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In this review, we introduce recently developed plasma-based approaches for depositing and treating piezoelectric nanoparticles (NPs) and piezoelectric polymer films for nanogenerator (NG) and sensor applications. We also present the properties and an overview of recently synthesized or modified piezoelectric materials on piezoelectric polymers to highlight the existing challenges and future directions of plasma methods under vacuum, low pressure, and ambient air conditions. The various plasma processes involved in piezoelectric NGs and sensors, including plasma-based vapor deposition, dielectric barrier discharge, and surface modification, are introduced and summarized for controlling various surface properties (etching, roughening, crosslinking, functionalization, and crystallinity). [ABSTRACT FROM AUTHOR]

This paper aims to study the Mode-I penny-shaped crack problem of an infinite body of one-dimensional hexagonal piezoelectric quasicrystal. The problem is transformed into a mixed-boundary value problem in the context of electro-elasticity of quasicrystals, and the corresponding integro-differential equations are analytically solved. Two extreme cases of electrically impermeable and permeable crack surface are considered. By virtue of the generalized potential theory method, the three-dimensional complete analytical solutions of three-dimensional crack problems under symmetric concentrated and uniform loads are expressed in terms of elementary functions. Important parameters in fracture mechanics are explicitly derived, such as crack surface displacements, the distributions of generalized stresses at the crack tip and the corresponding generalized stress intensity factors. The validity of the proposed solutions and the coupling effect of phonon-phason-electric fields are investigagted through numerical examples. [ABSTRACT FROM AUTHOR]

Employing Landau theory and the Landau–Khalatnikov (L–K) equation of motion, we investigate the phase transitions in individual layers of antiferroelectric lead zirconate (PbZrO3), ferroelectric lead zirconate titanate (PbZrTiO3), and an antiferroelectric/ferroelectric PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer bulk structure. We examine the dielectric hysteresis loop behavior of the three systems, with a specific focus on the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer under different stabilities of the PbZrO3 layer. In addition, we explore cases where the coercive field of the bilayer structure is lower than that of the PbZrTiO3 individual layer. The recoverable electric energy for the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer increases significantly to 118 J/cm3 at an applied field of 7.5 × 108 V/m at 20 °C. In comparison, the PbZr(0.21)Ti(0.79)O3 layer reaches 71.8 J/cm3 under the same field and temperature conditions. This is much higher than those predicted experimentally by previous studies on thin film single and bilayer structures (15.6 and 28.2 J/Cm3 respectively), indicating that the antiferroelectric/ferroelectric PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer bulk structure could be used to target specific large-scale, long-term energy storage applications. Upon increasing the value of the coupling coefficient, the transition temperatures of the PbZrO3 layer and the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer are increased up to the transition temperature of the PbZr(0.21)Ti(0.79)O3 individual layer (450 °C). This increment in the transition temperature in the bilayer system contributes to its stability in storing energy at higher temperatures. Furthermore, the recoverable energy density of the PbZrO3/PbZr(0.21)Ti(0.79)O3 bilayer increases further with temperature from 20 to 440 °C correlated with the rise in the difference between the spontaneous and the remanent polarizations (Ps − Pr). The significant stored energy observed over a wide temperature range highlights the promise of this bilayer structure for creating high-power capacitors where stability at different temperatures is crucial and possesses greater energy storage capacity. [ABSTRACT FROM AUTHOR]

The increased micro-capacitance of a poly (vinylidene fluoride) (PVDF) matrix can effectively improve the piezoelectric properties of the composite material. This work used chemically modified carbon nanotubes (CNTs) as the main reinforcement material. Atom transfer radical polymerization (ATRP) was used to graft polyionic liquids (PILs) with different hydrophilic anions to the CNTs' surfaces. Solution casting and compressive melt molding were used to prepare the PVDF-composite piezoelectric films. Micro-capacitance formed by the PIL grafted CNTs dispersed well in the PVDF matrix, and their effects on the crystalline form and piezoelectric properties were studied. The hydrophobic hexafluorophosphate anion (-PF6-) can significantly improve the CNTs dispersion and enhance the micro-capacitance formation in the PVDF matrix. During solution crystallization, the synergistic effect of CNTs and PIL on the PVDF and the solvent effect made the content of β phase of PVDF/CNTs@PIL-PF6 film reach 80.2%, resulting in a high dielectric constant of 188 and a piezoelectric coefficient of 36. In the process of melt crystallization, due to shear stretching and extrusion, the CNTs@PIL-PF6 had an obvious nucleation effect on the polar crystalline phase of PVDF, with a β phase content up to 99.3%, leading to the higher dielectric constant of 530 and the piezoelectric coefficient of 31. The current discovery provides a development direction for smart piezoelectric polymer matrix composites, which have great potential in preparing piezoelectric energy storage materials. [ABSTRACT FROM AUTHOR]

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In this study, a method for the active shape control for carbon fiber-reinforced polymer (CFRC) reflectors using piezoelectric lead zirconate titanate (PZT) actuators is proposed. According to this method, a finite element model considering higher transverse shear deformation with independent voltage degrees of freedom is formulated by the Hamilton principle. An optimal shape controller that minimizes the discrete root mean square (RMS) error of a reflecting surface is applied. Then, the optimal arrangements of the PZT actuators are determined by numerical optimization methods, which are developed by modifying the classical Genetic Algorithm, with both single and multi-objective optimizations being studied. In the single optimization formulation, the number of actuators is considered as a constraint, and the RMS error of the reflector is regarded as the optimizing target. A hybrid method that combines the gradient projection method with an adaptive Genetic Algorithm is proposed to solve this problem. In the multi-objective optimization, the residual RMS errors and power consumption of the actuators are considered as the optimization targets. Pareto optimal solutions are obtained by an improved multi-objective Genetic Algorithm. Numerical examples are provided to show the effectiveness of the proposed methods. [ABSTRACT FROM AUTHOR]

Advanced photonic integrated circuits require large-scale integration of high-speed electro-optic (EO) functional components on a chip. Low power consumption and high operation speed are thus key metrics for almost all integrated EO devices. Here, we demonstrated a ring resonator modulator based on lead zirconate titanate (PZT) on a SiO2/Si substrate. The ridge waveguides were employed to keep a large spatial overlap between the optical field and the electric field within the PZT layer. The device exhibits a data rate of 56 Gbit/s and significant tuning efficiency, reaching up to 35.8 pm/V, corresponding to 1.17 V·cm. The demonstration of energy efficient and high-speed EO modulation paves the way for realizing dense PZT photonics integrated circuits. [ABSTRACT FROM AUTHOR]

