Piezoelectric Voltage Coefficient Research Articles

Silk nanoribbon films with enriched silk II structure and enhanced piezoelectricity for self-powered implantable and wearable devices

Piezoelectric biomaterials are intrinsically suitable to convert mechanical energy to electrical output and achieve electricity generation, in vivo/in vitro real-time monitoring, and sensing in biological systems. However, the inability to fabricate piezoelectric bio-materials with excellent piezoelectricity, full biodegradability, and good biocompatibility remains a challenge toward practical applications. As a solution, we present a bio-piezoelectric thin film with macroscopic piezoelectric output, high stability, fast response ability, flexibility, biocompatibility, and biodegradability based on nascent silk nanoribbons (SNRs) with high silk II-type structure. The solvent systems influence the meso/nanostructure and the piezoelectric performance of silk materials. Compared with other silk materials, the SNR fabricated by 2,2,6,6-tetramethylpiperidine-1-oxyl oxidation system (T-SNR) maintains higher silk II-type structure and more stable crystalline structure. The T-SNR film possesses electrostriction effect without electrical poling treatment. It presents an apparent piezoelectric constant (d33) of 7.7 pm/V and a piezoelectric voltage coefficient (g33) of 0.58 Vm/N, such values are superior to most reported bio-films. The piezoelectric T-SNR film can realize in vivo/in vitro real-time monitoring, sensing, and self-power ability. With its natural compatibility and degradability, the T-SNR film exhibits the potential for various implantable and wearable applications and may enable the development of fully biodegradable transient electromechanical devices.

Remarkable enhancement in piezoelectric performance of [001] textured Na0.4K0.1Bi0.5TiO3 ceramic

This study explores the dependence of dielectric and piezoelectric properties on the grain morphology, orientation, and electric field in the [001] textured Na0.4K0.1Bi0.5TiO3 (NKBT-T) piezoceramics, fabricated via reactive template grain growth and tape-casting methods. A high degree of [001] texturing with Lotgering factor (f) of ∼0.92 was confirmed by X-ray diffraction, electron backscattered diffraction, and bulk texture measurements. A large average plate length of ∼8.5 ± 1 μm with an aspect ratio of ∼11 was achieved in NKBT-T ceramic. An extremely large value of piezoelectric voltage coefficient (g33) of ∼100×10−3 Vm/N was observed in poled NKBT-T ceramics, originating from a low dielectric constant (∼230) and high piezoelectric charge coefficient (d33 ∼205 pC/N). The transduction coefficient (d33•g33) of NKBT-T ceramic was estimated at ∼20,000 × 10−15 m2N−1 and the mechanical energy harvesting responses of ∼1.8 µA and ∼4 V were recorded in the NKBT-T ceramic-based piezoelectric device.

Temperature-Dependent Ferroelectric Properties and Aging Behavior of Freeze-Cast Bismuth Ferrite-Barium Titanate Ceramics.

Lead-free BiFeO3-BaTiO3 (BF-BT) piezoceramics have sparked considerable interest in recent years due to their high piezoelectric performance and high Curie temperature. In this paper, we show how the addition of highly aligned porosity (between 40 and 60 vol %) improves the piezoelectric performance, sensing, and energy harvesting figures of merit in freeze-cast 0.70BiFeO3-0.30BaTiO3 piezoceramics compared to conventionally processed, nominally dense samples of the same composition. The dense and porous BF-BT ceramics had similar longitudinal piezoelectric coefficients (d33) immediately after poling, yet the dense samples were observed to age faster than those of porous ceramics. After 24 h, for example, the porous samples had significantly higher d33 values ranging from 112 to 124 pC/N, compared to 85 pC/N for the dense samples. Porous samples exhibited 3 and 5 times higher longitudinal piezoelectric voltage coefficient g33 and energy harvesting figure of merit d33g33 than dense samples due to the unexpected increase in d33 and decrease in relative permittivity with porosity. Spontaneous polarization (Ps) and remnant polarization (Pr) decrease as the porosity content increased from 37 to 59 vol %, as expected due to the lower volume of active material; however, normalized polarization values with respect to porosity level showed a slight increase in the porous materials relative to the dense BF-BT. Furthermore, the porous ceramics showed improved temperature-dependent strain-field response compared to the dense. As a result, these porous materials show excellent potential for use in high temperature sensing and harvesting applications.

