Showing papers on "Piezoelectricity published in 2017"
TL;DR: Trimethylchloromethyl ammonium trichloromanganese(II), an organic-inorganic perovskite ferroelectric crystal processed from aqueous solution, has a large d33 of 185 picocoulombs per newton and a high phase-transition temperature of 406 kelvin (K) (16 K above that of BTO), which makes it a competitive candidate for medical, micromechanical, and biomechanical applications.
Abstract: Molecular piezoelectrics are highly desirable for their easy and environment-friendly processing, light weight, low processing temperature, and mechanical flexibility. However, although 136 years have passed since the discovery in 1880 of the piezoelectric effect, molecular piezoelectrics with a piezoelectric coefficient d33 comparable with piezoceramics such as barium titanate (BTO; ~190 picocoulombs per newton) have not been found. We show that trimethylchloromethyl ammonium trichloromanganese(II), an organic-inorganic perovskite ferroelectric crystal processed from aqueous solution, has a large d33 of 185 picocoulombs per newton and a high phase-transition temperature of 406 kelvin (K) (16 K above that of BTO). This makes it a competitive candidate for medical, micromechanical, and biomechanical applications.
644 citations
TL;DR: The study reveals the potential for utilizing piezoelectric 2D materials and their van der Waals multilayer structures in device applications.
Abstract: Piezoelectricity in 2D van der Waals materials has received considerable interest because of potential applications in nanoscale energy harvesting, sensors, and actuators. However, in all the systems studied to date, strain and electric polarization are confined to the basal plane, limiting the operation of piezoelectric devices. In this paper, based on ab initio calculations, we report a 2D materials system, namely, the recently synthesized Janus MXY (M = Mo or W, X/Y = S, Se, or Te) monolayer and multilayer structures, with large out-of-plane piezoelectric polarization. For MXY monolayers, both strong in-plane and much weaker out-of-plane piezoelectric polarizations can be induced by a uniaxial strain in the basal plane. For multilayer MXY, we obtain a very strong out-of-plane piezoelectric polarization when strained transverse to the basal plane, regardless of the stacking sequence. The out-of-plane piezoelectric coefficient d33 is found to be strongest in multilayer MoSTe (5.7–13.5 pm/V depending on t...
522 citations
TL;DR: In this paper, the first experimental evidence of out-of-plane piezoelectricity and ferroelectricity in van der Waals layered α-In2Se3 nanoflakes was reported.
Abstract: Piezoelectric and ferroelectric properties in the two-dimensional (2D) limit are highly desired for nanoelectronic, electromechanical, and optoelectronic applications. Here we report the first experimental evidence of out-of-plane piezoelectricity and ferroelectricity in van der Waals layered α-In2Se3 nanoflakes. The noncentrosymmetric R3m symmetry of the α-In2Se3 samples is confirmed by scanning transmission electron microscopy, second-harmonic generation, and Raman spectroscopy measurements. Domains with opposite polarizations are visualized by piezo-response force microscopy. Single-point poling experiments suggest that the polarization is potentially switchable for α-In2Se3 nanoflakes with thicknesses down to ∼10 nm. The piezotronic effect is demonstrated in two-terminal devices, where the Schottky barrier can be modulated by the strain-induced piezopotential. Our work on polar α-In2Se3, one of the model 2D piezoelectrics and ferroelectrics with simple crystal structures, shows its great potential in electronic and photonic applications.
475 citations
TL;DR: A pressure sensor with nanowires/graphene heterostructures for static measurements based on the synergistic mechanisms between strain-induced polarization charges in piezoelectric nanowire and graphene and the caused change of carrier scattering in graphene shows great potential in the applications of electronic skin and wearable devices.
