Showing papers on "Piezoelectricity published in 2016"
TL;DR: A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation.
Abstract: The discovery of ultrahigh piezoelectricity in relaxor-ferroelectric solid solution single crystals is a breakthrough in ferroelectric materials. A key signature of relaxor-ferroelectric solid solutions is the existence of polar nanoregions, a nanoscale inhomogeneity, that coexist with normal ferroelectric domains. Despite two decades of extensive studies, the contribution of polar nanoregions to the underlying piezoelectric properties of relaxor ferroelectrics has yet to be established. Here we quantitatively characterize the contribution of polar nanoregions to the dielectric/piezoelectric responses of relaxor-ferroelectric crystals using a combination of cryogenic experiments and phase-field simulations. The contribution of polar nanoregions to the room-temperature dielectric and piezoelectric properties is in the range of 50-80%. A mesoscale mechanism is proposed to reveal the origin of the high piezoelectricity in relaxor ferroelectrics, where the polar nanoregions aligned in a ferroelectric matrix can facilitate polarization rotation. This mechanism emphasizes the critical role of local structure on the macroscopic properties of ferroelectric materials.
464 citations
TL;DR: In situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors find that the piezoelectric effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone.
Abstract: Piezoelectricity describes interconversion between electrical charge and mechanical strain. As expected for lattice ions displaced in an electric field, the proportionality constant is positive for all piezoelectric materials. The exceptions are poly(vinylidene fluoride) (PVDF) and its copolymers with trifluoroethylene (P(VDF-TrFE)), which exhibit a negative longitudinal piezoelectric coefficient. Reported explanations exclusively consider contraction with applied electric field of either the crystalline or the amorphous part of these semi-crystalline polymers. To distinguish between these conflicting interpretations, we have performed in situ dynamic X-ray diffraction measurements on P(VDF-TrFE) capacitors. We find that the piezoelectric effect is dominated by the change in lattice constant but, surprisingly, it cannot be accounted for by the polarization-biased electrostrictive contribution of the crystalline part alone. Our quantitative analysis shows that an additional contribution is operative, which we argue is due to an electromechanical coupling between the intermixed crystalline lamellae and amorphous regions. Our findings tie the counterintuitive negative piezoelectric response of PVDF and its copolymers to the dynamics of their composite microstructure.
306 citations
TL;DR: Atomic-resolution polarization mapping by Z-contrast imaging reveals the intimate coexistence of rhombohedral (R) and tetragonal (T) phases inside nanodomains, that is, a structural origin for the R-T phase boundary in the present KNN system, suggesting the physical origin of high piezoelectric performance can be attributed to a nearly vanishing polarization anisotropy and thus low domain wall energy.
Abstract: Because of growing environmental concerns, the development of lead-free piezoelectric materials with enhanced properties has become of great interest. Here, we report a giant piezoelectric coefficient (d33) of 550 pC/N and a high Curie temperature (TC) of 237 °C in (1–x–y)K1–wNawNb1–zSbzO3–xBiFeO3–yBi0.5Na0.5ZrO3 (KNwNSz-xBF-yBNZ) ceramics by optimizing x, y, z, and w. Atomic-resolution polarization mapping by Z-contrast imaging reveals the intimate coexistence of rhombohedral (R) and tetragonal (T) phases inside nanodomains, that is, a structural origin for the R–T phase boundary in the present KNN system. Hence, the physical origin of high piezoelectric performance can be attributed to a nearly vanishing polarization anisotropy and thus low domain wall energy, facilitating easy polarization rotation between different states under an external field.
301 citations
TL;DR: This report reports, for the first time, the enhanced piezoelectric energy harvesting performance of the bilayer films of poled poly(vinylidene fluoride-trifluoroethylene) [PVDF-TrFE] and graphene oxide (GO).