Carbon fiber-reinforced polymers (CFRPs) are extensively employed in the aerospace industry due to their excellent properties. Delamination damage occurring at critical locations in CFRPs can seriously reduce the safety of in-service components. The detection and localization of delamination damage using Lamb waves hold significant potential for widespread application in non-destructive testing. However, the choice of damage localization algorithm may produce different delamination damage localization results. This research presented an IRAPID (improved reconstruction algorithm for probabilistic inspection of defects) method derived from the RAPID (reconstruction algorithm for probabilistic inspection of defects) method, aiming to improve the accuracy and reliability of delamination damage localization. Three CFRP curved plates, including a healthy curved plate and two curved plates with delamination damage sizes of Φ20 mm and Φ40 mm, were prepared in the experiment. The detection experiment of the CFRP curved plate using lead zirconate titanate (PZT) as a transducer to excite and receive Lamb waves was conducted, and the influence of excitation signal frequency on the performance of the proposed method was discussed. Under the condition of an excitation signal frequency of 220~320 kHz and a step size of 10 kHz, the accuracy of the delamination damage localization method proposed in this paper was compared with that of existing methods. The experimental results indicate that the IRAPID algorithm exhibits good stability in the localization of delamination damage across the range of frequency variations considered. The localization error of the IRAPID algorithm for delamination damage is significantly lower than that of the DaS (delay-and-sum) algorithm and the RAPID algorithm. As the size of the delamination damage increases, so does the localization error. The accuracy of delamination damage localization is lower in the X-axis direction than in the Y-axis direction. By averaging the localization results across various frequencies, we can mitigate the potential localization errors associated with single-frequency detection to a certain extent. For the localization of delamination damage, Lamb waves at multiple frequencies can be employed for detection, and the detection results at each frequency are averaged to enhance the reliability of localization. [ABSTRACT FROM AUTHOR]

Spectroscopic ellipsometry and ultraviolet-visible (UV-VIS) spectrometry were utilized to study the optical properties of ferroelectric lead lanthanum zirconate titanate (PLZT) films. These films were deposited on platinized silicon [Si(100)/ SiO2/TiO2/Pt(111)] substrates using the chemical solution deposition method. Films were annealed at two different temperatures (650 and 750 °C) using rapid thermal annealing. Shimadzu UV-1800 UV-VIS spectrophotometer with a resolution of 1 nm was used to measure the reflectance data in the spectral range of 300–1000 nm with a step size of 1 nm. The bandgap values were determined from the reflectance spectra using appropriate equations. A J.A. Woollam RC2 small spot spectroscopic ellipsometer was used to obtain the change in amplitude (Ψ) and phase (Δ) of polarized light upon reflection from the film surface. The spectra were recorded in the wavelength range of 210–1500 nm at an incident angle of 65°. Refractive index (n) and extinction coefficient (k) were obtained by fitting the spectra (Ψ, Δ) with the appropriate models. No significant changes were observed in the optical constants of PLZT films annealed at 650 and 750 °C. The optical transparency and the strong absorption in the ultraviolet (UV) region of PLZT films make them an attractive material for optoelectronic and UV sensing applications. [ABSTRACT FROM AUTHOR]

Piezoelectric materials are used for various commercial and strategic applications. For most of the current generation applications the usage temperature is about 150°C and therefore, ceramics like lead zirconate titanate or lead-free ceramics such as potassium sodium niobite which exhibit Curie temperature (TC) in between 350° and 450°C are useful. However, in the next-generation applications, the usage temperature is expected to be more than 500°C. As a thumb rule usage temperature of a ferroelectric ceramic is ½ of TC and hence, ceramics with a TC greater than 1000°C are required for such applications. Perovskite layer structure (PLS) piezoceramics exhibit TC well above 1000°C and thus, are the most promising materials for high temperature piezoelectric applications. With this background, we review the synthesis, fabrication and structural aspects of the PLS piezoceramics. We also discuss the peculiar microstructure and dielectric properties of these ceramics along with their advantages and limitations. [ABSTRACT FROM AUTHOR]

Lead zirconate titanate (Pb (Zrx, Ti1−x)O3: PZT) is a well-known ferroelectric compound, in which long-range polar order is usually developed. In the present study, it was clarified by distortion-corrected atomic-scale scanning transmission electron microscopy imaging that long-range polar order is disrupted in PZT by utilizing composition-modulated superlattice. Shape of unit cell was unusual both in the Pb(Zr0.65Ti0.35)O3 (PZT65) and Pb(Zr0.30Ti0.70)O3 (PZT30) layers, which was due to mutual in-plane lattice constraint. By taking account of this, first-principles calculations clarified that multiple directions can be energetically favorable for lead-ion displacement, which explains a reason why long-range polar order was disrupted. [ABSTRACT FROM AUTHOR]

Flexible and cost‐effective poly(vinylidene fluoride) (PVDF)‐based composites having excellent piezo performance are quite interesting for developing actuators, sensors, and nanogenerators. In this work, a hybrid PVDF‐based nanocomposite consisting of a fixed quantity of titanium dioxide (TiO2) and varying quantities of reduced graphene oxide (rGO) for increased mechanical and piezoelectric performance is reported for the first time. Compared to pure PVDF, there is a significant enhancement in mechanical properties for hybrid nanocomposites. The highest piezoelectric voltage as well as current values of 10.2 V and 0.78 μA are recorded for a hybrid nanocomposite containing 1 wt% of rGO for continuous finger‐tapping operation. A multicriteria decision‐making (MCDM)‐based material selection and optimization technique called TODIM is applied, and a sensitivity study is carried out to select the best material for mechanical energy harvesting applications. A hybrid nanocomposite based on PVDF‐TiO2 with 1% rGO loading is the most suitable material according to the TODIM (an acronym in Portuguese for Interactive Multicriteria Decision Making) approach. Highlights: PVDF‐TiO2‐rGO nanocomposites are fabricated by solvent casting.TODIM optimization technique is applied for the best material selection among samples.Material ranking consistency shows the reliability of the TODIM method.Conductive rGO increases interfacial polarization, resulting in enhanced ε values.An increment of 88% and 104% in tensile strength and elastic modulus, respectively. [ABSTRACT FROM AUTHOR]

