Piezoelectric Applications Research Articles

Discrete ZnO p-n homojunction piezoelectric arrays for self-powered human motion monitoring

Zinc oxide (ZnO), as a typical piezoelectric semiconductor, has gained significant attention in the field of wearable electromechanical coupling. However, the presence of an intrinsic screening effect becomes a bottleneck in developing high-performance ZnO-based piezoelectric devices. To address this limitation, we propose the formation of p-n homojunction by La doping in ZnO nanorods (NRs) as well as discrete structural design to improve their electrical output and flexibility. The enhanced performance and the mechanism behind it are explored and revealed in terms of morphology, structure, built-in electric field, depletion layer width, and junction capacitance, respectively. Benefitting from the excellent electromechanical coupling performance of the developed devices, different human motions can be recognized and classified with the aid of machine learning. These findings provide a new insight into the impact of doping on the output performance of piezoelectric semiconductor devices, thus facilitating advancements in piezoelectric device design and application exploration.

Impact of sintering time on structure and electrical properties of Pb-free BNT-BKT-SZ ceramics

The work focuses on preparing and characterising BNT-based ceramics via a solidstate method. To investigate the phase, microstructure, and physical and electrical properties of BNT-based ceramics.Lead-free piezoelectric bismuth sodium titanate – bismuth potassium titanate – stronsium zirconate (BNT-BKT-SZ) ceramics were fabricated by the solid-state reaction method. The effect of sintering temperature with soaking times of 2, 4, and 6 h at 1150C on structural, microstructure, density, porosity, and electrical properties was examined. The phase formation of the ceramics was examined using X-ray diffraction (XRD). Scanning electron microscopy (SEM) (JEOL JSM5910LV) was employed to investigate ceramic microstructure. The bulk density and mechanical properties of the sample were measured using Archimedes’ method, respectively. The electrical properties of ceramics, such as dielectrics, ferroelectrics, and piezoelectrics, were investigated.XRD showed all samples had a single perovskite structure and no secondary phase. All sintered samples at different temperatures have a coexisting phase boundary between the rhombohedral phase and the tetragonal phase. The sintered ceramic at 1150C with a soaking time of 4 h shows a maximum density of 5.89 g/cm3. In addition, the temperature at which the sintering process is carried out substantially impacts the electrical characteristics. Dielectric and electric field-induced strain (Smax) properties that sintered at 1150C with a soaking time of 4 h exhibited the highest values of 4.489 and 0.39% (d33* of 650 pm/V), respectively.The impact of the coercive field on the electrical breakdown characteristics of ceramics should be investigated further in the course of research that has to be carried out.The characterisation confirmed the effects of sintering temperature on the physical, phase, microstructure, and electrical properties of BNT-based ceramics.Such research demonstrates a suitable sintering temperature for producing BNT-BKT-SZ. The mechanical and electrical properties of a material are dependent on its sintering parameters. The ceramic system is suitable for piezoelectric and/or energy storage applications.

Interface structures of Al0.85Sc0.15N-on-Si thin films grown by reactive magnetron sputtering upon post-growth cyclic rapid thermal annealing

Al0.85Sc0.15N thin films, about 920 nm thick, have been deposited on the Si (001) substrate by reactive magnetron sputtering at 600 °C. X-ray diffraction and pole-figure measurements revealed [0002]-oriented texture structures of the nitride films without any phase separations before and after cyclic annealing at 600–900 °C for up to 48 min. Cross-sectional studies by transmission electron microscopy and energy dispersive x-ray analysis revealed an intermediate Al0.85Sc0.15N layer of ∼24.6 nm thick with smaller grains and tilted [0002]-orientations compared to its overlayer, i.e., a nucleation layer (NL), on the Si substrate. After annealing, apparent morphological changes have been observed at the near-interface regions, including the NL, the NL/Si interface, and the Si substrate, rather than in the Al0.85Sc0.15N overlay. Undesired oxygen has been observed in the nitride film and its composition increased during post-growth thermal annealing without forming oxides. These observations shed new light on crystal growth and post-growth thermal annealing of AlScN toward their high-performance piezoelectric applications.