Abstract: Ferroelectric materials have attracted interest in recent years due to their application in energy harvesting owing to its piezoelectric nature. Ferroelectric polymers are flexible and can sustain larger strains compared to inorganic counterparts, making them attractive for harvesting energy from mechanical vibrations. Herein, we report, for the first time, the enhanced piezoelectric energy harvesting performance of the bilayer films of poled poly(vinylidene fluoride-trifluoroethylene) [PVDF-TrFE] and graphene oxide (GO). The bilayer film exhibits superior energy harvesting performance with a voltage output of 4 V and power output of 4.41 μWcm–2 compared to poled PVDF-TrFE films alone (voltage output of 1.9 V and power output of 1.77 μWcm–2). The enhanced voltage and power output in the presence of GO film is due to the combined effect of electrostatic contribution from graphene oxide, residual tensile stress, enhanced Young’s modulus of the bilayer films, and the presence of space charge at the interface...
265 citations
TL;DR: In this article, an electricallyenhanced diffused polymorphic phase transition (EED-PPT) contributed to the boosted thermal stability of KNN based lead-free piezoceramics with high piezoelectricity.
Abstract: High piezoelectricity of (K,Na)NbO3 (KNN) lead-free materials benefits from a polymorphic phase transition (PPT) around room temperature, but its temperature sensitivity has been a bottleneck impeding their applications. We find that good thermal stability can be achieved in CaZrO3-modified KNN lead-free piezoceramics, in which the normalized strain d33* almost keeps constant from room temperature up to 140 oC. In situ synchrotron X-ray diffraction experiments combined with permitivity measurements disclose the occurrence of a new phase transformation under an electrical field, which extends the transition range between tetragonal and orthorhombic phases. It is revealed that such an electrically-enhanced diffused polymorphic phase transition (EED-PPT) contributed to the boosted thermal stability of KNN based lead-free piezoceramics with high piezoelectricity. The present approach based on phase engineering should also be effective in endowing other lead-free piezoelectrics with high piezoelectricity and good temperature stability.
250 citations
TL;DR: This work has fabricated a silicon-compatible thin-film cantilever actuator with a single flexoelectrically active layer of strontium titanate with a figure of merit comparable to that of state-of-the-art piezoelectric bimorph cantilevers.
Abstract: Flexoelectricity allows a dielectric material to polarize in response to a mechanical bending moment1 and, conversely, to bend in response to an electric field2. Compared with piezoelectricity, flexoelectricity is a weak effect of little practical significance in bulk materials. However, the roles can be reversed at the nanoscale3. Here, we demonstrate that flexoelectricity is a viable route to lead-free microelectromechanical and nanoelectromechanical systems. Specifically, we have fabricated a silicon-compatible thin-film cantilever actuator with a single flexoelectrically active layer of strontium titanate with a figure of merit (curvature divided by electric field) of 3.33 MV−1, comparable to that of state-of-the-art piezoelectric bimorph cantilevers.
245 citations
TL;DR: Control of polarization with an electric field applied during the peptide self-assembly process is shown, showing the strong piezoelectricity in diphenylalanine peptide and the power generation with a peptide-based power generator.
Abstract: Peptides have attracted considerable attention due to their biocompatibility, functional molecular recognition and unique biological and electronic properties. The strong piezoelectricity in diphenylalanine peptide expands its technological potential as a smart material. However, its random and unswitchable polarization has been the roadblock to fulfilling its potential and hence the demonstration of a piezoelectric device remains lacking. Here we show the control of polarization with an electric field applied during the peptide self-assembly process. Uniform polarization is obtained in two opposite directions with an effective piezoelectric constant d33 reaching 17.9 pm V−1. We demonstrate the power generation with a peptide-based power generator that produces an open-circuit voltage of 1.4 V and a power density of 3.3 nW cm−2. Devices enabled by peptides with controlled piezoelectricity provide a renewable and biocompatible energy source for biomedical applications and open up a portal to the next generation of multi-functional electronics compatible with human tissue. Piezoelectricity in diphenylalanine peptide nanotubes (PNTs) suggests an avenue towards green piezoelectric devices. Here the authors show ‘smart’ PNTs whose polarization can be controlled with an electric field, and a resultant power generator which harvests biomechanical energy with high power density.
220 citations
TL;DR: Self-standing films of native cellulose nanofibrils (CNFs) were synthesized and characterized to suggest that CNF is a suitable precursor material for disposable piezoelectric sensors, actuators, or energy generators with potential applications in the fields of electronics, sensors, and biomedical diagnostics.