This study presents an advanced two‐step hot‐pressing process for fabricating the 1‐3 type Pb(ZrTi)O3/poly(vinylidene fluoride‐trifluoroethylene) (PZT/P(VDF‐TrFE)) piezoelectric composite sheets, demonstrating significant potential for nondestructive evaluation and information storage applications. The engineered columnar architecture within these composites induces a two‐phase clamping effect, which, upon polarization, facilitates the elongation of PZT and suppresses its lateral vibrations, thus enhancing the electromechanical coupling effect as verified by COMSOL simulations. A notable dielectric constant of 2200 at 100 Hz and a coupling coefficient of 0.725 was achieved with specific geometric modifications to the PZT/P(VDF‐TrFE) sheets. These findings suggest that P(VDF‐TrFE) as a polymer matrix exceeds the performance of conventional epoxy matrices, offering a novel approach to designing 1‐3 type piezoelectric composites. Highlights: P(VDF‐TrFE) effectively drives the elongation strain of internal PZT columns.COMSOL simulation clarifies the clamping effect of piezoelectric P(VDF‐TrFE).PZT/P(VDF‐TrFE) shows a higher kt of 0.725 than that of pure PZT samples. [ABSTRACT FROM AUTHOR]

Ferroelectric materials have important applications in transduction, data storage, and nonlinear optics. Inorganic ferroelectrics such as lead zirconate titanate possess large polarization, though they are rigid and brittle. Ferroelectric polymers are light weight and flexible, yet their polarization is low, bottlenecked at 10 μC cm−2. Here we show poly(vinylidene fluoride) nanocomposite with only 0.94% of self-nucleated CH3NH3PbBr3 nanocrystals exhibits anomalously large polarization (~19.6 μC cm−2) while retaining superior stretchability and photoluminance, resulting in unprecedented electromechanical figures of merit among ferroelectrics. Comprehensive analysis suggests the enhancement is accomplished via delicate defect engineering, with field-induced Frenkel pairs in halide perovskite stabilized by the poled ferroelectric polymer through interfacial coupling. The strategy is general, working in poly(vinylidene fluoride-co-hexafluoropropylene) as well, and the nanocomposite is stable. The study thus presents a solution for overcoming the electromechanical dilemma of ferroelectrics while enabling additional optic-activity, ideal for multifunctional flexible electronics applications. Wang et al. report large nonvolatile polarization in stretchable polymer ferroelectrics incorporating perovskite nanocrystals. The built-in electric field from poled ferroelectrics stabilises Frenkel defects via interfacial coupling, which can also enhance the polarization of nonferroelectrics. [ABSTRACT FROM AUTHOR]

A 1-3 type poly(vinylidene-trifluoroethylene)/lead zirconate titanate (P(VDF-TrFE)/Pb(Zr0.52Ti0.48)O3) piezoelectric composite is prepared using a two-step hot-pressing method, showing a considerable dielectric constant (εr ~ 4614) and a very low dielectric loss factor (tanδ) of 0.05 and at 100 Hz are obtained in PZT/P(VDF-TrFE) sheet with a thickness of 1.2 mm. Because the polarized P(VDF-TrFE) has a clamping pressure on the engineered columnar architecture by the inverse piezoelectric effect, the elongation of PZT is improved by suppressing its lateral vibrations, which is well expressed by COMSOL simulations. As such, an attractive electrical coupling coefficient (kt) of 0.733 is achieved with specific geometric modifications to the PZT/P(VDF-TrFE) sheets. These findings indicate that piezoelectric P(VDF-TrFE) to replace conventional epoxy resin as the polymer matrix offers a route to construct 1-3 type piezoelectric composites. [ABSTRACT FROM AUTHOR]

Defect engineering via doping exhibits considerable potential for improving the performance of environment-friendly lead-free piezoelectric materials. Owing to the susceptibility to lattice vibrations and the micro-local chemical environment, the readily available Mn/Fe transition metal elements (TMEs) facilitate the construction of defect structures. However, the role of TMEs in shaping the domain structures and the corresponding promotional mechanism of piezoelectricity need to be further decoded. Herein, we propose the different influence mechanisms of Mn and Fe ions on the ferroelectric domain and piezoelectric properties. Different concentrations of (M n Nb/Ta ′ - V O • • ) • and (F e Nb/Ta ″ - V O • • ) × defect dipoles are obtained based on the synergy of Mn/Fe ions with oxygen vacancies. Diverse ferroelectric behaviors resulting from (M n Nb/Ta ′ - V O • • ) • and (F e Nb/Ta ″ - V O • • ) × defect dipoles are observed. Furthermore, the variation of the dielectric diffusiveness with the defect dipole concentration is investigated. Trace concentration of (M n Nb/Ta ′ - V O • • ) • generates strong diffusiveness. With the characterization of the ferroelectric domain, this strong diffusiveness is attributed to the lattice-like domain structure. Thereafter, the mechanisms of Mn/Fe defect dipoles on the formation of domain structures are clarified. Macroscopically, the dielectric and piezoelectric properties are measured with Mn/Fe ion components. Trace Mn doping and the resulting lattice-like domain significantly enhance the piezoelectric coefficient, resulting in an increase of nearly 50% for K(Ta,Nb)O3 single crystals. This work highlights the tremendous potential of TME-induced defect dipoles for modifying the ferroelectric domain and provides a reference paradigm for improving piezoelectricity through defect engineering. [ABSTRACT FROM AUTHOR]

This study presents a review of progress in the sol-gel method for the synthesis of powders of ferroelectric ceramics based on the PbTiO3–PbZrO3 system, which involves the controlled hydrolysis of the mixtures of salts or organometallic compounds of lead, zirconium, and titanium. To obtain materials based on the PbTiO3–PbZrO3 system, attention is paid to the sol-gel conditions, heat treatment conditions, raw materials, conditions to obtain precursors, gels drying, and PbTiO3–PbZrO3 powder crystallization. [ABSTRACT FROM AUTHOR]

In response to the growing global demand for both energy and a clean environment, there has been an unprecedented rise in the utilization of renewable energy. Wind energy plays a crucial role in striving for carbon neutrality due to its eco-friendly characteristics. Despite its significance, wind energy infrastructure is susceptible to damage from various factors including wind or sea waves, rapidly changing environmental conditions, delamination, crack formation, and structural deterioration over time. This research focuses on investigating non-destructive testing (NDT) of wind turbine blades (WTBs) using approaches based on the vibration of the structures. To this end, WTBs are first made from glass fiber-reinforcement polymer (GFRP) using composite molding techniques, and then a short pulse is generated in the structure by a piezoelectric actuator made from lead zirconate titanate (PZT-5H) to generate guided waves. A numerical approach is presented based on solving the elastic time-harmonic wave equations, and a laser Doppler vibrometer (LDV) is utilized to collect the vibrational data in a remote manner, thereby facilitating the crack detection of WTBs. Subsequently, the wave propagation characteristics of intact and damaged structures are analyzed using the Hilbert–Huang transformation (HHT) and fast Fourier transformation (FFT). The results reveal noteworthy distinctions in damaged structures, where the frequency domain exhibits additional components beyond those identified by FFT, and the time domain displays irregularities in proximity to the crack region, as detected by HHT. The results suggest a feasible approach to detecting potential cracks of WTBs in a non-contact and reliable way. [ABSTRACT FROM AUTHOR]

