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Pb-based piezoelectric ceramics with excellent piezoelectric response and low dielectric loss are crucial for advanced applications but still challenging to achieve. Herein, an approach based on synergistic effect of defect engineering and localized heterogeneous structures was developed to prepare 0.11 Pb(In 0.5 Nb 0.5)O 3 -0.89 Pb(Hf 0.47 Ti 0.53)O 3 + x mol%(Sb5++Nd3+) advanced piezoelectric ceramics by solid phase reaction method. Effects of ion co-doping on physical phase structures, defect concentrations, and electric domain morphologies of ceramics were all investigated. A mapping relationship between defect concentration, formation of localized heterogeneous structure, and modulation of piezoelectric and dielectric properties of ceramics was extracted. Values of d 33 , T C , ε r , tanδ (%), and k p of ceramics obtained at x = 0.4 mol% were determined as respectively 607 pC/N, 313.1°C, 3407.81, 1.42, and 0.66, showing excellent overall performances. The doping of (Sb5++Nd3+) skillfully modulated the concentration of defects inside ceramics, resulting in excellent piezoelectric response and reduced dielectric loss. On the other hand, lattice distortion induced by doping generated nanodomains formed localized heterostructures and significantly reduced the Gibbs free-energy barrier, resulting in excellent piezoelectric response and dielectric properties. These effects can mainly be attributed to synergistic action of defect engineering and localized heterostructures. Overall, proposed ceramics and strategy look promising for preparing Pb-based piezoelectric ceramics with excellent comprehensive performance. [ABSTRACT FROM AUTHOR]

The regularities of the influence of the growth temperature on the geometrical parameters, the concentration of the dopant nitrogen and the type of defects formed in carbon nanotubes grown on a molybdenum sublayer are established in this paper. It is shown that the best piezoelectric and resistive properties are observed in nitrogen-doped carbon nanotubes (N-CNTs) grown at a temperature of 525°C, which is due to the highest concentration of dopant nitrogen and high aspect ratio of nanotubes. Based on the results of thermodynamic analysis, the dependence of the dopant nitrogen concentration and the defect type on the tendency to form molybdenum nitrides and carbides during the growth of N-CNTs is shown. The obtained results can be used in the development of nanopiezotronic devices based on arrays of vertically aligned N-CNTs: nanogenerators, strain sensors and memory elements. [ABSTRACT FROM AUTHOR]

In this study, the effect of porosity on the structural and functional (dielectric, ferroelectric, nonlinear, and piezoelectric) properties in Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramics was investigated. Various levels of microporosity in the range of 3% to 31 vol.% have been produced using poly(methyl methacrylate) microspheres as sacrificial templates. The structural investigation indicates a phase coexistence, as expected for this composition at room temperature. The maximum permittivity decreases with increasing porosity, from around 7000 (ceramic with 3 vol.% porosity) down to 3500 (ceramic with 31 vol.% porosity), and the Curie temperature shifts from 47 to 67°C when increasing porosity, related to the possible porosity‐induced structural and internal stress modifications. An enhanced piezoelectric response was found in the Ba0.85Ca0.15Ti0.90Zr0.10O3 ceramic with intermediate porosity around 18 vol.%, with the highest value of piezoelectric response of 470 pC/N and a figure of merit of 7.3 pm2/N. The optimum piezoelectric properties at the intermediate porosity level are related to the microstructural changes (pore shape and connectivity) and possible field‐induced structural modifications. The piezoelectric energy harvesting measurement results have shown the possibility of using Pb‐free porous ferroelectric materials in devices for energy harvesting applications. [ABSTRACT FROM AUTHOR]

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

Aluminum nitride (AlN) films suffer from poor piezoelectric response due to the local hexagonal symmetry of wurtzite crystal structure. The fundamental mechanism of improving piezoelectric response in Ta-doped AlN thin films has not been fully understood. Here, we report that composition-tunable AlTa alloys, instead of Al and Ta individual sputtering targets, can be employed to deposit (002)-oriented Ta x Al (1−x) N films by magnetron-sputtering, where Ta-doping ratio is tunable by changing Al:Ta composition ratio of the AlTa alloys. Importantly, Ta-doping enhances spontaneous polarization to improve piezoelectricity significantly, as suggested by a threefold increase of the effective piezoelectric coefficients (d 33,eff) upon doping 7 at.% Ta. A better alignment of spontaneous polarization for stronger piezoelectric response originates from the reduction in point defects and crystalline disorder in the reduced-symmetrical wurtzite structure by doping Ta in the Ta x Al (1−x) N. This study provides significant insights in improving piezoelectric response in AlN for the development of high-performance film-bulk-acoustic-resonators. • It is challenging to control Ta-doping ratio at a constant level by co-sputtering Al and Ta individual targets because the sputtering yields of Al and Ta is different. Here, we report for the first time that composition-tunable AlTa alloys, instead of aluminum (Al) and tantalum (Ta) individual sputtering targets, can be employed to deposit (002)-oriented Ta-doped Ta x Al (1−x) N films by magnetron-sputtering, where Ta-doping ratio is tunable by changing Al:Ta composition ratio of the AlTa alloy. • It is unambiguously revealed that Ta-doping allows to enhance spontaneous polarization of wurtzite structured Ta x Al (1−x) N for the significantly improved piezoelectricity, as suggested by a threefold enhancement of the effective piezoelectric coefficient d 33,eff upon doping 7 at.% Ta in AlN films. • The fundamental mechanism for the enhanced piezoelectricity in the Ta-doped AlN thin films has not been fully understood and is currently in controversy. Here, it is disclosed that doping Ta allows to reduce point defects and crystalline disorder in the columnar grains, leading to a lower phonon scattering and a better alignment of spontaneous polarization for larger internal strain sensitivity. [ABSTRACT FROM AUTHOR]

