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[Display omitted] • XYH 2 monolayers offer tunable bandgaps (3.37 eV ∼ 4.30 eV) by the electronegativity of Y (S > Se > Te). • The increase of Y- p states and the decrease of X- s states at the Γ point make the transition of indirect-direct semiconductor. • XYH 2 monolayers exhibits a superior out-of-plane piezoelectric coefficient d 31 compared to bulk phase XY. • CdSH 2 monolayer shows a large d 31 of −1.8 pm/V. Piezoelectric materials have been widely used in various fields such as sensing and energy catalysis. This paper primarily investigates the structural, electronic and piezoelectric properties of hydrogenated II-VI monolayer semiconductor XYH 2 (X = Zn, Cd; Y = S, Se, Te) by density functional theory. Results reveal that XYH 2 monolayers exhibit stable hexagonal structures and tunable bandgaps ranging from 3.27 eV to 4.30 eV. Density functional perturbation theory is employed to investigate the out-of-plane piezoelectric coefficients of XYH 2 monolayers. CdSH 2 exhibits a value of −1.8 pm/V of out-of-plane piezoelectric coefficients which surpasses typical piezoelectric materials such as bulk ZnS (0.076 pm/V), ZnO (0.21 pm/V), CdS (0.143 pm/V), CdSe (0.104 pm/V), BN (0.33 pm/V) and GaN (0.96 pm/V). Our results indicate that hydrogenated II-VI monolayers can be a new type of novel piezoelectric semiconductors and hold a potential application for the piezoelectric devices. [ABSTRACT FROM AUTHOR]

• PC with good compatibility with PVDF is introduced into each fiber in the form of a fiber core. • The piezoelectric properties of all-organic piezoelectric polymers can be improved while retaining high flexibility. • The PPC-2 fiber membrane has the best piezoelectric properties. In this investigation, we report the synthesis of a novel core–shell structured organic composite piezoelectric material through the application of coaxial electrospinning technology. This approach not only markedly enhances the piezoelectric properties but also preserves the inherent flexibility of the underlying piezoelectric polymer. Specifically, the incorporation of a non-piezoelectric polymer core (PC) within the PVDF nanofibers resulted in an increase in the piezoelectric coefficient (d 33) from 8 pC/N for pristine PVDF to 11 pC/N, reflecting an approximate 37.5% enhancement. Our findings represent a substantial advancement in the field of all-organic piezoelectric composite material development. [ABSTRACT FROM AUTHOR]

[Display omitted] • The novel 2H-MOene and its Janus structure are predicted to be a promising piezoelectric material. • The novel 2D-MOene shown a superior piezoelectric coefficient d11 (d11 = 6.09 pm/V for Ti2OH2). • MOene and its Janus structure satisfy the rule of d 11 (_F) < d 11 (_Cl) < d 11 (_Br) < d 11 (_I). Two-dimensional (2D) piezoelectric materials have been widely studied because of their broad application prospects. In this paper, the piezoelectric properties of a MXene-like 2D material (MOene) and its Janus structure are reported by first-principles calculations. The dynamic stability of these 2D materials are verified based on phonon spectra. The semiconductor properties of materials are based on the calculation of energy bands. The origin of piezoelectric polarization of MOene and its Janus structure is explained based on differential charge density and Bader charge analysis. The piezoelectric stress tensor of the material is calculated based on density functional perturbation theory (DFPT). The theoretical prediction results show that the piezoelectric properties of MOene and its Janus structure are better than those of 2D 2H-MoS 2 , and the in-plane piezoelectric coefficient d 11 of Ti 2 OH 2 reaches 6.09 pm/V. Our research shows that MOene and its Janus structure add an important member to the 2D piezoelectric material library, and provide a new sample for the study of piezoelectric properties based on the 2D material library. [ABSTRACT FROM AUTHOR]

• 0.4PZN-0.6PZT ceramics densified to ∼ 98 % at lower sintering temperature of 950 °C. • Stable unipolar strain of ∼ 0.14–0.16 % with η hys < 10 % was observed even close to T C. • Robustness in unipolar strain response is observed up to 106 cycles till 200 °C. • Thermal and fatigue endurance showcases the potential use for actuator applications. Piezo-ceramics with low sintering temperature (<1000 °C), enhanced strain (>0.1 %), low degree of hysteresis (<10 %), fatigue resistance (>106 cycles) with better thermal stability are extremely important characteristics for the development of high performance and cost-effective actuators. In this study, temperature (−50 to 250 °C) and fatigue (100 to 106) dependence of ferro/piezoelectric (P-E/S-E) characteristics of low temperature sintered (950 °C) (0.4[Pb(Zn 1/3 Nb 2/3)O 3 -0.6Pb(Zr 0.49 Ti 0.51)O 3 ]) ceramics was investigated. A thermally stable strain response with a maximum of 0.17 % and degree of strain hysteresis (η h ys) of < 10 % was observed till 250 °C. The fatigue studies revealed a robust unipolar strain stability till 106 cycles even up to 200 °C. Interestingly, a very minimal strain asymmetry (γ S) was observed only after 104 cycles till 200 °C, unlike PZT-5A, PIC151 and PMN-PT. This study demonstrates an exceptional thermal and fatigue resistant strain response even close to the Curie transition temperature (T C ∼ 280 °C) and suggests that the low temperature sintered 0.4PZN-0.6PZT ceramics could be a promising material, exclusively for high-precision actuator applications over a wide temperature range with a cost-effective solution. [ABSTRACT FROM AUTHOR]