Abstract: The piezoelectric effect is widely applied in pressure sensors for the detection of dynamic signals. However, these piezoelectric-induced pressure sensors have challenges in measuring static signals that are based on the transient flow of electrons in an external load as driven by the piezopotential arisen from dynamic stress. Here, we present a pressure sensor with nanowires/graphene heterostructures for static measurements based on the synergistic mechanisms between strain-induced polarization charges in piezoelectric nanowires and the caused change of carrier scattering in graphene. Compared to the conventional piezoelectric nanowire or graphene pressure sensors, this sensor is capable of measuring static pressures with a sensitivity of up to 9.4 × 10–3 kPa–1 and a fast response time down to 5–7 ms. This demonstration of pressure sensors shows great potential in the applications of electronic skin and wearable devices.
402 citations
TL;DR: In this article, the structural and physical origin of lead-free substitutes with high piezoelectricity and temperature stability are investigated. But the structural/physical origin for their high piezo-lectric properties is still unclear, which hinders property optimization.
Abstract: Lead-based piezoelectric materials are currently facing global restrictions due to their lead toxicity. Thus it is urgent to develop lead-free substitutes with high piezoelectricity and temperature stability, among which, potassium-sodium niobate [(K,Na)NbO3, KNN] has the most potential. It is very difficult to simultaneously achieve high piezoelectric performance and reliable stability in KNN-based systems. In particular, the structural/physical origin for their high piezoelectricity is still unclear, which hinders property optimization. Here we report the achievement of high temperature stability (less than 10% variation for electric field-induced strain from 27 °C to 80 °C), good fatigue properties (stable up to 106 cycles) as well as an enhanced piezoelectric coefficient (d33) of 525 pC N−1 in (1 − x)(K1−yNay)(Nb1−zSbz)O3–xBi0.5(Na1−wKw)0.5HfO3 (KNNS–BNKH) ceramics through manipulating the rhombohedral–tetragonal (R–T) phase boundary. The structural origin of their high piezoelectric performance can be attributed to a hierarchical nanodomain architecture, where the local structure inside nanodomains comprises R and T nanotwins. The physical origin can be attributed to low domain wall energy and nearly vanishing polarization anisotropy, facilitating easy polarization rotation among different states. We believe that the new breakthrough will open a window for the practical applications of KNN-based ceramics.
364 citations
TL;DR: Flexible piezoelectric nanogenerator can be applied as self-powered flexible sensor work in a noncontact mode for detecting air pressure and wearable sensors for detecting some human vital signs including different modes of breath and heartbeat pulse, which shows its potential applications in flexible electronics and medical sciences.
Abstract: Piezoelectric nanogenerators with large output, high sensitivity, and good flexibility have attracted extensive interest in wearable electronics and personal healthcare. In this paper, the authors propose a high-performance flexible piezoelectric nanogenerator based on piezoelectrically enhanced nanocomposite micropillar array of polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE))/barium titanate (BaTiO3 ) for energy harvesting and highly sensitive self-powered sensing. By a reliable and scalable nanoimprinting process, the piezoelectrically enhanced vertically aligned P(VDF-TrFE)/BaTiO3 nanocomposite micropillar arrays are fabricated. The piezoelectric device exhibits enhanced voltage of 13.2 V and a current density of 0.33 µA cm-2 , which an enhancement by a factor of 7.3 relatives to the pristine P(VDF-TrFE) bulk film. The mechanisms of high performance are mainly attributed to the enhanced piezoelectricity of the P(VDF-TrFE)/BaTiO3 nanocomposite materials and the improved mechanical flexibility of the micropillar array. Under mechanical impact, stable electricity is stably generated from the nanogenerator and used to drive various electronic devices to work continuously, implying its significance in the field of consumer electronic devices. Furthermore, it can be applied as self-powered flexible sensor work in a noncontact mode for detecting air pressure and wearable sensors for detecting some human vital signs including different modes of breath and heartbeat pulse, which shows its potential applications in flexible electronics and medical sciences.
312 citations
TL;DR: In this article, a series of derivative Janus structures for piezoelectric materials, including Ga2SSe, Ga2STe, Ga 2SeTe, In2SeTe and GaInTe2, were designed.