As legislative restrictions on the use of hazardous lead-containing materials are approaching and the demand for environmentally-benign piezoelectric materials continues to grow, there is an urgent need for viable lead-free piezoelectric alternatives. (K,Na)NbO 3 (KNN)-based ceramics are environmentally-friendly, however, their piezoelectric properties still fall short of those of commercial lead-based ceramics. Herein, we report an alternative KNN material with the composition of (100- x)(K 0.49 Na 0.49 Li 0.02)(Nb 0.8 Ta 0.2)O 3 - x BaZrO 3 + 2 wt % MnO ceramics prepared by a conventional solid-reaction approach. The addition of BaZrO 3 produces finer domains and thus improves the piezoelectric and dielectric properties. MnO acts as sintering aid to reduce alkaline elements volatilization by lowering the sintering temperature. The mitigated volatilization of alkaline elements significantly reduces the concentration of oxygen vacancies, and thus contributes to enhanced piezoelectric properties. An optimal normalized strain (d 33 *) up to 476 pm/V at room temperature with a low driving electric field of 1.5 kV/mm is achieved at x = 4. More encouragingly, the ceramics also possess excellent temperature stability and fatigue resistance. [ABSTRACT FROM AUTHOR]

BiGaO3 doped BiFeO3–BaTiO3 ceramics were prepared by the traditional solid-phase synthesis process. The phase analysis, microstructure, piezoelectric, ferroelectric, dielectric properties, and thermal stability of 0.7BiFeO3-(0.3 − x)BaTiO3-xBiGaO3 (Abbreviated as BF–BT-xBG) were investigated. The results show that the ceramics have rhombohedral (R) and tetragonal (T) structures. Particle dimensions gradually get bigger with the increase of BiGaO3 concentration, and dense ceramic grains were observed through SEM. Electrical properties of BF–BT-xBG are improved after adding a small amount of BiGaO3: piezoelectric constants d33 = 141 pC/N, electromechanical coupling coefficient kp = 0.314, mechanical Quality Factor Qm = 56.813, dielectric loss tanδ = 0.048, residual polarization intensity Pr = 18.3 µC/cm2, Curie temperature Tc = 485.2 °C, depolarization temperature Td = 465 °C for x = 0.003. The "temperature-piezoelectric performance" curve under in situ d33 indicates that piezoelectric properties d33 increase rapidly with increasing temperature. Remarkably, the piezoelectric response d33 reaches a maximum of 466 pC/N at a temperature T = 340 °C, and afterward, reduces gradually to zero with increasing temperature until 450 °C. [ABSTRACT FROM AUTHOR]

The effect of epitaxial strain on the electrical properties of ferroelectric films has been widely investigated. However, this kind of strain is generally attributed to the substrate clamping constraints and is easily relaxed when the thickness of films is over 100 nm. In this work, a vertically epitaxial strain was introduced into lead-free piezoelectric K0.5Na0.5NbO3 films to improve the electrical properties of ferroelectric films. Two-phase, vertically epitaxial composite KNN-ZnO thin films were grown on the (001) STO substrate using a pulsed laser deposition (PLD) method. The highly (001) preferentially oriented KNN phase and (11 2 ¯ 0)-oriented ZnO phase were orderly arranged. Two types of morphologies of "square-like" and "stripe-looking" grains were observed in the surface image. An asymmetric "square" out-of-plane phase hysteresis loop and a "butterfly" displacement loop were exhibited in the KNN phase, whereas the ZnO phase showed a closed phase hysteresis loop and a slim displacement-voltage loop. Two different kinds of polarization behaviors for domains were also observed under applied electric fields, in which the domain of the KNN phase is easily switched to the opposite state, whereas the ZnO phase keeps a stable domain state when applying a DC bias of ±50 V. the vertically epitaxial growth of the KNN-ZnO composited films in this work provides a new way to fabricate complex nanoscale materials. [ABSTRACT FROM AUTHOR]

The optimal molar ratio of poly(vinylidene fluoride) (PVDF): dimethyl sulfoxide (DMSO) was investigated that promoted the β -phase formation, used during the PVDF film synthesis. The solution cast method was used for doping the PVDF films with ytterbium (III) nitrate salt hexahydrate. In general, Yb-doping in PVDF films improves thermal resistance, promotes β -phase formation, modifies the monomer conformation, reduces reversibility to electrochemical processes, and increases the d _33 coefficient of piezoelectricity. The β -phase formation caused by Yb-doping alters the internal structures of the trans-gauche-trans-gauche’ (TGTG’) and all-trans (TTTT) chains inside the polymeric network. The coexistence between the trans-gauche and all-trans structures provides in both films the α -phase and β -phase coexistence. The presence of self-polarized CH _2 -CF _2 dipoles, where the concentration of fluorine remains the same and the CH _2 drastically increases after Yb ^3+ incorporation. The quasi-reversible shape shown in both voltammetry cyclic curves is related to irreversible oxidation and reduction reactions. Yb-PVDF exhibits specific pseudocapacitance values that are 30% higher than those of the PVDF films. Finally, the piezoelectric properties were improved with ytterbium incorporation.