Hydrothermally grown pure and Er-doped ZnS nanocrystals based flexible piezoelectric nanogenerator for energy harvesting and sensing applications

Pure zinc sulphide (ZnS) and Er-doped ZnS nanocrystals were grown by hydrothermal method at low temperature. Powder XRD analysis reveals the formation of wurtzite hexagonal phase structure for both pure and Er-doped ZnS samples. Morphology of 2D nanocrystals for both pure and doped ZnS nanocrystals was confirmed by FESEM technique. Presence of Er element in Er-doped ZnS was confirmed by energy-dispersive X-ray spectroscopy. Further, both pure and Er-doped nanocrystals have been used as piezoelectric fillers in polydimethylsiloxane (PDMS) for the fabrication of flexible piezoelectric nanogenerators. The Er-doped ZnS based nanogenerator showed almost 9 times (∼ 36 V) higher open circuit voltage as compared to pure ZnS based nanogenerator (∼ 4 V). Then, Er-doped ZnS nanocrystals based device was used to harvest the mechanical energy under the human walking and running conditions. Also, this device generated significant electrical signal under the human elbow bending. The output performances of Er-doped ZnS based device indicates that it can be a potential candidate for mechanical energy harvesting under various human body motions as well as for wearable piezoelectric sensor applications.

Experimental and theoretical study of Gd2O3 added pseudo-tetragonal Bi3TaTiO9-based ceramics for ferroelectric, electric and high-temperature piezoelectric applications

The present global energy crisis, along with the development of modern technologies, has compelled the scientists to search for smart materials, which possess the multifunctional properties simultaneously. Among such materials, bismuth-layered structure ferroelectrics (BLSFs) containing a perovskite structure have demonstrated the tendency to play a vital role. Herein, we report an engineered Gd2O3 added Bi3TiTa0·5Nb0·5O9 (BTTN) based material with composition Bi3TiTa0·5Nb0·5O9:xwt%Gd2O3 (BTTN:xGd) with x = 0–0.20 ceramics to investigate the ferroelectric, electric, piezoelectric and dielectric properties of the material. Highly dense (relative density of ∼96%) BTTN:0.15Gd has shown the best merits among all other compositions with improved remnant polarization (Pr ∼ 7.86 μC/cm2), energy conversion efficiency (ƞ) of ∼63.48%, resistance of ∼2.2 × 1010 Ω and high piezoelectric co-efficient (d33 ∼ 25 pC/N) at room temperature, which are much improved than pure BTTO or BTTN ceramics. Nonetheless, ceramic has shown the stable resistivity of ∼104 Ω at 500 °C, with a stable d33 value of 22 pC/N (just 12% drop) after annealing at 600 °C. The ferroelectric to paraelectric phase transition of ceramic with the highest dielectric constant is reported at Curie temperature (TC) of 859 °C. Additionally, Density-Functional-Theory (DFT) and Density-Functional-Perturbation-Theory (DFPT) measurements are performed by employing generalized gradient approximation using the Quantum-ESPRESSO code. Structural, ferroelectric and electronic properties of BTTO, BTTN and Gd-added BTTN compounds are investigated. The calculated formation energies confirmed the thermodynamic stability of pseudo-tetragonal Gd-added BTTN compounds. Using the Berry-phase approach for piezoelectric materials, the calculated maximum polarization is 54.00 μC/cm2, which is in agreement with values obtained experimentally. Mentioned outcomes of the material clearly represent the potential of the BTTN:0.15Gd ceramic for the utilization in high-temperature piezoelectric devices.

Piezoelectric Applications of Low-Dimensional Composites and Porous Materials.