Abstract: Piezoelectricity is a unique material property that converts mechanical energy into electricity or vice versa. Starting from the group-III monochalcogenide monolayers, we design a series of derivative Janus structures for piezoelectric materials, including Ga2SSe, Ga2STe, Ga2SeTe, In2SSe, In2STe, In2SeTe, GaInS2, GaInSe2, and GaInTe2. Our first-principles calculations show that these Janus structures are thermodynamically and dynamically stable. They have a bandgap in the range of 0.89–2.03 eV, lower than those of the perfect monolayers, and Ga2STe, Ga2SeTe, In2STe, and In2SeTe monolayers are direct gap semiconductors. They possess piezoelectric coefficients up to 8.47 pm/V, over four times the maximum value obtained in perfect group-III monochalcogenide monolayers. Moreover, the broken mirror symmetry of these Janus structures induces out-of-plane dipolar polarization, yielding additional out-of-plane piezoelectric coefficients of 0.07–0.46 pm/V. The enhanced piezoelectric properties enable the developme...
288 citations
TL;DR: Local poling experiments and local switching spectroscopy piezoresponse force microscopy demonstrates the enhanced ferroelectricity and domain mobility from a microscopic view and Thermally stimulated depolarization currents analysis reveals the reduced defects and improved ferro electricity in MnO2-doped piezoceramics from a macroscopic view.
Abstract: With growing concern over world environmental problems and increasing legislative restriction on using lead and lead-containing materials, a feasible replacement for lead-based piezoceramics is desperately needed. Herein, we report a large piezoelectric strain (d33*) of 470 pm/V and a high Curie temperature (Tc) of 243 °C in (Na0.5K0.5)NbO3-(Bi0.5Li0.5)TiO3-BaZrO3 lead-free ceramics by doping MnO2. Moreover, excellent temperature stability is also observed from room temperature to 170 °C (430 pm/V at 100 °C and 370 pm/V at 170 °C). Thermally stimulated depolarization currents (TSDC) analysis reveals the reduced defects and improved ferroelectricity in MnO2-doped piezoceramics from a macroscopic view. Local poling experiments and local switching spectroscopy piezoresponse force microscopy (SS-PFM) demonstrates the enhanced ferroelectricity and domain mobility from a microscopic view. Distinct grain growth and improvement in phase angle may also account for the enhancement of piezoelectric properties.
287 citations
TL;DR: In this article, the role of polarization charges and free charges in piezoelectric catalysis by doping the PZT with a spherical morphology was investigated and the relationship between deformation and catalytic performance was clarified.
235 citations
TL;DR: This work studies the effect of addition of barium titanate nanoparticles in nucleating piezoelectric β-polymorph in 3D printable polyvinylidene fluoride (PVDF) and fabrication of the layer-by-layer and self-supporting piezOElectric structures on a micro- to millimeter scale by solvent evaporation-assisted 3D printing at room temperature.
Abstract: Development of a 3D printable material system possessing inherent piezoelectric properties to fabricate integrable sensors in a single-step printing process without poling is of importance to the creation of a wide variety of smart structures Here, we study the effect of addition of barium titanate nanoparticles in nucleating piezoelectric β-polymorph in 3D printable polyvinylidene fluoride (PVDF) and fabrication of the layer-by-layer and self-supporting piezoelectric structures on a micro- to millimeter scale by solvent evaporation-assisted 3D printing at room temperature The nanocomposite formulation obtained after a comprehensive investigation of composition and processing techniques possesses a piezoelectric coefficient, d31, of 18 pC N–1, which is comparable to that of typical poled and stretched commercial PVDF film sensors A 3D contact sensor that generates up to 4 V upon gentle finger taps demonstrates the efficacy of the fabrication technique Our one-step 3D printing of piezoelectric nanocomp
186 citations
TL;DR: In this article, a piezoelectric energy harvester module based on polyvinylidene fluoride (PVDF) polymer for roadway applications was presented, which exhibited stable performance and durability over the repeated number of bending cycles.
TL;DR: These multipiezo properties of sensitive piezoluminescence in a piezoelectric matrix are ideal for microstress sensing, damage diagnosis, electro-mechano-optical energy conversion, and multifunctional control in optoelectronics.