Lead-free piezoelectric ceramics with nominal composition at morphotropic phase boundary Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) prepared by different processing routes and sintered either by conventional solid-state reaction or by spark plasma sintering (SPS) techniques were comparatively investigated to observe the role of structural modifications and of microstructures on the dielectric, ferroelectric, piezoelectric and electrocaloric responses. The ceramics presented relative densities from 75% to 97% and showed variations in their phase composition as a result of variable mixing and different synthesis and sintering parameters providing local compositional heterogeneity. As result, all of the ceramics showed diffuse phase transition and ferroelectric switching responses, with parameters affected mostly by density (Pr between 3.6 to 10.1 μC/cm2). High values for the electrocaloric response in the Curie range were found for the ceramics with predominantly orthorhombic character. Field-induced structural modifications were probed by tunability anomalies and by XRD experiments in remanence conditions. Piezoelectric effects with notably high figure of merit values were assigned to the better densification and poling efficiency of BCTZ ceramics. [ABSTRACT FROM AUTHOR]

Bismuth layer-structured ferroelectrics with a high Curie temperature (T c) have great potential applications in optoelectronic fields. Sm doped (10- x)Bi 4 Ti 3 O 12 - x Na 0.5 Bi 2.5 Nb 2 O 9 ((10- x)BIT- x NBN:Sm) composite ceramics have been prepared. The effect of NBN content on the microstructure, electrical properties, photoluminescence (PL) and photochromic (PC) properties of the ceramics have been investigated. It is found that the composite ceramics exist with BIT and NBN phases and 1BIT-9NBN:Sm ceramics have the best comprehensive electrical properties (saturated polarization, d 33 = 10 pC/N). Furthermore, the PC and fluorescence modulation performances are dependent on the oxygen vacancy content of composite ceramics. Reversible PC reaction and fast response time as short as 1s have been achieved. Moreover, the influence of natural light on PC reaction has been properly eliminated. The research results indicate that regulating the compositions of (10- x)BIT- x NBN:Sm can not only optimize the electrical properties but also the PC performances. A vivid display via the quick PC reaction has been demonstrated. [ABSTRACT FROM AUTHOR]

Ultrasonic vibration and light irradiation can be used together to slow down the rapid recombination of light-induced charges during the catalytic process. One way to enhance the catalytic performance is by introducing different elements into the structure. In this study, pure bismuth ferrite (BiFeO 3) and manganese (Mn)-doped bismuth ferrite (BFMO) nanomaterials were successfully synthesized by electrostatic spinning. These materials were then tested for their ability to degrade rhodamine B (RhB). The best-performing material was BiFe 0.85 Mn 0.15 O 3 , which achieved almost complete removal of RhB within 100 min. The degradation rate of this material was 3.3 times higher than that of pristine BiFeO 3. This enhanced catalytic activity can be attributed to the wider range of light absorption and the synergistic enhancement of the piezoelectric response, which promotes the movement of free carriers. In addition, the synthesized catalysts have good stability and reusability, with little metal leaching after multiple uses. Free radical scavenging experiments tests showed that ·OH and holes are the main active species in the catalytic process. This work paves a new approach for creating highly efficient piezoelectric catalysts and expands the application of BiFeO 3 -based materials for wastewater purification. • BiFeO 3 and Mn-doped BiFeO 3 nanomaterials were successfully synthesized by electrostatic spinning. • The piezoelectric photocatalytic performance of BiFeO 3 was significantly enhanced after appropriate Mn doping. • This work achieves efficient piezoelectric degradation of organic pollutants in water. [ABSTRACT FROM AUTHOR]

Since their discovery, ferroelectric materials have shown excellent dielectric responses, pyroelectricity, piezoelectricity, electro-optical effects, nonlinear optical effects, etc. They are a class of functional materials with broad application prospects. Traditional pure inorganic piezoelectric materials have better piezoelectricity but higher rigidity; pure organic piezoelectric materials have better flexibility but havetoo small a piezoelectric coefficient. The material composite, on the other hand, can combine the advantages of both, so that it has both flexibility and a high piezoelectric coefficient. In this paper, a new molecular piezoelectric material (C5H11NO)2PbBr4 with a high Curie temperature Tc and a large piezoelectric voltage constant g33, referred to as (ATHP)2PbBr4, was used to prepare a 0-3 type piezoelectric composite film by compounding with an organic polymer material polyvinylidene fluoride (PVDF), and its ferroelectricity was investigated. The results show that the 0-3 type (ATHP)2PbBr4 piezoelectric composite film has good ferroelectricity and piezoelectricity, and the calculated piezoelectric voltage constant g33 after polarization is about 358.6 × 10−3 Vm/N, which is higher than that of PVDF material, and is important for the fabrication of high-performance piezoelectric sensors. [ABSTRACT FROM AUTHOR]

Organic fouling and biofouling represents a critical challenge encountered by the membrane-based water treatment process. Herein, a piezoelectric PVDF membrane (PEM), capable of generating electrical responses to hydraulic pressure stimuli, was synthesized and employed for mitigating the fouling in surface water treatment. The surface-hydrophobilized PEM demonstrated sensitive and enhanced underwater output performance in response to increasing transmembrane pressure (TMP) during constant-flux filtration, with signals reaching up to ∼800 mV at a TMP of ∼80 kPa. This in-situ piezoelectric response significantly reduced TMP growth in both short-term (1 h) and long-term (15 days) filtration trials, demonstrating a strong capability to mitigate membrane fouling. Moreover, continuous piezoelectric stimulation effectively inhibited microbial activity and the accumulation of extracellular polymeric substances (EPS) on PEM surface, surpassing the dominant electrokinetic repulsion mechanisms observed in short-term trials. Microbial community analysis suggests that this evolution is primarily due to the targeted impact of piezoelectric stimulation on microbial metabolic behavior. The piezoelectric-induced electrical microenvironment inhibited the growth of microbes associated with high EPS production while promoting the proliferation of electrically active microbes involved in biopolymer digestion. In addition, the PEM demonstrated enhanced permeate quality throughout the filtration process, with DOC and UV 254 removal rates increasing from 11.7 % and 15.6 % initially to 28.6 % and 19.5 % by the 15th day, respectively. Given the performance and self-powered capability of PEM compared to current electrified antifouling methods that require an external power supply, these attributes are anticipated to hold practical significance in developing innovative and energy-efficient strategies for mitigating both organic fouling and biofouling., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

