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Solar-driven semiconductor photocatalysts are highly appealing in applications of environmental remediation and energy conversion. However, photocatalytic reactions, particularly oxygen evolution reaction (OER), are often constrained by the swift recombination of electron–hole pairs, thereby resulting in low reaction efficiency. Although it is effective to separate charge carriers by constructing heterojunctions to form built-in electric field, the lattice mismatch and inefficient interlayer charge transfer of heterojunctions in the photocatalysts limit their further development. Here, we propose a new strategy by constructing an internal electric field for OER through an individual piezoelectric two-dimensional material. The results indicate that the piezoelectric effect regulates the electronic structure, reduces bandgap, improves light absorption efficiency, and that the displacement of positive and negative charge centers is the key factor in the enhanced OER. This research indicates the feasibility of combining piezoelectric properties of two-dimensional materials with OER (1.19 eV), providing new insights and guidance for applying the piezoelectric effect in the OER and opening up a way to promote efficient separation of charge carriers. [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]

Using piezoelectric bionanomaterials to promote the generation of reactive oxygen species (ROS) is being increasingly recognized in ultrasound (US)‐triggered tumor treatments. The mechanism underlying this innovative treatment involves US irradiation, which activates the built‐in electric field (BIEF) and induces energy‐band bending in piezoelectric materials (PEMs). In this study, Sr0.5Ba0.5Nb2O6 (SBN) nanorods (NRs) are synthesized using a molten salt method. Subsequently, oxygen‐vacancy (OV)‐rich SBN/Sr2Nb2O7 (SBN/SNO) heterojunction nanocomposites (NCs) are fabricated via H2 annealing of the SBN NRs. The engineering strategy focused on enhancing ROS generation, thereby augmenting the piezoelectric catalytic activity of the NCs. This configuration ensures that the BIEF and heterojunction‐induced field act synergistically to provide a sustained driving force for the separation of electron‐hole (e−‐h+) pairs. Importantly, the OVs on the surfaces of the H2‐annealed SBN NRs create electron‐rich sites, which substantially enhance their piezocatalytic capabilities. In vitro and in vivo analyses of hepatocellular carcinoma (HCC) models demonstrate the significant cytotoxic and tumor‐inhibitory capabilities of this rich OV‐mediated sonopiezoelectric therapy (SPT) and illustrate its potential as a promising therapeutic approach against cancer. [ABSTRACT FROM AUTHOR]

Electrostrictive materials based on (Na0.5Bi0.5)TiO3 are promising lead-free candidates for high-precision actuation applications, yet their properties require further improvement. This study aims to enhance the electromechanical properties of a predominantly electrostrictive composition, 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3, by using templated grain growth. Textured ceramics were prepared with 1~9 wt% NaNbO3 templates. A high Lotgering factor of 95% was achieved with 3 wt% templates and sintering at 1200 °C for 12 h. Polarization and strain hysteresis loops confirmed the ergodic nature of the system at room temperature, with unipolar strain significantly improving from 0.09% for untextured ceramics to 0.23% post-texturing. A maximum normalized strain, Smax/Emax (d33*), of 581 pm/V was achieved at an electric field of 4 kV/mm for textured ceramics. Textured ceramics also showed enhanced performance over untextured ceramics at lower electric fields. The electrostrictive coefficient Q33 increased from 0.017 m4C−2 for untextured ceramics to 0.043 m4C−2 for textured ceramics, accompanied by reduced strain hysteresis, making the textured 0.685(Na0.5Bi0.5)TiO3-0.065BaTiO3-0.25SrTiO3 composition suitable for high-precision actuation applications. Dielectric properties measured between −193 °C and 550 °C distinguished the depolarization, Curie–Weiss and Burns temperatures, and activation energies for polar nanoregion transitions and dc conduction. Dispersive dielectric constants were found to observe the "two" law exhibiting a temperature dependence double the value of the Curie–Weiss constant, with shifts of about 10 °C per frequency decade where the non-dispersive THz limit was identified. [ABSTRACT FROM AUTHOR]

2D piezoelectric catalysts with strong piezoresponse and high piezoelectric potential have valuable applications in catalytic degradation of organic pollutants and antibiotics, but the development of novel nanomaterials with powerful piezopotential still remains a serious challenge. Bismuth oxysulfide (Bi2O2S) nanosheets possessing large piezoelectric potentials were prepared using a low-heating solid-state chemical reaction and used for the first time for piezoelectric catalysis in this work. Moreover, Bi2O2S nanosheets can degrade pollutants universally, and the degradation efficiencies of methyl blue and rhodamine B are as high as 97.7% and 92.9% within 60 min under ultrasonication, respectively, which is superior to most piezoelectric materials reported in the literature. [ABSTRACT FROM AUTHOR]

In the current electromechanical model of cantilevered piezoelectric energy harvesters, the assumption of uniform electric field strength within the piezoelectric layer is commonly made. This uniform electric field assumption seems reasonable since the piezoelectric layer looks like a parallel-plate capacitor. However, for a piezoelectric bender, the strain distribution along the thickness direction is not uniform, which means the internal electric field generated by the spontaneous polarization cannot be uniform. In the present study, a non-uniform electric field in the piezoelectric layer is resolved using electrostatic equilibrium equations. Based on these, the traditional distributed parameter electromechanical model is corrected and simplified to a practical single mode one. Compared with a traditional model adopting a uniform electric field, the bending stiffness term involved in the electromechanical governing equations is explicitly corrected. Through comparisons of predicted power output with two-dimensional finite element analysis, the results show that the present model can better predict the power output performance compared with the traditional model. It is found that the relative corrections to traditional model have nothing to do with the absolute dimensions of the harvesters, but only relate to three dimensionless parameters, i.e., the ratio of the elastic layer's to the piezoelectric layer's thickness; the ratio of the elastic modulus of the elastic layer to the piezoelectric layer; and the piezoelectric materials' electromechanical coupling coefficient squared, k 31 2 . It is also found that the upper-limit relative corrections are only related to k 31 2 , i.e., the higher k 31 2 is, the larger the upper-limit relative corrections will be. For a PZT-5 unimorph harvester, the relative corrections of bending stiffness and corresponding resonant frequency are up to 17.8% and 8.5%, respectively. An inverse problem to identify the material parameters based on experimentally obtained power output performance is also investigated. The results show that the accuracy of material parameters identification is improved when considering a non-uniform electric field. [ABSTRACT FROM AUTHOR]