Nanocomposite represents the backbone of many industrial fabrication applications and exerts a substantial social impact. Among these composites, metal nanostructures are often employed as the active constituents, thanks to their various chemical and physical properties, which offer the ability to tune the application scenarios in thermal management, energy storage, and biostable materials, respectively. Nanocellulose, as an emerging polymer substrate, possesses unique properties of abundance, mechanical flexibility, environmental friendliness, and biocompatibility. Based on the combination of flexible nanocellulose with specific metal fillers, the essential parameters involving mechanical strength, flexibility, anisotropic thermal resistance, and conductivity can be enhanced. Nowadays, the approach has found extensive applications in thermal management, energy storage, biostable electronic materials, and piezoelectric devices. Therefore, it is essential to thoroughly correlate cellulose nanocomposites' properties with different metallic fillers. This review summarizes the extraction of nanocellulose and preparation of metal modified cellulose nanocomposites, including their wide and particular applications in modern advanced devices. Moreover, we also discuss the challenges in the synthesis, the emerging designs, and unique structures, promising directions for future research. We wish this review can give a valuable overview of the unique combination and inspire the research directions of the multifunctional nanocomposites using proper cellulose and metallic fillers. [ABSTRACT FROM AUTHOR]

Global concerns over energy availability and the environment impose an urgent requirement for sustainable manufacturing, usage, and disposal of electronic components. Piezoelectric and photovoltaic components are being extensively used. They contain the hazardous element, Pb (e.g., in widely used and researched Pb(Zr,Ti)O3 and halide perovskites), but they are not being properly recycled or reused. This work demonstrates the fabrication of upside‐down composite sensor materials using crushed ceramic particles recycled from broken piezoceramics, polycrystalline halide perovskite powder collected from waste dye‐sensitized solar cells, and crystal particles of a Cd‐based perovskite composition, C6H5N(CH3)3CdBr3xCl3(1–x). The piezoceramic and halide perovskite particles are used as filler and binder, respectively, to show a proof of concept for the chemical and microstructural compatibility between the oxide and halide perovskite compounds while being recycled simultaneously. Production of the recycled and reusable materials requires only a marginal energy budget while achieving a very high material densification of >92%, as well as a 40% higher piezoelectric voltage coefficient, i.e., better sensing capability, than the pristine piezoceramics. This work thus offers an energy‐ and environmentally friendly approach to the recycling of hazardous elements as well as giving a second life to waste piezoelectric and photovoltaic components. [ABSTRACT FROM AUTHOR]

Poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) doped with 4-N,N-dimethylamino-4-N-methyl-stilbazolium tosylate (DAST) composites with various concentrations of DAST dye is prepared using the casting method. The crystal structure and optical properties of the pure and P(VDF-HFP)/DAST composites with various contents of DAST dye are investigated using various techniques such as UV–Vis spectroscopy, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and polarized optical microscopy (POM). The analysis of XRD data and FTIR spectra revealed that the β-fraction has been improved in the composite samples with increasing the content of DAST dye. Analysis of UV spectra displayed that the optical band gap of P(VDF-HFP) pure copolymer is 5.41 eV and has been reduced to be 3.75 eV for P(VDF-HFP)/10 wt% DAST that will be suitable for efficient systems of energy conversion and multijunction-based layer solar cells. Also, it is found that the nonlinear and linear optical parameters of the composite samples are DAST dye-dependent. Thermally stimulated depolarization current (TSDC) technique has been applied to investigate the dipolar and space charge relaxations of the composites. Moreover, it is observed that the pyroelectricity and piezoelectricity are enhanced with increasing the content of DAST dye. The highest content of the DAST dye showed maximum values of the pyroelectric and the piezoelectric coefficients of ~ 4 × 10–5 C/m2 K and ~ 34 pC/N at stress of 6.27 × 105 Pa, respectively. Our results of the polymer/dye composites give an opportunity of a promising material for flexible piezoelectricity devices used in many potential applications and energy harvesting systems. [ABSTRACT FROM AUTHOR]

Generally, a high temperature (>1100°C) is required to sinter Lead Zirconate Titanate (PZT) ceramics. Such a high sintering temperature results in significant lead oxide evaporation which is a major environmental problem due to its toxicity. In this work, we have performed flash sintering of Lead zirconate Titanate (Pb (Zr 0.5 Ti 0.5) O 3)) using a novel setup and compared the phase and microstructural evolution, dielectric, piezoelectric properties and lead loss with conventionally sintered Lead zirconate Titanate (PZT). The lead oxide evaporation has been reduced by 5–10 times compared to conventionally sintered PZT. Results also show that the flash-sintered samples' dielectric constant is about ∼ six times higher than the conventionally sintered samples with similar dielectric loss. Ferroelectric and piezoelectric properties of flash sintered PZT on the other hand are lower than conventionally sintered PZT. The mechanisms behind the anomalous properties are discussed using structural and microstructural observations. [ABSTRACT FROM AUTHOR]

The screening effect in ZnO nanowires (NWs) coming from the high density of free electrons has emerged as one of the major issues for their efficient integration into piezoelectric devices. Herein, the compensatory Cu doping of ZnO NWs grown by chemical bath deposition in the high‐pH region using Cu(NO3)2 and ammonia as chemical additives is developed and the effects of a postdeposition thermal annealing under oxygen atmosphere are investigated. It is shown that the Cu dopants are incorporated into ZnO NWs with an atomic [Cu]/[Zn] ratio in the range of 50–65 ppm and undergo a migration process into their bulk after thermal annealing. Importantly, the electrical resistivity of Cu‐doped ZnO NWs is found to increase by a factor of 4 compared to unintentionally n‐doped ZnO NWs. The increase is even more pronounced after different thermal annealing, reaching a factor exceeding 100, which is explained by the redistribution of hydrogen‐ and nitrogen‐related defects along with the thermal activation of Cu dopants. Additionally, it is revealed that a rigid piezoelectric nanogenerator based on a Cu‐doped ZnO NW matrix exhibits the highest output voltage and effective piezoelectric coefficient d33eff thanks to the reduction of the screening effect, opening perspectives in the field of piezoelectric devices. [ABSTRACT FROM AUTHOR]