Mechanism and application of lead-free KNN-based ceramics with superior piezoelectricity

Piezoelectric ultrasonic energy harvesters (PUEHs) have recently attracted increasing attention. For minimizing the energy losses during energy transfer, it is crucial for core piezoelectric materials to maintain high piezoelectric coefficient (d33), mechanical quality factor (Qm), and piezoelectric voltage coefficient (g33). Herein, a simple way of hardening strategy improves the piezoelectric properties of KNN-based ceramics, combined with optimizing grain growth. The enhanced d33 (∼340 pC/N), high Qm (∼211) and TC (∼305 °C) are obtained simultaneously in this system, accompanied by superior d33×g33=8770×10−15 m2/N. Through variable temperature resonance test, the polarization rotation diversity caused by phase structure difference is found to closely related to the temperature stability of Qm value. A prototype of PUEH device was further designed and fabricated, with adjustable ultrasound-induced output voltage up to 8.2 V. Our work exhibits an effective way to improve performance of PUEHs by optimizing piezoelectric materials, which is helpful for further developing PUEHs.

Piezoelectric and Pyroelectric Properties of Organic MDABCO-NH4Cl3 Perovskite for Flexible Energy Harvesting

This study describes the synthesis and characterization of the lead-free organic ferroelectric perovskite N-methyl-N’-diazabicyclo [2.2.2]octonium)-ammonium trichloride (MDABCO-NH4Cl3). The electrospinning technique was employed to obtain nanofibers embedded with this perovskite in a PVC polymer for hybrid fiber production. The dielectric, piezoelectric, and pyroelectric properties of these fibers were carefully examined. Based on measurements of the dielectric permittivity temperature and frequency dependence, together with the pyroelectric results, a transition from a high temperature paraelectric to a ferroelectric phase that persisted at room temperature was found to occur at 438 K. The measured pyroelectric coefficient yielded values as high as 290 μC K−1 m−2, which is in between the values reported for MDABCO-NH4I3 and the semiorganic ferroelectric triglycine sulfate (TGS). The hybrid nanofibers exhibited good morphological characteristics and demonstrated very good piezoelectric properties. Specifically, a piezoelectric coefficient of 42 pC/N was obtained when applying a periodical force of 3 N and a piezoelectric voltage coefficient of geff = 0.65 V mN−1. The performance of these fibers is on par with that of materials discussed in the existing literature for the fabrication of nano energy-harvesting generators. Importantly, the perovskite nanocrystals within the fibers are protected from degradation by the surrounding polymer, making them a promising environmentally friendly platform for flexible mechanical energy harvesting.

Elastic Polarization Configuration Coupled with Activity Rattling Space Boosts Energy Harvesting Performance of Lead‐Free Piezoceramic

AbstractPiezoelectric energy harvesting technology is drawing substantial attention as an eco‐friendly method to promote energy transformation, which is at the forefront of current scientific research. However, the difficulties involved in obtaining a stable output voltage (Vout) and a controllable output current density (Iout) represent bottlenecks in the development of piezoelectric energy harvesters (PEHs) for practical applications. Here, a novel strategy that couples elastic polarization configuration with activity rattling space in lead‐free potassium sodium niobate‐based piezoceramics is proposed to break through this barrier. The cantilever beam‐type PEHs assembled using the rationally designed piezoceramic system show a stable Vout (≈22 V) and a controllable Iout over the range from 6.09 to 20.16 µA cm−2, which is sufficient to drive multiple types of wireless sensors that have the same rated voltage but different rated current requirements. These fantastic power generation performances are associated with a stable piezoelectric voltage coefficient (g33), an increasing piezoelectric charge coefficient (d33), and a weakened electrostrictive coefficient (Q33) that stem from polarization configuration optimization in combination with introduction of the activity rattling space design. This work provides a good approach to modulation of the overall performance of piezoelectric materials to meet the demands of advanced PEH applications.