The scattering of flexural waves in piezoelectric thin plates with defects effects the electro-mechanical coupling property. Theoretical analysis for flexural waves is lack of a suitable decoupling function. Here, we have developed a method based on applied electric field to make a solution of the dynamic moment concentration factor (DMCF) for flexural waves scattering problems. The DMCFs of the piezoelectric materials have been found that it is significantly larger than those of the ordinary elastic materials because of electro-mechanical coupling. In the region of low frequency, DMCFs have a dependence on applied electric field and independent on the incident angle. Those opposite phenomena are observed as the frequency increasing. Those results provide theoretical guidance for dynamic analysis and strength design of piezoelectric material structures. [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]

We discovered large electric-field-induced strain in pyro-vanadate-phosphate Cu2−xZnxV1.8P0.2O7. Distinct from conventionally used piezoelectric materials including lead-zirconate-titanate, this material expands almost isotropically at room temperature when an electric field is applied. This volume change, exceeding 1000 ppm under the field of E = 3900 V/cm, is of the largest class induced by an electric field. The strain is phenomenologically interpreted as electrostriction because it is symmetric about E = 0 and because it obeys a higher term than E-linear such as E squared. The present x-ray diffraction experiments suggest that the applied electric field distorts the crystal lattice, although there is no structural phase transition. This material performs a volume-change-driven actuator function that is distinct from the strain-driven counterpart of piezoelectric materials. The discovery of actuator functionality in a material system with a non-perovskite structure, unlike the actuator materials developed to date, is a major breakthrough for future actuator engineering. [ABSTRACT FROM AUTHOR]

The lead-free piezoelectric ceramics used in piezoelectric actuators have attracted extensive attention owing to their substantial electric-field-induced strain. In this study, The (1- x)Bi 0.5 (Na 0.41 K 0.09)TiO 3 - x Sr(Hf 0.5 Sb 0.4)O 3 (BNKT- x SHS) piezoelectric ceramics were synthesized using the conventional solid-state reaction method. The impact of SHS substitution on the microstructure and electrical properties was systematically explored. Among them, the BNKT-0.015SHS sample, featuring ergodic relaxor states, demonstrates a high piezoelectric strain coefficient (d 33 *) of 785 p.m./V under a low electric field of 50 kV/cm(Strain = 0.392 %). It exhibits a repeatable strain value of 0.47 % under an 80 kV/cm electric field(d 33 * = 590 p.m./V). Moreover, the strain values remain around 0.4 % between room temperature and 100 °C, with variations within 90 %. The heightened repeatable strain response is considered to be linked to the electric field-induced reversible phase transition occurring within the ergodic relaxor state. The higher strain temperature stability is ascribed to the coexistence of quadrilateral polar nanoregions and rhombic polydomain nanoregions. This study provides an effective example for achieving significant strain responses, presenting a feasible candidate material for applications in piezoelectric actuators. [ABSTRACT FROM AUTHOR]

Piezoelectric actuators have been extensively utilized as micro-displacement devices because of their advantages of large output displacement, high sensitivity, and immunity to electromagnetic interference. Here, we propose a straightforward approach to design <110>-oriented defect dipoles by introducing A-site vacancies and oxygen vacancies in (K0.48Na0.52)0.99NbO2.995 ceramics. As a result, we achieve ultrahigh electrostrains of 0.7% at 20 kV cm-1 (with an effective piezoelectric strain coefficient d33* = 3500 pm V-1), outperforming the performance of existing piezoelectric ceramics at the same driving field. The exceptional electrostrain is primarily attributed to the large stretching of defect dipoles when subjected to an applied electric field, a phenomenon that has been experimentally confirmed. Moreover, the strong interaction between these defect dipoles and <110> spontaneous polarizations plays a critical role in minimizing hysteresis and ensuring excellent fatigue resistance. Our findings present a practical and effective strategy for developing high-performance piezoelectric materials tailored for advanced actuator applications. [ABSTRACT FROM AUTHOR]

Piezoelectric materials can develop mechanical strain upon applying electric voltage and vice-versa. A piezoelectric bimorph, widely used in various sensors and actuator applications, essentially behaves like a beam and consists of a nonpiezoelectric material substrate layer glued between two piezoelectric layers. The application of an electric field alone can induce the bending of such a beam. Studies on the modeling of the piezoelectric bimorph are mostly restricted to the small deflection regime. In the present work, a simple numerical method is proposed to obtain the large deflection response of any piezoelectric bimorph. To begin with, the governing equation of a cantilever bimorph under electric field and end load is obtained. The nonlinear governing equation is then linearized with respect to the current time step. Subsequently, the linearized equation is solved using the RK4 method. From the numerical results, it is found that the response of the key design parameter, namely free displacement is considerably different from that predicted from small deflection analysis. Also, as the entities involved are suitably nondimensionalized, the results are directly relatable to all classes of piezoelectric materials. The nondimensionalization has also paved the way for better insight into the physical problem by rendering a simple mathematical representation. [ABSTRACT FROM AUTHOR]

BaTiO3 is a well-known piezoelectric material with commercial uses. The ferroelectric state of BaTiO3 generally comprises electrically polarized domains separated by domain walls (DWs). The DW alters local polarization vectors by an angle of 90° for 90° DW or 180° for 180° DW. The DW is crucial to piezoelectric properties such as response time and fatigue. Furthermore, the DW structure and its dynamics in BaTiO3 are not well understood. Hence, for the first time, we theoretically obtained the atomistic structure of the 90° DW via molecular dynamics simulations at 300 K with the core–shell interatomic potential, using a large-scale system with a side length of 2.8 × 10 3 Å. The width of the 90° DW thereby obtained was approximately 30 Å, which was 20 Å wider than that of the 180° DW. Under the external electric field E → ext parallel to the DW, we observed an extension of a domain having a polarization vector with a positive component along the E → ext -direction. The migration velocity of the 90° DW was approximately two times that of the 180° DW at the same E ext in the range 7 – 20 MV / m. For E ext ≥ 15 MV / m , the migration velocity of the 90° DW in the direction with a positive component along the polarization vector of the extending domain was substantially higher than that in the opposite direction. The physical causes of the difference in the migration velocities of the 90° DW in the two directions were analyzed. [ABSTRACT FROM AUTHOR]