Abstract: Self-standing films (45 μm thick) of native cellulose nanofibrils (CNFs) were synthesized and characterized for their piezoelectric response. The surface and the microstructure of the films were evaluated with image-based analysis and scanning electron microscopy (SEM). The measured dielectric properties of the films at 1 kHz and 9.97 GHz indicated a relative permittivity of 3.47 and 3.38 and loss tangent tan δ of 0.011 and 0.071, respectively. The films were used as functional sensing layers in piezoelectric sensors with corresponding sensitivities of 4.7–6.4 pC/N in ambient conditions. This piezoelectric response is expected to increase remarkably upon film polarization resulting from the alignment of the cellulose crystalline regions in the film. The CNF sensor characteristics were compared with those of polyvinylidene fluoride (PVDF) as reference piezoelectric polymer. Overall, the results suggest that CNF is a suitable precursor material for disposable piezoelectric sensors, actuators, or energy gene...
192 citations
TL;DR: It is demonstrated that the output power from the PNG can directly drive the light-emitting diode (LED) and charge capacitor and demonstrate that BiFeO3 nanomaterials have the potential for large-scale lead-free piezoelectric nanogenerator applications.
Abstract: Perovskite ferroelectric BiFeO3 has been extensively researched in many application fields, but has rarely been investigated for the energy conversion of tiny mechanical motions in electricity in spite of its large theoretical remnant polarization. Here we demonstrate the fabrication of a flexible piezoelectric nanogenerator based on BiFeO3 nanoparticles (NPs), which were synthesized using a sol–gel process. The BiFeO3 NPs–PDMS composite device exhibits an output open circuit voltage of ∼3 V and short circuit current of ∼250 nA under repeated hand pressing. The output generation mechanism from the PNG is discussed on the basis of the alignment of electric dipoles in the composite film. It is demonstrated that the output power from the PNG can directly drive the light-emitting diode (LED) and charge capacitor. These results demonstrate that BiFeO3 nanomaterials have the potential for large-scale lead-free piezoelectric nanogenerator applications.
192 citations
TL;DR: In this article, the authors report directional dependent piezoelectric effects in chemical vapor deposition grown monolayer MoS2 for flexible PEG nanogenerators (NGs) for powering low power consuming electronics and realizing self-powered sensors.
189 citations
TL;DR: In this article, a piezoelectric-composite slurry with BaTiO3 nanoparticles (100nm) was 3D printed using Mask-Image-Projection-based Stereolithography (MIP-SL) technology.
TL;DR: In this paper, the authors describe the principles of design, fabrication, and operation of a piezoelectric optomechanical crystal with which they demonstrate bi-directional conversion of energy between microwave and optical frequencies.
Abstract: We describe the principles of design, fabrication, and operation of a piezoelectric optomechanical crystal with which we demonstrate bi-directional conversion of energy between microwave and optical frequencies. The optomechanical crystal has an optical mode at 1523 nm co-located with a mechanical breathing mode at 3.8 GHz, with a measured optomechanical coupling strength gom/2π of 115 kHz. The breathing mode is driven and detected by curved interdigitated transducers that couple to a Lamb mode in suspended membranes on either end of the optomechanical crystal, allowing the external piezoelectric modulation of the optical signal as well as the converse, the detection of microwave electrical signals generated by a modulated optical signal. We compare measurements to theory where appropriate.
TL;DR: In this article, a hybrid piezoelectric nanogenerator based on a composite of polydimethylsiloxane polymer and FAPbBr3 nanoparticles is fabricated.
Abstract: Organic–inorganic lead halide perovskite materials have recently attracted much attention in the field of optoelectronic devices. Here, a hybrid piezoelectric nanogenerator based on a composite of piezoelectric formamidinium lead halide perovskite (FAPbBr3) nanoparticles and polydimethylsiloxane polymer is fabricated. Piezoresponse force spectroscopy measurements reveal that the FAPbBr3 nanoparticles contain well-developed ferroelectric properties with high piezoelectric charge coefficient (d33) of 25 pmV−1. The flexible device exhibits high performance with a maximum recordable piezoelectric output voltage of 8.5 V and current density of 3.8 μA cm−2 under periodically vertical compression and release operations. The alternating energy generated from nanogenerators can be used to charge a capacitor and light up a red light-emitting diode through a bridge rectifier. This result innovatively expands the feasibility of organic–inorganic lead halide perovskite materials for application in a wide variety of high-performance energy harvesting devices.
