oxygen into the highly ordered heptazine structure causes partial substitution of nitrogen sites, which is primarily responsible for generating room-temperature ferromagnetism and piezoelectricity. As a result, the strain in wrinkles can effectively modulate the domain behavior and piezoelectric potential at room temperature. The addition of RT ferromagnetic-semiconductor-piezoelectric material based on sp-electrons to the family of two-dimensional materials opens up numerous possibilities for novel applications in fundamental research and spin electronic devices. [ABSTRACT FROM AUTHOR]

With the increasing demand for flexible piezoelectric sensor components, research on polyvinylidene fluoride (PVDF) based piezoelectric polymers is mounting up. However, the low dipole polarization and disordered polarization direction presented in PVDF hinder further improvement of piezoelectric properties. Here, we constructed an oriented tertiary structure, consisting of molecular chains, crystalline region, and MXene sheets, in MXene/PVDF nanocomposite via a temperature-pressure dual-field regulation method. The highly oriented PVDF molecular chains form approximately 90% of the β phase. In addition, the crystalline region structure with long-range orientation achieves out of plane polarization orientation. The parallel orientation arrangement of MXene effectively enhances the piezoelectric performances of the nanocomposite, and the current output of the device increases by nearly 23 times. This high output device is used to monitor exercise action, exploring the potential applications in wearable electronics. [ABSTRACT FROM AUTHOR]

A novel fabrication process for a vertical wavy structured stretchable piezoelectric sensor combining dip coating and micro-corrugation process is proposed. By changing the dip coating withdrawal speed, the thickness of PVDF-TrFE (poly(vinylidene fluoride-trifluoroethylene)) films deposited on metal foils was controlled; the wave shape fabricated by the micro-corrugation process was influenced by the PVDF-TrFE film thickness. By reducing the PVDF-TrFE film thickness to less than 5 μm, the wave shape exhibited a high aspect ratio (wave height divided by wave pitch). From estimations obtained by measuring the change in substrate length before and after the microcorrugation process, the predicted stretchability is expected to be greater than 30%. The fabricated vertical wavy structured piezoelectric sensor with a PVDF-TrFE film thickness of approximately 2 μm showed more than 50% stretchability. The fabricated sensor was used as a finger-bending sensor for a virtual reality system, and the proposed process is a promising method for fabricating stretchable sensors. [ABSTRACT FROM AUTHOR]

This study presents a review of progress in the sol-gel method for the synthesis of powders of ferroelectric ceramics based on the PbTiO3–PbZrO3 system, which involves the controlled hydrolysis of the mixtures of salts or organometallic compounds of lead, zirconium, and titanium. To obtain materials based on the PbTiO3–PbZrO3 system, attention is paid to the sol-gel conditions, heat treatment conditions, raw materials, conditions to obtain precursors, gels drying, and PbTiO3–PbZrO3 powder crystallization. [ABSTRACT FROM AUTHOR]

A signal is primarily generated when two objects collide, with one falling from a specific height and the other disrupting its balance. This signal contains an important component that aids in the diagnosis of material damage. In this work, a piezoelectric thin film sensor made of polyvinylidene fluoride (PVDF) was employed to monitor the impact signal and process the recorded signal. By stacking a left and right piezoelectric film sensor, drop impact experiments were performed on rubber sheet material. The data-acquisition system captured the impact signal, and a signal processing tool was used to assess its performance. To determine the time-frequency domain visibility of the impact signal, the short-time Fourier transform (STFT) and continuous wavelet transform (CWT) were used. The detection of the elastic signal and impact force on the material is suitable for piezoelectric film. A steel impactor strikes a silicon rubber sheet at a speed of 3.43 m/s and exerts an average impact force of 72.6 kN. To make the impact signal more visible, the noise signal can be denoised using a bandpass filter. The continuous wavelet transform has a high time-frequency resolution compared to the short-time Fourier transform. Additionally, the analysis of non-stationary signals is improved by using STFT and CWT approaches. Thus, the elastic signal detection in the material may be recognized using the average total of the signals identified by the sensor. [ABSTRACT FROM AUTHOR]