One of the important requirements for piezoelectric materials for use as high strain actuators is that they exhibit large unipolar electrostrain with minimum hysteresis. While large unipolar electrostrain >1% is generally achievable in good quality single crystals, most polycrystalline piezoelectric show low values < 0.4%. Unipolar electrostrain 0.5%–0.7% in polycrystalline piezoelectrics has often been reported in Na0.5Bi0.5TiO3-based compositions at the non-ergodic ergodic boundary. Not amenable to poling, such materials exhibit almost nearly zero direct piezoelectric coefficient (d33 ∼ 0 pC/N) and cannot be simultaneously used as a sensor. In this paper, we report a combination of large unipolar electrostrain of ∼0.6% with small strain hysteresis of 25% in a Sn-modified relaxor ferroelectric system PbTiO3–Bi(Ni1/2Zr1/2)O3. It exhibits d33 ∼ 340 pC/N, which is stable up to 130 °C, and large signal converse piezoelectric coefficient d33* ∼ 1200 pm/V. A combination of large d33 and d33* in the same material makes it an important candidate for simultaneous use as a sensor and high strain actuators. X-ray diffraction study in situ with the electric field suggests that large electrostrain with low strain hysteresis in this system is because of the increased reversible switching of the field stabilized tetragonal ferroelastic domains. [ABSTRACT FROM AUTHOR]

Probing Janus materials with significant piezoelectric polarization to enhance electromechanical conversion efficiency has been a hot research topic in recent years. Here, a Janus MoSSiX2 (X = N, P, As) structure is proposed, and its piezoelectric properties are explored using first-principles calculations. The result shows that the in-plane coefficients d11 of MoSSiN2, MoSSiP2, and MoSSiAs2 are 1.87, 4.59, and 5.35 pm V−1, respectively. Meanwhile, the non-mirror symmetry leads to nonzero out-of-plane piezoelectric coefficients d31 of 0.16, 0.16, and 0.35 pm V−1 for MoSSiN2, MoSSiP2, and MoSSiAs2. It is found that the outstanding piezoelectric coefficients of MoSSiAs2 are attributed to the elastic flexibility. Meanwhile, the electronegativity difference ratio is in line with the trend of piezoelectric coefficient variations, and the large built-in electric field strength enables the MoSSiAs2 monolayer to exhibit the strongest vertical polarization. The work establishes a robust theoretical foundation for supporting the potential utilization of Janus MoSSiX2 monolayers in nanodevices and micro-electro-mechanical systems. [ABSTRACT FROM AUTHOR]

BaTiO3 is a well-known piezoelectric material, which is widely used in various devices. In general, the ferroelectric state of BaTiO3 is composed of polarized domains. The growth of these domains due to an applied electric field or stress is related to the piezoelectric performance. We investigated the effects of various point defects, monovacancies {VBa, VTi, VO}, and first- and second-neighbor divacancies {VBa–VO, VTi–VO} on polarized domain growth in BaTiO3 under an applied electric field by molecular dynamics simulations using the core–shell inter-atomic potential. We found that (i) the first-neighbor divacancy VBa–VO is the most effective in assisting the domain growth under an applied electric field (i.e., a smaller coercive electric field) in an asymmetrical manner with respect to the electric field direction. This is mainly due to the creation of an electric field around VBa–VO by significant Ti shifts toward VBa with the assistance of VO. (ii) Domain growth proceeds in a 1 + 2 dimensional manner. The domain growth velocity in the direction of the applied electric field is approximately two orders of magnitude higher than that in the perpendicular direction. (iii) Increasing the density of the divacancy VBa–VO further lowers the coercive electric field when the applied electric field is parallel to the divacancy dipoles. The present results will be essential for designing the type, orientation, and density of defects to modify the coercive electric field of BaTiO3 in defect engineering. [ABSTRACT FROM AUTHOR]

Wurtzite ferroelectric materials are promising candidates for energy‐efficient memory technologies, particularly for applications requiring high operating temperatures. Asymmetric wake‐up behaviors, in which the polarization reversal depends both on polarity and cycle number for the first few dozen cycles, must be better understood for reliable device operation. Here, the detailed analysis of the asymmetric wake‐up behavior of thin film Al0.94B0.06N was performed combining time‐resolved switching measurements with Rayleigh analysis, piezoelectric measurements, and etching experiments of progressively switched samples. The analysis shows that the gradual opening of the polarization hysteresis loops associated with wake‐up is driven by a gradual increase in the domain‐wall density and/or domain‐wall mobility with electric field cycle to the polarity opposite to the growth polarity. The insights of this discovery will help to guide interface and polarity design in the eventual deployment of reliable devices based on these materials. [ABSTRACT FROM AUTHOR]

By the finite-element method, we study the stress-strain state of an interface crack in a piezoelectric bimaterial polarized in the direction perpendicular to the crack faces and subjected at infinity to the action of an electric field parallel to the crack and stresses parallel to the axis of polarization. On the crack faces, we consider the main versions of electrostatic boundary conditions, namely, impermeability (insulation), electric permeability, electric conductivity, and also a version of mixed boundary conditions, i.e., electric conductivity of a middle part of the top face and insulation of the remaining part of the crack. The formation of zones of mechanical contact between the faces is possible. The problem is considered in the statement of plane deformation. The energy release rates are found with the help of the virtual crack closure integral method. It is shown that the type of boundary conditions strongly affects the parameters of fracture. [ABSTRACT FROM AUTHOR]

In this paper, a theoretical model of the propagation of a shear horizontal wave in a piezoelectric semiconductor semi-infinite medium is established using the optimized spectral method. First, the basic equations of the piezoelectric semiconductor semi-infinite medium are derived with the consideration of biased electric fields. Then, considering the propagation of a shear horizontal wave in the piezoelectric semiconductor semi-infinite medium, two equivalent mathematical models are established. In the first mathematical model, the Schottky junction is theoretically treated as an electrically imperfect interface, and an interface characteristic length is utilized to describe the interface effect of the Schottky junction. To legitimately confirm the interface characteristic length, a second mathematical model is established, in which the Schottky junction is theoretically treated as an electrical gradient layer. Finally, the dispersion and attenuation curves of shear horizontal waves are numerically calculated using these two mathematical models to discuss the influence of the Schottky junction on the dispersion and attenuation characteristics of shear horizontal waves. Utilizing the equivalence of these two mathematical models and the above numerical results, the numerical value of the interface characteristic length is reliably legitimately confirmed; this value is independent of the thickness of the upper metal layer, the doping concentration of the lower n-type piezoelectric semiconductor substrate, and biasing electric fields. Only the biasing electric field parallel to the Schottky junction can provide an evident influence on the attenuation characteristics of shear horizontal waves and enhance the interface effect of the Schottky junction. Since the second mathematical model is also a validation of our previous mathematical model established through the state transfer equation method, some numerical results calculated using these two mathematical models are compared with those obtained using the previous method to verify the correctness and superiority of the research work presented in this paper. Since these two mathematical models can better calculate the dispersion and attenuation curves of high-frequency waves in micro- and nano-scale piezoelectric semiconductor materials, the establishment of mathematical models and the revelation of physical mechanisms are fundamental to the analysis and optimization of micro-scale resonators, energy harvesters, and amplifications. [ABSTRACT FROM AUTHOR]

