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Showing papers on "Piezoelectricity published in 2020"


Journal ArticleDOI
TL;DR: In this paper, a formal theory for nanogenerators is presented starting from the Maxwell's equations, which includes both the medium polarizations due to electric field (P) and non-electric field induced polarization terms, from which, the output power, electromagnetic behavior and current transport equation for a NG are systematically derived.

377 citations


Journal ArticleDOI
15 Jan 2020-Nature
TL;DR: This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectric domain engineering, and is expected to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices.
Abstract: Transparent piezoelectrics are highly desirable for numerous hybrid ultrasound–optical devices ranging from photoacoustic imaging transducers to transparent actuators for haptic applications1–7. However, it is challenging to achieve high piezoelectricity and perfect transparency simultaneously because most high-performance piezoelectrics are ferroelectrics that contain high-density light-scattering domain walls. Here, through a combination of phase-field simulations and experiments, we demonstrate a relatively simple method of using an alternating-current electric field to engineer the domain structures of originally opaque rhombohedral Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) crystals to simultaneously generate near-perfect transparency, an ultrahigh piezoelectric coefficient d33 (greater than 2,100 picocoulombs per newton), an excellent electromechanical coupling factor k33 (about 94 per cent) and a large electro-optical coefficient γ33 (approximately 220 picometres per volt), which is far beyond the performance of the commonly used transparent ferroelectric crystal LiNbO3. We find that increasing the domain size leads to a higher d33 value for the [001]-oriented rhombohedral PMN-PT crystals, challenging the conventional wisdom that decreasing the domain size always results in higher piezoelectricity8–10. This work presents a paradigm for achieving high transparency and piezoelectricity by ferroelectric domain engineering, and we expect the transparent ferroelectric crystals reported here to provide a route to a wide range of hybrid device applications, such as medical imaging, self-energy-harvesting touch screens and invisible robotic devices. The use of alternating-current electric fields to control domain size in ferroelectric crystals affords excellent transparency, piezoelectricity and birefringence.

311 citations


Journal ArticleDOI
21 Jun 2020-Sensors
TL;DR: The goal of this paper is to review current methods of energy harvesting, while focusing on piezoelectric energy harvesting and present several circuits used to maximize the energy harvested.
Abstract: The goal of this paper is to review current methods of energy harvesting, while focusing on piezoelectric energy harvesting The piezoelectric energy harvesting technique is based on the materials' property of generating an electric field when a mechanical force is applied This phenomenon is known as the direct piezoelectric effect Piezoelectric transducers can be of different shapes and materials, making them suitable for a multitude of applications To optimize the use of piezoelectric devices in applications, a model is needed to observe the behavior in the time and frequency domain In addition to different aspects of piezoelectric modeling, this paper also presents several circuits used to maximize the energy harvested

244 citations


Journal ArticleDOI
TL;DR: In this paper, polydopamine (PDA) was introduced as a surface modification agent to modify barium titanate (BaTiO3, BTO), which was then blended with poly(vinylidene fluoride) matrix in different ratios to form uniform and homogeneous PDA@BTO/PVDF composites.
Abstract: Flexible pressure sensors based on piezoelectric materials have been intensively investigated for their wide applications in wearable electronics. However, traditional films based on inorganic/organic composite piezoelectric materials face the bottleneck of defects and cracks or poor dispersion, which hinders the performance of pressure sensors. Herein, polydopamine (PDA) was introduced as a surface modification agent to modify barium titanate (BaTiO3, BTO), which was then blended with poly(vinylidene fluoride) (PVDF) matrix in different ratios to form uniform and homogeneous PDA@BTO/PVDF composites. Afterwards, the flexible piezoelectric pressure sensor was fabricated by a facial solution-casting method. This PDA-modification strategy can improve the dispersion of BTO into PVDF matrix, as well as reduce the interface hole defects and cracks between the two components. As a result, the 17 wt% PDA@BTO/PVDF sensor exhibited a fast response of 61 ms and a remarkable piezoelectric output voltage of 9.3 V, which showed obvious improvement as compared to the pristine PVDF and BTO/PVDF composite counterparts. In addition, as an energy supplier, the sensor could produce a maximum power of 0.122 μW/cm2 even with high load resistance of 70 MΩ. This pressure sensor was sensitive to various human motions, showing great potential in the applications of wearable electronics.