BiGaO3 doped BiFeO3–BaTiO3 ceramics were prepared by the traditional solid-phase synthesis process. The phase analysis, microstructure, piezoelectric, ferroelectric, dielectric properties, and thermal stability of 0.7BiFeO3-(0.3 − x)BaTiO3-xBiGaO3 (Abbreviated as BF–BT-xBG) were investigated. The results show that the ceramics have rhombohedral (R) and tetragonal (T) structures. Particle dimensions gradually get bigger with the increase of BiGaO3 concentration, and dense ceramic grains were observed through SEM. Electrical properties of BF–BT-xBG are improved after adding a small amount of BiGaO3: piezoelectric constants d33 = 141 pC/N, electromechanical coupling coefficient kp = 0.314, mechanical Quality Factor Qm = 56.813, dielectric loss tanδ = 0.048, residual polarization intensity Pr = 18.3 µC/cm2, Curie temperature Tc = 485.2 °C, depolarization temperature Td = 465 °C for x = 0.003. The “temperature-piezoelectric performance” curve under in situ d33 indicates that piezoelectric properties d33 increase rapidly with increasing temperature. Remarkably, the piezoelectric response d33 reaches a maximum of 466 pC/N at a temperature T = 340 °C, and afterward, reduces gradually to zero with increasing temperature until 450 °C.

In view of the excellent piezoelectric performances of bismuth layered structure ferroelectrics at high temperature, Na 0.5 Bi 4.5 Ti 4 O 15 : x Er3+ ceramics have been successfully manufactured by the traditional high temperature solid state method. The influence of additive (Er3+) concentration on the phase structure, morphology and electrical properties of ceramics has been investigated. After Er3+ ion introduction, the ferroelectric properties are palpably enhanced, and the 2 P r reaches 30 μC/cm2 at x = 0.004. Furthermore, the ferroelectric domain structure of ceramics was characterized by PFM for the first time. Meanwhile, a reversible photochromic (PC) reaction and the associated luminescence modulation are achieved. It is found that a higher Δ I dec of 83.6% is obtained using down-conversion (DC) mode than up-conversion (UC) one. More importantly, an additional exposure to natural light can further enhance the Δ I dec from 73% to 80.5% after 407 nm irradiation. The present investigation suggests that the modified NBT ceramics with multiple performances facilitate the development of multifunctional materials used in electric devices, anti-counterfeiting and information storage. [ABSTRACT FROM AUTHOR]

The effect of epitaxial strain on the electrical properties of ferroelectric films has been widely investigated. However, this kind of strain is generally attributed to the substrate clamping constraints and is easily relaxed when the thickness of films is over 100 nm. In this work, a vertically epitaxial strain was introduced into lead-free piezoelectric K0.5Na0.5NbO3 films to improve the electrical properties of ferroelectric films. Two-phase, vertically epitaxial composite KNN-ZnO thin films were grown on the (001) STO substrate using a pulsed laser deposition (PLD) method. The highly (001) preferentially oriented KNN phase and (112¯ 0)-oriented ZnO phase were orderly arranged. Two types of morphologies of “square-like” and “stripe-looking” grains were observed in the surface image. An asymmetric “square” out-of-plane phase hysteresis loop and a “butterfly” displacement loop were exhibited in the KNN phase, whereas the ZnO phase showed a closed phase hysteresis loop and a slim displacement-voltage loop. Two different kinds of polarization behaviors for domains were also observed under applied electric fields, in which the domain of the KNN phase is easily switched to the opposite state, whereas the ZnO phase keeps a stable domain state when applying a DC bias of ±50 V. the vertically epitaxial growth of the KNN-ZnO composited films in this work provides a new way to fabricate complex nanoscale materials.

Piezoelectric activity has always been the most concerned performance for PbTiO 3 -based relaxor ferroelectrics. Recently, the alternating current poling (ACP) method has been developed as a simple and economical technique to optimize piezoelectric performance. However, the mechanism of the ACP method is still debatable. In this work, we carried out the ACP on the 0.27Pb(In 1/2 Nb 1/2)O 3 -0.46Pb(Mg 1/3 Nb 2/3)O 3 -0.27PbTiO 3 single crystal, a noticeable piezoelectric improvement of 20% has been achieved in comparison with the direct current poled sample, meanwhile, the dielectric loss is reduced by 26%. We found that the ACP sample demonstrates a uniform domain pattern with a large domain size dominated by 109° domain walls, in contrary to the complicated domain structures which contain both 109° and 71° domains in the DCP sample. With this uniform and simple domain structure, the crystal lattice is weakly constrained and very susceptive to external stimulation, resulting in enhanced piezoelectric response in ACP poled sample. Meanwhile, dielectric loss is reduced for the low domain wall density. The current work gives a comprehensive description of the ACP poled samples, including the microscopic domain structure, the quantitative estimation of contributions arise from lattice deformation and domain wall motions, and reveals the interactions between domain structure and the macro performance, which provide important guidelines for the design of high-performance ferroelectrics utilizing domain tailoring techniques. [ABSTRACT FROM AUTHOR]