BaTiO3 nanofibers (BT NFs), prepared by electrospinning, were used as a filler for electrospun poly(vinylidene fluoride‐co‐trifluoroethylene) (PVDF‐TrFE) nanocomposite mats. The phase structure and the effect of poling conditions on the piezoelectric properties of PVDF‐TrFE/BT nanocomposites were investigated. The results showed an improved degree of crystallinity (78.6%) and a high β‐crystal phase (up to 98.3%) in all electrospun samples, independent of the nanofiber content. The two‐step poling method, applying electric fields of opposite polarity, led to significantly improved piezoelectric constants d33 (−31.7 pC N−1), strongly dependent on the added BaTiO3 nanofibers. The inclusion of piezoelectric ceramic nanofibers into a polymer matrix, easily carried out by means of electrospinning, followed by an ad hoc optimized poling treatment, allowed to develop flexible materials with enhanced piezoelectric properties, potentially exploitable in innovative conversion systems used in wearable and sensing devices. [ABSTRACT FROM AUTHOR]

Two problems plague the field of electro-strain research: low electro-strain performance and high hysteresis. These two key factors are often difficult to optimise simultaneously. Therefore, a novel texture engineering strategy is proposed to obtain ultra-high strain while effectively reducing strain hysteresis. Synergistically optimized textured ceramics with a high degree of orientation in <001> direction were achieved by improving the preparation process based on the conventional TGG method through a heterogeneous template distinct from the ceramic substrate. Finally, the normalized strain of 951 pm/V at 40 kV/cm is obtained in the BNT-based lead-free system, and the strain hysteresis is only 43 %. At the same time, a series of in-situ electric field structural characterization reveal the source of high strain and low hysteresis of the textured ceramics: heterogeneous templates caused high polarization and formed a large number of PNRs. This result is of great significance for the study of electro-strain in lead-free piezoelectric materials and the development of actuators. [ABSTRACT FROM AUTHOR]

Piezoelectric materials are used in a wide range of engineering applications as sensors, actuators, and transducers due to their intrinsic properties. However, analyzing these devices is not straightforward because of the material anisotropy and coupled electromechanical nature of the problems. In this study, a stabilized non-ordinary state-based peridynamic model for linear piezoelectricity is proposed. Fully coupled electromechanical simulation is conducted using an implicit method, and the tangent stiffness matrix is obtained via perturbation technique. Three two-dimensional electromechanical problems with combined static loading and various boundary conditions are used to validate the proposed technique. Then, the crack-opening displacements, and induced electric field on the crack-face are presented for a center-cracked PZT-5H plate. Hence, this study demonstrates that the proposed technique is capable of modeling linear piezoelectric materials and provides a promising method to study fracture and damage progression in piezoelectric materials. • A stabilized, fully coupled, non-ordinary peridynamic model for linear piezoelectricity is formulated. • The boundary effects are significantly decreased by the proposed implicit solution technique. • The zero-energy modes are prevented by a stabilization technique. • Two different polarization directions, causing uniaxial tension-compression and shear, are considered. • A center-cracked piezoelectric plate under combined electromechanical loading is modeled by the proposed PD model. [ABSTRACT FROM AUTHOR]

Polymorphic phase transition boundary (PPB) strategy is effective in designing high-performance piezoelectric materials in (K 0.5 Na 0.5)NbO 3 (KNN)-based systems. However, the underlying mechanism of large piezoelectric response in KNN-based is still blurry and thus needs to be explored properly. In this paper, it is found that the domain reorientation becomes easier and more sufficient in the KNN-based ceramics with two-phase coexistence. Moreover, in situ transmission electron microscope experiments disclose the occurrence of a new intermediate phase under an external electric filed, which could relieve the internal stress generated by the domain reorientation and then facilitate the further domain switching along the electric field direction. The enhanced domain reorientation contributes to the high piezoelectric response in PPB region (d 33 = 438 pC/N, k p = 48%, d 33 * = 520 p.m./V at 1.5 kV/mm). Our work provides an in-depth understanding of the contribution of the domain switching and electric-filed-induced phase transition to piezoelectric properties in KNN-based ceramics, which shall benefit the design of new lead-free high-performance piezoelectric materials. [ABSTRACT FROM AUTHOR]

The electroelastic problem of the stress state of an electroelastic transversely isotropic medium in which a rigid disk-shaped inclusion is displaced under a load non-centrally applied to its surface is solved exactly. Closed analytical expressions for displacements and stress distributions in the piezoelectric material below the inclusion are derived. The solutions of the static electroelastic equations for a transversely isotropic body represented in terms of harmonic functions are used. The problem is reduced to pair integral equations. Expressions for the stress state of a purely elastic transversely isotropic material with a disk-shaped inclusion under non-central load on its surface the follow from the obtained analytical formulas as partial cases. The effect of the coupling of the mechanical and electric fields on the stress distribution below the rigid inclusion under non-central loading is studied numerically. [ABSTRACT FROM AUTHOR]

Surface‐enhanced Raman spectroscopy (SERS) has emerged as a distinctive fingerprinting technique, offering a broad spectrum of applications encompassing environmental monitoring, chemical detection, and biomolecular analysis. Electrically modulated SERS (E‐SERS) stands as a technique which leverages an electric field to finely control the Raman signal based on the foundational principles of SERS. Through the manipulation of the physicochemical attributes of a metal or 2D material substrate, E‐SERS brings about an enhancement of the SERS signal. This enhancement occurs through a charge transfer process and modulation of the plasma resonance. This article showcases recent strides in the domain of E‐SERS, encompassing advancements such as the integration of paired integrated electrodes, piezoelectric materials, and pyroelectric materials in the construction of substrates. An exhaustive analysis of the mechanism underpinning the enhancement of the Raman signal is undertaken, alongside an exploration of the prominent attributes characterizing diverse methods for conditioning Raman signals. Elucidations are provided on the significance of employed electric fields in the augmentation of SERS and their manifold applications in drug identification, chemical detection, and catalysis. In summation, a delineation of challenges and perspectives inherent to E‐SERS substrates is presented, delineating a path for prospective comprehensive exploration within this auspicious realm of research. [ABSTRACT FROM AUTHOR]