For ferroelectrics lead zirconate titanate and barium titanate, an exponential dependence of the dielectric constant on temperature is shown, provided that the Curie–Weiss law is satisfied. The temperature of equality of ferroelectric dielectric constants for activation processes caused by the interaction of domain walls with point defects, as well as the corresponding activation energies, have been determined. [ABSTRACT FROM AUTHOR]

The optimization of the processing condition of polyvinylidene fluoride (PVDF) plays a pivotal role in determining the structural, dielectric, and energy storage behavior. The present work addresses the effect of annealing on the structural, dielectric, piezoelectric, and energy storage behavior of the PVDF thick film. X-ray diffractogram/Fourier transform infrared spectroscopy/RAMAN reveals the enhancement in the β crystalline phase of PVDF with annealing temperature which is highest for the film annealed at 110 °C. The film annealed at 110 °C exhibited the dielectric constant, dielectric loss, and piezoelectric coefficient as 14.02, 0.05 at 100 Hz and 24 pC/N, respectively. A systematic enhancement of 21% in dielectric constant, 46% in discharge energy density, and 87% in piezoelectric coefficient is reported for the PVDF film annealed at 110 °C as compared to the film annealed at 50 °C. The enhancement in dielectric and energy storage properties is attributed to the alignment of CH2–CF2 by virtue of molecular motion in the PVDF chain. This work suggests the adaptation of annealing for modifying the dielectric and energy storage behavior which is momentous for various electronic applications. [ABSTRACT FROM AUTHOR]

The avalanche dynamics of ferroelectric switching in lead zirconate titanate ceramics was investigated using acoustic emission. Two distinct power-law regimes for ferroelectric switching events were identified by an anomaly in the histogram of probability density, in contrast to the single power-law behavior observed in BaTiO3 single crystals. Such an anomaly is ascribed to the different minimum cut-offs of two power-law distributions. The critical energy exponents were determined to be 1.25 ± 0.10 for energies <103 aJ and 1.51 ± 0.14 for energies >103 aJ. The events in both regimes can be attributed to the depinning of domain walls from two distinct types of defects. The events in the lower energy regime are associated with domain wall junctions due to long-range electric and elastic interactions, whereas the latter is related to extrinsic defects, such as vacancies and dislocations. Moreover, for both regions, the rate of aftershocks follows the Omori power-law, indicating the same critical temporal correlations between the avalanches. [ABSTRACT FROM AUTHOR]

A method for simulating coupled electromagnetic and mechanical vibrations on arbitrarily shaped piezoelectric structures is presented. This method is based on weak forms and can be implemented in any finite-element-method software, allowing editable access to their definitions. No quasi-static approximation is imposed, meaning that magnetic fields generated by displacement currents within piezoelectric materials are captured, enabling the flow of electromagnetic energy inside and around structures containing such material to be accurately simulated. The method is particularly relevant to the design of piezoelectric antennas, resonators, and waveguides exploiting either bulk or surface-acoustic waves. The accuracy and capabilities of the method are demonstrated by simulating, in COMSOL Multiphysics, (i) a Rayleigh mode on the surface of Z-cut lithium niobate crystal and (ii) a torsional mode of a cylinder of lead zirconium titanate (PZT-5H) ceramic functioning as a micro-antenna. [ABSTRACT FROM AUTHOR]

Uniformly acceptor doped Pb(Zr0.48Ti0.52)O3 (PZT) films with 2 mol. % Mg or Fe prepared by chemical solution deposition exhibited decreased dielectric constants and remanent polarizations relative to undoped PZT. For highly accelerated lifetime testing (HALT) at 200 °C and an electric field of 300 kV/cm in the field up direction, the HALT lifetimes (t50) for undoped, Mg-doped, and Fe-doped PZT films were shortened from 2.81 ± 0.1 to 0.21 ± 0.1 and 0.54 ± 0.04 h, respectively. Through thermally stimulated depolarization current measurement, significant V O ∙ ∙ electromigration was found in homogeneously Mg-doped PZT thin films, a major factor in their short HALT lifetime. Because the concentration of oxygen vacancies increases with uniform acceptor doping, the lifetime decreases. In contrast, when a thin layer of Mg-doped or Fe-doped PZT was deposited on undoped PZT or Nb-doped PZT (PNZT), the HALT lifetimes were longer than those of pure PZT or PNZT films. This confirms prior work on PNZT films with a Mn-doped top layer, demonstrating that the HALT lifetime increases for composite films when a layer with multivalent acceptors is present near the negative electrode during HALT. In that case, the compensating electrons are trapped, presumably on the multivalent acceptors, thus increasing the lifetime. [ABSTRACT FROM AUTHOR]

In this paper, a ground-based experimental system for solar array active vibration suppression has been established. Firstly, in order to establish an accurate model of the solar array, the solar array is regarded as a flexible cantilevered thin plate, and the corresponding dynamical equations are derived using the absolute nodal coordinate method. In addition, in this paper, the more advanced MFC piezoelectric patch is used instead of the traditional PZT piezoelectric ceramic patch. The electromechanical coupling finite element model of the P1-type MFC patch is established and substituted into the kinetic equation of the solar array. Finally, the accuracy of the electromechanical coupling modeling and the control effect of active vibration suppression were verified using the PID control. A set of experimental frameworks for evaluating the active vibration suppression effect, including the free vibration test, sinusoidal perturbation test, and white noise perturbation test, as well as the analysis strategy of the test data, are established. [ABSTRACT FROM AUTHOR]