The morphotropic phase boundary (MPB) region of the BFO-BTO solid solution is studied by comprehensive macroscopic and local methods, focusing on the synthesis conditions that influence the final phase composition and functional response. The difference between the phase distribution and local switching behavior in two sets of the BFO-BTO solid solutions prepared with different applied pressures is revealed and attributed to the local chemical inhomogeneity forming due to certain differences in the solid-state sintering reactions. More homogeneous mixing of the polar and non-polar phases stimulates the non-polar-to-polar phase transition and widening the MPB region. [ABSTRACT FROM AUTHOR]

Featured Application: Shapeable piezo-magnetic sensors. This work aimed to study the influence of the hybrid interface in polyvinylidene fluoride (PVDF)-based composite thin films on the local piezoelectric response. Our results provide evidence of a surprising contradiction: the optimization process of the β-phase content using nano-inclusions did not correspond to the expected nanoscale piezoelectric optimization. A large piezoelectric loss was observed at the nanoscale level, which contrasts with the macroscopic polarization measurement observations. Our main goal was to show that the dispersion of metallic ferromagnetic nano-inclusions inside the PVDF films allows for the partial recovery of the local piezoelectric properties. From a dielectric point of view, it is not trivial to expect that keeping the same amount of the metallic volume inside the dielectric PVDF matrix would bring a better piezoelectric response by simply dispersing this phase. On the local resonance measured by PFM, this should be the worst due to the homogeneous distribution of the nano-inclusions. Both neat PVDF films and hybrid ones (0.5% in wt of nanoparticles included into the polymer matrix) showed, as-deposited (un-poled), a similar β-phase content. Although the piezoelectric coefficient in the case of the hybrid films was one order of magnitude lower than that for the neat PVDF films, the robustness of the polarized areas was reported 24 h after the polarization process and after several images scanning. We thus succeeded in demonstrating that un-poled polymer thin films can show the same piezoelectric coefficient as the poled one (i.e., 10 pm/V). In addition, low electric field switching (50 MV/m) was used here compared to the typical values reported in the literature (100–150 MV/m). [ABSTRACT FROM AUTHOR]

Dynamic integration of aligned nanostructures fabricated on different surfaces has prompted the needs for a novel nanoelectromechanical energy harvester. This study describes the morphologies of as-synthesized zinc oxide (ZnO) nano rod-like structures grown onto a bare sputtered substrate and patterned microcontact electrode (IDE), using a simple chemical bath deposition method (CBD). Local piezoresponse measurements were conducted to detect the piezoelectric response and polarization switching in Zinc oxide nanorods. The morphological characteristics and electromechanical response of the grown nanostructures on the printed electrode have been investigated, as a step towards enhancing the performance of piezoelectric nanogenerators. The growth characteristics and energy harvesting ability of nanostructured ZnO on interdigitated microelectrode (IDE) were reported. AFM analysis indicated that the average seed layer thickness of the ZnO film deposited before the lithographic pattern of the IDE was about ~267.5 nm. The FESEM images and XRD analysis confirmed that the ZnO nanorods possessed a hexagonal wurtzite structure having the c-axis crystal orientation preferentially in the (002) plane. FTIR spectrum confirmed the secondary vibrations of the Zn–O bonding at 669.75 cm−1 even with the adjustment in the microstructural features of ZnO. Finally, the Piezoresponse Force Microscopy (PFM) analysis confirmed the converse piezoelectric response of the grown nanorods.

We present the electrical properties of zinc phthalocyanine covalently conjugated to cellulose nanocrystals (CNC@ZnPc). Thin films of CNC@ZnPc sandwiched between two gold electrodes showed pronounced hysteresis in their currentâ€"voltage characteristics. The layered metalâ€"organicâ€"metal sandwich devices exhibit distinct high and low conductive states when bias is applied, which can be used to store information. Density functional theory results confirmed wave function overlap between CNC and ZnPc in CNC@ZnPc, and helped visualize the lowest (lowest unoccupied molecular orbital) and highest molecular orbitals (highest occupied molecular orbital) in CNC@ZnPc. These results pave the way forward for all-organic electronic devices based on low cost, earth abundant CNCs and metallophthalocyanines. [ABSTRACT FROM AUTHOR]

This paper presents the results of experimental studies of the influence of the growth temperature and the thickness of the catalytic layer on the geometric and structural parameters of carbon nanotubes (CNTs). It is shown that the use of a TiN-based sublayer makes it possible to provide a low resistivity in the direct growth of CNTs on a conducting contact. It has been established that, to generate the best piezoelectric response, it is necessary to form the most defective CNTs. It is shown that the degree of defectiveness of CNTs can be controlled in the process of their growth. A relationship has been established between the geometric and structural parameters of CNTs that affect the piezoelectric response. The potential applicability of CNTs for the creation of nanopiezotronic devices (nanogenerators, energy nanoharvesters) based on them is shown. [ABSTRACT FROM AUTHOR]

In this work, the influence of the material of the contact sublayer and the growth temperature on the geometric dimensions and the value of the piezoelectric response of carbon nanotubes for their use in nanopiezotronic devices is investigated. The thermodynamic laws that characterize the processes occurring in the "catalyst/sublayer/substrate" system have been established. It was found that with an increase in temperature, the carbon nanotubes density decreases from 1.1 to 0.001 µm−2 for Mo, and from 26 to 0.1 µm−2 for Cr. The value of the piezoelectric response was estimated, which ranged from 8 to 14 nA for the Cr sublayer and from 3 to 23 nA for the Mo sublayer. It is shown that the obtained structures are promising for the creation of nanopiezotronic elements (nanogenerators, energy nanoharvesters). [ABSTRACT FROM AUTHOR]