Abstract: Red-emitting piezoluminescence (elasticoluminescence) is achieved by doping rare earth Pr3+ into the well-known piezoelectric matrix, LiNbO3 . By precisely tuning the Li/Nb ratio in nonstoichiometric Li x NbO3 :Pr3+ , a material that exhibits an unusually high piezoluminescence intensity, which far exceeds that of any well-known piezoelectric material, is produced. Li x NbO3 :Pr3+ shows excellent strain sensitivity at the lowest strain level, with no threshold for stress sensing. These multipiezo properties of sensitive piezoluminescence in a piezoelectric matrix are ideal for microstress sensing, damage diagnosis, electro-mechano-optical energy conversion, and multifunctional control in optoelectronics.
TL;DR: In this paper, the authors show that the choice of solvent used to dissolve the polyvinylidenefluoride-co-trifluoroethylene (P(VDF-TrFE) significantly influences its properties in terms of energy harvesting.
Abstract: Poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)), as a ferroelectric polymer, offers great promise for energy harvesting for flexible and wearable applications. Here, this paper shows that the choice of solvent used to dissolve the polymer significantly influences its properties in terms of energy harvesting. Indeed, the P(VDF-TrFE) prepared using a high dipole moment solvent has higher piezoelectric and pyroelectric coefficients and triboelectric property. Such improvements are the result of higher crystallinity and better dipole alignment of the polymer prepared using a higher dipole moment solvent. Finite element method simulations confirm that the higher dipole moment results in higher piezoelectric, pyroelectric, and triboelectric potential distributions. Furthermore, P(VDF-TrFE)-based piezoelectric, pyroelectric, and triboelectric nanogenerators (NGs) experimentally validate that the higher dipole moment solvent significantly enhances the power output performance of the NGs; the improvement is about 24% and 82% in output voltage and current, respectively, for piezoelectric NG; about 40% and 35% in output voltage and current, respectively, for pyroelectric NG; and about 65% and 75% in output voltage and current for triboelectric NG. In brief, the approach of using a high dipole moment solvent is very promising for high output P(VDF-TrFE)-based wearable NGs.
TL;DR: It is shown that W Se2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe2 bilayer with Bernal stacking.
Abstract: Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal-boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal-stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)-grown WSe2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD-grown WSe2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe2 for which the device performance becomes degraded above a strain of 0.63%.
TL;DR: This work reports a lead-free and one-composition molecular ferroelectric trimethylbromomethylammonium tribromomanganese(II) (TMBM-MnBr3) with a large piezoelectric coefficient d33 of 112 pC/N along polar axis, comparable with those of typically one- composition piezoceramics such as BaTiO3 along polaraxis.
Abstract: Piezoelectric materials have been widely used in various applications, such as high-voltage sources, actuators, sensors, motors, fre-quency standard, vibration reducer, and so on. In the past decades, lead zirconate titanate (PZT) binary ferroelectric ceramics have dominated the commercial piezoelectric market due to their excellent properties near the morphotropic phase boundary (MPB), although they contain more than 60% toxic lead element. Here, we report a lead-free and one-composition molecular ferroelectric trimethylbromomethylammonium tribromomanganese (ΙΙ) (TMBM-MnBr3) with a large piezoelectric coefficient d33 of 112 pC/N along polar axis, comparable with those of typically one-composition piezoceramics such as BaTiO3 along polar axis [001] (~90 pC/N) and much greater than those of most known molecular ferroelectrics (almost below 40 pC/N). More significantly, the effec-tive local piezoelectric coefficient of TMBM-MnBr3 films is comparable to that of its bulk crystals. In terms of ferroelectric pe...
TL;DR: In this paper, a lead-free piezoelectric ceramics with a large piezoresponse is presented, and the strain can maintain a considerable value of 0.12% at the temperature as high as 190°C.
TL;DR: In this paper, a piezoelectric composite nanogenerator with FAPbBr3 NPs and polyvinylidene fluoride (PVDF) was proposed.