Piezoelectric ceramics with high strain response and low hysteresis are highly in demand for high-performance actuator applications. Unfortunately, the trade-off relationship between large field-induced strain and low hysteresis in piezoelectric ceramics is a key challenge for designing high-performance piezoelectric actuators. Herein, y mol%La-doped 0.10 Pb(In 1/2 Nb 1/2)O 3 - x PbZrO 3 -(0.90 – x)PbTiO 3 [0.10PIN- x PZ-(0.90-x)PT: y mol%La] ternary relaxor ferroelectric ceramics were prepared by conventional solid-state reaction technique. Pb(In 1/2 Nb 1/2)O 3 (PIN) as a relaxor end member was introduced into (Pb,La) (Zr,Ti)O 3 (PLZT) system to improve relaxor characteristics and strain properties. A giant strain of 0.23% was obtained in 0.10PIN-0.59PZ-0.31 PT: 8mol%La ceramic at the electric field of 20 kV/cm, with a high piezoelectric d 33 * of 1150 pm/V and low hysteresis H y of 6.4%, exhibiting a potential application in high-performance piezoelectric actuators. Furthermore, the effects of La ion doping and components on the ferroelectric, dielectric and electric field-induced strain properties were investigated, and provides a new way for improve the strain properties of piezoelectric materials. [ABSTRACT FROM AUTHOR]

This paper is offered as a complementary adjunct to the many treatments of the electronic and photonic properties of cubic III–V and II–VI compounds appearing in the literature. These crystals typically exhibit piezoelectricity, due to the molecular dissymmetry, thereby allowing the inclusion of classical mechanical/acoustic features along with the quantum. We discuss the history of this modality and then illustrate its use by applying it to an electro‐elastic problem that has the estimable virtues of having an exact solution, along with wide practical applicability: determination of the piezocoupling values governing the excitation of thickness vibrations in thin cubic films or plates of arbitrary crystallographic orientation by electric fields directed either along, or lateral to, the thickness. Explicit results are given for orientations along the great‐circle paths connecting the principal directions [100], [110], and [111]. The formalism is then applied to GaAs as an example; it is further demonstrated that various results, such as the orientational variations of piezocoupling factors, are generally applicable to other members of the III–V and II–VI families by scaling. Ancillary aspects, such as errors due to misorientations, nonlinearities, and equivalent circuit representations, are described and discussed. This work is dedicated to Gerald W. Farnell (1925–2015), Prof. Emeritus, McGill University, Montréal, Canada. [ABSTRACT FROM AUTHOR]

This paper presents elasticity solutions for functionally graded piezoelectric plates under electric fields in cylindrical bending. Based on the generalized Mian and Spencer plate theory, the assumption of the material parameters which can vary along the thickness direction of the plate in an arbitrary fashion is kept; however, the materials are extended from elastic materials to piezoelectric materials. The electric potential function is constructed following the forms of the displacement functions in Mian and Spencer plate theory. The essential idea of Mian and Spencer plate theory (J Mech Phys Solids 46:2283–2295, 1998) is that the three-dimensional elasticity equations for inhomogeneous materials can be obtained by two-dimensional solution for homogeneous materials by straightforward substitutions. Through rigorous derivation, the corresponding elasticity solutions of cylindrical bending of functionally graded piezoelectric plates under electric fields are obtained. In the numerical examples, the accuracy of the present solutions is verified and the responses of plates subjected to electrical potential difference and electrical displacement are investigated, respectively. [ABSTRACT FROM AUTHOR]

The formulation of the problem of surface control of an electroactive unidirectional multicomponent elastic wave propagation in an infinite piezoelectric waveguide over a finite time interval is discussed. Based on the conditions for conjugation of electromechanical fields on the surface of piezoelectric media, as well as on the nature of possible surface electromechanical effects, a variety of surface dynamic effects is considered through the components of the elastic displacement vector, the mechanical stress tensor, the tangential component of the electric field strength and the normal component of the electric field displacement. The possibility of setting the control problem in the case of three-component electroacoustic waves depending on the anisotropy of the piezoelectric material of the waveguide is studied. The anisotropy of a piezoelectric medium leads to the formulation of an initial-boundary mathematical problem for controlling the motion of a multicomponent system. The variety of surface actions leads to the formulation of heterogeneous initial-boundary mathematical problems with surface actions of the first kind, with surface actions of the second kind, as well as for the case of mixed surface actions. An invariant record of heterogeneous initial-boundary mathematical problems is proposed in the form of a system of inhomogeneous quasi-static electro-elasticity equations, with homogeneous boundary conditions and inhomogeneous conditions of the initial and final states. [ABSTRACT FROM AUTHOR]

Piezoelectric biomaterials have attracted great attention owing to the recent recognition of the impact of piezoelectricity on biological systems and their potential applications in implantable sensors, actuators, and energy harvesters. However, their practical use is hindered by the weak piezoelectric effect caused by the random polarization of biomaterials and the challenges of large-scale alignment of domains. Here, we present an active self-assembly strategy to tailor piezoelectric biomaterial thin films. The nanoconfinement-induced homogeneous nucleation overcomes the interfacial dependency and allows the electric field applied in-situ to align crystal grains across the entire film. The β-glycine films exhibit an enhanced piezoelectric strain coefficient of 11.2 pm V−1 and an exceptional piezoelectric voltage coefficient of 252 × 10−3 Vm N−1. Of particular significance is that the nanoconfinement effect greatly improves the thermostability before melting (192 °C). This finding offers a generally applicable strategy for constructing high-performance large-sized piezoelectric bio-organic materials for biological and medical microdevices. Piezoelectric biomaterials are limited by the challenges in domain orientation alignment and a weak piezoelectric effect. Here, Zhang et. al. present an active self-assembly strategy via nanoconfinement and in-situ poling, to obtain large-scale, high performance piezoelectric β-glycine nanocrystalline films. [ABSTRACT FROM AUTHOR]