TL;DR: In this article, the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing are reviewed.
Abstract: Ferroelectric materials are well-suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro-optic devices, and nonvolatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a noncentrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change in properties with decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, whereas in bulk ceramics, changes in properties from the values of large-grained specimens is most notable in samples with grain sizes below several micrometers. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article, the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics is reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. In many cases, multiple mechanisms combine to produce the observed scaling effects.
TL;DR: Single-crystal perovskite solar cells with a lateral structure yield an efficiency enhancement 44-fold that of polycrystalline thin films, due to the much longer carrier diffusion length.
Abstract: Single-crystal perovskite solar cells with a lateral structure yield an efficiency enhancement 44-fold that of polycrystalline thin films, due to the much longer carrier diffusion length. A piezoelectric effect observed in perovskite single-crystal and the strain-generated grain-boundaries enable ion migration to form a p-i-n structure.
TL;DR: The results reveal that self-polarization due to grain orientation along the spontaneous polarization direction plays an important role in achieving large piezoelectric response in a domain motion-confined material.
Abstract: A rapid surge in the research on piezoelectric sensors is occurring with the arrival of the Internet of Things. Single-phase oxide piezoelectric materials with giant piezoelectric voltage coefficient (g, induced voltage under applied stress) and high Curie temperature (Tc) are crucial towards providing desired performance for sensing, especially under harsh environmental conditions. Here, we report a grain-oriented (with 95% texture) modified PbTiO3 ceramic that has a high Tc (364 °C) and an extremely large g33 (115 × 10-3 Vm N-1) in comparison with other known single-phase oxide materials. Our results reveal that self-polarization due to grain orientation along the spontaneous polarization direction plays an important role in achieving large piezoelectric response in a domain motion-confined material. The phase field simulations confirm that the large piezoelectric voltage coefficient g33 originates from maximized piezoelectric strain coefficient d33 and minimized dielectric permittivity ɛ33 in [001]-textured PbTiO3 ceramics where domain wall motions are absent.
TL;DR: In this article, a novel sound-absorbing material was developed using electrospun piezoelectric polyvinylidene fluoride (PVDF) membranes, which exhibited high surface area providing a large number of contact sites with the sound waves.
TL;DR: In this article, an adaptive elastic metamaterial integrated with shunted piezoelectric patches has been performed in a deep subwavelength scale, where the tunable bandgap capacity, as high as 45%, is physically realized by using both hardening and softening shunted circuits.
Abstract: The ability to control elastic wave propagation at a deep subwavelength scale makes locally resonant elastic metamaterials very relevant. A number of abilities have been demonstrated such as frequency filtering, wave guiding, and negative refraction. Unfortunately, few metamaterials develop into practical devices due to their lack of tunability for specific frequencies. With the help of multi-physics numerical modeling, experimental validation of an adaptive elastic metamaterial integrated with shunted piezoelectric patches has been performed in a deep subwavelength scale. The tunable bandgap capacity, as high as 45%, is physically realized by using both hardening and softening shunted circuits. It is also demonstrated that the effective mass density of the metamaterial can be fully tailored by adjusting parameters of the shunted electric circuits. Finally, to illustrate a practical application, transient wave propagation tests of the adaptive metamaterial subjected to impact loads are conducted to valida...
TL;DR: In this article, CH3NH3PbI3 perovskite thin films were applied to fluorine-doped SnO2 (FTO)/glass and Au/Ti/polyethylene terephthalate (PET) substrates via a two-step process, which involved depositing a CH 3NH3I (MAI) solution onto PbI2 films via spincoating followed by crystallization at temperatures of 100 °C.
Abstract: CH3NH3PbI3 (MAPbI3) perovskite thin films were applied to fluorine-doped SnO2 (FTO)/glass and Au/Ti/polyethylene terephthalate (PET) substrates via a two-step process, which involved depositing a CH3NH3I (MAI) solution onto PbI2 films via spin-coating followed by crystallization at temperatures of 100 °C. The 500 nm-thick crystallized MAPbI3 perovskite thin films showed a Curie temperature of ∼328 K, a dielectric permittivity of ∼52, a dielectric loss of ∼0.02 at 1 MHz, and a low leakage current density of ∼10−7 A cm−2 at ±3 V. The polarization–electric field (P–E) hysteresis loop and piezoresponse force microscopy (PFM) results showed that the films had well-developed ferroelectric properties and switchable polarization. Poling at an electrical field of 80 kV cm−1 enhanced the power density of the generator. The values for output voltage and current density of the poled films reached 2.7 V and 140 nA cm−2, respectively, which were 2.7-fold higher than those of the non-poled samples.