219 citations


Journal ArticleDOI
TL;DR: The results suggest that the glycine–chitosan composite is a promising new biobased piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics.
Abstract: This paper presents flexible pressure sensors based on free-standing and biodegradable glycine-chitosan piezoelectric films. Fabricated by the self-assembly of biological molecules of glycine within a water-based chitosan solution, the piezoelectric films consist of a stable spherulite structure of β-glycine (size varying from a few millimeters to 1 cm) embedded in an amorphous chitosan polymer. The polymorphic phase of glycine crystals in chitosan, evaluated by X-ray diffraction, confirms formation of a pure ferroelectric phase of glycine (β-phase). Our results show that a simple solvent-casting method can be used to prepare a biodegradable β-glycine/chitosan-based piezoelectric film with sensitivity (∼2.82 ± 0.2 mV kPa-1) comparable to those of nondegradable commercial piezoelectric materials. The measured capacitance of the β-glycine/chitosan film is in the range from 0.26 to 0.12 nF at a frequency range from 100 Hz to 1 MHz, and its dielectric constant and loss factor are 7.7 and 0.18, respectively, in the high impedance range under ambient conditions. The results suggest that the glycine-chitosan composite is a promising new biobased piezoelectric material for biodegradable sensors for applications in wearable biomedical diagnostics.

184 citations



Journal ArticleDOI
TL;DR: A new piezoelectric nanogenerator with a three-dimensional intercalation electrode is developed to reach 290 μA cm −2 by creating and utilizing many boundary interfaces, which contributes to an increased current density.
Abstract: The low output current density of piezoelectric nanogenerators (PENGs) severely restricts their application for ambient mechanical energy harvest. This has been a key challenge in the development of PENG. Here, to conquer this, based on a piezoelectric material with high piezoelectric coefficient (Sm-PMN-PT), a new design of PENG with a three-dimensional intercalation electrode (IENG) is proposed. By creating many boundary interfaces inside the piezoelectric material, the total amount of surface polarization charges increased, which contributes to an increased current density. The IENG can output a maximum peak short-circuit current of 320 μA, and the corresponding current density 290 μA cm−2 is 1.93 and 1.61 times the record values of PENG and triboelectric nanogenerator (TENG), respectively. It can also charge a 1 μF capacitor from 0 V to 8 V in 21 cycles, and the equivalent surface charge density 1690 μC m−2 is 1.35 times the record value of TENG. Increasing the output current density is the key challenge for nanogenerators. Here, a new piezoelectric nanogenerator with a three-dimensional intercalation electrode is developed to reach 290 μA cm−2 by creating and utilizing many boundary interfaces.

135 citations


Journal ArticleDOI
Jiagang Wu1
TL;DR: In this article, the authors provide an overview of key advances related to the structures and properties of lead-free piezoelectrics, including (K,Na)NbO3, BaTiO3 and BiFeO3.
Abstract: The ability of piezoelectric devices to convert mechanical energy to electrical energy and vice versa has inspired remarkable growth in research on piezoelectric materials. However, based on the Restriction of Hazardous Substances legislation, it is necessary to eliminate the lead from currently used piezoelectric ceramics. Together with the increasing market share and improved performance of lead-free piezoelectrics, this growing recognition that the use of lead should be limited in piezoelectric materials has promoted the development of lead-free piezoelectric ceramics. Some devices with excellent performance based on lead-free piezoelectric ceramics have been reported, and their applications are expected to increase in the near future. This perspective provides an overview of key advances related to the structures and properties of lead-free piezoelectrics, including (K,Na)NbO3, BaTiO3, Bi0.5Na0.5TiO3, and BiFeO3. Future prospects are also discussed based on the performances of lead-free piezoelectric materials investigated to date.

