Piezoelectric Coefficient D33 Research Articles

Simultaneously enhanced of energy storage and energy harvesting performances of [(Bi0.5Na0.5)TiO3–BaTiO3] ceramics by addition of SrTiO3

As is well known, relaxor dielectrics are characterized by high energy storage efficiency (η), while high recoverable energy storage density (Wrec) can be achieved by anti-ferroelectric ceramics. Herein, our approach is to find relaxor- anti-ferroelectric coexistence phases of (Bi0.5Na0.5)TiO3- BaTiO3 ceramics for achieving high performance in energy storage and energy harvesting as well. Therefore, [(0.9-x) ( Bi0.5Na0.5)TiO3-xSrTiO3-0.1BaTiO3] (abbreviation (0.9-x) NBT-0.1BT-xST) (0.0 ≤ x ≤ 0.4) were synthesized via the solid-state reaction route in air. The tolerance factor (τ) increased from 0.9901 to 0.9998 when ST-content increased from 0.0 to 0.4, indicating an increase in crystal lattice symmetry. The FT-IR de-convolution vibration modes shown in the TiO6 octahedra exhibit two peaks at ∼550 and 650 cm−1, which indicate present coexistence phases of the crystal structure. Ferroelectric to relaxor phase crossover has been detected by the addition of ST with the present anti-ferroelectric phase in particular dopant ST = 0.2. The increasing into the diffused phase transition (γ) is signified by enhancement of the relaxor degree of NBT-BT at high content of ST. The rapidly suppressed remnant polarization (Pr) at high content of ST is due to substitute iso-valence (Sr2+) by tri-valence (Bi3+) and mono-valence (Na1+). Ultrahigh Wrec = 1.13 J/ cm3 with excellent η = 92.62% were obtained at ST = 0.3 at low electric field (E = 110 kV cm−1). A remarkable response of the strain with a high converse piezoelectric coefficient ( d33* = 390.47 pm V−1) at ST = 0.2 was obtained due to decreasing the non-revisable 180° domain switching. Based on the obtained results, the addition of ST to NBT-BT ceramics can provide a head start in the implementation of ceramic capacitors for potential effective into energy harvesting and energy storage applications.

Modified Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 ceramics with high d33，large Qm and high Tc

The development of piezoelectric ceramics with large piezoelectric coefficient (d33), high Curie temperature (Tc) and high mechanical quality factor (Qm) is still a key challenge for practical application for high-power device. Herein, a series of Sm3+ and Mn2+ ions co-doped 0.15Pb(Mg1/3Nb2/3)O3-(0.85-x)PbZrO3-xPbTiO3 ceramics were prepared by the solid-state sintering method. The optimum piezoelectric properties were achieved at x = 0.435 mol% with a large d33 ∼ 450 pC/N and a high Qm ∼ 1968 near the morphotropic phase boundary (MPB), and with high Tc ∼ 296 °C. The origin of this excellent piezoelectric properties was explained by the phase structure, piezoelectric and dielectric analysis. The composition near MPB region and the appearance of defect dipoles leaded to final excellent piezoelectric properties, and made a harmonization between d33, Tc and Qm. This work demonstrated a rational strategy to obtain large d33, high Tc and high Qm for high-power piezoceramics.

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.

Simultaneously realizing reversal of piezoelectric coefficient and enhancement of piezoresponse by chromium-doping in aluminum nitride films

Polarity inversion is an interesting phenomenon in non-centrosymmetric wurtzite-structured aluminum nitride (AlN), which offers an important platform to establish acoustic devices with heteropolar junctions. However, previous studies showed that switching polarity generally resulted in only reversing the piezoelectric coefficient (d33) in AlN films. Here, we discovered that appropriate Cr-doping would not only allow to reverse d33 but also improve piezoelectric response in the c-axis oriented AlN films by co-sputtering dual targets of Cr and Al. Specifically, the d33 was reversed from +2.6 pC/N for the undoped AlN to −2.6 pC/N for the 6.2 at. % Cr-doped CrxAl(1−x)N films. As the Cr-doping ratio increased to 9.3 at. %, d33 was −7.0 pC/N, which was 1.7 times higher than that of the undoped AlN films. Independent PFM phase image measurement offered further evidence of the polarity inversion by comparing the undoped and 9.3 at. % Cr-doped CrxAl(1−x)N films. This work offers a simple doping strategy that allows for simultaneous reversal of piezoelectric coefficient and enhancement of piezoresponse. As a result, it establishes a promising foundation for the design and development of acoustic wave devices featuring heteropolar junctions.