TL;DR: In this paper, the authors summarize the idea of designing high property BaTiO3 piezoceramic through domain engineering, defect-doping, as well as morphotropic phase boundary (MPB).
Abstract: Due to issues with Pb toxicity, there is an urgent need for high performance Pb-free alternatives to Pb-based piezoelectric ceramics. Although pure BaTiO3 material exhibits fairly low piezoelectric coefficients, further designing of such a material system greatly enhances the piezoelectric response by means of domain engineering, defects engineering, as well as phase boundary engineering. Especially after the discovery of a Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 system with extraordinarily high piezoelectric properties (d33 > 600 pC/N), BaTiO3-based piezoelectric ceramics are considered as one of the promising Pb-free substitutes. In the present contribution, we summarize the idea of designing high property BaTiO3 piezoceramic through domain engineering, defect-doping, as well as morphotropic phase boundary (MPB). In spite of its drawback of low Curie temperature, BaTiO3-based piezoelectric materials can be considered as an excellent model system for exploring the physics of highly piezoelectric materials. The relevant material design strategy in BaTiO3-based materials can provide guidelines for the next generation of Pb-free materials with even better piezoelectric properties that can be anticipated in the near future.
TL;DR: In this article, a porosity-aligned PZirconate (PZT) poramics with aligned pore channels and varying fractions of porosity were manufactured in a water-based suspension using freeze-casting.
Abstract: This paper demonstrates the significant benefits of exploiting highly aligned porosity in piezoelectric and pyroelectric materials for improved energy harvesting performance. Porous lead zirconate (PZT) ceramics with aligned pore channels and varying fractions of porosity were manufactured in a water-based suspension using freeze-casting. The aligned porous PZT ceramics were characterized in detail for both piezoelectric and pyroelectric properties and their energy harvesting performance figures of merit were assessed parallel and perpendicular to the freezing direction. As a result of the introduction of porosity into the ceramic microstructure, high piezoelectric and pyroelectric harvesting figures of merits were achieved for porous freeze-cast PZT compared to dense PZT due to the reduced permittivity and volume specific heat capacity. Experimental results were compared to parallel and series analytical models with good agreement and the PZT with porosity aligned parallel to the freezing direction exhibited the highest piezoelectric and pyroelectric harvesting response; this was a result of the enhanced interconnectivity of the ferroelectric material along the poling direction and reduced fraction of unpoled material that leads to a higher polarization. A complete thermal energy harvesting system, composed of a parallel-aligned PZT harvester element and an AC/DC converter, was successfully demonstrated by charging a storage capacitor. The maximum energy density generated by the 60 vol% porous parallel-connected PZT when subjected to thermal oscillations was 1653 μJ cm−3, which was 374% higher than that of the dense PZT with an energy density of 446 μJ cm−3. The results are beneficial for the design and manufacture of high performance porous pyroelectric and piezoelectric materials in devices for energy harvesting and sensor applications.
TL;DR: This study paves a new pathway to develop lead-free piezoelectrics with both low strain hysteresis and high piez Zoelectric coefficient, and represents a very exciting discovery with potential application of BT-based ceramics in high-precision pieZoelectric actuators.
Abstract: Both low strain hysteresis and high piezoelectric performance are required for practical applications in precisely controlled piezoelectric devices and systems. Unfortunately, enhanced piezoelectric properties were usually obtained with the presence of a large strain hysteresis in BaTiO3 (BT)-based piezoceramics. In this work, we propose to integrate crystallographic texturing and domain engineering strategies into BT-based ceramics to resolve this challenge. [001]c grain-oriented (Ba0.94Ca0.06)(Ti0.95Zr0.05)O3 (BCTZ) ceramics with a texture degree as high as 98.6% were synthesized by templated grain growth. A very high piezoelectric coefficient (d33) of 755 pC/N, and an extremely large piezoelectric strain coefficient (d33* = 2027 pm/V) along with an ultralow strain hysteresis (Hs) of 4.1% were simultaneously achieved in BT-based systems for the first time, which are among the best values ever reported on both lead-free and lead-based piezoceramics. The exceptionally high piezoelectric response is mainly...