116 citations


Journal ArticleDOI
19 Aug 2020-Nature
TL;DR: This study enriches the functionalities of heterostructure interfaces, offering a distinctive approach to realizing energy transduction beyond the conventional limitation imposed by intrinsic symmetry.
Abstract: Interfaces in heterostructures have been a key point of interest in condensed-matter physics for decades owing to a plethora of distinctive phenomena-such as rectification1, the photovoltaic effect2, the quantum Hall effect3 and high-temperature superconductivity4-and their critical roles in present-day technical devices However, the symmetry modulation at interfaces and the resultant effects have been largely overlooked Here we show that a built-in electric field that originates from band bending at heterostructure interfaces induces polar symmetry therein that results in emergent functionalities, including piezoelectricity and pyroelectricity, even though the component materials are centrosymmetric We study classic interfaces-namely, Schottky junctions-formed by noble metal and centrosymmetric semiconductors, including niobium-doped strontium titanium oxide crystals, niobium-doped titanium dioxide crystals, niobium-doped barium strontium titanium oxide ceramics, and silicon The built-in electric field in the depletion region induces polar structures in the semiconductors and generates substantial piezoelectric and pyroelectric effects In particular, the pyroelectric coefficient and figure of merit of the interface are over one order of magnitude larger than those of conventional bulk polar materials Our study enriches the functionalities of heterostructure interfaces, offering a distinctive approach to realizing energy transduction beyond the conventional limitation imposed by intrinsic symmetry

104 citations


Journal ArticleDOI
TL;DR: In this paper, flexible pressure sensors based on PVDF-PZT nanocomposite with different PZT volume fractions were prepared in the form of fibers through an electrospinning method for piezoelectric energy harvesting application.

99 citations


Journal ArticleDOI
TL;DR: These results add piezoelectricity to the known properties of monolayer hBN, which makes it a desirable candidate for novel electromechanical and stretchable optoelectronic devices, and pave a way to control the local electric field and carrier concentration in van der Waals heterostructures via strain.
Abstract: 2D hexagonal boron nitride (hBN) is a wide-bandgap van der Waals crystal with a unique combination of properties, including exceptional strength, large oxidation resistance at high temperatures, and optical functionalities. Furthermore, in recent years hBN crystals have become the material of choice for encapsulating other 2D crystals in a variety of technological applications, from optoelectronic and tunneling devices to composites. Monolayer hBN, which has no center of symmetry, is predicted to exhibit piezoelectric properties, yet experimental evidence is lacking. Here, by using electrostatic force microscopy, this effect is observed as a strain-induced change in the local electric field around bubbles and creases, in agreement with theoretical calculations. No piezoelectricity is found in bilayer and bulk hBN, where the center of symmetry is restored. These results add piezoelectricity to the known properties of monolayer hBN, which makes it a desirable candidate for novel electromechanical and stretchable optoelectronic devices, and pave a way to control the local electric field and carrier concentration in van der Waals heterostructures via strain. The experimental approach used here also shows a way to investigate the piezoelectric properties of other materials on the nanoscale by using electrostatic scanning probe techniques.

Journal ArticleDOI
04 Mar 2020
TL;DR: In this article, under precise molecular modifications, the authors successfully designed and regulated four high-temperature multiaxial molecular ferroelectrics, [(CH3)3NCH2X]FeBr4 (X = F, Cl, Br, I).
Abstract: Summary Ferroelectrics, as piezoelectric materials with reversal polarization, have great appeal in energy signal harvesting and conversion. Their polarization and piezoelectricity are widely used in various smart devices such as data storage, sensors, solar cells, and self-powered systems. Among them, multiaxial molecular ferroelectrics with multiple equivalent polarization directions are highly preferred for such applications. However, designing and regulating multiaxial molecular ferroelectrics has always been a huge challenge, especially in those with excellent piezoelectric performance. Here, under precise molecular modifications, we successfully designed and regulated four high-temperature multiaxial molecular ferroelectrics, [(CH3)3NCH2X]FeBr4 (X = F, Cl, Br, I). More strikingly, piezoresponse force microscopy demonstrates that [(CH3)3NCH2F]FeBr4 exhibits a relatively large piezoelectric response comparable with that of polyvinylidene fluoride. This precise molecular design strategy provides an effective means for the acquisition and regulation of multiaxial molecular ferroelectrics, offering new opportunities for modern energy and artificial intelligence.