TL;DR: A new flexible piezoelectric tactile sensor array based on polyvinylidene fluoride (PVDF) film is proposed for measuring three-axis dynamic contact force distribution that can be easily integrated onto a curved surface, such as robotic and prosthetic hands, due to its excellent flexibility.
Abstract: A new flexible piezoelectric tactile sensor array based on polyvinylidene fluoride (PVDF) film is proposed for measuring three-axis dynamic contact force distribution. The array consists of six tactile units arranged as a 3 × 2 matrix with spacing 8 mm between neighbor units. In each unit, a PVDF film is sandwiched between four square-shaped upper electrodes and one square-shaped lower electrode, forming four piezoelectric capacitors. A truncated pyramid bump is located above the four piezoelectric capacitors to improve force transmission. A three-axis contact force transmitted from the top of the bump will lead to the four piezoelectric capacitors underneath undergoing different charge changes, from which the normal and shear components of the force can be calculated. A series of dynamic tests have been carried out by exerting sinusoidal forces with amplitudes ranging from 0 to 0.5 N in the x-axis, 0 to 0.5 N in the y-axis, and 0 to 1.5 N in the z-axis, separately. The tactile units show good sensitivities with 14.93, 14.92, and 6.62 pC/N in the x-, y-, and z-axes, respectively. They can work with good linearity, relatively low coupling effect, high repeatability, and acceptable frequency response in the range of 5–400 Hz to both normal and shear load. In addition, dynamic three-axis force measurement has been conducted for all of the tactile units. The average errors between the applied and calculated forces are 10.68% ± 6.84%. Furthermore, the sensor array can be easily integrated onto a curved surface, such as robotic and prosthetic hands, due to its excellent flexibility.
TL;DR: In this paper, a vertical contact-separation mode triboelectric generator based on lead-free perovskite, zinc stannate (ZnSnO3)-polyvinylidene fluoride (PVDF) composite and polyamide-6 (PA6) membrane is demonstrated.
TL;DR: In this paper, an analytical solution procedure for the nonlinear postbuckling analysis of piezoelectric functionally graded carbon nanotubes reinforced composite (FG-CNTRC) cylindrical shells subjected to combined electro-thermal loadings, axial compression and lateral loads is presented.
Abstract: This paper presents an analytical solution procedure for the nonlinear postbuckling analysis of piezoelectric functionally graded carbon nanotubes reinforced composite (FG-CNTRC) cylindrical shells subjected to combined electro-thermal loadings, axial compression and lateral loads. The carbon nanotubes are assumed to be aligned and straight with uniform and functionally graded distributions in the thickness direction. The kinematics and constitutive relations are written on the basis of the classic theory and the von Karman nonlinear strain–displacement relations of large deformation. Applying the Ritz energy approach, analytical solutions are proposed for the nonlinear critical axial load, lateral pressure as well as the load-shortening ratio of the piezoelectric FG-CNTRC shell. Numerical results are presented to study the effects of dimensional parameters, CNT volume fraction, distribution type of the reinforcement and piezoelectric thickness on the nonlinear buckling behavior of the piezoelectric nanocomposite shell. It is revealed that the carrying capacity of the structure increases as the shell is integrated by the piezoelectric layers and reinforced by higher CNT volume fraction. Furthermore, FGX- and FGO- CNTRC piezoelectric shells are indicated to have higher and lower carrying capacities compared to UD-CNTRC piezoelectric shells, respectively.
TL;DR: In this paper, two dependent design of experiments (DOEs) were utilized to systematically control the dimensions of electrospun poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) to produce nanofibers having their diameter ranging from 1000 to sub-100 nm.