Interfacial Polarization Locked Flexible β-Phase Glycine/Nb2 CTx Piezoelectric Nanofibers.

Biomolecular piezoelectric materials show great potential in the field of wearable and implantable biomedical devices. Here, a self-assemble approach is developed to fabricating flexible β-glycine piezoelectric nanofibers with interfacial polarization locked aligned crystal domains induced by Nb2 CTx nanosheets. Acted as an effective nucleating agent, Nb2 CTx nanosheets can induce glycine to crystallize from edges toward flat surfaces on its 2D crystal plane and form a distinctive eutectic structure within the nanoconfined space. The interfacial polarization locking formed between O atom on glycine and Nb atom on Nb2 CTx is essential to align the β-glycine crystal domains with (001) crystal plane intensity extremely improved. This β-phase glycine/Nb2 CTx nanofibers (Gly-Nb2 C-NFs) exhibit fabulous mechanical flexibility with Young's modulus of 10 MPa, and an enhanced piezoelectric coefficient of 5.0 pCN-1 or piezoelectric voltage coefficient of 129×10-3 VmN-1 . The interface polarization locking greatly improves the thermostability of β-glycine before melting (≈210°C). A piezoelectric sensor based on this Gly-Nb2 C-NFs is used for micro-vibration sensing in vivo in mice and exhibits excellent sensing ability. This strategy provides an effective approach for the regular crystallization modulation for glycine crystals, opening a new avenue toward the design of piezoelectric biomolecular materials induced by 2D materials.

Enhanced piezoelectric properties in low-temperature sintered Pb(Zr,Ti)O3-based ceramics via Yb2O3 doping

Pb(Mg[Formula: see text]W[Formula: see text])O3–Pb(Ni[Formula: see text]Nb[Formula: see text])O3–Pb(Zr[Formula: see text]Ti[Formula: see text])O3 (PNN–PMW–PZT) piezoceramics were sintered at a low temperature of 900∘C by the mixed metal oxide powder solid-state reaction route. CaCO3 and Li2CO3 as sintering aids and Yb2O3 as a dopant were added into the PNN–PMW–PZT ceramic system for low-temperature sintering and enhancement of electrical properties, respectively. The effects of different Yb2O3 doping amounts on the microstructure, dielectric, piezoelectric and ferroelectric properties of the samples were systematically investigated. The piezoceramics doped with 0.1[Formula: see text]mol% Yb2O3 have optimal electrical properties ([Formula: see text][Formula: see text]pC/N, [Formula: see text], [Formula: see text] (1[Formula: see text]kHz), [Formula: see text] (1[Formula: see text]kHz), and [Formula: see text]C). While the piezoceramics doped with 0.3[Formula: see text]mol% Yb2O3 have optimal energy conversion properties: the piezoelectric voltage coefficient [Formula: see text][Formula: see text]Vm/N and the effective piezoelectric energy conversion coefficient [Formula: see text][Formula: see text]m2/N.

Oxide-Halide Perovskite Composites for Simultaneous Recycling of Lead Zirconate Titanate Piezoceramics and Methylammonium Lead Iodide Solar Cells.

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)3CdBr3 xCl3(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.

Organic-Inorganic Rare-Earth Double Perovskite Ferroelectric with Large Piezoelectric Response and Ferroelasticity for Flexible Composite Energy Harvesters.