Low-dimensional (LD) materials, with atomically thin anisotropic structures, exhibit remarkable physical and chemical properties, prominently featuring piezoelectricity resulting from the absence of centrosymmetry. This characteristic has led to diverse applications, including sensors, actuators, and micro- and nanoelectromechanical systems. While piezoelectric effects are observed across zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D) LD materials, challenges such as effective charge separation and crystal structure imperfections limit their full potential. Addressing these issues requires innovative solutions, with the integration of LD materials with polymers, ceramics, metals, and other porous materials proving a key strategy to significantly enhance piezoelectric properties. This review comprehensively covers recent advances in synthesizing and characterizing piezoelectric composites based on LD materials and porous materials. The synergistic combination of LD materials with other substances, especially porous materials, demonstrates notable performance improvements, addressing inherent challenges. The review also explores future directions and challenges in developing these composite materials, highlighting potential applications across various technological domains.

Nano-electro-mechanical conduct of boron nitride nanotube as piezoelectric nanogenerators and nanoswitches

This study investigates various aspects related to the Internet of Things (IoT) and piezoelectric nanoswitches applications, including the frequency band and set-up of piezoelectric nanogenerators, the electrical-mechanical interactions of nanoswitch arrays and their switching times. To address these issues, the molecular dynamics simulations conducted to investigate the performance of a boron nitride nanotube (BNNT) in piezoelectric nanogenerator and nanoswitch applications. For the piezoelectric nanogenerator, BNNT with a diameter-to-length ratio of 0.09 and subjected to 1% compressing exhibited a bistable configuration with a snap-through activation energy of 0.8 meV and a resonance frequency of 48 GHz. These resonance conditions can be achieved by millimeter-wave frequencies under the U-band (40–60 GHz), resulting in axial polarization of 4 mC.m−2 and axial voltage of 13.4 volts. These results demonstrate the potential of BNNT as a broadband and non-linear piezoelectric nanogenerator. For piezoelectric nanoswitches applications, the BNNT zigzag type with a diameter-to-length ratio of 0.32 and subjected to 2.5% compressing displayed 0.017 C.m−2 axial polarization, 22 V axial voltage, and a rapid switching time of approximately 2.0 ns.

Organic Polar Crystals, Second Harmonic Generation, and Piezoelectric Effects from Heteroadamantanes in the Space Group R3m.

Polar crystalline materials, a subset of the non-centrosymmetric materials, are highly sought after. Their symmetry properties make them pyroelectric and also piezoelectric and capable of second-harmonic generation (SHG). For SHG and piezoelectric applications, metal oxides are commonly used. The advantages of oxides are durability and hardness - downsides are the need for high-temperature synthesis/processing and often the need to include toxic metals. Organic polar crystals, on the other hand, can avoid toxic metals and can be amenable to solution-state processing. While the vast majority of polar organic molecules crystallize in non-polar space groups, we found that both 7-chloro-1,3,5-triazaadamantane, for short Cl-TAA, and also the related Br-TAA (but not I-TAA) form polar crystals in the space group R3m, easily obtained from dichloromethane solution. Measurements confirm piezoelectric and SHG properties for Cl-TAA and Br-TAA. When the two species are crystallized together, solid solutions form, suggesting that properties of future materials can be tuned continuously.

Unveiling the role of vanadium doping in modulating morphological and electrical properties of piezoelectric Na0.46K0.46Li0.08NbO3 ceramics for energy harvesting

We report the enhancement of ferro/piezo-electric properties of lead-free alkali based perovskite Na0.46K0.46Li0.08NbO3 (NKLN) by vanadium doping (NKLNV) for high performing piezoelectric devices. Lead-free NKLN and NKLNV ceramics are synthesized via solid state reaction route as a substitute to the lead-based ceramic for the applications in sensors, transducers, and other electronic devices. The structural phase of synthesized ceramics is found to be pure perovskite as observed from powder X-ray diffraction. In dielectric studies, Curie temperature is found to be around 450 °C for both the samples. SEM images revealed the formation of homogeneous microstructure with well-defined grains. Dense polycrystalline ceramics having grain size of about 5 μm are obtained as a result of sintering at optimised temperature of 1050 °C. The micrographs showed that the grain size begins to evolve with reduced porosity in vanadium doped NKLN. Vicker's microhardness indentation test is performed for different loads at dwell time of 30 s, in which it was observed that the V-doping has enhanced the hardness. In ferroelectric studies, NKLNV shows higher value of remnant polarization as compared to NKLN as observed in P-E hysteresis loop. Fine microstructure and larger grain size felicitated the movement and reorientation of dipoles which resulted in enhanced piezoelectric coefficient for vanadium substituted NKLN ceramics. Flexible energy harvesters were fabricated by making a composite with PDMS, and then coating a thick film over ITO/PET sheet. NKLNV-based flexible device showed an improvement in open-circuit output voltage of 13.8 V under gentle finger tapping. NKLNV ceramics are a viable lead-free alternative for dielectric, piezoelectric, and ferroelectric applications.