The results of studies of the structure, as well as piezoelectric, and dielectric properties, of lead zirconate-titanate ceramics modified with various concentrations of lanthanum (PLZT) are presented. It is found that with an increase in the La content, the grain size and the average size of the domains increase. The PLZT 12/40/60 samples contain both labyrinthine-like and periodic domains and different lateral sizes ranging from several hundred nanometers to 3 μm in diameter. It is found that with an increase in the size of domains in samples with a high content of lanthanum the signal of the piezoelectric response is enhanced. The fact of the existence of areas on the surface of PLZT x/40/60 ceramics, having an internal bias field, as indicated by the asymmetry along the voltage axis of the residual piezoelectric hysteresis loops, is established. In the PLZT 5/40/60 and PLZT 12/40/60 samples, a significant dispersion of the dielectric constant ε(f) and the maximum tangent of the dielectric loss angle in the frequency range from 105 to 106 Hz are observed. This is due to the presence of ionic relaxation polarization. It is found that the value of the dielectric constant increases markedly with an increase in La, which confirms the appearance of a rigid unipolar state in the grains of the PLZT 12/40/60 ceramics. In the samples under study, at low frequencies of the measuring field, an increase in the dielectric loss tangent is observed, which is related to the contribution of the conductivity to tan δ. The dependences of the dielectric loss factor ε'' on the dielectric constant ε' are plotted. They have the form of Cole–Cole diagrams, which indicates the presence of a spectrum of relaxation times, and it is found that the spectral width in the PLZT 5/40/60 samples is approximately half that in the PLZT 12/40/60 samples. [ABSTRACT FROM AUTHOR]

Lead-free piezoelectric ceramics with nominal composition at morphotropic phase boundary Ba0.85Ca0.15Ti0.9Zr0.1O3 (BCTZ) prepared by different processing routes and sintered either by conventional solid-state reaction or by spark plasma sintering (SPS) techniques were comparatively investigated to observe the role of structural modifications and of microstructures on the dielectric, ferroelectric, piezoelectric and electrocaloric responses. The ceramics presented relative densities from 75% to 97% and showed variations in their phase composition as a result of variable mixing and different synthesis and sintering parameters providing local compositional heterogeneity. As result, all of the ceramics showed diffuse phase transition and ferroelectric switching responses, with parameters affected mostly by density (Pr between 3.6 to 10.1 μC/cm2). High values for the electrocaloric response in the Curie range were found for the ceramics with predominantly orthorhombic character. Field-induced structural modifications were probed by tunability anomalies and by XRD experiments in remanence conditions. Piezoelectric effects with notably high figure of merit values were assigned to the better densification and poling efficiency of BCTZ ceramics.

Since their discovery, ferroelectric materials have shown excellent dielectric responses, pyroelectricity, piezoelectricity, electro-optical effects, nonlinear optical effects, etc. They are a class of functional materials with broad application prospects. Traditional pure inorganic piezoelectric materials have better piezoelectricity but higher rigidity; pure organic piezoelectric materials have better flexibility but havetoo small a piezoelectric coefficient. The material composite, on the other hand, can combine the advantages of both, so that it has both flexibility and a high piezoelectric coefficient. In this paper, a new molecular piezoelectric material (C5H11NO)2PbBr4 with a high Curie temperature Tc and a large piezoelectric voltage constant g33, referred to as (ATHP)2PbBr4, was used to prepare a 0-3 type piezoelectric composite film by compounding with an organic polymer material polyvinylidene fluoride (PVDF), and its ferroelectricity was investigated. The results show that the 0-3 type (ATHP)2PbBr4 piezoelectric composite film has good ferroelectricity and piezoelectricity, and the calculated piezoelectric voltage constant g33 after polarization is about 358.6 × 10−3 Vm/N, which is higher than that of PVDF material, and is important for the fabrication of high-performance piezoelectric sensors.

• Li+ and W6+ Doping shortened the B O bond and enhanced the B-site ionic shift. • Microdomains caused by octahedral distortion of oxygen improved the properties. • Octahedral distortion and defect chemistry enhanced thermal stability. Electromechanical devices require functional materials possessing excellent piezoelectric properties, good thermal stability, and high electromechanical coupling coefficients. To modulate the piezoelectric, dielectric, and electromechanical characteristics of 0.89Pb(Hf 0.47 Ti 0.53)O 3 -0.11Pb(In 1/2 Nb 1/2)O 3 (PHT-PIN) piezoelectric ceramics, heterovalent ions of lithium (Li) and tungsten (W) were doped through a traditional solid-phase reaction approach. On the one hand, large lattice distortions caused by the doped W6+ resulted in the shortening of B O bonds while an increase in the local displacement of B-site ions. Moreover, a mismatch occurred for the oxygen octahedral dimensions, and a subsequent disruption of the long-ranged ordered ferroelectric domains was observed, which resulted in the formation of microdomains. On the other hand, the changes in the concentration of oxygen vacancy defects induced by the Li and W doping inside the ceramic were comprehensively analyzed. The decrease in the concentration of oxygen vacancies was found to be accompanied by the enhancement of piezoelectric properties of the material. Excellent comprehensive performance (piezoelectric coefficient d 33 = 655 pC N−1, Curie temperature T c = 321.1 °C, dielectric constant ε r = 3352.31, electromechanical coupling coefficient k p = 0.67, and residual polarization strength P r = 55 μC cm−2) was obtained for 0.2 mol % doping amount of Li+ and W6+ ions. This work, therefore, proposes a novel strategy for the origin of piezoelectric properties and inspires doping of other heterovalent ions to improve the piezoelectric properties of ceramics. It further promotes the development of Pb-based piezoelectric ceramics for electromechanical devices that can efficiently operate under high-temperature environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Benzene-1,4-dicarboxamide (BDA) exhibited a columnar LC phase with an 8 1 -helix. • The axial polarization was generated by 1-D hydrogen bonding between amide units. • Two distinct polymorphs were stably obtained at RT depending on the thermal treatments. • Only the columnar polymorph at RT exhibited a significant piezoelectric response. Polymorphism is a fascinating research subject as it enables diverse functionalities to be achieved from a single molecule. In this study, we present the synthesis and polymorphic behavior of a liquid crystalline (LC) benzene-1,4-dicarboxamide (BDA) derivative (1). Depending on specific thermal treatments, two distinct polymorphs can be obtained at room temperature. These include a metastable glassy columnar (Col gla) and thermodynamically stable monoclinic crystalline (Cry) phases. Through the electric analysis, the Col gla polymorph exhibits a significant piezoelectric response, while the Cry polymorph shows a negligible piezoelectric signal. Notably, the BDA molecule exhibits an 8 1 -helix columnar assembly (Col hel) in the LC phase, comprising syn -conformers with non-zero dipole moments. According to density functional theory (DFT) calculations, the amide group is tilted by 25° with respect to the central benzene ring. The piezoelectric response of the Col hel is comparable to that of the Col gla polymorph. Therefore, it can be inferred that the polar character of the Col gla polymorph is transferred from the Col hel LC phase during the cooling process. Simulation and spectroscopic analyses further reveal that the axial polarizations of both the Col gla and Col hel are driven by the hydrogen-bonding interactions between adjacent amide units in head-to-tail. These findings shed light on the underlying mechanisms of the polymorphic behavior and piezoelectric properties exhibited by the BDA molecule. [ABSTRACT FROM AUTHOR]