Hybrid organic-inorganic perovskite (HOIP) ferroelectric materials have great potential for developing self-powered electronic transducers owing to their impressive piezoelectric performance, structural tunability and low processing temperatures. Nevertheless, their inherent brittle and low elastic moduli limit their application in electromechanical conversion. Integration of HOIP ferroelectrics and soft polymers is a promising solution. In this work, a hybrid organic-inorganic rare-earth double perovskite ferroelectric, [RM3HQ]2 RbPr(NO3 )6 (RM3 HQ = (R)-N-methyl-3-hydroxylquinuclidinium) is presented, which possesses multiaxial nature, ferroelasticity and satisfactory piezoelectric properties, including piezoelectric charge coefficient (d33 ) of 102.3 pCN-1 and piezoelectric voltage coefficient (g33 ) of 680×10-3 V m N-1 . The piezoelectric generators (PEG) based on composite films of [RM3HQ]2 RbPr(NO3 )6 @polyurethane (PU) can generate an open-circuit voltage (Voc ) of 30V and short-circuit current (Isc ) of 18µA, representing one of the state-of-the-art PEGs to date. This work has promoted the exploration of new HOIP ferroelectrics and their development of applications in electromechanical conversion devices.

Grain morphology‐dependent dielectric and piezoelectric properties of lead‐free KBT ceramics

AbstractK0.5Bi0.5TiO3 ceramics with cuboid (KBT‐C), rod (KBT‐R), and plate (KBT‐P)‐shaped grains were fabricated via solid‐state reaction and reactive template grain growth (using K2Ti6O13 and K0.5Bi4.5Ti4O15) methods, and the strong dependence of electrical properties on the grain morphology was demonstrated. The average grain sizes of KBT‐R, KBT‐P, and KBT‐C were ∼30 ± 10 μm, 7 ± 1 μm, and 350 ± 50 nm, respectively. While the room temperature dielectric constant decreased for KBT‐R (∼240) and KBT‐P (∼230) from ∼500 for KBT‐C, a significant enhancement in the piezoelectric charge coefficient (d33) was noticed for KBT‐R (∼95 pC/N) and KBT‐P (∼105 pC/N) samples compared to that of KBT‐C ceramic (∼60 pC/N). Accordingly, a large improvement in piezoelectric voltage coefficient (g33) of almost 300% in poled KBT‐R (∼45 × 10−3 Vm/N) and 400% in KBT‐P (∼54 × 10−3 Vm/N) samples over the KBT‐C ceramic was obtained. Interestingly, a significantly lower activation energy (Ea) for KBT‐C (∼0.71 eV) below the temperature of the dielectric maximum (Tm) was noticed compared to KBT‐R (∼1.07 eV) and KBT‐P (∼1.00 eV), suggesting a strong dependence of DC conduction on grain morphology. Furthermore, chronoamperometry measurements confirmed a mixed electronic and ionic conduction at higher temperatures in all samples.

Enhanced Piezoelectric and Dielectric Properties of Lead Free Textured KNN - Epoxy 0-3 Composites

Lead-free textured potassium sodium niobate, (K0.476, Na0.524) NbO3 (KNN), prepared using templated grain growth method (TGG) is used as the filler for the preparation of textured KNN - Epoxy piezoelectric composites. The composites were prepared for 10, 20, 30, 40, 50 volume percent of the filler particles. The prepared composites were polished, electroded and were poled at the rate of 2kV/mm. Lotgering orientation factor (LOF) of 21% is obtained for particles prepared by templated grain growth method. The piezoelectric charge coefficient (d33), dielectric constant and piezoelectric voltage coefficient (g33) were measured. It has been observed that, there is an increase in the piezoelectric and dielectric properties while increasing the KNN filler percentage. The experimentally obtained piezoelectric and dielectric properties have been analyzed and is fitted using the analytical model proposed by Yamada for 0-3 composites for different volume fractions of the constituents.