As smart structures are becoming increasingly ubiquitous in our daily life, the need for efficient modeling electromechanical coupling devices is also rapidly advancing. Smart structures are often made of piezoelectric materials such as lead zirconate titanate (PZT), which exhibits strong nonlinear behavior known as hysteresis effect under a large applied electric field. There have been numerous modeling techniques that are able to capture such an effect; some techniques are suitable for obtaining physical insights into the micro-structure of the material, while other techniques are better-suited to practical structural analyses. In this paper, we aim to achieve the latter. We propose a simplified phenomenological macroscopic model of a nonlinear ferroelectric actuator. The assumption is based on the direct relation between the irreversible strain and irreversible electric field, and the consequently irreversible polarization. The proposed model is then implemented in a finite element framework, in which the main features such as local return mapping and the tangent moduli are derived. The outcomes of the model are compared and validated with experimental data. Therefore, the development presented in this paper can be a useful tool for the modeling of nonlinear ferroelectric actuators. [ABSTRACT FROM AUTHOR]

In this article, analytical solutions of piezoelectric bimorph and unimorph actuator in cantilever configurations are developed using the second-order constitutive equation. Tip deflection ratio (TDR), a dimensionless parameter, is defined to analyze the effect of second-order coefficients of piezoelectric materials on the response of bimorph and unimorph actuators. Four piezoelectric unimorphs of varying geometries are fabricated and tested to verify the nonlinear response under applied electric field. Furthermore, second-order coefficients of lead zirconate titanate (PZT; APC 850) are derived by fitting the experimental data with nonlinear analytical solution. The nonlinear response of all the piezoelectric unimorphs compares well with the experimental results. [ABSTRACT FROM AUTHOR]

Photo(electro)catalytic technologies employ renewable solar energy to address the energy crisis and mitigate environmental pollution. However, solar-energy-based applications suffer from limitations owing to low conversion efficiencies, mainly because the driving force for charge separation and transfer within photoelectrode materials is insufficient. Herein, we review the formation mechanisms of polarized electric fields in piezoelectric and ferroelectric photo(electro)catalytic materials, describe the photocatalytic properties of these materials, and discuss recent research progress. Moreover, the application of defect engineering to construct internally polarized electric fields is discussed. Constructing polarization internal fields via defect engineering is an effective method for driving charge separation and transfer in photoelectrode materials without intrinsic polarized electric fields. Reversible dipoles can be constructed by introducing defect dipoles and developing adjustable ferroelectric-like fields through the synergistic regulation of domain and grain boundaries. The mechanism of polarization in bulk materials is complicated, and controlling the induction and regulation of piezoelectric internal polarized electric fields is difficult. We aim to identify the key factors of constructed internal fields involved in the regulation of photo(electro)catalytic performance, clarify the structure-activity relationships between internal electric fields and photo(electro)catalytic characteristics, and guide the design and preparation of highly active photo(electro)catalytic materials. [Display omitted] • The role of internal fields in regulating photo(electro)catalysis was reviewed. • The review summarized current researches on piezoelectric and ferroelectric materials. • Defect engineering in constructing internal polarized electric fields was introduced. • The review discussed the future development directions and trends of internal fields. [ABSTRACT FROM AUTHOR]

The use of piezo-catalysis for H 2 production from water at ambient conditions has recently gained significant attention, yet the importance of cocatalyst engineering has been largely overlooked. In this study, AuPt alloy nanoparticles were used as cocatalysts on the piezoelectric material BiOCl for H 2 evolution driven by sonication. The Au:Pt ratio of 3:1 significantly enhanced the reaction, resulting in a doubling of H 2 production compared to Au alone and a tripling compared to Pt alone. Experiments and simulations showed that AuPt alloys promote H* adsorption and facilitate the separation of piezoelectric carriers. Additionally, the cocatalysts enhance the piezo-catalytic reaction by increasing the stress and deformation of the BiOCl microplates. Unlike the photocatalytic process, the piezo-catalytic H 2 evolution on BiOCl succeeded due to the suppression of BiOCl reduction by the periodically accumulated piezo-electrons and holes. This research highlights the critical role of cocatalyst engineering in optimizing piezo-catalytic H 2 production and presents a promising strategy for efficient H 2 generation. [Display omitted] • AuPt alloy nanoparticles were added to BiOCl microplates using photo-deposition. • AuPt/BiOCl performed better than Au/BiOCl and Pt/BiOCl for piezo-catalytic hydrogen production. • AuPt is more active and better at trapping charges. • Cocatalysts increased the stress and deformation of BiOCl during sonication. • Piezo-catalysis is more effective than photocatalysis due to its reversible electric field. [ABSTRACT FROM AUTHOR]

BiVO 4 is a promising photoanode material. However, achieving only a 2.67 % maximum ABPE while having a theoretical solar conversion efficiency of 9.2 % highlights the need for an effective carrier regulation strategy. In this study on the piezoelectric material BiVO 4 , Cl--embedded modification through synthetic post-treatment changes the oxygen evolution reaction (OER) pathway and suppresses surface charge recombination. In addition, the surprising finding of Cl- bonding with Bi3+ causing distortion in the BiO 8 polar groups not only enhances the piezoelectric response but also significantly improves the performance of piezo-photoelectric chemical (Piezo-PEC) water oxidation. In the absence of any co-catalyst or sacrificial agent, the photocurrent density of Cl--embedded modified BiVO 4 reached 0.268 mA/cm2 at 1.23 V RHE (5 times that of bare BiVO 4). The data indicate that the piezoelectric polarized electric field successfully reduces electron-hole recombination. Cl--embedded modification amplifies the electric field intensity of the surface electric dipole in an ultrasonic environment, facilitating hole access to the catalytically active sites on the surface. Furthermore, the modified surface layer creates a rapid channel for hole migration, with the hole trapping process intricately linked to isolated electrons and intermediate Cl atoms. This embedded modification of polar groups serves as a reference for further exploration into the macroscopic polarization of piezoelectric materials and offers an optimization concept for the field of Piezo-PEC catalysis. [Display omitted] • The post-synthesis treatment embeds Cl- into the BiVO 4 surface BiO 8 polar groups of Piezo- PEC cells. • The bonding of Cl- to Bi3+ improves the surface piezoelectric polarization electric field strength. • Cl- trapped hole produces [–Cl·(H 2 O) x ] radical, complexed with water to form ·OH, accelerating O 2 formation. • Ultrasound-induced piezoelectric polarization electric field accelerates the separation of photogenerated carriers. • Optimal sample exhibits a fivefold increase in photocurrent density compared to pure BiVO 4 at 1.23 V RHE. [ABSTRACT FROM AUTHOR]

The aim of this paper was to extend the traditional plane wave expansion method to calculate the band structure of a proposed piezoelectric phononic crystal (PC) nanobeam with surface effect. The first four orders were chosen to investigate the influence of electrical fields, surface effects, and geometric parameters upon bandgaps. We chose the external electrical voltage applied as the influencing parameter related to electric field. Residual surface stress and material intrinsic length were chosen as the influencing parameters related to surface effect. The influencing geometric parameters were the length of PZT-5H material and epoxy in a unit cell, along with the width and thickness of the PC nanobeam. We hypothesized that data arising from these investigations would be helpful in designing piezoelectric nanobeam-based devices. [ABSTRACT FROM AUTHOR]