• Lead-free (1− x) KNN- x BTO nanoparticles were prepared by solid state reaction method. • The composite films were made by mixing the nanoparticles into Polydimethylsiloxane. • Composite film made of 10 wt% nanoparticles generates the maximum electrical output. • The nanogenerator device is used as an active sensor for sleep monitoring system. A flexible composite film based piezoelectric nanogenerator has been explored using lead-free (1− x) KNaNbO 3 - x BaTiO 3 NPs (x = 0.02, 0.04, 0.06 and 0.08) (used as KNN- x BTO) nanoparticles (NPs). The composite films were made of KNN-x BTO NPs impregnated into a Polydimethylsiloxane (PDMS) matrix. BTO was doped into the KNN lattice without affecting the orthorhombic phase of KNN. Structural analysis such as XRD and Raman spectroscopy were used to confirm the phase formation and atomic vibrations of the piezoelectric materials. Further the electrical analysis of the piezoelectric composite nanogenerator (PCNG) has been performed and the device generates a maximum electrical output of 58 V, 450 nA. Then the PCNG was used as an active sensor for sleep monitoring system by placing the PCNG in the hands and legs of human body and monitor the body movements. This type of system helps to diagnose the sleeping disorder in humans and to be a future advancement in mobile health care monitoring. [ABSTRACT FROM AUTHOR]

Highlights • A piezoelectric scaffold was fabricated by electrospinning. • Cells were seeded onto scaffolds and exposed to hydrostatic pressure. • Piezoelectricity and hydrostatic pressure positively affect differentiation. Abstract Synchronized effects of piezoelectricity and hydrostatic pressure on chondrogenic differentiation of stem cells have been studied. Cells were seeded onto scaffolds and exposed to hydrostatic pressure (HP) (5 MPa, 0.5 Hz, 1 h/day) for 7 days. Glycosaminoglycan synthesis was higher in piezoelectric scaffolds comparing non-piezoelectric ones either with or without HP. SOX9 mRNA level was promoted in the concurrent presence of piezoelectricity and HP. Aggrecan (AGG) mRNA level was enhanced in the presence of hydrostatic pressure but not piezoelectricity and type ⅠⅠ collagen (COL ⅠⅠ) was irrespective of either piezoelectricity or HP. [ABSTRACT FROM AUTHOR]

Highlights • Development of 1–2 type BaTiO 3 /CoFe 2 O 4 magnetoelectric thin films. • Synthesis of individually free-standing TiO 2 nanotubes via Ti anodizing. • Hydrothermal conversion of BaTiO 3 from TiO 2 nanotubes. • Dense filling of CoFe 2 O 4 in an interspace between BaTiO 3 nanotubes. Abstract In this study, individually free-standing piezoelectric nanotubes-based magnetoelectric thin films were synthesized by complexation of one-dimensional (1D) BaTiO 3 as the piezoelectric phase, and CoFe 2 O 4 as the magnetostrictive phase. Particularly, the individually TiO 2 free-standing nanotubes were developed onto a Ti substrate via metal anodizing to obtain a high standing stability of 1D piezoelectric structure and a filling volume of magnetostrictive phase, simultaneously for fabrication of magnetoelectric thin films. After BaTiO 3 perovskite conversion from the TiO 2 nanotubes, an enough volume still remains for sufficient self-filling of CoFe 2 O 4 between the BaTiO 3 nanotubes. Finally, BaTiO 3 /CoFe 2 O 4 magnetoelectric films were found to exhibit a dense structure being suitable for strong magnetostriction-mediated piezoelectric voltages. The structure design, based on individually free-standing nanotubes, would be feasible for flexible magnetoelectric devices such as health monitoring sensors, energy harvesters, and memory devices. [ABSTRACT FROM AUTHOR]

Highlights • Two-step sintering suppressed abnormal grain growth in CuO-doped KNLNT ceramics. • Two-step sintered CuO-doped KNLNT ceramic had superior piezoelectric properties. • Homogeneous multi-layered ceramic was fabricated by two-step sintering. Abstract A two-step sintering method for the fabrication of homogeneous microstructures in CuO-doped [(K 0.485 Na 0.515) 0.935 Li 0.065 ](Nb 0.99 Ta 0.01)O 3 (KNLNT) ceramics without abnormal grain growth is studied. The CuO-doped KNLNT ceramics prepared by normal sintering at temperatures greater than 900 °C resulted in inhomogeneous microstructures with a bimodal grain size distribution. In contrast, two-step sintering (920–930 °C for 0 h in the first step and 880 °C for 1–12 h in the second step) resulted in a homogeneous microstructure with a grain size of a few micro-meters. The samples prepared by two-step sintering had superior piezoelectric properties and piezoelectric energy harvester (PEH) figure of merit comparable to samples prepared by normal sintering. Multi-layered PEH with CuO-doped KNLNT ceramic layers with homogeneous microstructures were successfully fabricated by a two-step sintering method and their harvesting characteristics were measured. [ABSTRACT FROM AUTHOR]