Piezoelectric self-power supply driven by ferroelastic host–guest supramolecule with considerable electromechanical conversion capability

Crown ether supramolecules with host–guest structure bring the two most advanced application categories, namely information storage and energy conversion. The former was awarded the 2016 Nobel Prize in Chemistry, but the latter has thus far exhibited suboptimal electromechanical conversion properties. Enhancing the piezoelectric properties of such supramolecules has become a continuous and fascinating challenge. Here, we have made breakthrough progress in a crown ether-based ferroelastic supramolecular rotator [(N,N-dimethylethylenediammonium)(18-crown-6)]BF4 (MCBF) under the guidance of the crystallographic engineering. MCBF shows the record-high piezoelectric voltage coefficient (∼1000 × 10-3 V m N−1) and piezoelectric coefficient (∼46.1 pC N−1), which represent respectively improvements of 41.7% and 9.8% compared to the latest reported counterpart (J. Am. Chem. Soc. 145 (2023) 3187–3195). Notably, theoretical calculations elucidate that the ferroelasticity of MCBF contributes to its large piezoelectric response. In addition, an energy harvesting device is successfully achieved for the first time to evaluate its potential as a piezoelectric self-power supply, and LEDs are successfully lit by harvesting mechanical energy. This work takes an important step towards artificial supramolecular machines and arouses broad interest in self-powered flexible devices.

Enhanced piezoelectric properties and depolarization temperature in textured (Bi0.5Na0.5)TiO3-based ceramics via homoepitaxial templated grain growth

Enhanced piezoelectric response was usually achieved in (Bi0.5Na0.5)TiO3 (BNT)-based ceramics with sacrifice of depolarization temperature Td, seriously limiting their usage range in electromechanical applications. In this work, we propose to explore piezoelectric anisotropy and domain engineering in composition & microstructure-controlled textured ceramics to resolve this issue. [001]c-textured 0.94(Bi0.5Na0.5)TiO3–0.06BaTiO3 (0.94BNT-0.06BT) ceramics with Lotgering factor F001∼91% were fabricated through homoepitaxial templated grain growth (TGG) via using 0.94BNT-0.06BT microplatelet templates. The textured samples exhibited more ordered domains with facilitated domain switching behavior, being consistent with saturated high polarization achieved at lower electric fields. Increasing F001 to above 60% enables rapid enhancement of piezoelectric response. Notably, compared to non-textured counterpart, the maximally textured ceramics exhibited ∼236% enhanced piezoelectric coefficient (d33∼302 pC/N) and ∼280% enhanced piezoelectric voltage coefficient (g33∼49.8 × 10−3 Vm/N), together with slightly increased depolarization temperature (Td∼106 °C). Moreover, those values are approaching or even higher than the single-crystal values. This work not only provides important guidelines for design and synthesis of novel textured ceramics with improved comprehensive electrical properties, but also can expand application fields of BNT-based ceramics.

Nanostructured Electrospun Fibers with Self-Assembled Cyclo-L-Tryptophan-L-Tyrosine Dipeptide as Piezoelectric Materials and Optical Second Harmonic Generators.

The potential use of nanostructured dipeptide self-assemblies in materials science for energy harvesting devices is a highly sought-after area of research. Specifically, aromatic cyclo-dipeptides containing tryptophan have garnered attention due to their wide-bandgap semiconductor properties, high mechanical rigidity, photoluminescence, and nonlinear optical behavior. In this study, we present the development of a hybrid system comprising biopolymer electrospun fibers incorporated with the chiral cyclo-dipeptide L-Tryptophan-L-Tyrosine. The resulting nanofibers are wide-bandgap semiconductors (bandgap energy 4.0 eV) consisting of self-assembled nanotubes embedded within a polymer matrix, exhibiting intense blue photoluminescence. Moreover, the cyclo-dipeptide L-Tryptophan-L-Tyrosine incorporated into polycaprolactone nanofibers displays a strong effective second harmonic generation signal of 0.36 pm/V and shows notable piezoelectric properties with a high effective coefficient of 22 pCN-1, a piezoelectric voltage coefficient of geff=1.2 VmN-1 and a peak power density delivered by the nanofiber mat of 0.16μWcm-2. These hybrid systems hold great promise for applications in the field of nanoenergy harvesting and nanophotonics.