TL;DR: In this article, the piezoelectric properties of Hf1-xZrxO2 (HZO) and pure ZrO2 films with a layer thickness of up to 390 nm were investigated using a double-beam laser interferometer and piezoresponse force microscopy.
Abstract: Ferroelectric and piezoelectric properties of Hf1-xZrxO2 (HZO) and pure ZrO2 films with a layer thickness of up to 390 nm prepared by chemical solution deposition (CSD) are investigated. The piezoelectric properties are measured using a double-beam laser interferometer (DBLI) and piezoresponse force microscopy. It is shown that for 100 nm thick films, the maximum remanent polarization is found for pure ZrO2 and reduces for the increasing hafnium content. A stable remanent polarization of 8 μC/cm2 is observed for ZrO2 film thicknesses between 195 and 390 nm. A piezoelectric coefficient of 10 pm/V is extracted from unipolar DBLI measurements. The observed thickness limitation for atomic layer deposition deposited HZO based ferroelectrics can be overcome by the CSD deposition technique presented in this work. Thick ZrO2 films are promising candidates for energy related applications such as pyroelectric and piezoelectric energy harvesting and electrocaloric cooling as well as for microelectromechanical systems.
TL;DR: In this paper, an enhanced EPAM process is proposed that applies a higher electric field during 3D printing of piezoelectric sensors using BaTiO3 (BTO) filler in a polyvinylidene) fluoride (PVDF) matrix through electric in situ poling during the printing process.
Abstract: This paper presents 3D printing of piezoelectric sensors using BaTiO3 (BTO) filler in a poly(vinylidene) fluoride (PVDF) matrix through electric in situ poling during the 3D printing process. Several conventional methods require complicated and time-consuming procedures. Recently developed electric poling-assisted additive manufacturing (EPAM) process paves the way for printing of piezoelectric filaments by incorporating polarizing processes that include mechanical stretching, heat press, and electric field poling simultaneously. However, this process is limited to fabrication of a single PVDF layer and quantitative material characterizations such as piezoelectric coefficient and β-phase percentage are not investigated. In this paper, an enhanced EPAM process is proposed that applies a higher electric field during 3D printing. To further increase piezoelectric response, BTO ceramic filler is used in the PVDF matrix. It is found that a 55.91% PVDF β-phase content is nucleated at 15 wt% of BTO. The output current and β-phase content gradually increase as the BTO weight percentage increases. Scanning electron microscopy analysis demonstrates that larger agglomerates are formulated as the increase of BTO filler contents and results in increase of toughness and decrease of tensile strength. The highest fatigue strength is observed at 3 wt% BTO and the fatigue strength gradually decreases as the BTO filler contents increases.
TL;DR: A dynamic loading device that can simulate the force of human motion and provide periodic load to piezoelectric materials when co-cultured with cells was designed to obtain a realistic expression of piezOElectric effect on bone repair.
Abstract: The piezoelectric effect of biological piezoelectric materials promotes bone growth. However, the material should be subjected to stress before it can produce an electric charge that promotes bone repair and reconstruction conducive to fracture healing. A novel method for in vitro experimentation of biological piezoelectric materials with physiological load is presented. A dynamic loading device that can simulate the force of human motion and provide periodic load to piezoelectric materials when co-cultured with cells was designed to obtain a realistic expression of piezoelectric effect on bone repair. Hydroxyapatite (HA)/barium titanate (BaTiO3) composite materials were fabricated by slip casting, and their piezoelectric properties were obtained by polarization. The d33 of HA/BaTiO3 piezoelectric ceramics after polarization was 1.3 pC/N to 6.8 pC/N with BaTiO3 content ranging from 80% to 100%. The in vitro biological properties of piezoelectric bioceramics with and without cycle loading were investigated. When HA/BaTiO3 piezoelectric bioceramics were affected by cycle loading, the piezoelectric effect of BaTiO3 promoted the growth of osteoblasts and interaction with HA, which was better than the effect of HA alone. The best biocompatibility and bone-inducing activity were demonstrated by the 10%HA/90%BaTiO3 piezoelectric ceramics.