Highlights • A unique in-situ Berlincourt-type high temperature d 33 meter was designed. • The depolarization is directly related to the structural phase transition. • Compared with ex-situ technology, in-situ test data are more accurate. Abstract Thermal depolarization is an insurmountable obstacle to the application of piezoceramics and there is still controversy about its physical origin. In this work, taking four representative piezoceramics (0.94(Na 0.5 Bi 0.5)TiO 3 -0.06BaTiO 3 , 0.2Pb(Zn 1/3 Nb 2/3)O 3 -0.8Pb(Zr 0.5 Ti 0.5)O 3 , 0.36BiScO 3 -0.64PbTiO 3 and Ba 0.85 Ca 0.15 Ti 0.9 Zr 0.1 O 3) as an example, by using a designed in-situ Berlincourt-type high-temperature d 33 meter, combined with variable temperature X-ray diffraction and dielectric temperature spectrum test, it was confirmed the depolarization behavior is directly related to the structural phase transition, meanwhile it is reasonable to apply the peak value of piezoelectric coefficient with temperature, T dp , as the depolarization characteristic temperature. More importantly, the original in-situ varied temperature d 33 meter design helps to investigate the temperature dependent piezoelectric mechanism of various piezoceramics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Polarization conditions is important for the piezoelectric property. • Particle distribution and dispersion are critical factors for piezoelectricity. • Composite with no cytotoxicity is benefical for the cell adhesion and application. Abstract Polycaprolactone materials with excellent bio-properties are of great interest to scientists and have broad potential applications in tissue engineering. In this paper, polycaprolactone was composited with barium titanate particles to prepare piezoelectric an intelligent material for tissue engineering. The polarization conditions and the mechanism were discussed. The piezoelectric property of the composites was improved by the barium titanate particles. The distribution and dispersion of the particles are the critical factor for the improvement of piezoelectric property. The composite with no cytotoxicity is beneficial cell adhesion and has potential applications in tissue engineering. [ABSTRACT FROM AUTHOR]

• ACP was used to improve the properties of 2–2 PSCCs for the first time. • Improvement of d 33 of 36% was achieved in ACP samples. • A high d 33 of 1700 pC/N was obtained, surpassing reported piezocomposites. Piezoelectric single-crystal composites with 2–2 type (2–2 PSCCs) have attracted widespread attention in acoustic transducer applications due to the higher hydroacoustic piezoelectricity and electromechanical coupling performance compared to traditional ceramic piezoelectric composites. At present, alternating current polarization (ACP) has been proven as an effective method to improve the performance of piezoelectric materials. Here, to optimize the conditions of ACP, the influence of ACP on the properties of 2–2 PSCCs with different amplitudes, frequencies, and polarization cycles of the electric field was investigated. Compared to direct current polarized (DCP) samples, the piezoelectric coefficient (d 33), the relative free dielectric permittivity (ε 33 T / ε 0), and the thickness electromechanical coupling factor (k t) of ACP samples were improved by 36%, 60%, and 3.5% respectively. Furtherly, the domain structure of DCP and ACP samples was compared, and the result demonstrates that the improvement in piezoelectric and dielectric properties is related to the grown domain size in single crystals. This work shows a simple and effective method to improve the performance of 2–2 PSCCs. [ABSTRACT FROM AUTHOR]

In this work, PZN–PZT piezoelectric nanoceramics were fabricated by SPS of nanocrystalline powders. It was found that Mn-doped nanoceramic possessed not only high mechanical properties, but also high FOM off . Under high acceleration of 70 m/s 2 , Mn-doped PZN–PZT harvester can still work properly without damage, and the output power density is as high as 162 × 10 −3  μW/mm 3 . This research shows the Mn-doped nanoceramic having the potential application for building multi-layer micro-piezoelectric energy harvester. [ABSTRACT FROM AUTHOR]

This letter reports that a plasticized poly vinyl chloride (PVC) exhibits high dielectric constant with low Young’s modulus which drastically improves its piezoelectric property and strain sensing behavior. PVC was plasticized by poly[di(ethylene glycol) adipate] (PDEGA) and PDEGA-PVC was fabricated by simple solvent mixing process. As increasing the PDEGA content, the dielectric constant of PDEGA-PVC increases meanwhile its Young’s modulus and yield strength decrease, which results in great improvement of the piezoelectric charge constant of PDEGA-PVC (51.2 pC/N), much higher than the pristine PVC (0.34 pC/N). A strain sensor with PDEGA-PVC was tested and its durable strain sensing behavior is demonstrated. The developed PDEGA-PVC is applicable for sensors of wearable and portable devices and soft actuators. [ABSTRACT FROM AUTHOR]

Hybrid biodegradable piezoelectric electrospun fibrous scaffolds based on polyhydroxybutyrate (PHB) and polyaniline (PANI, emeraldine salt) were fabricated. Fourier transform infrared spectroscopy and X-ray diffraction confirmed the presence of PANi in the structure of hybrid PHB-based scaffolds. The piezoelectric coefficient d 33 and surface electric potential under cyclic mechanical stress at the frequency of 4 Hz were increased in 4.2 times and 3.5 times, respectively, in the case of hybrid PHB scaffolds with the addition of 2% PANi compared with pure PHB ones. [ABSTRACT FROM AUTHOR]

PVDF fibers were prepared via electrospinning with different electric field and rotating speed, respectively. The values of piezoelectric output of the devices assembled by PVDF fibrous membrane linearly fit with the product of the numerical values ( C EP , content of effective piezo-phase) of crystallinity and β-phase proportion in electrospun fibers. With the optimized parameters of electric field (15 kV) and rotation speed (500 rpm) in electrospinning, the maximal output of 2.8 V and 1.32 μA were obtained. The controllable crystal structure of PVDF and definite relationship between preparation parameters and piezoelectric behavior is beneficial for modulating the mechanical-to-electrical conversion in device. [ABSTRACT FROM AUTHOR]

• Soft piezoelectric nanofibers with core–shell structure were prepared. • Lattice strains can be calculated from the relationship between interplanar spacing and lattice constant. • The direct piezoelectric voltages were measured at 10 Hz and 100 Hz to be approximately 3.0 V and 3.5 V. • The converse piezoelectric effect were measured through in situ synchrotron wide-angle X-ray scattering. Soft piezoelectric composite nanofibers composed of poly (vinylidene fluoride-trifluoroethylene), denoted as P(VDF-TrFE), and poly (vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene), P(VDF-TrFE-CTFE), were prepared by the coaxial electrospinning technique. The relationship between crystal structures and the piezoelectric responses was investigated. The piezoelectric voltages of the composite nanofibers are about 3.0 V and 3.5 V at 10 Hz and 100 Hz, respectively. In-situ Wide-angle X-ray scattering (WAXS) was used to observe the effect of applied voltage on lattice strains in different lattice orientations. Crystallographic studies on the composite nanofibers revealed co-crystallization, which led to higher piezoelectric voltages in the composite nanofibers. [ABSTRACT FROM AUTHOR]