A nonlinear phenomenological model of flexoelectricity in thermoelastic solids is presented within the frame of continuum mechanics and extended thermodynamics, incorporating the quasi-electrostatic approximation where the time derivative of the electric displacement vector can be neglected in Maxwell–Ampère's law. An expression for the energy flux is proposed, including many internal variables. An advantage of the proposed model is that it presents a unified approach to study several thermo-electromechanical couplings, including electrostriction, piezoelectricity, dependence of entropy and spontaneous polarization on flexoelectricity, among others. The model may be of interest in revealing the effects of such couplings on the properties of polarizable media, in particular ferroelectrics, when simple boundary conditions prevail. For a fully dynamic description of flexoelectricity, Hamilton's principle and the variational principle for external forces should be used instead. [ABSTRACT FROM AUTHOR]

In order to improve the accuracy and efficiency of piezoelectric structure design, the static mechanic-electric coupling of two-dimensional piezoelectric material problems are investigated by a cell-based smoothed isogeometric analysis (CS-IGA) in this work. The CS-IGA was developed on the basis of the isogeometric analysis by using strain smoothing technology. Based on the generalized Galerkin weak form and the constitutive equation of piezoelectric structures, the equilibrium equation of piezoelectric material in the problem of mechanic-electric coupling is obtained. For further improving the calculation precision of the algorithm, average strain is defined in the element domains. It completely avoids the gradient calculation of rational NURBS basis function in the stiffness matrix formula and further improves the computational efficiency. Besides, numerical example results can verify the precision, correctness and reliability of the proposed method in comparison with the finite element method in the analysis of piezoelectric material problems. Overall, this work can provide a help for analyzing the problems of piezoelectric structures. [ABSTRACT FROM AUTHOR]

Failure analyses of piezoelectric structures and devices are of engineering and scientific significance. In this paper, a fourth-order phase-field fracture model for piezoelectric solids is developed based on the Hamilton principle. Three typical electric boundary conditions are involved in the present model to characterize the fracture behaviors in various physical situations. A staggered algorithm is used to simulate the crack propagation. The polynomial splines over hierarchical T-meshes (PHT-splines) are adopted as the basis function, which owns the C1 continuity. Systematic numerical simulations are performed to study the influence of the electric boundary conditions and the applied electric field on the fracture behaviors of piezoelectric materials. The electric boundary conditions may influence crack paths and fracture loads significantly. The present research may be helpful for the reliability evaluation of the piezoelectric structure in the future applications. [ABSTRACT FROM AUTHOR]

Currently, in the modification methods of K0.5Na0.5NbO3(KNN) ceramics to enhance their piezoelectric performance, key parameters such as Curie temperature are usually sacrificed. However, this trade-off limits the practical application of piezoelectric materials. Thus, addressing the trade-off between different performance parameters of piezoelectric ceramics becomes a major challenge.The present research employs the conventional solid phase sintering process and utilizes controlled doping of (Bi0.5Li0.5)0.9Sr0.1ZrO3 to regulate the ceramic system, K0.44Na0.55Ag0.01Nb0.95Ta0.05O3, at its polycrystalline phase boundary, thereby achieving a trade-off between performance. The ceramic samples of the system formed a compact solid solution with a single-phase perovskite structure and formed orthorhombic-tetragonal and rhombohedral-tetragonal polycrystalline phase boundaries at 0.02 ≤ x ≤ 0.03 and 0.035 ≤ x ≤ 0.06, respectively, according to XRD, SEM, and EDS analysis. The electrical properties test results show that in the multiphase coexisting region of x = 0.035, the ceramics of the system show excellent electrical properties, respectively d33 = 312 pC/N, kp = 46.5%, εr = 1019, tanδ = 3.78%, Pr = 20.08 μC/cm2, Ec = 12.97 kV/cm, and TC = 342 ℃. These results show that the properties of the system ceramics have reached a relatively high level, which provides an effective strategy for the practical application of piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