TL;DR: Li et al. as discussed by the authors proposed an integrated 3D printing process with corona poling to fabricate piezoelectric polyvinylidene fluoride (PVDF) sensors without post poling process.
Abstract: This paper presents a novel process to fabricate piezoelectric films from polyvinylidene fluoride (PVDF) polymer using integrated fused deposition modeling (FDM) 3D printing and corona poling technique Corona poling is one of many effective poling processes that has received attention to activate PVDF as a piezoelectric responsive material The corona poling process occurs when a PVDF polymer is exposed to a high electric field created and controlled through an electrically charged needle and a grid electrode under heating environment FDM 3D printing has seen extensive progress in fabricating thermoplastic materials and structures, including PVDF However, post processing techniques such as poling is needed to align the dipoles in order to gain piezoelectric properties To further simplify the piezoelectric sensors and structures fabrication process, this paper proposes an integrated 3D printing process with corona poling to fabricate piezoelectric PVDF sensors without post poling process This proposed process, named 'Integrated 3D Printing and Corona poling process' (IPC), uses the 3D printer's nozzle and heating bed as anode and cathode, respectively, to create poling electric fields in a controlled heating environment The nozzle travels along the programmed path with fixed distance between nozzle tip and sample's top surface Simultaneously, the electric field between the nozzle and bottom heating pad promotes the alignment of dipole moment of PVDF molecular chains The crystalline phase transformation and output current generated by printed samples under different electric fields in this process were characterized by a Fourier transform infrared spectroscopy and through fatigue load frame It is demonstrated that piezoelectric PVDF films with enhanced β-phase percentage can be fabricated using the IPC process In addition, mechanical properties of printed PVDF was investigated by tensile testing It is expected to expand the use of additive manufacturing to fabricate piezoelectric PVDF-based devices for applications such as sensing and energy harvesting
TL;DR: In this paper, the axial extension of an n-type ZnO piezoelectric semiconductor nanofiber under an axial force was analyzed, and simple and analytical expressions for the electromechanical fields and electron concentration in the fiber were obtained.
Abstract: This paper presents a theoretical analysis on the axial extension of an n-type ZnO piezoelectric semiconductor nanofiber under an axial force. The phenomenological theory of piezoelectric semiconductors consisting of Newton's second law of motion, the charge equation of electrostatics and the conservation of charge was used. The equations were linearized for small axial force and hence small electron concentration perturbation, and were reduced to one-dimensional equations for thin fibers. Simple and analytical expressions for the electromechanical fields and electron concentration in the fiber were obtained. The fields are either totally or partially described by hyperbolic functions relatively large near the ends of the fiber and change rapidly there. The behavior of the fields is sensitive to the initial electron concentration and the applied axial force. For higher initial electron concentrations the fields are larger near the ends and change more rapidly there.
TL;DR: In this paper, a piezoelectric sandwich plate is used to simulate the orthotropic visco-Pasternak model and a proportional-derivative (PD) controller is employed to control the phase velocity in the structure.
TL;DR: The enhanced high output enables the hybrid nanogenerator to instantaneously light up LEDs and charges capacitors quickly, which shows extensive application prospects in the field of self-powered systems or sensor networks.
Abstract: A wave-shaped hybrid nanogenerator (NG) with mutually enhanced piezoelectric and triboelectric output is presented in this work. By sandwiching piezoelectric P(VDF-TrFE) nanofibers between wave-shaped Kapton films, the device forms a three-layer structure, which can generate piezoelectric and triboelectric outputs simultaneously in one press and release cycle. Through systematic situational analysis and experimental validation, the three-layer structure can achieve obvious improvement of the output performance for both parts. When triggered with 4 Hz external force, the piezoelectric part generates a peak output and current of 96 V and 3.8 μA, which is ∼2 times higher than its initial output. Meanwhile, the performance of triboelectric parts also increases 8 V and 16 V with the assistance of piezoelectric potential. The enhanced high output enables the hybrid nanogenerator to instantaneously light up LEDs and charges capacitors quickly, which shows extensive application prospects in the field of self-powered systems or sensor networks.