• Developed epoxy-bonded distributed disc structured magnetoelectric (ME) composite. • Epoxy modulated multi-fold enhancement in magnetoelectric response. • Peak quasi-static ME response of 2.33 V/cm Oe for four-disc structured composite. • Remarkable resonant ME output of 163 V/cm Oe for four-disc composite. The authors had previously reported a novel magnetoelectric (ME) composite configuration termed as distributed disc structured (DDS) configuration, which was proposed as epoxy-free ME composite to enable them to operate at elevated temperatures. However, a topological study on the epoxy-free DDS composites reveal that the absence of epoxy led to material discontinuity and generation of voids at the magnetostrictive/piezoelectric interface, thereby adversely affecting the output ME response. In this study, the voids at the magnetostrictive/piezoelectric interface in the DDS composites have been filled using epoxy material and quasi-static and resonant ME measurements show a remarkable improvement over their epoxy-free counterparts. The maximum ME coefficient of 2.33 V/cm Oe (enhancement of 430 %) and a peak value of 163 V/cm Oe is observed for four-disc structured configuration under quasi-static and resonant operating conditions, respectively. Thus, for the first time, the advantage of the DDS configuration has been combined with the use of epoxy leads to achieve a remarkable enhancement in ME response of Ni/PZT composites. [ABSTRACT FROM AUTHOR]

Nanoporous (NP) GaN thin films with low nucleation density were fabricated via UV-assisted electrochemical etching approach. Under different applied biases, two NP samples with different porosities were fabricated. Piezoelectric characteristics of the fabricated samples were investigated using piezoresponse force microscopy. It was found that the nanopores have great influence on its piezoelectric characteristics such as weakening of piezoresponse and change of polarization orientation. During the performance of devices, the weakening of piezoresponse should be propitious to the optoelectronic and electronic stabilities of GaN-based devices. [ABSTRACT FROM AUTHOR]

The effects of ZnO modification on the microstructure and piezoelectric properties of Pb(Mg 1/3 Nb 2/3 ) 0.65 Ti 0.35 O 3 (PMNT) ceramics were investigated. The grain size tended to increase with increasing ZnO content. Secondary phases were observed in the ceramics with 4.0 and 11.0 mol%ZnO. The piezoelectric properties of the PMNT ceramics were enhanced by introduction of 0.4–4.0 mol%ZnO. The piezoelectric properties deteriorated when higher ZnO contents were used. Among all the investigated compositions, the highest piezoelectric performance was observed for the PMNT/0.4 mol%ZnO ceramic. This makes the PMNT/0.4 mol%ZnO ceramic promising for piezoelectric applications. [ABSTRACT FROM AUTHOR]

CaZrO 3 (CZ)-doped Na 0.5 K 0.5 NbO 3 (NKN)-based single crystals with 20 mm over were prepared by a seed-free solid-state crystal growth (SFSSCG) method. The microstructure, piezoelectric and dielectric properties of the crystal were investigated. The results show that the piezoelectric constant d 33 of this crystal is evidently enhanced up to 488 pC/N with the addition of CZ. Two dielectric anomalies appear at 391 and 149 °C, corresponding to the tetragonal → cubic and orthorhombic → tetragonal phase transition, respectively. There exists two domains (90° and 180°) in the crystal. These results show that this NKN-based crystal is a promising lead-free piezoelectric material for applications. [ABSTRACT FROM AUTHOR]

We report piezoresponse force microscopy (PFM) studies of single electrospun polyvinylidene fluoride (PVDF) nanofibers on the Pt/Ti electrode substrate. The out-of-plane piezoelectric response is much stronger than the in-plane, which is dependent on the parameters of the electrospinning technique. Further, the local polarization switching of the thin nanofibers can be quantitatively characterized by the amplitude-voltage butterfly loop and phase-voltage hysteresis loop. The piezoelectric coefficient ( d 33 ) of the nanofibers is diameter-dependent. The thinnest nanofiber studied here is 30 nm and has the maximal | d 33 | of 38.5 pm V −1 . The excellent piezoelectric properties of these low-dimensional nanofibers can facilitate the development in sensing and energy harvesting applications. [ABSTRACT FROM AUTHOR]

This letter presents the analytical and experimental results of piezoelectrically generating bistability via Macro Fiber Composite (MFC) actuators. Two stable configurations are exhibited when piezoelectric strain anisotropy is induced within a [0 MFC /90 MFC ] T laminate. This is achieved by bonding two MFCs in their actuated states and releasing the voltage post cure to create in-plane residual stresses. The resulting shapes are cylindrical and can be snapped through and back with only piezoelectric actuation. A [0 MFC /90 MFC ] T laminate is modeled, manufactured, and experimentally characterized. This adaptive laminate functions as both the actuator and the primary structure and its snap through capability allows full configuration control necessary in morphing, without continuous energy input or any mechanical assistance. [ABSTRACT FROM AUTHOR]

In this work, it is shown that the electrospun poly(vynilidene fluoride) (PVDF) nanofibers have polymer chains re-oriented along the fiber axis and the β-phase content reaches 72.7%, therefore being able to be implemented into electroactive device components. Further, nanoscale domain imaging and local piezoelectric coefficient d 33 of the nanofibers have been intensively studied using piezoresponse force microscopy (PFM). The piezoelectric response (PR) imaging and butterfly amplitude loop have been demonstrated to confirm that the nanodomains result from the out-of-plane displacement and the d 33 has an uneven distribution with the higher values on the fiber periphery. [ABSTRACT FROM AUTHOR]