Abstract: Piezoelectricity-based energy harvesting from wasted mechanical energies has garnered an increasing attention as a clean energy source. Especially, flexible organic piezoelectric materials provide an opportunity to exploit their uses in mechanically challenging areas where brittle inorganic counterparts have mechanical limitations. In this regard, electrospinning has shown its advantages of producing poly(vinylidene fluoride) (PVDF)-based nanofibrous structures without the necessity of a secondary processing to induce/increase piezoelectric properties. However, the effects of electrospun fiber dimension, one of the main morphological parameters in electrospun fibers, on piezoelectricity have not been fully understood. In this study, two dependent design of experiments (DOEs) were utilized to systematically control the dimensions of electrospun poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) to produce nanofibers having their diameter ranging from 1000 to sub-100 nm. Such a dimensional reduction resulted in the increase of piezoelectric responsible electroactive phase content and the degree of crystallinity. These changes in crystal structure led to approximately 2-fold increase in piezoelectric constant as compared to typical P(VDF-TrFE) thin films. More substantially, the dimensional reduction also increased the Young's modulus of the nanofibers up to approximately 80-fold. The increases in piezoelectric constant and Young's modulus collectively enhanced piezoelectric performance, resulting in the exponential increase in electric output of nanofiber mats when the fiber diameters were reduced from 860 nm down to 90 nm. Taken together, the results suggest a new strategy to improve the piezoelectric performance of electrospun P(VDF-TrFE) via optimization of their electromechanical and mechanical properties.
TL;DR: Experimental and theoretical research on ScN- and CrN-based transition-metal nitride materials for thermoelectrics are reviewed, drawing parallels with piezoelectricity.
Abstract: The last few years have seen a rise in the interest in early transition-metal and rare-earth nitrides, primarily based on ScN and CrN, for energy harvesting by thermoelectricity and piezoelectricity. This is because of a number of important advances, among those the discoveries of exceptionally high piezoelectric coupling coefficient in (Sc,Al)N alloys and of high thermoelectric power factors of ScN-based and CrN-based thin films. These materials also constitute well-defined model systems for investigating thermodynamics of mixing for alloying and nanostructural design for optimization of phase stability and band structure. These features have implications for and can be used for tailoring of thermoelectric and piezoelectric properties. In this highlight article, we review the ScN- and CrN-based transition-metal nitrides for thermoelectrics, and drawing parallels with piezoelectricity. We further discuss these materials as a models systems for general strategies for tailoring of thermoelectric properties by integrated theoretical–experimental approaches.
TL;DR: The domain configuration of lead-free ceramics with rhombohedral-tetragonal morphotropic phase boundary, accounting for the high piezoelectric property and good thermal stability, was systematically studied.
Abstract: The domain configuration of lead-free (K0.48Na0.52)(Nb0.96Sb0.04)O3–Bi0.50(Na0.82K0.18)0.50ZrO3 ceramics with rhombohedral–tetragonal morphotropic phase boundary, accounting for the high piezoelectric property and good thermal stability, were systematically studied. Short domain segments (before poling) and long domain stripes with wedge-shaped or furcated ends (after poling) were found to be typical domain configurations. The reduced elastic energy, lattice distortion, and internal stress, due to the coexistence of rhombohedral and tetragonal phases, result in much easier domain reorientation and domain wall motion, responsible for the high piezoelectric properties, being on the order of 460 pC/N, in which the extrinsic contribution from irreversible domain switching was estimated to be around 50% of the total piezoelectricity. Minor piezoelectric property variations (<6% over a temperature range from −50 to 100 °C) were observed as a function of temperature, showing a good thermal stability. In addition...
TL;DR: By applying the Euler-Bernoulli model and using the consistent size-dependent theory, the nonlinear formulation of functionally graded piezoelectric material nanobeam is developed.
Abstract: In this article, by applying the Euler–Bernoulli model and using the consistent size-dependent theory, the nonlinear formulation of functionally graded piezoelectric material nanobeam is developed....
TL;DR: Free vibration behavior of carbon nanotube reinforced composite plates integrated with piezoelectric layers at the bottom and top surfaces is analyzed and it is shown that, fundamental frequency of a closed circuit plate is always higher than a plate with open circuit boundary conditions.