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.

Attempt for excellent piezoelectric performance in Sb-free (K,Na)NbO3-based ceramics

Piezoelectric temperature stability is often a very important item for piezoelectric materials when putting them into practical applications like filters and ultrasonic transducers. Phase transitions of (K,Na)NbO3-based compositions that contain neither toxic Pb nor Sb elements were tailored to simultaneously acquire enhanced piezoelectric properties and good piezoelectric temperature stability in this study. Specifically, dense 0.94(K0.48Na0.52)NbO3-0.03BaZrO3-0.01BaSnO3-0.02(Bi0.5Na0.5)ZrO3 ceramic and its further compositionally modified one by 1 wt% MnO2 were prepared. Both of these two ceramics display quite weak piezoelectric temperature dependence in the usage temperature range between −30 °C–100 °C, but the one modified by MnO2 has the significantly improved piezoelectric properties with a high piezoelectric coefficient d33 of 310 pC/N and large electromechanical coupling factors kp and k33 of 0.57 and 0.73 at room temperature. The obtained excellent piezoelectric performance is considered to be associated closely with the stable piezoelectric characteristic of the orthorhombic phase and the diffused rhombohedral-orthorhombic and orthorhombic-tetragonal phase transitions.

Multiscale Structural Engineering Boosts Piezoelectricity in Na0.5Bi2.5Nb2O9-Based High-Temperature Piezoceramics.

High-temperature piezoelectric materials, which enable the accurate and reliable sensing of physical parameters to guarantee the functional operation of various systems under harsh conditions, are highly demanded. To this end, both large piezoelectricity and high Curie temperature are pivotal figures of merit (FOMs) for high-temperature piezoceramics. Unfortunately, despite intensive pursuits, it remains a formidable challenge to unravel the inverse correlation between these FOMs. Herein, a conceptual material paradigm of multiscale structural engineering was proposed to address this dilemma. The synergistic effects of phase structure reminiscent of a polymorphic phase boundary and refined domain morphology simultaneously contribute to a large piezoelectric coefficient d33 of 30.3 pC/N and a high Curie temperature TC of 740 °C in (LiCeNd) codoped Na0.5Bi2.5Nb2O9 (NBN-LCN) ceramics. More encouragingly, the system has exceptional thermal stability and is nonsusceptible to mechanical loading. This study not only demonstrates that the high-performance and robust NBN-LCN high-temperature piezoceramics hold great potential for implements under harsh conditions but also opens an avenue for integrating antagonistic properties for the enhancement of the collective performance in functional materials.

Enhanced dielectric, ferroelectric and piezoelectric properties of lead-free (Ba,Ca)(Sn,Ti)O3 ceramics by optimisation of sintering temperature

Lead-zirconate-titanate [Pb(Zr,Ti)O3 PZT] crystals possess superior ferroelectric, dielectric and piezoelectric properties. However, due to the toxicity of lead there is a demand for lead-free alternatives. In the present work, we focus on the production of the lead-free (Ba,Ca)(Sn,Ti)O3 (BCST) ceramics via solid-state synthesis method. BCST ceramics calcined at 1050°C, 1100°C, 1150°C, 1200°C and 1250°C were characterized using XRD analysis which showed that at temperatures above 1150°C the structure was free from impurities. Rietveld refinements confirmed a tetragonal structure with P4mm space group for the material calcined at 1150°C. Scanning electron microscopy image analysis of samples sintered at 1200°C, 1250°C and 1300°C showed an increase in grain size and density with temperature. The material sintered at 1300°C had a higher dielectric constant compared to other ceramics. A larger grain size facilitated high ferroelectric polarisation (3.38 μC/cm2), dielectric constant (6100) and d33 piezoelectric coefficient (236 pC/N) for the ceramics. This study demonstrates the potential for using lead-free BCST ceramics for device applications, such as piezoelectric actuators, transducers and ultrasonic motors.