This paper presents the numerical simulation of permeable, semi-permeable and impermeable crack interaction study in 2D piezoelectric domains using an element-free Galerkin method (EFGM). The electric and displacement fields are described by introducing the singularity terms into an approximation function. This study is performed with respect to effects of electrical loading, crack surface boundary conditions, crack orientation angles, aspect ratio and number of cracks in order to examine these effects on fracture parameters. Multiple inclined equidistant cracks are considered in piezoelectric domain under different crack surface boundary conditions. The proposed enrichment criterion accurately estimates fracture parameters which shows the robustness, efficacy and applicability of EFGM approach. [ABSTRACT FROM AUTHOR]

This paper introduces a new approach of testing piezoelectric nanofibers as antibacterial mat. In this work, both Polyvinylidene fluoride (PVDF) and PVDF embedded with thermoplastic polyurethane nanofibers are synthesized as nanofibers mat via electrospinning technique. Then, such mat is analyzed as piezoelectric material to generate electric voltage under different mechanical excitations. Furthermore, morphological and chemical characteristics have been operated to prove the existence of beta sheets piezoelectricity of the synthesized nanofibers mats. Then, the synthesized nanofibers surfaces have been cyclically stretched and exposed to bacteria specimen. It has been noticed that the generated voltage and the corresponding localized electric field positively affect the growth of bacteria and reduces the formation of K. penomenue samples bacteria colonies. In addition, the effect of both stretching frequency and pulses numbers have been studied on the bacteria count, growth kinetics, and protein leakage. Our contribution here is to introduce an innovative way of the direct impact of the generated electric field from piezoelectric nanofibers on the reduction of bacteria growth, without depending on traditional anti-bacterial nanoparticles. This work can open a new trend of the usability of piezoelectric nanofibers through masks, filters, and wound curing mats within anti-bacterial biological applications. [ABSTRACT FROM AUTHOR]

The complex process of wound healing depends on the coordinated interaction between various immunological and biological systems, which can be aided by technology. This present review provides a broad overview of the medical applications of piezoelectric and triboelectric nanogenerators, focusing on their role in the development of wound healing technology. Based on the finding that the damaged epithelial layer of the wound generates an endogenous bioelectric field to regulate the wound healing process, development of technological device for providing an exogenous electric field has therefore been paid attention. Authors of this review focus on the design and application of piezoelectric and triboelectric materials to manufacture self-powered nanogenerators, and conclude with an outlook on the current challenges and future potential in meeting medical needs and commercialization. [ABSTRACT FROM AUTHOR]

The aim of this article is to investigate the scattering of anti-plane shear waves by elliptic notches in a quarter-space piezoelectric material. The wave field and electric field expressions in this region are derived using the wave function expansion method. An infinite linear system of equations is established by applying the boundary conditions of no traction and no potential. The results obtained are accurate due to the good convergence of the wave function. The displacement amplitude and dynamic stress in the vicinity of the elliptic arc notch under different characteristic parameters and different wave numbers are computed numerically. [ABSTRACT FROM AUTHOR]

Introducing piezoelectric materials with the built-in electric field caused by mechanical force has been confirmed as an effective strategy to boost the separation efficiency of photoexcited charge carriers that determines the photocatalytic performance. In this study, we introduced Bi4Ti3O12 with superior piezoelectric properties into BiVO4–Bi4V2O10 materials to synthesize a 2D Bi4Ti3O12–BiVO4–Bi4V2O10 photocatalyst via a facile hydrothermal method. Compared with bare BiVO4, the Bi4Ti3O12–BiVO4–Bi4V2O10 piezo-photocatalytic activity towards Cr(VI) removal and oxygen evolution is boosted remarkably under both illumination and ultrasound treatments. The promoted photocatalytic activity can be ascribed to the accelerated photoexcited carrier separation efficiency driven by the polarization electric field and the synergy effect in the heterostructure. This work provides a simple and sustainable strategy for the design and development of piezo-photocatalysts with high photoredox activity capacity. [ABSTRACT FROM AUTHOR]

Solar‐driven overall water splitting is an ideal way to generate renewable energy while still challenging. For the first time, this work combined covalent organic frameworks (COFs) and piezoelectric material by covalent linkages to form Z‐scheme core@shell heterostructure for overall water splitting. Benefiting from the synergistic effect between the polarized electric field and photo‐generated charges, as well as the precise adjustment of shell thickness, the carrier separation and utilization efficiency is greatly improved. The optimal BiFeO3@TpPa‐1‐COF photocatalyst revealed hydrogen (H2) and oxygen (O2) production rates of 1416.4 and 708.2 μmol h−1 g−1 under the excitation of ultrasonication coupled with light irradiation, which is the best performance among various piezo‐ and COF‐based photocatalysts. This provides a new sight for the practical application of highly efficient photocatalytic overall water splitting. [ABSTRACT FROM AUTHOR]

With the great success on verifying its effectiveness on relaxor-PbTiO3 (PT) single crystals (SCs), alternating current poling (ACP) has been taking a center as a new domain engineering method in the last few years. Compared with the conventional direct current poling (DCP), ACP enables enhanced piezoelectric and dielectric properties. In this article, research progress in ACP and perspectives are introduced. Initially, optimized conditions of ACP for relaxor-PT SCs and unsolved issues on polycrystalline ceramics and spurious modes are reviewed. Second, the ferroelectric domain size dependence of piezoelectricity associated with ACP is discussed. We hypothesize that a tradeoff between domain and domain wall contributions exists for high piezoelectricity, suggesting an optimum 109° domain wall size, which is presumably dependent on compositions, crystallographic symmetries, and domain configurations. Finally, crystals synthesized by a solid-state crystal growth (SSCG) method are briefly introduced due to their unprecedented piezoelectricity obtained by ACP (${d}_{33} \sim 5500$ pC/N). We hope that this work helps to grasp the current status of ACP and to guide future tasks to be studied. [ABSTRACT FROM AUTHOR]