Development of flexible wearable electronic devices requires high-performance piezoelectric sensors, being advantageous in high sensitivity, ease to microintegration without external power supply. In this work, poly(vinyl alcohol) (PVA)/polyvinylidene fluoride (PVDF) fiber membranes with stable alternating multilayer structure were constructed through electrospinning and subsequent gas-phase crosslinking. The PVA/PVDF fiber was fully stretched with smooth surface and uniform diameter at appropriate PVDF concentration, exhibiting high porosity (88 %). The α-phase was transformed into the electroactive β-phase of PVDF in the electrospinning process, while the crystallinity and β-phase percentage (F β) were improved by mixing spinning of PVA and PVDF, with F β reaching above 90 %. The PVA/PVDF fiber membrane showed high mechanical strength/toughness and liquid absorbency (719.03 %). The significant electrical signal output (10.07 V and 166.42 nA) was generated, accompanying with high stress sensitivity, short response time and high stability, exhibiting excellent piezoelectricity and making the fiber membrane not only monitor large deformation movements of limbs as self-powered wearable sensor, but also sense weak signals of pulse, breathing etc. for monitoring human health, as well as environmental humidity. Meanwhile, the harvested energy could drive electronic device, showing prosperous potentials in fields of artificial intelligence. [Display omitted] • PVA/PVDF fiber membrane with stable alternate multilayer structure was fabricated. • The crystallinity and β-phase percentage were improved by mix spinning of PVA/PVDF. • PVA/PVDF fiber membrane exhibited high mechanical properties and liquid absorbency. • Fiber membrane with high piezoelectricity can monitor human health and humidity. • Fiber membrane shows promising potential in energy harvesting and wearable sensors. [ABSTRACT FROM AUTHOR]

We report on the correlated investigation between piezoelectric properties and crystalline structure of PbZr0.52Ti0.48O3 (PZT) films under different oxygen pressures in the process of pulsed laser deposition. A sharp increase of effective longitudinal-piezoelectric coefficient (305 pm/V) and especially, a high effective transverse-piezoelectric coefficient (−16.2 C/cm2) were achieved in the PZT film deposited at 0.10 mbar, where the preferred (100)-orientation and columnar-grains with an obelisk-shape microstructure were presented. The comparative discussions in this study provide valuable insights into the crystalline and microstructure contributions to improve the piezoelectric responses for wide applications in high-performance piezoelectric devices from capacitors to MEMS devices. [ABSTRACT FROM AUTHOR]

This work aimed to study the influence of the hybrid interface in polyvinylidene fluoride (PVDF)-based composite thin films on the local piezoelectric response. Our results provide evidence of a surprising contradiction: the optimization process of the β-phase content using nano-inclusions did not correspond to the expected nanoscale piezoelectric optimization. A large piezoelectric loss was observed at the nanoscale level, which contrasts with the macroscopic polarization measurement observations. Our main goal was to show that the dispersion of metallic ferromagnetic nano-inclusions inside the PVDF films allows for the partial recovery of the local piezoelectric properties. From a dielectric point of view, it is not trivial to expect that keeping the same amount of the metallic volume inside the dielectric PVDF matrix would bring a better piezoelectric response by simply dispersing this phase. On the local resonance measured by PFM, this should be the worst due to the homogeneous distribution of the nano-inclusions. Both neat PVDF films and hybrid ones (0.5% in wt of nanoparticles included into the polymer matrix) showed, as-deposited (un-poled), a similar β-phase content. Although the piezoelectric coefficient in the case of the hybrid films was one order of magnitude lower than that for the neat PVDF films, the robustness of the polarized areas was reported 24 h after the polarization process and after several images scanning. We thus succeeded in demonstrating that un-poled polymer thin films can show the same piezoelectric coefficient as the poled one (i.e., 10 pm/V). In addition, low electric field switching (50 MV/m) was used here compared to the typical values reported in the literature (100–150 MV/m).