Journal ArticleDOI
TL;DR: In this article, a synergistic design strategy is proposed to enhance the piezoelectricity in lead-free piezoceramics by flattening the Gibbs free energy density profile, via the coexistence of multiple phases and local structural heterogeneity.

Journal ArticleDOI
TL;DR: In this article, a lead-free Pb(Zr,Ti)O3-based ceramics with pseudo-cubic phase was studied, exhibiting high electric-field-induced strain of 0.38% (60 kV/cm) with large signal piezoelectric coefficient d33* of 720 kpm/V (40 kv/cm).

Journal ArticleDOI
TL;DR: In this paper, a novel strategy to increase the strain of a lead-free ferroelectric system via material structure design to create polar nano regions (PNRs) and point defects in the material while retaining the global phase was introduced.

Journal ArticleDOI
TL;DR: In this paper, the authors reported a lead-free PZT-based ceramics with high P4mm-p4mm phase transition transition threshold and showed that the porosity of the poramics can be improved by using a double-hysteresis polarization field loop.
Abstract: DOI: 10.1002/aelm.201900949 boundaries (MPB), where multiple ferroelectric polar structures coexist,[5,6] as exemplified by their complicated composition-temperature phase diagrams.[7–10] Coexisting fragile polar states can be easily altered by external stress or electric field, thereby resulting in a large piezoelectricity.[5,6,11–15] Among them, lead zirconium titanate (PZT) based ceramics with piezoelectric coefficient d33 = 300–700 pC N−1 (Figure 1) are market-dominating, and widely used in sensors, actuators, and other electronic devices due to their excellence properties.[16,17] In view of the environmental regulations against the use of toxic lead, tremendous efforts have been performed worldwide in search of alternative lead-free piezoelectric materials.[13,18–25] A milestone in the development of lead-free piezoelectric materials was the appearance of a large piezoelectric constant d33 of 416 pC N−1 in (K0.5Na0.5)NbO3 (KNN)-based textured ceramics via a doping-driven MPB approach using templated-graingrowth technique by Saito et al.,[18] which trigged an explosion of world-wide research activities.[5,13,15–17,19,20,23,26–29] In order to further enhance the piezoelectricity of lead-free materials, Liu et al. reported a high value of d33 ≈ 620 pC N−1 in Ba(Zr0.2Ti0.8) O3-x(Ba0.7Ca0.3)TiO3 ceramic system by constructing MPB from a tricritical triple point of a cubic nonpolar, ferroelectric rhombohedral, and tetragonal phases.[13] The development in piezoelectric coefficient enhancement at room temperature is summarized in Figure 1, also including a comparison with several typical PZT ceramics. With regards to actuator applications, the electromechanical properties have also been studied in lead-free piezoelectric materials. In 2007, Zhang et al. reported a giant electric-field induced stain in ternary (Na0.5Bi0.5)TiO3BaTiO3-(K0.5Na0.5)NbO3 (NBT-BT-KNN) ceramics,[22] consequently leading to a rapid surge in the research of macrostrain enhancement and microstructure understanding in bismuth– alkali-based systems.[25,30–34] The origin of the giant strain has been determined to be a phase transition from unclear initial state into a ferroelectric tetragonal phase (P4mm),[32] but the ground state remains controversial concerning whether it is a nonergodic relaxor with an average cubic symmetry according to the dielectric dispersion or antiferroelectric state with extremely small distortion based on its double-hysteresis polarization-field loop.[9,16,30] Either way, long range order was perlocated with rhombohedral R3c and tetragonal P4bm symmetries, as evidenced by high-resolution transmission electron microscopy.[5,9,15] Since industry-standard piezoelectric materials, such as lead zirconium titanate ceramics, contain toxic lead, a rapid surge in research on lead-free piezoelectric materials is occurring due to concerns over environmental safety and human health. A ternary lead-free (Na0.5Bi0.5)TiO3-BaTiO3-(K0.5Na0.5) NbO3 single crystal with a large field induced strain of ≈0.9% and a giant piezoelectric coefficient d33 of 840 pC N−1 at room temperature is reported. It is revealed that the electric-field-induced phase transition and phase boundary between energetically comparable polar states (i.e., R3c and P4mm) play an important role in achieving the ultrahigh piezoelectricity. Transmission electron microscopy and scan probe microscopy are employed to verify the weak-polar ferroelectric R3c and P4bm structure in the ground state. These unprecedentedly high piezoelectric properties make lead-free ternary single crystals a leading candidate for piezoelectric-based device applications, especially toward the era of smart homes and implantable medical devices.