Complete sets of elastic, piezoelectric and dielectric constants of [111] C poled (Na,K)(Nb, Ta)O 3 single crystal have been measured. The results show that the crystal with “3O” domain structure exhibits high shear but low longitudinal piezoelectric properties (d15=140 pC/N, k 15 =0.569, d 33 =64 pC/N and k 33 =0.450), which is similar to the “1O” single domain state, but different from the “4O” multi-domain state. The orientation-dependent longitudinal properties, e.g. , d 33 * , ε 33 * , s 33 * and k 33 * in the ( 0 1 ¯ 1 ) C plane have been calculated. The maximum piezoelectricity exists at the position of 38° away from [011] C , which is close to the [111] C direction. By comparing the measured and calculated parameters, it can be concluded that the piezoelectricity is dominated by the intrinsic contribution while the dielectricity is controlled by the extrinsic contributions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Zn-doped BST coating was successfully constructed on Ti surface. • Zn doping could improve the hydrophilicity of BST. • Zn doping showed significant inhibition of E. coli and S. aureus growth. Titanium (Ti) is a material commonly used in orthopedic implants. However, the lack of antimicrobial properties limits its application in implants. Herein, we constructed zinc (Zn)-doped barium strontium titanate (BST) films on Ti. The results show that the Zn-doped BST films can effectively improve the antibacterial ability of Ti substrates, which presents potential applications in bone repair. [ABSTRACT FROM AUTHOR]

• A phase field model on MPB with local compositional heterogeneity is developed. • Three-phase mixture forms due to the local compositional heterogeneity. • Polarization rotation under electric fields contribute to the piezoelectricity. • d 33 coefficient decreases due to the on-average more difficult polarization rotation. In this work, the effect of local compositional heterogeneity on the domain structure and piezoelectricity at ferroelectric morphotropic phase boundary (MPB) is studied by phase field simulations. It is found that the local compositional heterogeneity leads to a unique domain structure at MPB, i.e., a mixture of tetragonal, monoclinic and rhombohedral domains. Although polarization rotation occurs for both MPB samples with and without local compositional heterogeneity, the piezoelectric d 33 coefficient becomes reduced for the sample with local compositional heterogeneity because polarization rotation becomes more difficult on average. This work unravels the effect of local compositional heterogeneity on the piezoelectric property of ferroelectric MPB. [ABSTRACT FROM AUTHOR]

• In situ reversible tuning of resistance is achieved in LaMnO 3 /PMN-PT(0 1 1) structure. • Non-180° domain switching-induced strain causes nonvolatile resistance tuning. • In-plane tensile stain contributes to the weakened magnetization. The electric-field control of resistance change (Δ R / R) and magnetic properties has been investigated in the LaMnO 3 (LMO)/0.71Pb(Mg 1/3 Nb 2/3)O 3 -0.29PbTiO 3 (PMN-PT)(0 1 1) heterostructure. When the unipolar electric field (E) increases beyond the coercive field of PMN-PT, the Δ R / R vs E curve transforms from a loop-like behavior to a butterfly-like one. The electric-field-induced non-linear strain effect in the PMN-PT substrate realizes the modulation between low and high resistance states at room temperature. Moreover, different freezing temperatures of the LMO film are observed as the PMN-PT substrate is in the fully negative (P r -) and partially positive (P r / / ) polarization states. The observation of less magnetization for P r / / state than that for P r - state indicates that the in-plane tensile strain is beneficial to the Jahn-Teller distortion. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Synthesis of (1 − x)BiFeO 3 – x PbTiO 3 with respective crystalline textures. • Weak ferromagnetic behavior at room temperature due to canting of spin structure. • Enhanced ferroelectric characteristics with the addition of PbTiO 3 contents. • Room temperature magneto-electric coupling regarded as charge compensation effects. Abstract In this letter, we demonstrate an apparent magnetically activated electric polarization reorientation at room temperature through magneto-electric coupling in (1 − x)BiFeO 3 – x PbTiO 3 (x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5) composites. A change in magnetic field causes variation in electric polarization, attributed to the destruction of space modulated spin antiferromagnetic structure with the PbTiO 3 addition. This behavior also results in the increase in magnetic parameters as the coercive field of the composites increases with the increase in PbTiO 3 contents. The analysis demonstrates that the magneto-electric coupling in the prepared ferromagnetic/ferroelectric composites is dominant at room temperature, quite feasible for modern day devices. [ABSTRACT FROM AUTHOR]

• Ag nanoparticles modified Na 0.5 Bi 0.5 TiO 3 (Ag-NBTO) nanospheres were prepared by hydrothermal and chemical solution methods. • The synergistic effect of piezoelectric and plasmon effect of Ag-Na 0.5 Bi 0.5 TiO 3 improves the piezo-photocatalytic performance. • The piezo-photocatalysis of Ag-NBTO is higher than that of individual piezocatalysis and photocatalysis. Piezo-photocatalysis has attracted tremendous interest in dealing with organic pollutants. In this work, silver (Ag) nanoparticles modified Na 0.5 Bi 0.5 TiO 3 nanospheres (hereinafter referred to as Ag-NBTO) were prepared by hydrothermal and chemical solution methods. Our results show that 98.6 % RhB is degraded in 120 min under the simultaneous excitation of ultraviolet light and ultrasound with the assistance of Ag-NBTO. The corresponding rate constant k is 0.0329 min−1, which is 10 times higher than that of Na 0.5 Bi 0.5 TiO 3. The excellent piezo-photocatalytic performance may be attributed to the local surface plasmon resonance (LSPR) effect. This work offers great potential for eliminating environmental pollution and can be extended to other piezoelectric materials. [ABSTRACT FROM AUTHOR]