Communication with hand gestures plays a significant role in human‐computer interaction by providing an intuitive and natural way for humans to communicate with machines. Ultrasound‐based devices have shown promising results in contactless hand gesture recognition without requiring physical contact. However, it is challenging to fabricate a densely packed wearable ultrasound array. Here, a stretchable ultrasound array is demonstrated with closely packed transducer elements fabricated using surface charge engineering between pre‐charged 1–3 Lead Zirconate Titanate (PZT) composite and thin polyimide film without using a microscope. The array exhibits excellent ultrasound properties with a wide bandwidth (≈57.1%) and high electromechanical coefficient (≈0.75). The ultrasound array can decipher gestures up to 10 cm in distance by using a contactless triboelectric module and identify materials from the time constant of the exponentially decaying impedance based on their triboelectric properties by utilizing the electrostatic induction phase. The newly proposed metric of the areal‐time constant is material‐specific and decreases monotonically from a highly positive human body (1.13 m2 s) to negatively charged polydimethylsiloxane (PDMS) (0.02 m2 s) in the triboelectric series. The capability of the closely packed ultrasound array to detect material along with hand gesture interpretation provides an additional dimension in the next‐generation human‐robot interaction. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tube (CFST) members have been widely used in civil engineering due to their advanced mechanical properties. However, internal defects such as the concrete core voids and interface debonding in CFST structures are likely to weaken their load-carrying capacity and stiffness, which affects the safety and serviceability. Visualizing the inner defects of the concrete cores in CFST members is a critical requirement and a challenging task due to the obvious difference in the material mechanical parameters of the concrete core and steel tube in CFST members. In this study, a curved ray theory-based travel time tomography (TTT) with a least square iterative linear inversion algorithm is first introduced to quantitatively identify and visualize the sizes and positions of the concrete core voids in CFST members. Secondly, a numerical investigation of the influence of different parameters on the inversion algorithm for the defect imaging of CFST members, including the effects of the model weighting matrix, weighting factor and grid size on the void's imaging quality and accuracy, is carried out. Finally, an experimental study on six CFST specimens with mimicked concrete core void defects is performed in a laboratory and the mimicked defects are visualized. The results demonstrate that TTT can identify the sizes and positions of the concrete core void defects in CFST members efficiently with the use of optimal parameters. [ABSTRACT FROM AUTHOR]

For the application of high-frequency current detection in power systems, such as very fast transient current, lightning current, partial discharge pulse current, etc., current sensors with a quick response are indispensable. Here, we propose a high-frequency magnetoelectric current sensor, which consists of a PZT piezoelectric ceramic and Metglas amorphous alloy. The proposed sensor is designed to work under d15 thickness-shear mode, with the resonant frequency around 1.029 MHz. Furthermore, the proposed sensor is fabricated as a high-frequency magnetoelectric current sensor. A comparative experiment is carried out between the tunnel magnetoresistance sensor and the magnetoelectric sensor, in the aspect of high-frequency current detection up to 3 MHz. Our experimental results demonstrate that the d15 thickness-shear mode magnetoelectric sensor has great potential for high-frequency current detection in smart grids. [ABSTRACT FROM AUTHOR]

Among electroactive polymers, polyvinylidene fluorine (PVDF) and its copolymers present the highest piezoelectric response which makes them very attractive for applications combining flexibility and piezoelectricity. The use of composites with the incorporation of electroactive ceramics (with a very high piezoelectric coefficient compared to polymers) into the fluorinated polymer matrix allows for an increase in the material piezoelectric response while keeping ductility. The review presents in the first part an overview of the impact of the ceramic particle size and dimension and the filler content. In ceramic/polymer composites, the interface between both constituents is generally weak and has to be strengthened. This review summarizes in the second part different strategies used to improve the interface between the electroactive fillers and the piezoelectric fluorinated polymer matrix to increase the piezoelectric performance of composites. Molecular coupling agents (CAs) are presented and polymer‐based CAs synthesized from "grafting to" and "grafting from" techniques are described. In the last part, the combination of antiparallel poling of ceramic and polymer piezoelectric responses is reported in the composites and the potential of such materials for future development is finally discussed. Highlights: Piezoelectric properties of composites with electroactive ceramic fillers in fluorinated polymer matrix are discussed.Different strategies used to improve the interface between electroactive fillers and piezoelectric fluorinated polymer matrix are presented.The synthesis of molecular CAs or polymer‐based CAs from "grafting to" or "grafting from" techniques is described.The piezoelectric response of ceramic/polymer composites poled in parallel and anti‐parallel are summarized.The antiparallel poling of electroactive ceramic and piezoelectric polymer contributions is a promising way to maximize piezoelectric performances. [ABSTRACT FROM AUTHOR]

In the present study, a numerical and experimental investigation is carried out on vibration-based energy harvesting from unimorph cantilever tapered composite beams. A uniform and various configurations of a tapered composite structure embedded with piezoelectric material are considered to identify the electrical energy generated by the piezoelectric material when dynamic energy is imparted on the structure. Lead zirconate titanate (PZT) of 5-H grade piezoelectric material is considered to be embedded on a cantilever beam made of glass fiber reinforced polymer matrix composite. The numerical modeling and analysis are performed on the composite structure embedded with PZT to calculate the total amount of electrical energy that can be generated by the PZT material using commercially available ANSYS APDL software. Various parametric studies are also carried out to investigate the effects of varying the location of the PZT patch and the configuration of the PZT patches on the electrical energy developed by the PZT. Further, the power generated through unimorph composite structure with PZT material connected in series and parallel are explored. [ABSTRACT FROM AUTHOR]

A typical piezoelectric energy harvester is a bimorph cantilever with two layers of piezoelectric material on both sides of a flexible substrate. Piezoelectric layers of lead-based materials, typically lead zirconate titanate, have been mainly used due to their outstanding piezoelectric properties. However, due to lead toxicity and environmental problems, there is a need to replace them with environmentally benign materials. Here, our main efforts were focused on the preparation of hafnium-doped barium titanate (BaHfxTi1−xO3; BHT) sol–gel materials. The original process developed makes it possible to obtain a highly concentrated sol without strong organic complexing agents. Sol aging and concentration can be controlled to obtain a time-stable sol for a few months at room temperature, with desired viscosity and colloidal sizes. Densified bulk materials obtained from this optimized sol are compared with a solid-state synthesis, and both show good electromechanical properties: their thickness coupling factor kt values are around 53% and 47%, respectively, and their converse piezoelectric coefficient d 33 ∗ values are around 420 and 330 pm/V, respectively. According to the electromechanical properties, the theoretical behavior in a bimorph configuration can be simulated to predict the resonance and anti-resonance frequencies and the corresponding output power values to help to design the final device. In the present case, the bimorph configuration based on BHT sol–gel material is designed to harvest ambient vibrations at low frequency (<200 Hz). It gives a maximum normalized volumetric power density of 0.03 µW/mm3/Hz/g2 at 154 Hz under an acceleration of 0.05 m/s2. [ABSTRACT FROM AUTHOR]