TL;DR: In this article, a new form of the magnetoelectric effect based on the valley DOF in two-dimensional Dirac materials is reported, which is independent of in-plane magnetic field, linearly proportional to the inplane current density.
Abstract: Magnetoelectric (ME) effect, the phenomenon of inducing magnetization by application of an electric field or vice versa, holds great promise for magnetic sensing and switching applications. Studies of the ME effect have so far focused on the control of the electron spin degree of freedom (DOF) in materials such as multiferroics and conventional semiconductors. Here, we report a new form of the ME effect based on the valley DOF in two-dimensional (2D) Dirac materials. By breaking the three-fold rotational symmetry in single-layer MoS2 via a uniaxial stress, we have demonstrated the pure electrical generation of valley magnetization in this material, and its direct imaging by Kerr rotation microscopy. The observed out-of-plane magnetization is independent of in-plane magnetic field, linearly proportional to the in-plane current density, and optimized when the current is orthogonal to the strain-induced piezoelectric field. These results are fully consistent with a theoretical model of valley magnetoelectricity driven by Berry curvature effects. Furthermore, the effect persists at room temperature, opening possibilities for practical valleytronic devices.
TL;DR: This paper introduces core-shell-structured piezoelectric polyvinylidene fluoride (PVDF) nanofibers chemically wrapped by graphene oxide (GO) lamellae ( PVDF/GO nan ofibers), in which the polar β-phase nanocrystals are formed and uniaxially self-oriented by the synergistic effect of mechanical stretching, high-voltage alignment, and chemical interactions.
Abstract: Piezoelectricity in macromolecule polymers has been gaining immense attention, particularly for applications in biocompatible, implantable, and flexible electronic devices. This paper introduces core–shell-structured piezoelectric polyvinylidene fluoride (PVDF) nanofibers chemically wrapped by graphene oxide (GO) lamellae (PVDF/GO nanofibers), in which the polar β-phase nanocrystals are formed and uniaxially self-oriented by the synergistic effect of mechanical stretching, high-voltage alignment, and chemical interactions. The β-phase orientation of the PVDF/GO nanofibers along their axes is observed at atomic scale through high resolution transmission electron microscopy, and the β-phase content is found to be 88.5%. The piezoelectric properties of the PVDF/GO nanofibers are investigated in terms of piezoresponse mapping, local hysteresis loops, and polarization reversal by advanced piezoresponse force microscopy. The PVDF/GO nanofibers show a desirable out-of-plane piezoelectric constant (d33) of −93.75...
TL;DR: The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.
Abstract: High-performance piezoelectric materials constantly attract interest for both technological applications and fundamental research. The understanding of the origin of the high-performance piezoelectric property remains a challenge mainly due to the lack of direct experimental evidence. We perform in situ high-energy x-ray diffraction combined with 2D geometry scattering technology to reveal the underlying mechanism for the perovskite-type lead-based high-performance piezoelectric materials. The direct structural evidence reveals that the electric-field-driven continuous polarization rotation within the monoclinic plane plays a critical role to achieve the giant piezoelectric response. An intrinsic relationship between the crystal structure and piezoelectric performance in perovskite ferroelectrics has been established: A strong tendency of electric-field-driven polarization rotation generates peak piezoelectric performance and vice versa. Furthermore, the monoclinic ${M}_{A}$ structure is the key feature to superior piezoelectric properties as compared to other structures such as monoclinic ${M}_{B}$, rhombohedral, and tetragonal. A high piezoelectric response originates from intrinsic lattice strain, but little from extrinsic domain switching. The present results will facilitate designing high-performance perovskite piezoelectric materials by enhancing the intrinsic lattice contribution with easy and continuous polarization rotation.