• MoS 2 nanoflowers with few-layer structure were synthesized using hydrothermal route. • The MoS 2 nanoflowers were used for piezo-photocatalytic reduction of Cr6+ ions. • The removal rate of Cr6+ under piezo photocatalytic is up to 96.22 % within 20 min. • This work explores a new approach for highly efficient Cr6+ removal. The reduction of Cr6+ is very important for sewage treatment. Here, a strategy is proposed for the highly efficient reduction of Cr6+ by co-utilizing the photocatalysis and piezoelectric effect of MoS 2 nanoflowers. Under both solar-irradiation (300 W Xe lamp) and ultrasonication, the Cr6+ removal rate catalyzed by few-layer MoS 2 nanoflowers (10 mg) increases with increasing ultrasonication power, and a maximum of 96.22 % is achieved under solar irradiation and ultrasonication (100 W) for 20 min, ∼3.65-fold of that under only solar irradiation. The fast Cr6+ removal rate can be ascribed to the synergistic effect of light induced reduction effect and ultrasound induced piezoelectric field. This work explores a new approach for highly efficient Cr6+ removal. [ABSTRACT FROM AUTHOR]

Grain-oriented lead-free piezoceramics 0.83(Bi 0.5 Na 0.5 )TiO 3 -0.17(Bi 0.5 K 0.5 )TiO 3 was synthesized with different grain orientation along the <00l> crystallographic orientation using plate-like NaNbO 3 templates. The effects of degree of texturing on the microstructure, phase transition temperature and resulting changes in piezoelectric and strain response of ceramics were explored. The electromechanical properties increased monotonously with increasing the degree of texturing. A high <00l> texture degree of 91% was obtained, giving rise to larger electromechanical properties of d 33 =217pC/N, k p =35%, S =0.246%, and S max / E max =410 pm/V in textured samples relative to the conventional polycrystalline counterparts. Furthermore, the grain oriented ceramics exhibited improved temperature stability as compared to its randomly oriented form. This work opens the possibility of achieving BNT-based high performance ceramics. [ABSTRACT FROM AUTHOR]

(Ba 0.95 Ca 0.05 )(Ti 0.94 Sn 0.06 )O 3 - x mol% CuO ceramics were fabricated to investigate their domain structures and piezoelectric properties. The CuO additive significantly improved the densification behavior of the ceramics, resulting in a reduced sintering temperature by ~150 °C. Increasing x shifted the orthorhombic-tetragonal phase transition towards lower temperatures, and caused the specific ratio of tetragonal to orthorhombic phase to increase at room temperature. The herringbone domain patterns became much simpler and their number substantially decreased. The watermarks and parallel strips are the dominant domain configuration in ceramics with x =0.50 which show the optimum piezoelectric properties: d 33 ~516 pC/N, d 33 * ~996 pC/N, k p ~0.42, and Q m ~352. The underlying physical mechanisms for the enhanced piezoelectricity in the CuO-doped ceramics were discussed. [ABSTRACT FROM AUTHOR]

We present a simple all-thin-film magnetoelectric memory cell with ferromagnetic film of Fe 70 Ga 30 grown on ferroelectric film of 50Ba(Zr 0.2 Ti 0.8 )O 3 –50Ba 0.7 Ca 0.3 TiO 3 (50BZT-50BCT) based on converse magnetoelectric effect. The heterostructure exhibits well-defined magnetic and piezoelectric behaviors. The 50BZT-50BCT layer acquires different strain states when an electric field is applied to the cell. Mechanical transduction couples this strain to the mechanically coupled Fe 70 Ga 30 layer, which then changes its magnetic anisotropy and thus the magnetoresistance. Thus, a magnetoelectric memory cell with resistance as the media and electric field as the writing field was realized. The demonstrated electric field control of resistance states is a significant step towards exploring magnetoelectrically controlled spintronic devices for low-power and high density magnetic data storage applications. [ABSTRACT FROM AUTHOR]

This work reports, for the first time, the electrospinning of the piezoelectric and ferroelectric polymer polyvinylidene fluoride (PVDF) by means of the bubble electrospinning technique. We focus our study in the effect of different applied voltages on the morphological and crystalline features of the PVDF bubble-electrospun nanofibers. The crystallinity of PVDF nanofibers that were obtained by this process was higher than that observed in traditionally synthesized PDVF powders. Is important to highlight that production rate of the obtained PVDF nanofibers was higher (13.93 mL/h) than that of the reported traditional electrospinning (1–5 mL/h). [ABSTRACT FROM AUTHOR]

At room temperature, high sensitivity for detecting ethanol has been achieved from α-Fe 2 O 3 /ZnO nanowire piezo-nanogenerator as self-powered gas sensor. Such ethanol sensing can be ascribed to piezo-surface coupling effect of the heterostructured nanocomposites. The results demonstrate a novel approach for room-temperature ethanol sensors and promote the development of self-powered sensing. [ABSTRACT FROM AUTHOR]

Lead–zirconate–titanate PbZr (1− x ) Ti x O 3 (PZT), materials for piezoelectric applications are the dominant piezoceramics since their properties are high. However PZTs need to be substituted by safer materials due to health and environmental problems of lead. In this work, the crystal structure modifications of BaTiO 3 induced by cobalt doping and niobium/cobalt co-doping were investigated in the range 0.1–25 at%. Low Co and Co/Nb doping level significantly improve piezoelectric properties of BaTiO 3 . The piezoelectric constant, obtained for BaTiO 3 doped with 0.075 at% of Cobalt ( d 33 =200 pC/N), is twice of that measured for pure BaTiO 3 . At high doping concentration, the structure of BaTi 1− x Co x O 3 and BaTi 1− x Co x Nb x O 3 change from tetragonal to hexagonal while BaTi 1− x Co x Nb 2 x O 3 remains tetragonal and gradually turns into cubic. It suggests that the ionic charge defect is balanced by oxygen vacancies formation when Ti 4+ are substituted by Co 2+ /Co 3+ . [ABSTRACT FROM AUTHOR]