In this work, laterally excited bulk acoustic wave resonators (XBARs) are designed for high-frequency applications in the 5 GHz range which have applications in MEMS sensors and fifth-generation (5G) mobile networks. XBARs are simulated with 400 nm thick LiNbO3 and narrow fingers of Interdigital transducer (IDT) placed periodically with a pitch of 26 µm to excite the lamb wave resonances at 4.49 GHz with a high electromechanical coupling coefficient (kt2) of 32%. The working of XBARs is investigated by Finite element method (FEM) based COMSOL Multiphysics simulation and analytical model. The XBAR schematic is depicted graphically, together with its deformation, impedance response with corresponding asymmetric displacement modes, and device equivalent MBVD model. The performance of XBARs with different piezoelectric materials was investigated, and it was discovered that XBARs using LiNbO3 as piezoelectric materials and Au electrodes performed best. Following that, Au electrodes are used to create A1 (anti-symmetric lamb) modes with spurious mode mitigation. Furthermore, numerous geometrical aspects such as piezoelectric material thickness, IDT finger width, the pitch of IDT and the ratio of IDT finger width to finger gap were examined in order to enhance kt2 and the Quality factor (Q) of the device. The third and fifth harmonics of XBAR were found at 13.41 and 22.39 GHz, respectively. The modified Butterwort-Van Dyke model (MBVD) is intended to discover the XBAR equivalent circuit model. [ABSTRACT FROM AUTHOR]

In this work, a novel multiscale topology optimization method has been proposed for the design of electromechanical energy-harvesting systems converting mechanical vibrations into electric currents made of non-piezoelectric materials. At the microscopic scale, the material is assumed to be periodic, porous, and flexoelectric, although not piezoelectric. A first step of topology optimization is performed, in order to maximize the effective (homogenized) flexoelectric properties of the material, where a flexoelectric homogenization model is first formulated. As a result, the effective material, although made of a non-piezoelectric material, has apparent piezoelectric properties. In a second step, these properties are used to model the behavior of a dynamic electromechanical energy-harvesting system structure. A second topology optimization step, this time performed at the structural scale, aims to maximize the system electromechanical coupling factor (ECF) for a given forced vibration frequency, including the micro-inertial effect. At both scales, an isogeometric analysis method is employed to solve the strain-gradient problems numerically. We show that the optimized structure obtained offers significant gains in terms of ECF (by a factor of between 2 and 20) compared with non-optimized structures of the same volume, over a wide range of excitation frequencies. The procedure could open up new possibilities in the design of energy recovery systems without the use of piezoelectric materials. [ABSTRACT FROM AUTHOR]

With the rapid development and applications of micro/nano electromechanical systems in engineering fields, piezoelectric materials have been widely used in these systems due to their excellent physical and mechanical properties. Generally, these systems work in complex thermoelastic environments, to depict the thermal-electro-mechanical behaviors of piezoelectric material structures at microscale, the existing theories need to be developed due to the arising size-dependent effect, thermal relaxation effect and flexoelectric effect etc. To this end, the present work intends to generalize the size-dependent theories by considering the thermal-electro-mechanical coupling behaviors in piezoelectric material structures at microscale. Based on the nonlocal strain gradient theory and the generalized heat conduction model, a new model is established and the corresponding constitutive equations and the governing equations of equilibrium are derived. To illustrate the application of this new model, a piezoelectric micro-beam with flexoelectricity is considered and the closed form solutions of bending deflection and the free vibration response are obtained in terms of the boundary conditions. Based on the numerical results, the size-dependent effect, the piezo-flexoelectric effect and the thermal-lagging effect on the bending and vibration responses of the microbeam are examined and illustrated graphically. This work may be potentially helpful for the efficient, optimized and adaptive designs of the NEMS/MEMS devices. [ABSTRACT FROM AUTHOR]