Journal ArticleDOI
TL;DR: In this article, a 3D-printed multilayer β-phase PVDF-TrFE copolymer is presented, which does not require high temperature annealing or complicated transfer processes and exhibits a much higher effective piezoelectric coefficient (d33 ∼ 130 pC N−1 for six 10 μm layers).
Abstract: Piezoelectric polymers are characterized by their flexibility and ease of processing into shapes, however, their piezoelectric coefficients, such as d33, are quite low (∼24 pC N−1). Here we report a 3D-printed multilayer β-phase PVDF-TrFE copolymer which does not require high temperature annealing or complicated transfer processes and exhibits a much higher effective piezoelectric coefficient (d33 ∼ 130 pC N−1 for six 10 μm layers). In order to confirm its high power density, a rugby ball-shaped energy harvester, which operates via a flextensional mechanism, was prepared using the multilayer copolymer. The experimental results show that it can produce a peak voltage of ∼88.62 Vpp and a current of 353 μA, which are 2.2 and 10 times those of a single-layer PVDF-TrFE harvester, respectively, under a pressure of 0.046 MPa. Notably, its peak output power density was as high as 16.4 mW cm−2 (according to Ppeak = (VpeakIshort)/2); while at a load of 568 kΩ, it was still 5.81 mW cm−2. The proposed copolymer processing method and flextensional mechanism in a rugby ball configuration show great potential for future micro-energy development in flexible, wearable electronic devices and wireless sensor networks.

Journal ArticleDOI
17 Jul 2020-Science
TL;DR: The formation of local heterogeneity with nanopillar regions in the perovskite oxide thin films could be the basis for a general approach to designing and optimizing various functional materials.
Abstract: High-performance piezoelectric materials are critical components for electromechanical sensors and actuators. For more than 60 years, the main strategy for obtaining large piezoelectric response has been to construct multiphase boundaries, where nanoscale domains with local structural and polar heterogeneity are formed, by tuning complex chemical compositions. We used a different strategy to emulate such local heterogeneity by forming nanopillar regions in perovskite oxide thin films. We obtained a giant effective piezoelectric coefficient d 33 , f * of ~1098 picometers per volt with a high Curie temperature of ~450°C. Our lead-free composition of sodium-deficient sodium niobate contains only three elements (Na, Nb, and O). The formation of local heterogeneity with nanopillars in the perovskite structure could be the basis for a general approach to designing and optimizing various functional materials.