Pure and iron doped (0.2 mol%) sodium para-nitrophenolate dihydrate (SPNPD and FSPNPD) non-linear optical single crystals were grown by slow evaporation technique. Structural characterizations have been carried out using SXRD and PXRD and analyses. EDAX analysis confirmed the incorporation of iron into the host crystal lattice SPNPD. Various functional groups in both crystals were identified by FTIR analysis. Optical properties of doped crystal have been preserved. Dielectric analysis revealed that dielectric constant value increases with decrease in dielectric loss on doping. The Piezoelectric charge coefficient d 33 of doped crystal was found to be about 10 times (2.24 to 24 pC/N) larger than that of pure crystal which make it a better candidate for piezoelectric devices applications. The incorporation of iron also increases the SHG efficiency of SPNPD crystals. In hysteresis loop, coercive field was decreased significantly, as a result of doping. [ABSTRACT FROM AUTHOR]

The obvious conflicts between large piezoelectricity and high strain could be solved by adding new components in BNT. Moreover, this urgent problem has been solved and induced a large strain as well as a high piezoelectricity in BNT. Large normalized strain ( d 33 * =526–597 pm/V) and high strain (0.342%–0.388%) were achieved at the composition range of 0.0025≤ x ≤0.0050, suggesting that such a system is a promising lead-free candidate for electromechanical actuator applications. Furthermore, high d 33 values of 141–204 pC/N have also been attained at the above composition range due to adding new components. [ABSTRACT FROM AUTHOR]

Straight polyvinylidene difluoride (PVDF)/nanoclay nanofibers with enhanced piezoelectric properties were fabricated by a “near distance-wheeling” electrospinning (NWS) method. In this method, the fibers were electrospun under centimeter scale spinning distance, high electric field and high mechanical stretching. The XRD and FT-IR spectra showed that the oriented β crystal form was dominant in the straight composite fiber, which may be caused by the cooperative effect of NWS and nanoclay. The electrospun fibers were in-situ assembled into full-fiber sensors. The full-fiber sensor based on the straight PVDF/nanoclay fibers showed notable piezoelectric properties with good response speed and reproducibility, which can be applied on intelligent clothes. [ABSTRACT FROM AUTHOR]

Thin film capacitors of the lead-free (K 0.5 Na 0.5 )NbO 3 (KNN) with (100) orientation were grown on Pt/Ti/SiO 2 /SOI (silicon-on-insulator) substrates by pulsed laser deposition. The films are pure phases and do not show other crystal orientations. The remnant polarization P r , saturation polarization P sat , longitudinal d 33,f and transverse ( d 31,f and e 31,f ) piezoelectric coefficients of the KNN films were determined ( P r =12.6 µC/cm 2 , P sat =25.0 µC/cm 2 , d 33,f =58 pm/V, d 31,f =−42 pm/V and e 31,f =−5.6 C/m 2 ). These values are well comparable with the highest values reported for lead-free films of different compositions and therefore these KNN films form a potential alternative to PZT films in lead-free MEMS applications. [ABSTRACT FROM AUTHOR]

Ho, Mn co-doped Bi 5 Ti 3 FeO 15 films were prepared and the microstructures, ferroelectric properties, piezoelectric properties, magnetic properties as well as magnetoelectric effect were investigated. It shows that the ferroelectric, piezoelectric, ferromagnetic, magnetoelectric properties are enhanced obviously after doping with Ho and Mn. The origin of thus enhanced multiferroic and magnetoelectric properties was discussed detailedly. The present results suggest a candidate for magnetoelectric materials. [ABSTRACT FROM AUTHOR]

Er 2 O 3 doped (K,Na)NbO 3 (KNN) ceramics with the composition around the morphotropic phase boundary was synthesized by the conventional solid state reaction. Compared to pure KNN ceramics, KNN doped Er 3+ ceramics exhibited enhanced ferroelectric, piezoelectric properties owing to the donor doping effect. And the maximum value of d 33 =132 pC/N and k p=0.44 were obtained for the ceramics with the addition of 0.5 mol% Er 2 O 3 . Meantime, the intensity of absorb spectra and photoluminescence were obviously enhanced in this kind of sample owing to the lattice distortion induced by the polarization reorientation during poling process. The present work indicated the proposed system exhibited potential application in multifunctional integration device. [ABSTRACT FROM AUTHOR]

Unsaturated elliptical P-E hysteresis loops in sodium para-nitrophenolate dihydrate single crystal and its Fe 3+ doped analogue are due to dielectric loss not to ferroelectric properties. Dielectric anomaly at 28 °C does not correspond to a ferroelectric phase transition. Initial polarity for piezoelectric single crystals is not necessary. The doping can not cause over 10-fold increase in the value of the piezoelectric coefficient. [ABSTRACT FROM AUTHOR]