Heterostructures consisting of PbZr0.2Ti0.8O3 epitaxial films on a SrTiO3 (100) substrate with a La0.67Sr0.33MnO3 bottom electrode were prepared by pulsed laser deposition. Plane-parallel capacitor structures were investigated by dielectric spectroscopy and piezoelectric measurement. Shift in a piezoelectric loop indicates that a sample has a small imprinted internal field, directed towards the copper top electrode. Temperature-dependent measurements in a range of 300–500 K were performed to obtain information on the frequency-depending response of the metal– ferroelectric–metal (MFM) structure and to analyze the effect of charge injection through the two Schottky-like contacts. The charge injection process greatly increases the conductivity in the low-frequency region. [ABSTRACT FROM AUTHOR]

Lead Zirconium Titanate (PZT) is a potential piezoelectric material for sensor and transducer applications due to its outstanding piezoelectric coupling near the morphotropic phase boundary (MPB). This is because PZT can switch between tetragonal and rhombohedral phases. PZT is still considered to be one of the piezoelectric materials that has received the greatest amount of attention from researchers and is used the most frequently. Modification with Lithium will improve the piezoelectric properties. In this study, the structural properties and morphological studies of Lead zirconium titanate and Lead zirconium titanate with Lithium modification have been evaluated. Various Scherrer's models and other models, such as the Williamson-Hall model and Size-strain plots model, were used to display the observed fluctuations in crystallite size. Morphological analysis was used to determine the particle size. Graphs showing the distribution of particle sizes were drawn. [ABSTRACT FROM AUTHOR]

The authors studied the effect of the percent fraction of microscopic lead zirconate titanate particles in a polyvinylidene fluoride-based composite material on its mechanical, piezoelectric, and structural properties. We found that an additional 10% of lead zirconate titanate particles enhances the piezoelectric response by increasing the degree of polymer crystallinity for this concentration while the ultimate stress values of the material remain in the range used for obtaining mechanical impact sensors. [ABSTRACT FROM AUTHOR]

High-performance vector hydrophones have been gaining attention for underwater target-monitoring applications. Nevertheless, there exists the mutual constraint between sensitivity and bandwidth of a single hydrophone. To solve this problem, a four-unit array piezoelectric bionic MEMS vector hydrophone (FPVH) was developed in this paper, which has a cross-beam and a bionic fish-lateral-line-nerve-cell-cilia unit array structure. Simulation analysis and optimization in the design of the bionic microstructure have been performed by COMSOL 6.1 software to determine the structure dimensions and the lead zirconate titanate (PZT) thin film distribution. The FPVH was manufactured using MEMS technology and tested in a standing wave bucket. The results indicate that the FPVH has a sensitivity of up to −167.93 dB@1000 Hz (0 dB = 1 V/μPa), which is 12 dB higher than that of the one-unit piezoelectric MEMS vector hydrophone (OPVH). Additionally, the working bandwidth of the FPVH reaches 20 Hz~1200 Hz, exhibiting a good cosine curve with an 8-shape. This work paves a new way for the development of multi-unit piezoelectric vector hydrophones for underwater acoustic detectors. [ABSTRACT FROM AUTHOR]

Transient implantable piezoelectric materials are desirable for biosensing, drug delivery, tissue regeneration, and antimicrobial and tumor therapy. For use in the human body, they must show flexibility, biocompatibility, and biodegradability. These requirements are challenging for conventional inorganic piezoelectric oxides and piezoelectric polymers. We discovered high piezoelectricity in a molecular crystal HOCH2(CF2)3CH2OH [2,2,3,3,4,4-hexafluoropentane-1,5-diol (HFPD)] with a large piezoelectric coefficient d33 of ~138 picocoulombs per newton and piezoelectric voltage constant g33 of ~2450 × 10−3 volt-meters per newton under no poling conditions, which also exhibits good biocompatibility toward biological cells and desirable biodegradation and biosafety in physiological environments. HFPD can be composite with polyvinyl alcohol to form flexible piezoelectric films with a d33 of 34.3 picocoulombs per newton. Our material demonstrates the ability for molecular crystals to have attractive piezoelectric properties and should be of interest for applications in transient implantable electromechanical devices. [ABSTRACT FROM AUTHOR]

With increasing concerns about noise pollution, the pursuit of highly dependable piezoelectric acoustic sensors for real‐time noise monitoring has come to the forefront of scientific research. Lead‐based perovskite piezoelectric films, exemplified by lead zirconate titanate Pb(Zr,Ti)O3 (PZT), surpass traditional piezoelectric materials such as ZnO and AlN in their piezoelectric properties, promising substantial advancements in next‐generation acoustic sensor technologies. However, the toxic nature of lead in PZT materials poses formidable environmental and human health risks. In an unprecedented breakthrough, it presents the pioneering development of an environmentally benign lead‐free piezoelectric Micro‐Electro‐Mechanical System (MEMS) acoustic sensor based on potassium sodium niobate (K,Na)NbO3 (KNN) film. High‐quality <001> textured 3 µm‐thick KNN film is successfully integrated into commercially used Si substrate, rendering exceptional piezoelectricity (transverse piezoelectric coefficients e31* of ≈8.5 C m−2) with satisfactory thermal stability. The atomic‐scale Z‐contrast imaging and piezoresponse force microscopy characterizations reveal that the outstanding piezoresponse originates from the local coexistence of multiple phases and the enhancement of extrinsic piezoelectric contributions from in‐plane polarization anisotropy. Finite element simulation is employed to design the triangular cantilever structure and annular diaphragm structure, each corresponding to different operating bandwidths. The resultant MEMS acoustic sensors stand out with outstanding acoustic performance (the high sensitivity and expansive receiving field of view), which are attributed to the microstructural engineering at multi‐length scales for the excellent piezoelectric properties of KNN film. These features enable sensitive acoustic monitoring in various environments, including large‐scale power grids and urban traffic. [ABSTRACT FROM AUTHOR]

Understanding and controlling the vibration of piezoelectric components induced by oscillating external stimuli is essential to develop smart sensing and energy harvesting devices that convert mechanical energy into electricity. Piezoelectric polymers based on poly(vinylidenefluoride) (PVDF) thin films are amongst the most widely studied materials for flexible sensors and harvesters. Despite the large amount of research on these materials, their electromechanical response under acoustic sound stimuli has not yet been studied in detail. In this work, a thorough investigation on the mechanical vibrations and electrical response of PVDF circular plates of different diameters in response to multiple sound wave frequencies (100 Hz–10 kHz) has been carried out to gain further understanding of the resonance behavior and acousto-electric conversion mechanisms of vibrating PVDF thin films. The work is based on experimental data generated using an integrated piezo-acoustic laser vibrometry system and on a theoretical framework based on the continuum theory of thin plates. The developed model enables the prediction of the resonance frequencies in dependence of the plates' diameter, and suggests that the electrical voltage generated during vibrations is not solely originating from the piezoelectric properties of the films, but might be affected by additional factors, including the triboelectric effect. The results of this study are expected to have a strong impact on the investigation of piezoelectric vibrating plates and on the development of different types of transducers and energy harvesting devices. [ABSTRACT FROM AUTHOR]