Journal ArticleDOI
TL;DR: The ZnO nanoparticle-PVDF composite thin film was demonstrated as a flexible wearable motion sensor, where different hand gestures were detected by the device with distinctive output voltage amplitudes and patterns and it was demonstrated that the energy harvested from finger tapping at ~2 Hz can charge a capacitor with a large output power density.
Abstract: Piezoelectric nanomaterial-polymer composites represent a unique paradigm for making flexible energy harvesting and sensing devices with enhanced devices' performance. In this work, we studied various metal doped ZnO nanostructures, fabricated and characterized ZnO nanoparticle-PVDF composite thin film, and demonstrated both enhanced energy generation and motion sensing capabilities. Specifically, a series of flexible piezoelectric nanogenerators (PENGs) were designed based on these piezoelectric composite thin films. The voltage output from cobalt (Co), sodium (Na), silver (Ag), and lithium (Li) doped ZnO-PVDF composite as well as pure ZnO-PVDF samples were individually studied and compared. Under the same experimental conditions, the Li-ZnO based device produces the largest peak-to-peak voltage (3.43 Vpp) which is about 9 times of that of the pure ZnO based device, where Co-ZnO, Na-ZnO and Ag-ZnO are 1.2, 4.9 and 5.4 times, respectively. In addition, the effect of doping ratio of Li-ZnO is studied, and we found that 5% is the best doping ratio in terms of output voltage. Finally, we demonstrated that the energy harvested by the device from finger tapping at ~2 Hz can charge a capacitor with a large output power density of 0.45 W/cm3 and light up an ultraviolet (UV) light-emitting diode (LED). We also showed the device as a flexible wearable motion sensor, where different hand gestures were detected by the device with distinctive output voltage amplitudes and patterns.

Journal ArticleDOI
TL;DR: The existence of in-plane piezoelectricity is experimentally reported for multilayer BP along the armchair direction and can lead to further understanding of this mechanism in monoelemental materials.
Abstract: Recently, piezoelectric characteristics have been a research focus for 2D materials because of their broad potential applications. Black phosphorus (BP) is a monoelemental 2D material predicted to be piezoelectric because of its highly directional properties and non-centrosymmetric lattice structure. However, piezoelectricity is hardly reported in monoelemental materials owing to their lack of ionic polarization, but piezoelectric generation is consistent with the non-centrosymmetric structure of BP. Theoretical calculations of phosphorene have explained the origin of piezoelectric polarization among P atoms. However, the disappearance of piezoelectricity in multilayer 2D material generally arises from the opposite orientations of adjacent atomic layers, whereas this effect is limited in BP lattices due to their spring-shaped space structure. Here, the existence of in-plane piezoelectricity is experimentally reported for multilayer BP along the armchair direction. Current-voltage measurements demonstrate a piezotronic effect in this orientation, and cyclic compression and release of BP flakes show an intrinsic current output as large as 4 pA under a compressive strain of -0.72%. The discovery of piezoelectricity in multilayer BP can lead to further understanding of this mechanism in monoelemental materials.

Journal ArticleDOI
TL;DR: In this paper, a review of the piezoelectric and ferroelectric properties of zinc oxide (ZnO) nanostructures is presented, which provides a useful insight into various processes which may induce ferro-electricity and enhance the PPE of non-ferroelectric and weak PPE.

Journal ArticleDOI
TL;DR: In this paper, a self-powered photo-active piezoelectric energy harvester was fabricated by a composite of room temperature processed all-inorganic cesium lead bromide (CsPbBr3) perovskite rod and polyvinylidene fluoride (PVDF) nanofiber.

Journal ArticleDOI
TL;DR: In this paper, the authors showed that the BiCl3/PVDF nanofiber film based piezoelectric nanogenerator is a promising mechanical energy harvesters for portable electronic and wearable devices.