Electromechanical properties of uniaxial polar ionic plastic crystal [(C2H5)4N][FeBrCl3

Abstract Ferroelectric plastic crystals are an emerging class of materials that combine room temperature ferroelectricity and piezoelectricity with a high temperature plastic mesophase prior to melting. These materials offer possibilities for accessing different property parameter spaces from the state-of-the-art metal oxide and polymer ferroelectrics. Tetraethylammonium bromotrichloroferrite, [(C2H5)4N][FeBrCl3], has a unipolar wurtzite-like structure and thus may have potential for small but stable piezoelectric coefficients like the iso-symmetrical AlN. In this study, density functional theory was used to compute elastic compliance, piezoelectric coefficients, and dielectric constant values. Single crystals grown from aqueous solutions were evaluated via single crystal synchrotron x-ray diffraction, impedance spectroscopy and high and weak-field electromechanical characterization. Diffraction studies revealed that the anion tetrahedra orientated preferentially so that the Br− ion had a 30% alignment with the polarization vector. Electromechanical measurements found piezoelectric coefficients in the 5–9 pC N−1 and pm V−1 range. The piezoelectric coefficient (d 33) was most stable with 3.4% variation between 0.4 and 90 Hz and 0.5 and 3 V. Additional piezoelectric stability measurements were made as a function of DC bias field and temperature. Impedance measurements indicate contributions from either intrinsic effects unique to ionic plastic crystals, such as molecular rotation, or the extrinsic effect of electrode interfaces, both of which can play a role in the electromechanical response of the materials. The results show that [(C2H5)4N][FeBrCl3] has potential as a small signal piezoelectric that has a softer elastic moduli than AlN but a stiffer moduli than polyvinylidene fluoride, and thus occupies a unique parameter space.

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.

Enhancing the piezoelectric properties and thermal stability of PMN-PMS-PSZT high-power piezoelectric ceramics through defect engineering

The development of high-power piezoelectric ceramics with superior piezoelectric properties and broad temperature usage ranges is vital for the thriving progress of electromechanical applications. However, achieving high piezoelectricity, high mechanical quality factor, and temperature stability often presents a trade-off. In this study, we present an advanced ceramic material with excellent high-power piezoelectric properties and superior temperature stability. The piezoelectric coefficient d33 reaches 348 pC N−1, the electromechanical coupling factor kp is 54%, the mechanical quality factor Qm is 1501, the dielectric loss tanδ is 0.35%, and the d33 variation is less than 10% within 25–210 °C in 0.05Pb(Mg1/3Nb2/3)O3-0.05Pb(Mn1/3Sb2/3)O3-0.9Pb0.95Sr0.05(Zr0.48Ti0.52)O3 ceramic. The excellent piezoelectricity is attributed to the enhancement of intrinsic ionic displacement and reversible domains wall motion because of symmetry-conforming short-range distribution of oxygen vacancy, while the high Qm is a result of increased domain size and oxygen vacancy. The outstanding temperature stability is related to the stable non-180°domains structure due to the oxygen vacancy pinning effect. These properties hold great potential for advanced applications, particularly for piezoelectric high-power applications requiring constant d33 over a broad temperature range.

Longitudinal and transverse piezoelectric effects of ferroelectret metamaterials with positive and negative Poisson's ratios

A theoretical model has been developed to express the longitudinal and transverse piezoelectric effects in ferro/piezoelectrets. This model is an extension of the classic model based on layer-dielectric structures that focuses on the longitudinal piezoelectric effect. The improved model reveals that the relation between the longitudinal piezoelectric d33 coefficient and the transverse piezoelectric d31 coefficient is associated with Poisson's ratio μ13 (or μ31) and Young's moduli Y1 and Y3. The polarity of the two coefficients is opposite for materials with a positive Poisson's ratio as normally observed in conventional piezoelectric materials, and the same for materials with a negative Poisson's ratio, i.e., auxetic materials. The experimental results available in the literature and obtained from ferroelectret metamaterials with a honeycomb cross-sectional structure and two-dimensional (2D) symmetric structure, called 2D ferroelectret metamaterials, designed and prepared in this study reasonably agree with theoretical predictions. This study not only extends the scope of the metamaterials by inducing the concept of ferroelectret metamaterials but also provides a strategy for designing ferroelectrets with designable properties.