In the past two decades, thin lead zirconate titanate (PZT) sensors have been widely used in the electro-mechanical impedance (EMI) technique for sensing applications, particularly for monitoring civil structures. They are typically surface bonded using an industrial adhesive to the monitored structure. The bond between a PZT sensor and structure must be sufficiently strong to transmit the response of the structure to the sensor. In this study, acrylic cubes bonded with PZT patches are subjected to high compressive strains above 2000 με to develop a better understanding of bonding conditions when structures undergo such high strains. Acrylic can undergo such high strains without developing fissures or cracks. Thus, the recorded EMI response only reflects changes in the bonding condition due to the development of strains. The experiments are also numerically supplemented by simulating various debonding conditions. At higher strains, it was observed that the admittance signatures tend to behave similarly to a freely vibrating PZT patch, indicating debonding around the periphery. Even after the complete unloading of the structure, the signatures did not return to their initial state, indicating a permanent partial debonding. The strains developed on a loaded structure are not uniform and can be localized due to structural imperfections, resulting in higher strains in the region where a sensor is bonded. The insights from this study will aid in expanding the scope of the application of PZT sensors for monitoring civil structures through better comprehension of the PZT-structure bond under high compressive strains. [ABSTRACT FROM AUTHOR]

In the present study, the effect of processing parameters like annealing temperature, excess of lead (Pb) content, and film thickness on the crystallographic orientation, dielectric and ferroelectric properties of PLZT (Pb/La/Zr/Ti: 92/8/52/48) films are investigated. For the investigation, PLZT films were prepared on Pt/Ti/SiO2/Si substrate by chemical solution deposition method and annealed at different temperatures (600, 625, 650, 675, and 700 °C). Diverse growth orientation was observed for different annealing temperatures that gave rise to modified electrical properties in the PLZT films. Comparative studies on processing temperature exhibited improved ferroelectric properties in 650 °C annealed PLZT film, which is attributed to its crystallinity (Full width at half maximum, FWHM101 = 0.49°) and texture coefficient (γ = 0.832). Excess Pb content (3 wt.%) yielded improved ferroelectric properties in PLZT film with a ~ 10% increment in domain switching. The PLZT film with 3 wt.% Pb-excess content showed an ASTM class 5B adhesion on Pt/Ti/SiO2/Si substrate, a nano-hardness value of 7894.43 MPa, and a Young's modulus value of 143.05 GPa. To further study the effect of process control parameters on PLZT film, variation of thicknesses (492, 768, and 1500 nm) was studied for 3 wt.% Pb-excess film. The study showed considerable domain switching (switching current = 58.10 μA at 40 kV/cm), improved dielectric constant (~ 2750), higher polarization (Pmax = 71.4 μC/cm2) at a low electric field 334 kV/cm and low leakage current for 1500 nm thick PLZT film. A total energy storage density of ~ 26 J/cm3 at 1020 kV/cm and tunability of 68.46% at ~ 200 kV/cm was achieved for PLZT film with 3 wt.% excess Pb. [ABSTRACT FROM AUTHOR]

We are currently investigating the ultrasound imaging of a sensor that consists of a randomized encoding mask attached to a single lead zirconate titanate (PZT) oscillator for a puncture microscope application. The proposed model was conducted using a finite element method (FEM) simulator. To increase the number of measurements required by a single element system that affects its resolution, the transducer was rotated at different angles. The image was constructed by solving a linear equation of the image model resulting in a poor quality. In a previous work, the phase information was extracted from the echo signal to improve the image quality. This study proposes a strategy by integrating the weighted frequency subbands compound and a super-resolution technique to enhance the resolution in range and lateral direction. The image performance with different methods was also evaluated using the experimental data. The results indicate that better image resolution and speckle suppression were obtained by applying the proposed method. [ABSTRACT FROM AUTHOR]

Electrospinning (ES) methods that can produce piezoelectricity in polymer nanofibers have attracted tremendous research attention. These electrospun polymer nanofibers can be employed for sensors, energy harvesting, tissue engineering, and filtration applications. This paper reviews the performance of a variety of electrospun piezoelectric polymer nanofibers produced by different ES methods, including near‐field electrospinning and conventional far‐field electrospinning methods. Herein, it is described how the ES method can affect the piezoelectric properties of various polymer nanofibers, including poly(vinylidene difluorine), poly(vinylidene fluoride‐trifluoroethylene), nylon 11, poly(l‐lactic acid), and poly(α‐benzyl‐l‐glutamate). Due to the varied matrix structures of piezoelectric polymer nanofibers, the ES method may conduct variable effects on the piezoelectric properties of polymer nanofibers. After characterizations by X‐ray diffraction, Fourier transform infrared spectrum, dielectric spectra, and piezoelectric coefficient measurements, it is found that the piezoelectric properties of the polymer nanofibers can be significantly affected by the ES parameters. Most of previous review articles focus on the output performance of electrospun polymer nanofibers. A detailed description of how different ES methods affect the piezoelectricity of polymer nanofibers is still lacking. In this review paper, the basic principle behind ES methods and the way in which different ES methods affect the properties of polymer nanofibers are examined. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of temperature and preload force on capacitance and electromechanical impedance of lead zirconate titanate piezoelectric wafer active sensors for structural health monitoring of bolts. We explain the influence of temperature on the basis of the phenomenological thermodynamic theory of ferroelectricity by Landau, Ginsburg and Devonshire. The article illustrates the effect of damping the radial deformation of piezoelectric sensors on the capacitance and electromechanical impedance spectra in structural health monitoring of bolts. We also explains the similarities between the effects of temperature and preload force on the electromechanical impedance spectra. We establish a clear correlation between the mechanical strain in the region of the sensor (here due to a preload force), the capacitance and the electromechanical impedance spectra and thus show that piezoelectric sensors made of lead–zirconate–titanate can be used excellently in areas of variable mechanical strain. The article enhances the understanding of the measurement method and facilitates the transfer of the measurement method to other problems in structural health monitoring. Furthermore, the acquired knowledge serves as a solid basis for verifying the plausibility of data sets containing electromechanical impedance spectra. [ABSTRACT FROM AUTHOR]