Journal ArticleDOI
TL;DR: A new KNN-based lead-free ceramic material is presented, which features a large piezoelectric coefficient (d33) exceeding 500 pC/N and a high Curie temperature (Tc) of ∼200°C and a hierarchical domain architecture composed of nano-sized domains along the submicron domains was detected in this material system, which further contributes to the high piez Zoelectricity.
Abstract: Due to growing concern for the environment and human health, searching for high-performance lead-free piezoceramics has been a hot topic of scientific and industrial research. Despite the significant progress achieved toward enhancing piezoelectricity, further efforts should be devoted to the synergistic improvement of piezoelectricity and its thermal stability. This study provides new insight into these topics. A new KNN-based lead-free ceramic material is presented, which features a large piezoelectric coefficient (d33) exceeding 500 pC/N and a high Curie temperature (Tc) of ∼200°C. The superior piezoelectric response strongly relies on the increased composition-induced structural flexibility due to lattice softening and decreased unit cell distortion. In contrast to piezoelectricity anomalies induced via polymorphic transition, this piezoelectricity enhancement is effective within a broad temperature range rather than a specific small range. In particular, a hierarchical domain architecture composed of nano-sized domains along the submicron domains was detected in this material system, which further contributes to the high piezoelectricity.

Journal ArticleDOI
TL;DR: The electromechanical properties of these compounds suggest their potential in lightweight and high-energy-density devices, and the strategy described here could inspire the development of next-generation piezoelectrics and electroactive materials based on hybrid ferroelectrics.
Abstract: Materials that can produce large controllable strains are widely used in shape memory devices, actuators and sensors Great efforts have been made to improve the strain outputs of various material systems Among them, ferroelastic transitions underpin giant reversible strains in electrically-driven ferro/piezoelectrics and thermally- or magneticallydriven shape memory alloys However, large-strain ferroelastic switching in conventional ferroelectrics is very challenging while magnetic and thermal controls are not desirable for applications Here, we demonstrate an unprecedentedly large shear strain up to 215 % in a hybrid ferroelectric, C6H5N(CH3)3CdCl3 The strain response is about two orders of magnitude higher than those of top-performing conventional ferroelectric polymers and oxides It is achieved via inorganic bond switching and facilitated by the structural confinement of the large organic moieties, which prevents the undesired 180-degree polarization switching Furthermore, Br substitution can effectively soften the bonds and result in giant shear piezoelectric coefficient (d35 ~ 4800 pm/V) in Br-rich end of the solid solution, C6H5N(CH3)3CdBr3xCl3(1-x) The superior electromechanical properties of the compounds promise their potential in lightweight and high energy density devices, and the strategy described here should inspire the development of next-generation piezoelectrics and electroactive materials based on hybrid ferroelectrics

Journal ArticleDOI
TL;DR: In this article, the tuning of piezoelectric and energy-harvesting are realized in solvothermal synthesized Cl doped ZnO nanorods (NRs), which is designed to boost the coupling effect of piezo-photocatalysis for dye decomposition.
Abstract: In this work, the tuning of piezoelectric and energy-harvesting are realized in solvothermal synthesized Cl doped ZnO nanorods (NRs), which is designed to boost the coupling effect of piezo-photocatalysis for dye decomposition. For the optimal sample 5%-Cl-ZnO, the coupling constant is about 24.4 times greater than that of pure ZnO, which is benefited from the synergistic effect of the increased radial piezoelectric properties and the superiority of nanorods structure. Optimal 5%-Cl-ZnO NRs not only maintains high migration efficiency for photo-generated carriers in the axial direction, but also separate more thoroughly and transmit faster in the radial direction. This work clearly demonstrates a high correlation between piezoelectricity and coupling effect of piezo-photocatalysis, and provides a new strategy for optimizing the transport of photogenerated carriers in 1D photocatalyst.