Biodegradable ferroelectric molecular crystal with large piezoelectric response.

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.

A Chiral B−N Adduct as a New Frontier in Ferroelectrics and Piezoelectric Energy Harvesting

AbstractWithin the burgeoning field of electronic materials, B−N Lewis acid‐base pairs, distinguished by their partial charge distribution across boron and nitrogen centers, represent an underexplored class with significant potential. These materials exhibit inherent dipoles and are excellent candidates for ferroelectricity. However, the challenge lies in achieving the optimal combination of hard‐soft acid‐base pairs to yield B−N adducts with stable dipoles. Herein, we present an enantiomeric pair of B−N adducts [R/SC6H5CH(CH3)NH2BF3] (R/SMBA‐BF3) crystallizing in the polar monoclinic P21 space group. The ferroelectric measurements on RMBA‐BF3 gave a rectangular P‐E hysteresis loop with a remnant polarization of 7.65 μC cm−2, a value that aligns with the polarization derived from the extensive density‐functional theory computations. The PFM studies on the drop‐casted film of RMBA‐BF3 further corroborate the existence of ferroelectric domains, displaying characteristic amplitude‐bias butterfly and phase‐bias hysteresis loops. The piezoelectric nature of the RMBA‐BF3 was confirmed by its direct piezoelectric coefficient (d33) value of 3.5 pC N−1 for its pellet. The piezoelectric energy harvesting applications on the sandwich devices fabricated from the as‐made crystals of RMBA‐BF3 gave an open circuit voltage (VPP) of 6.2 V. This work thus underscores the untapped potential of B−N adducts in the field of piezoelectric energy harvesting.

A Chiral B-N Adduct as a New Frontier in Ferroelectrics and Piezoelectric Energy Harvesting.

Within the burgeoning field of electronic materials, B-N Lewis acid-base pairs, distinguished by their partial charge distribution across boron and nitrogen centers, represent an underexplored class with significant potential. These materials exhibit inherent dipoles and are excellent candidates for ferroelectricity. However, the challenge lies in achieving the optimal combination of hard-soft acid-base pairs to yield B-N adducts with stable dipoles. Herein, we present an enantiomeric pair of B-N adducts [R/SC6H5CH(CH3)NH2BF3] (R/SMBA-BF3) crystallizing in the polar monoclinic P21 space group. The ferroelectric measurements on RMBA-BF3 gave a rectangular P-E hysteresis loop with a remnant polarization of 7.65 μC cm-2, a value that aligns with the polarization derived from the extensive density-functional theory computations. The PFM studies on the drop-casted film of RMBA-BF3 further corroborate the existence of ferroelectric domains, displaying characteristic amplitude-bias butterfly and phase-bias hysteresis loops. The piezoelectric nature of the RMBA-BF3 was confirmed by its direct piezoelectric coefficient (d33) value of 3.5 pC N-1 for its pellet. The piezoelectric energy harvesting applications on the sandwich devices fabricated from the as-made crystals of RMBA-BF3 gave an open circuit voltage (VPP) of 6.2 V. This work thus underscores the untapped potential of B-N adducts in the field of piezoelectric energy harvesting.

BaHf0.05Ti0.95O3 Ceramics from Sol-Gel and Solid-State Processes: Application to the Modelling of Piezoelectric Energy Harvesters.

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 d33∗ 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.