Active self-assembly of piezoelectric biomolecular films via synergistic nanoconfinement and in-situ poling

Piezoelectric biomaterials have attracted great attention owing to the recent recognition of the impact of piezoelectricity on biological systems and their potential applications in implantable sensors, actuators, and energy harvesters. However, their practical use is hindered by the weak piezoelectric effect caused by the random polarization of biomaterials and the challenges of large-scale alignment of domains. Here, we present an active self-assembly strategy to tailor piezoelectric biomaterial thin films. The nanoconfinement-induced homogeneous nucleation overcomes the interfacial dependency and allows the electric field applied in-situ to align crystal grains across the entire film. The β-glycine films exhibit an enhanced piezoelectric strain coefficient of 11.2 pm V−1 and an exceptional piezoelectric voltage coefficient of 252 × 10−3 Vm N−1. Of particular significance is that the nanoconfinement effect greatly improves the thermostability before melting (192 °C). This finding offers a generally applicable strategy for constructing high-performance large-sized piezoelectric bio-organic materials for biological and medical microdevices.

Novel lead-free 2–1–2 composite: predicted high piezoelectric sensitivity and significant hydrostatic response

A parallel-connected composite with 2–1–2 connectivity and two lead-free single-crystal (SC) components is proposed. Its high piezoelectric sensitivity is highlighted and its large hydrostatic parameters are described. The first type of composite layer represents a ferroelectric domain-engineered [001]-poled [Li, (K, Na)](Nb, Ta)O3 SC. In the second type of composite layer, piezoelectric Li2B4O7 SC rods in the form of an elliptic cylinder are regularly aligned in a large polymer matrix. The effective electromechanical properties of the composite were found in three stages, using the effective field and matrix methods that are applicable to piezoelectric media. A new orientation effect was studied, linked with rotations of SC rod bases in the polymer medium that forms the second type of layer. Since these rotations are in a Li2B4O7 SC with a unique elastic and piezoelectric anisotropy, the second type of layer exhibits a noticeable influence on the piezoelectric performance and hydrostatic response of the composite. A variation of the aspect ratio of the Li2B4O7 rod base becomes another important factor that can improve the hydrostatic parameters of the composite. Some effective parameters of related 2–1–2 composites were compared for different polymer components. Three diagrams were first constructed for the high-performance 2–1–2 [Li, (K, Na)](Nb, Ta)O3/Li2B4O7/polyethylene composite to show the ranges of rotation angles and volume fractions that correspond to the longitudinal piezoelectric voltage coefficient > 500 mV m N−1, hydrostatic piezoelectric coefficient > 200 mVm N−1 and hydrostatic figure of merit >10−11 Pa−1. These effective parameters are important in piezoelectric sensors and hydroacoustic and other applications of novel lead-free composites.

Boosting the piezoelectric coefficients of flexible dynamic strain sensors made of chemically-deposited ZnO nanowires using compensatory Sb doping

The piezoelectric devices made of ZnO nanowires have received a great interest in the past decade as potential nanogenerators and sensors. However, their characteristics are still limited significantly by the screening of the piezoelectric potential generated under mechanical solicitations, originating from the high density of free electrons in ZnO nanowires. In order to tackle that issue, we develop the compensatory Sb doping of ZnO nanowires grown by chemical bath deposition, both in the low- and high-pH regions using Sb glycolate and ammonia as chemical additives. The adsorption process of Sb(III) species on the positively charged surfaces of ZnO nanowires proceeds through attractive electrostatic forces, resulting in the significant incorporation of Sb dopants with an atomic ratio in the range of 0.11–0.45%. The optical properties of Sb-doped ZnO nanowires exhibit additional phonon modes related to Sb dopants in the range of 500–750 cm-1 in the Raman spectra, and some specific characteristics in the nature and intensity of radiative recombination in the cathodoluminescence spectra. Importantly, the integration of Sb-doped ZnO nanowires encapsulated in PMMA and grown on PDMS into flexible piezoelectric dynamic strain sensors is shown to drastically boost the piezoelectric charge and voltage coefficients by a factor of 2.65 and 1.91, following the significant incorporation of Sb dopants. A subsequent thermal annealing under oxygen atmosphere is revealed to further increase the piezoelectric charge and voltage coefficients by an additional factor of 1.38 and 1.49, following the activation of Sb doping and engineering of hydrogen-related defects. Two figures-of-merit are eventually derived from the piezoelectric charge and voltage coefficients and their values for flexible piezoelectric composites made of annealed Sb-doped ZnO nanowires are compared to more conventional piezoelectric materials, showing their high potential for medical devices. The present findings highlight the strategy consisting in simultaneously introducing compensatory acceptors and engineering hydrogen-related defects to reduce the screening effect, representing an additional powerful way to enhance the characteristics of the piezoelectric devices integrating ZnO nanowires.