Abstract: In the present research, free vibration behavior of carbon nanotube reinforced composite (CNTRC) plates integrated with piezoelectric layers at the bottom and top surfaces is analyzed. Plate is modeled according to the first order shear deformation plate theory. Distribution of CNTs across the plate thickness may be functionally graded (FG) or uniformly distributed (UD). Properties of the composite media are obtained according to a modified rule of mixtures approach which contains efficiency parameters. Distribution of electric potential across the piezoelectric thickness is assumed to be linear. The complete set of motion and Maxwell equations of the system are obtained according to the Ritz formulation suitable for arbitrary in-plane and out-of-plane boundary conditions. Besides, two types of electrical boundary conditions, namely, closed circuit and open circuit are considered for the free surfaces of the piezoelectric layers. Chebyshev polynomials are used as the basis functions in Ritz approximation. The resultant eigenvalue system is solved to obtain the frequencies of the system as well as the mode shapes. It is shown that, fundamental frequency of a closed circuit plate is always higher than a plate with open circuit boundary conditions.
TL;DR: In this article, a high-temperature bismuth scandium lead titanate (BiScO3-PbTiO3, abbreviated as BSPT) ceramic is reported which has a high Curie temperature point around 450 °C and its application for high temperature vibration energy harvesting.
Abstract: Conventionally, effective mechanical vibration energy harvesting is based on (Pb,Zr)TiO3 (PZT) ceramics, poly(vinylidene fluoride) (PVDF) polymers or PVDF/PZT or other piezoelectric composite materials, and their working temperature is normally limited to room temperature (R-T) or below 150 °C. Here, bismuth scandium lead titanate (BiScO3-PbTiO3, abbreviated as BSPT) ceramic is reported which has a high Curie temperature point around 450 °C and its application for high-temperature (H-T) vibration energy harvesting. Experimental results show that it exhibits an excellent H-T piezoelectricity, converting mechanical vibration energy into electric power effectively in a wide temperature range from R-T till 250 °C. This research shows the BSPT piezoelectric energy harvester having the potential application for self-power source of wireless sensor network system in high temperature circumstance.
TL;DR: In this article, a new strategy was proposed to construct recoverable mechanoluminescence (ML) materials by doping piezoelectric hosts with luminescent lanthanide ions, which simultaneously created luminecent centers and carrier traps in the host lattice.
Abstract: Recoverable mechanoluminescence (ML), characterized by nondestructive and repetitive luminescence in response to a mechanical stress, has shown considerable promise in a variety of practical applications including lighting and display, as well as stress sensing and imaging. However, the progress in utilizing ML processes has been constrained by the difficulties in developing new ML materials and in ascertaining ML mechanism. In this paper, we report a new strategy to constructing recoverable ML materials by doping piezoelectric hosts with luminescent lanthanide ions, which simultaneously create luminescent centers and carrier traps in the host lattice. The viability of the strategy has been confirmed by assessing a series of Pr3+ activated calcium niobates composed of mCaO·Nb2O5 (m = 1, 2, and 3). Furthermore, systematical characterizations of the series of calcium niobates also reveal an unusual host dependent ML phenomenon. Our results are expected to expand the scope of designing ML materials and to de...
TL;DR: The piezo-phototronic effect provides a promising method to enhance the light emission of LEDs based on piezoelectric semiconductors through applying static strains, and may find perspective applications in various optoelectronic devices and integrated systems.
Abstract: Wurtzite materials exhibit both semiconductor and piezoelectric properties under strains due to the non-central symmetric crystal structures. The three-way coupling of semiconductor properties, piezoelectric polarization and optical excitation in ZnO, GaN, CdS and other piezoelectric semiconductors leads to the emerging field of piezo-phototronics. This effect can efficiently manipulate the emission intensity of light-emitting diodes (LEDs) by utilizing the piezo-polarization charges created at the junction upon straining to modulate the energy band diagrams and the optoelectronic processes, such as generation, separation, recombination and/or transport of charge carriers. Starting from fundamental physics principles, recent progress in piezo-phototronic-effect-enhanced LEDs is reviewed; following their development from single-nanowire pressure-sensitive devices to high-resolution array matrices for pressure-distribution mapping applications. The piezo-phototronic effect provides a promising method to enhance the light emission of LEDs based on piezoelectric semiconductors through applying static strains, and may find perspective applications in various optoelectronic devices and integrated systems.