Journal ArticleDOI
TL;DR: In this article, the biaxial strain is applied to tune the electronic properties of the septuple-atomic-layer VSi2P4, and it spans a wide range of properties upon increasing the strain from a ferromagnetic metal (FMM) to a spin-gapless semiconductor (SGS).
Abstract: The septuple-atomic-layer VSi2P4 with the same structure of experimentally synthesized MoSi2N4 is predicted to be a spin-gapless semiconductor (SGS) with the generalized gradient approximation (GGA). In this work, the biaxial strain is applied to tune the electronic properties of VSi2P4, and it spans a wide range of properties upon increasing the strain from a ferromagnetic metal (FMM) to SGS to a ferromagnetic semiconductor (FMS) to SGS to a ferromagnetic half-metal (FMHM). Due to broken inversion symmetry, the coexistence of ferromagnetism and piezoelectricity can be achieved in FMS VSi2P4 with the strain range of 0% to 4%. The calculated piezoelectric strain coefficients d11 for 1%, 2% and 3% strains are 4.61 pm V-1, 4.94 pm V-1 and 5.27 pm V-1, respectively, which are greater than or close to a typical value of 5 pm V-1 for bulk piezoelectric materials. Finally, similar to VSi2P4, the coexistence of piezoelectricity and ferromagnetism can be realized by strain in the VSi2N4 monolayer. Our works show that VSi2P4 in the FMS phase with intrinsic piezoelectric properties can have potential applications in spin electronic devices.

Journal ArticleDOI
TL;DR: It is concluded that negative longitudinal piezoelectric coefficients arise from the negative longitudinal electrostriction in the crystalline domain of the polymers, independent of amorphous and crystalline‐amorphous interfacial regions.
Abstract: Piezoelectric polymers are well-recognized to hold great promise for a wide range of flexible, wearable, and biocompatible applications. Among the known piezoelectric polymers, ferroelectric polymers represented by poly(vinylidene fluoride) and its copolymer poly(vinylidene fluoride-co-trifluoroethylene) possess the best piezoelectric coefficients. However, the physical origin of negative longitudinal piezoelectric coefficients occurring in the polymers remains elusive. To address this long-standing challenge, several theoretical models proposed over the past decades, which are controversial in nature, have been revisited and reviewed. It is concluded that negative longitudinal piezoelectric coefficients arise from the negative longitudinal electrostriction in the crystalline domain of the polymers, independent of amorphous and crystalline-amorphous interfacial regions. The crystalline origin of piezoelectricity offers unprecedented opportunities to improve electromechanical properties of polymers via structural engineering, i.e., design of morphotropic phase boundaries in ferroelectric polymers.

Journal ArticleDOI
TL;DR: In this paper, the wave propagation and vibration of a porous beam embedded via nanocomposite piezoelectric layers were considered through modified Halpin-Tsai micromechanics model to approximate the Young modulus and Poisson's ratio of graphene/pieziolectric polymer layers.
Abstract: This paper deals with wave propagation and vibration of a porous beam embedded via nanocomposite piezoelectric layers Various patterns of reinforcement of the face sheets by non-uniform graphene nanoplatelets (GPLs) are considered through modified Halpin-Tsai micromechanics model to approximate the Young modulus and Poisson's ratio of graphene/piezoelectric polymer layers The sandwich's face sheets, due to their characteristics, are regarded as sensor and actuator with which the wave velocity and frequency of structure can be controlled and for this reason, a proportional-differential (PD) controller is handled So as to model the structure much more realistic, the material characteristic of whole system are hypothesized as viscoelastic state according to Kelvin-Voigt model and Kerr viscoelastic foundation is developed which include two springs, two dampers and one shear elements as well For mathematical modelling of system, refined zigzag theory (RZT) is exercised and using energy method, the motion equations are obtained Analytical procedure is utilized for solving the governing equations as well as calculating the wave velocity and frequency of the sandwich structure A precise parametric study is carried out focusing GPLs volume percent and distribution pattern, geometrical parameter of every layer, piezoelectric properties of GPLs, porosity dispersion of the core, exerted voltage and structural damping and their effects on the wave propagation and vibration of system Results show that increase in the porous coefficient lead to decline in the wave velocity and frequency In addition, considering the piezoelectric properties of GPLs enhances the wave velocity and frequency of the sandwich structure

Journal ArticleDOI
TL;DR: In this paper, phase structure engineered high-performance potassium sodium niobate [(K,Na)NbO3, KNN]-based ceramics and its potential application on ultrasonic transducers were presented.