• Synthesis of highly printable ceria-based electrolyte for a solid oxide fuel cell. • Polymeric 20 mol% gadolinium-doped ceria nanoparticle ink formulated. • Printed gadolinium-doped ceria films of thickness 130 nm obtained. • Proper adjustment of ink rheology and particle size ensures successful printing. We propose a simple ink formulation and a rapid preparation technique to deposit a 20 mol% gadolinium-doped ceria electrolyte utilizing nanopowders and a polymeric dispersant. The ink was assessed for printability and was successfully printed using a piezoelectric inkjet materials printer. The ejected drops were investigated using built-in stroboscopic imaging during ejection, and the deposited thin films were characterised using optical microscopy and surface profilometry. Inkjet material deposition provides a highly repeatable process for the fabrication of solid oxide fuel cells (SOFCs) that can be up-scaled to industrial levels. [ABSTRACT FROM AUTHOR]

• Elastomer-based sandwich material with enhanced piezoelectric performances. • emarkable stability in harsh environments. • Low cost and simple fabrication process. Polydimethylsiloxane (PDMS) sponges are widely used in many application areas due to their porous structure. In this paper, we present a PDMS sponge-based piezoelectric material which is composed of a PTFE-PDMS composite sponge sandwiched between a pair of Polytetrafluoroethylene (PTFE) solid films. After corona charging, pores inside the sandwich material are internally charged, and charges of positive or negative polarity are produced. The introduction of PTFE nano-particles creates PTFE-PDMS interface traps that can trap charges with stability. The design of the sandwich structure enhances the breakdown strength of the sandwich material, which avoids the early breakdown during poling. The results of the experiments demonstrate the sandwich material exhibits excellent piezoelectric performance and stability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using artificial neural networks to optimize piezoelectric devices allows skipping the construction of physical models. • The ball impact energy harvesting device is more suitable for human energy harvesting. • Considering different optimization algorithms can effectively improve the predictive power of artificial neural networks. • It is necessary to adjust the initial learning rate of the algorithm. Converting actions of human's body into electrical energy via wearable energy harvesters is an exciting area. This study presents a ball impact piezoelectric energy converter consisting of two circular ceramic piezoelectric sheets to obtain energy from arm swing. 2264 sets of data were measured to train the artificial neural network (ANN) modes. The performance of ANN optimized by three different algorithms (Nadam, Adamax, and Adadelta) was compared and discussed. Treadmill experiments verified and confirmed the prediction results from ANN, an effective voltage of 11.3 V was demonstrated at a running speed of 9 km/h. Our results show that ANN can speed up the optimizing process for designing better energy harvesters. [ABSTRACT FROM AUTHOR]

• The d 11 of the 2D Janus BiOI reached 34.36 pm/V. • The ternary bismuth-based compound BiXY exhibits the rule of d 11 (_Cl) < d 11 (_Br) < d 11 (_I). • The response of the BiOI model is sensitive, and its I-V curve and charge density change very regularly. Piezoelectric materials can realize the direct conversion of strain and voltage, and have been widely used in the field of energy supply of micro-nano devices and pressure sensing. Based on the unique Janus structure, the electronic structures and piezoelectric properties of the BiOX (X = Cl, Br and I) monolayers were systematically studied by using first principles calculations. The results of the calculations show that the BiOI monolayer exhibits a largest in-plane piezoelectric coefficients (d 11) value of 34.36 pm/V, which is far higher than the previously reported two-dimensional (2D) materials, such as MoS 2 (3.73 pm/V) and BiXY (the largest BiSI is 23.11 pm/V), the sensitive and regular response of the BiOI model also broaden its application opportunities in micro-nano piezoelectric devices. [ABSTRACT FROM AUTHOR]

• High temperature piezoelectric properties of BTNO-15WM ceramics were studied. • The influence of ions with different radii on the distortion of BTNO is similar. • The distortion mode of A/B co-doped BTNO is inclined to "tilt" mode. Bi 2.99 (Li 0.5 Sm 0.5) 0.01 Ti 0.985 (W 2/3 M 1/3) 0.015 NbO 9 (abbreviated as B(LS)TNO-15WM, M is Al, Cr, and Sc) were prepared by solid state reaction sintering. The effects of B-site (W 2/3 M 1/3)5+ complex-ion substitution on and their microstructure, piezoelectric properties, and electrical performance were systematically studied. B(LS)TNO-15WCr obtains the highest piezoelectric coefficient (d 33). Through the calculation of XRD refined results, it is found that this is due to its greater distortion of BO6 octahedron. In this work, the possible sources of high performance of BTNO based ceramics doped at B-site are analyzed, which provides a certain theoretical support for future work. [ABSTRACT FROM AUTHOR]

Polycrystalline (Pb 0.94 La 0.04 ) Zr 0.6 Ti 0.4 O 3 thin films were fabricated by a sol–gel method on the Pt (111)/Ti/SiO 2 /Si (100) substrates. Results from X-ray diffraction reveal that a strain-induced low-asymmetry monoclinic ( M B ) phase exists in all the films as compared with its powder counterpart. Also, films exhibit a simple trend of pyrolysis-sensitive (100)-orient growth. Good piezoelectric longitudinal coefficient values are obtained in the films where a maximum around 130 pm/V is reached for the film pyrolyzing at 425 °C. These findings suggest that combined contributions of monoclinic phase and (100)-preferred orientation type as well as good surface quality will account for excellent piezoelectric properties for ferroelectric films. [ABSTRACT FROM AUTHOR]

The α -quartz could grow at the interface of silicon nanowires (SiNWs) after thermal treatment. The SiNW/ α -quartz composite was utilized as an active layer to fabricate piezoelectric nanogenerators on a flexible polyethylene terephthalate substrate, capable of converting mechanical energy into electricity. An insulative Al 2 O 3 layer was designed to fill the gaps of the composite to avoid the leakage of current by atomic layer deposition and reactive ion etching process. The flexible nanogenerators produced an average short-circuit current of 0.6 μA under the force of 60 N and the maximum power value reached about 380 nW with the load resistance of 20 MΩ. [ABSTRACT FROM AUTHOR]