Disclosing the dependencies of ferroelectric and piezoelectric performances on crystalline states of P(VDF‐TrFE) films by molecular dynamics simulations

AbstractWe present a molecular dynamics simulation method including x‐ray diffractometer pattern calculation, mean square displacement (MSD), and nonbonding energy distribution (NED) to disclose the dependencies of condensed structure on its crystalline process of the poly(vinylidene fluoride‐trifluoroethylene) (P(VDF‐TrFE)) films. For comparison, the P(VDF‐TrFE) solution is casted into the films, and followed that different thermal processes are performed to fabricate the crystalline states of the films. Simulation and experimental results have good consistency, indicating that high temperature annealing can effectively promote all‐trans β phase in the crystal region of P(VDF‐TrFE). As such, P(VDF‐TrFE) 80/20 mol% annealing at 140°C shows a higher MSD (~27.5 Å2) and a faster reducing rate of NED than that of other films, contributing to a large maximum polarization (Ps) of ~15.5 μC cm−2, high a remnant polarization (Pr) of ~11.8 μC cm−2, and an attractive piezoelectric strain coefficient (d33) of −27.1 pC N−1 under 200 MV m−1, respectively, and providing a reference for the applications of P(VDF‐TrFE) in flexible sensors, actuators, transducers, and so forth.

Rashba spin-splitting and spin Hall effect in Janus monolayers Sb2XSX’ (X, X’= S, Se, or Te; X ≠ X’)

The combined influence of spin–orbit coupling and spatial inversion asymmetry leads to an enhancement of electronic properties, including Rashba spin-splittings as well as spin Hall effect. Recent research has shown the possibility to create two-dimensional Janus materials with inherent structural asymmetry. In this work, the structural stability, piezoelectricity, electronic properties, and intrinsic spin Hall conductivity of quintuple-layer atomic Janus Sb2XSX’ (X, X’ = S, Se, Te; X ≠ X’) monolayers are investigated using first-principles calculations within the framework of density functional theory. They demonstrate relatively high in-plane piezoelectric coefficients (d22) and also possess out-of-plane piezoelectric coefficients (d31), which is due to the breaking of inversion symmetry in the crystal structure with the space group P3m1. Large Rashba parameters are obtained in Janus Sb2XSX’ monolayers, especially high for Sb2S2Te (1.62 eV Å) and Sb2SeSTe (1.33 eV Å) due to strong spin–orbit coupling. Moreover, Rashba-like spin-splitting is also observed in the edge-states as well, which is highest for Sb2SeSTe with 2.17 eV Å. Furthermore, Sb2S2Te and Sb2SeSTe monolayers reveal a significantly high Berry curvature (65.59 and 61.05 Bohr2), spin Berry curvature (−118.4 and −120.6 Bohr2), and spin Hall conductivity (1.8 and 1.6 e2/h). Our results suggest that Janus Sb2S2Te and Sb2SeSTe monolayers could be an excellent platform for multifunctional electronic applications.

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.

Enhancing Manufacturability of SU-8 Piezoelectric Composite Films for Microsystem Applications.

Piezoelectric thin films are extensively used as sensing or actuating layers in various micro-electromechanical systems (MEMS) applications. However, most piezoelectrics are stiff ceramics, and current polymer piezoelectrics are not compatible with microfabrication due to their low Curie Temperature. Recent polymer-composite piezoelectrics have gained interest but can be difficult to pattern. Photodefinable piezoelectric films could resolve these challenges by reducing the manufacturability steps by eliminating the etching process. But they typically have poor resolution and thickness properties. This study explores methods of enhancing the manufacturability of piezoelectric composite films by optimizing the process parameters and synthesis of SU-8 piezo-composite materials. Piezoelectric ceramic powders (barium titanate (BTO) and lead zirconate titanate (PZT)) were integrated into SU-8, a negative epoxy-based photoresist, to produce high-resolution composites in a non-cleanroom environment. I-line (365 nm) light was used to enhance resolution compared to broadband lithography. Two variations of SU-8 were prepared by thinning down SU-8 3050 and SU-8 3005. Different weight percentages of the piezoelectric powders were investigated: 5, 10, 15 and 20 wt.% along with varied photolithography processing parameters. The composites' transmittance properties were characterized using UV-Vis spectroscopy and the films' crystallinity was determined using X-ray diffraction (XRD). The 0-3 SU-8/piezo composites demonstrated resolutions < 2 μm while maintaining bulk piezoelectric coefficients d33 > 5 pm V-1. The films were developed with thicknesses >10 μm. Stacked layers were achieved and demonstrated significantly higher d33 properties.