Effect of bicontinuous minimal surface meso-scale geometry on piezoelectric performances of piezoelectric composites

This paper examines the effective piezoelectric properties of ceramic-based composite materials that contain bicontinuous minimal surface structures. Three structures are introduced bicontinuous Schwarz P, bicontinuous Gyroid, and bicontinuous I-WP and the material model is subjected to both compressive and tensile stresses. Using the finite element method, the relationship between the average piezoelectric coefficient and the volume fraction of piezoelectric ceramics is analyzed for different structures. The study reveals that the bicontinuous Gyroid structure exhibits the highest average piezoelectric coefficient of 501 pc/N under a compressive stress of 0.5 Gpa and a piezoelectric ceramic volume fraction of 50%. Additionally, the study compares the three bicontinuous minimal surface structures with 3–3 model piezoelectric composite materials (interconnected random distribution) to explore the piezoelectric ceramic transfer path and the impact of arrangement and combination on piezoelectric properties. The results show that bicontinuous minimal surface piezoelectric composite materials display superior piezoelectric properties, as demonstrated by their high piezoelectric charge coefficient, piezoelectric voltage coefficient, and energy harvesting figure of merit. Overall, this paper provides valuable insights into how the structure of piezoelectric ceramics can be altered to enhance the performance of piezoelectric composite materials.

High-Performance [00l]-Textured BiAlO3-Doped K0.5Bi0.5TiO3 Ceramics

[00l] grain-oriented 0.95K0.5Bi0.5TiO3–0.05BiAlO3 (named K5BA-T) ceramics were prepared via the reactive template grain growth (RTGG) and tape casting technique. High-aspect-ratio K5BA powder was prepared using a plate-shape 4-layer aurivillius oxide (K0.5Bi4.5Ti4O15) powder as the template. The effects of grain morphology modification and texturing on the structural, dielectric, and piezoelectric properties of K5BA-T were systematically investigated. The average plate size of ∼6.5 μm with a thickness of ∼400 nm was observed in the K5BA sample. X-ray diffraction (XRD) and bulk texture measurements confirmed the texturing of K5BA-T in the [00l] crystallographic direction with a calculated Lotgering factor of ∼80%. Two anomalies in the temperature-dependent dielectric plot of the poled K5BA-T sample signified additional poling-induced phase transition. A lower value of room-temperature (RT) dielectric constant (εr) of ∼ 200 (at 1 MHz) and a higher piezoelectric charge coefficient (d33) of ∼145 pCN–1 were obtained in the poled K5BA-T ceramic compared to that of the 0.95K0.5Bi0.5TiO3–0.05BiAlO3 ceramic with randomly oriented grains (named K5BA-R). Consequently, the piezoelectric voltage coefficient (g33) estimated for the textured ceramic showed a 650% increment (g33 ∼ 80 × 10–3 V mN–1) over the K5BA-R sample (g33 ∼ 12.5 × 10–3 V mN–1). The transduction coefficient (d33·g33) of K5BA-T ceramic was calculated to be ∼11 600 × 10–15 m2 N–1, which is nearly 9 times higher compared to its random counterpart. Further, a piezodevice fabricated using poled ceramic for energy harvesting showed an output voltage of ∼7 V with a current response of ∼2 μA under normal finger-tapping motion.