Bi 0.5 Na 0.5 TiO 3 is regarded a potential alternative to lead-based piezoelectric materials due to its large electro-strain. Generally, the improved electro-strain is considered to arise from a relaxor-ferroelectric transition, and the random fields play a critical role. In this study, to investigate the effect of random electric field or strain field on the strain value, the dopant Sb5+, Ta5+, Zr4+, and Hf4+ are introduced into the Bi 0.5 (Na 0.8 K 0.2) 0.5 Ti 1- x B x O 3 matrix, respectively. The 1 % Ta5+ doped sample has the largest unipolar electro-strain, up to 0.49 %, followed by the 3 % Zr4+ doped sample (∼0.448 %). The electro-strain of 1 % Sb5+ and 3 % Hf4+ samples are 0.404 % and 0.377 %, respectively. The results show the random electric field or strain field can effectively regulate the relaxor-ferroelectric transition temperature, which enhances strain, but the strain value cannot be determined directly. The strain value is determined by the lattice structure before and after the electric field is applied. [ABSTRACT FROM AUTHOR]

The present investigation focuses on magnetoelectric interactions in ferrite-piezoelectric bilayers in the ferromagnetic resonance (FMR) region. A dc electric field applied perpendicular to the sample plane gives rise to an in-plane strain that is transferred to the ferrite and produces a uniaxial thickness-dependent magnetic anisotropy. Expressions for microwave magnetic susceptibility are obtained taking into account the effects of flexural deformations. The results are applied to the specific case of yttrium iron garnet (YIG)/lead zirconate titanate (PZT). The study predicts the unique electric field dependence of FMR line broadening. For the specific YIG to PZT thickness ratio, magnetoelectric coupling results in a weak FMR line shift and considerable line broadening. The results are of interest for novel ferrite-piezoelectric microwave devices [ABSTRACT FROM AUTHOR]

The interfacial electric field of Bi 2 S 3 /Ni/CN composites has been found to enhance the piezo-catalytic performance in peroxymonosulfate activation for advanced oxidation processes (AOP) systems. This novel research field aims to strengthen AOP systems for pollutant control and degradation through the utilization of the piezo-catalysis. In this particular study, a hammer coral-like Bi 2 S 3 /Ni/CN composite with interfacial electric field was synthesized by incorporating bismuth sulfide into the Ni/CN matrix. The efficient separation of piezoelectric carriers and charge transfer between nickel and bismuth in the resulting Bi 2 S 3 /Ni/CN composite facilitate a synergistic effect in the activation of peroxymonosulfate (PMS). It has been observed that, when subjected to ultrasound, this composite can achieve a degradation rate exceeding 90% within a minute towards Rh B as a model dye. Notably, the degradation process is primarily driven by piezoelectric hole and mono-linear oxygen non-free radicals. Additionally, the interfacial electric field facilitates valence electron transfer and ultimately enhancing reaction efficiency. Experimental results further demonstrate that the removal efficiency of organic pollutants can surpass 98% within a pH range of 1–9 over a duration of 3 min, demonstrating wide pH response range and high catalytic activities. [Display omitted] • A hammer coral-like Bi 2 S 3 /Ni/CN composite with interfacial electric field was formed. • The interfacial electric field improves the piezoelectric effect under external stress. • The piezoelectric carriers and the transfer of charge promote a synergistic effect of AOP. • Piezoelectric hole and 1O 2 non-free radicals play a major role in AOPs. • It provides a new strategic approach for design of piezoelectric materials and its application in AOP. [ABSTRACT FROM AUTHOR]

For the practical implementation of Cr(Ⅵ) removal, effective and recyclable water treatment technology is essential. Polarized electric fields inside piezoelectric materials have proved to be a promising technique for facilitating photogenerated charge separation. In this work, Z-scheme heterojunction photocatalyst HKUST-1/BiVO 4 and organic piezoelectric material PVDF were combined through electrospinning to create a novel flexible fiber PVDF-HKUST-1/BiVO 4 (PVDF-HV) piezo-photocatalyst membrane. When the amount of HKUST-1/BiVO 4 powder was 2.4% and the diameter of the obtained fiber film was 10 cm, the optimal reduction efficiency can be achieved by the piezoelectric photocatalytic reduction in solution with initial pH=2, and the piezo-photocatalytic efficiency of PVDF-HV reached up to 85.33% within 120 min, which was about 1.35 times and 2.19 times greater than that of single photocatalysis and piezoelectric catalysis, respectively. It successfully promoted photo charge separation based on the piezoelectric field in PVDF and the heterojunction produced between HKUST-1 and BiVO 4. This research developed an efficient strategy for multi-path collection and exploitation of natural solar energy and vibration energy to boost photoactivity. [Display omitted] • Z-scheme HKUST-1/BiVO 4 and piezoelectric PVDF were combined through electrospinning. • Superior piezo-photocatalytic activity has been obtained by PVDF-HKUST-1/BiVO 4. • Synergistic effects of heterojunction and piezoelectricity was addressed. • The catalytic mechanism under ultrasound and visible light was revealed. [ABSTRACT FROM AUTHOR]

An interaction of electrically conductive and electrically permeable collinear cracks along an interface between two piezoelectric materials under the action of anti-plane mechanical loading and in-plane electric field is considered. It is assumed that the electric field is parallel to the crack faces and the materials polarization is co-directed with the crack fronts. Using the presentations of all required electromechanical quantities via sectionally analytic vector-function, a combined Dirichlet–Riemann boundary value problem is formulated. A closed-form analytical solution of this problem is presented for any distances between the cracks, any cracks lengths and any external loadings of the above-mentioned type. Analytical expressions for the shear stress, the electric field and their intensity factors as well as for the mechanical and electric displacement jumps are presented. The energy release rates are found for all crack tips, and their variation with respect to the external loading and the distance between the cracks is demonstrated. [ABSTRACT FROM AUTHOR]

Different from previous strategies utilized to improve the energy conservation efficiency of piezoelectric energy harvesters (PEHs) from the environment, by broadening the frequency-bandwidth of energy harvesters using a specifically designed structure or tuning their resonance frequency (RF) through changing the geometrical/dynamical constraints, we report a method—by applying a direct current (DC) electric field on piezoelectric elements—to tune the RF of PEH based on the phenomenon that the elastic parameters of piezoelectric material are related to its electric field boundary condition. The results of a confirmatory experiment revealed that with a pre-loading DC electric field of −0.5 to 0.75 kV/mm, the RF of a piezoelectric cantilever energy harvester can be tuned from 144 to 156 Hz. The effectiveness of this strategy was further verified by comparing the energy conservation output of the PEH at a frequency that deviates from its RF, and at the same frequency, with pre-loading DC electric field adjustment. [ABSTRACT FROM AUTHOR]