The piezoelectric response is a measure of the sensitivity of a material's polarization to stress or its strain to an applied field. Using in operando X-ray Bragg coherent diffraction imaging, we observe that topological vortices are the source of a 5-fold enhancement of the piezoelectric response near the vortex core. The vortices form where several low-symmetry ferroelectric phases and phase boundaries coalesce. Unlike bulk ferroelectric solid solutions in which a large piezoelectric response is associated with coexisting phases in the proximity of the triple point, the largest responses for pure BaTiO 3 at the nanoscale are in spatial regions of extremely small spontaneous polarization at vortex cores. The response decays inversely with polarization away from the vortex, analogous to the behavior in bulk ceramics as the cation compositions are varied away from the triple point. We use first-principles-based molecular dynamics to augment our observations, and our results suggest that nanoscale piezoelectric materials with a large piezoelectric response can be designed within a parameter space governed by vortex cores. Our findings have implications for the development of next-generation nanoscale piezoelectric materials.

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Effects of Sb doping on microstructure and electrical properties of Pb 0.99 Nb 0.02 [(Sn 0.30 Zr 0.70) 0.52 Ti 0.48 0.98 O 3 (PNSZT) ceramics have been systematically investigated. Experimental results reveal that Sb cations can be successfully incorporated into PNSZT lattice by substituting B-site cations, which leads to the formation of Pb vacancies, enhances the relaxation of Sb-doped PNSZT ceramics and decreases domain size. Hence, piezoelectric response of Sb-doped PNSZT ceramics is superior to pure PNSZT ceramics. Moreover, phase-field simulation is employed to verify successful doping of Sb ions and formation of polar nano-domains. Owing to Sb doping, high piezoelectric properties, such as d 33 = 530 pC/N and k p = 0.63, have been achieved at Sb 2 O 5 content of 0.8 wt%. Furthermore, detailed mechanism of improved piezoelectric response due to Sb doping is proposed. Current study presents novel route to enhance piezoelectric properties of PNSZT ceramics, which may be helpful to improve properties of similar materials in the future. [ABSTRACT FROM AUTHOR]

An inherent conflict of (Bi 0.5 Na 0.5)TiO 3 -based (BNT) lead-free piezoelectric ceramics is the optimizing piezoelectric response (d 33) with deteriorating depolarization temperature (T d), which severely restricts the further achievements of BNT-based ceramics. A new strategy is proposed in this work to simultaneously realize high piezoelectric property (d 33 = 140 pC/N) and thermal stability (T d = 232 °C) in BNT-based ceramics by integrating layered composite structure of 0.89(Bi 0.5 Na 0.5)TiO 3 -0.11BaTiO 3 with high T d and 0.87(Bi 0.5 Na 0.5)TiO 3 -0.11BaTiO 3 -0.02(Sm 0.5 K 0.5)TiO 3 with large d 33 (BNT1/BNT2) and thermal treatment processes. In the layered composite ceramics, the composition difference induces a built-in field (E b) that promotes the diffusion of ferroelectric-relaxor (FE-RE) phase transition in the ceramics, delaying the T d to 185 °C. In addition, the thermal treatment processes facilitate both the E b expansion, stabilize the d 33 over a wide temperature range, as well as enlarge the grain size to elevate the d 33 from 133 pC/N to 145 pC/N. Hence, the strategy we proposed is promising to offer a new paradigm for designing piezoelectric materials with high piezoelectric response over a wide temperature range. [Display omitted] • An innovative solution was proposed to significantly mitigate the conflict between d 33 and T d. • BNT-based piezoceramics not only achieve large d 33 over the temperature interval of -45 ℃-244 ℃ but also improve temperature stability of d 33. • The incompatibility between d 33 and T d in bilayer structured ceramic composites at elevated temperature is resolved. [ABSTRACT FROM AUTHOR]

Sputtered aluminum nitride (AlN) thin films were characterized by Piezoresponse Force Microscopy (PFM) technique using a methodology to decrease the contribution of the electrostatic forces to obtain a pure piezoelectric response. Our method is based on the sweeping of the DC voltage applied to the Atomic Force Microscope (AFM) tip under a fixed AC field to evaluate the contact surface potential difference (V CPD) between the tip and the sample used to measure the proper AlN piezoelectric coefficient (d 33,eff), minimizing the electrostatic contribution. Kelvin probe Force Microscopy (KPFM) was employed as reference standard technique to measure the surface potential, confirming the reliability of the proposed experimental procedure on ceramic piezoelectric films, and simultaneously overcoming the disadvantages of the KPFM technique. The capability to tune surface potential of materials over a wide range of values opens new perspectives for the design of devices with changeable surface potential. • Piezoelectric response (d 33) of AlN thin films analysed by PFM technique. • PFM analyses performed using two cantilevers with different contact stiffness k c. • High-k c cantilever reduces the electrostatic force contribution on d 33. • New methodology to improve d 33 measurement based on surface potential evaluation. • Better d 33 evaluation utilizing the surface potential method. [ABSTRACT FROM AUTHOR]

The analytical solution for the displacements of an anisotropic piezoelectric material in the uniform electric field is presented for practical use in the “global excitation mode” of piezoresponse force microscopy. The solution is given in the Wolfram Mathematica interactive program code, allowing the derivation of the expression of the piezoresponse both in cases of the anisotropic and isotropic elastic properties. The piezoresponse’s angular dependencies are analyzed using model lithium niobate and barium titanate single crystals as examples. The validity of the isotropic approximation is verified in comparison to the fully anisotropic solution. The approach developed in the paper is important for the quantitative measurements of the piezoelectric response in nanomaterials as well as for the development of novel piezoelectric materials for the sensors/actuators applications.