Janus Zn3CdC2 and ZnCd3C2 monolayers in carbides: A first-principles study

In this work, two Janus carbides, Zn3CdC2 and ZnCd3C2 monolayers, are designed. The stability, electronic, mechanical, piezoelectric, and light absorption properties are investigated using the first-principles calculations. The results demonstrate that both structures are chemically, dynamically, and thermodynamically stable. A direct bandgap semiconductor, the ZnCd3C2 monolayer has a bandgap of 1.82 eV, while the indirect bandgap semiconductor Zn3CdC2 monolayer has a slightly larger gap of 2.03 eV. However, Zn3CdC2 monolayer can be transformed into a direct bandgap semiconductor by applying biaxial compression at 2%. The mechanical properties indicate that both materials possess significant mechanical anisotropy, high flexibility, and distinctive deformation pattern. More strikingly, two Janus monolayers display out-of-plane piezoelectric properties due to their noninversion symmetry and out-of-plane asymmetry structures. At the same time, the different charge transfer amounts along the x and y directions give them unequal out-of-plane piezoelectric coefficients d31 and d32. For Zn3CdC2 monolayer, the value of d31 is −0.52 pm/V, and the value of d32 is 0.25 pm/V; The values of d31 and d32 for ZnCd3C2 monolayer reach −0.32 pm/V and 0.27 pm/V, respectively. In addition, Zn3CdC2 and ZnCd3C2 monolayers have strong light absorption coefficients as high as 105 cm−1 in visible and ultraviolet bands. Our works reveal that the two Janus monolayers have great potential in piezoelectric, photovoltaic, and other sustainable energy applications.

Macro-dipoles in soft/hard expanded-polytetrafluoroethylene + fluoroethylenepropylene (ePTFE + FEP) fluoropolymer-film systems for high-output piezoelectric ferroelectret-transducer applications

Multi-layer ferroelectrets consisting of fluoroethylenepropylene (FEP) copolymer and open-porous expanded polytetrafluoroethylene (ePTFE) films exhibit stable internal electret charges, high piezoelectric coefficients and heat resistance, making them promising candidates for wearable sensors or nanogenerators in body-area networks. Here, three- and five-layer (FEP/ePTFE/FEP and FEP/ePTFE/FEP/ePTFE/FEP) ferroelectret stacks were laminated and poled in a corona discharge. The resulting charge distributions were measured by use of the pulsed electro-acoustic (PEA) method and revealed that charges of opposite polarity were trapped at the interfaces between the FEP and ePTFE layers. Thus, the existence of one macro-dipole in the three-layer structure and of two macro-dipoles in the five-layer structure was directly shown for the first time. Moreover, electric-displacement-versus-electric-field (D-E) loops revealed that remnant polarization is given by the number of macro-dipoles in the respective stack. Due to the addition of the macro-dipoles, the piezoelectric d 33 coefficient of the FEP/ePTFE/FEP/ePTFE/FEP stack reaches 200 pC/N even under a potentially non-uniform compression of the soft ePTFE layers. The results should be useful for a better understanding and a performance optimization of ferroelectrets in self-powered intelligent devices.

Synthesis and Characterization of Mg and Ti Co-Doped Bismuth Ferrite for Piezoelectric Application

Synthesis and Characterization of Mg and Ti Co-Doped Bismuth Ferrite for Piezoelectric Application

(PS-PMMA-ZnO) nanocomposites fabrication and investigation their electrical properties for piezoelectric application

Nanocomposites have a cheap cost and a low weight, making them an attractive option for a variety of applications, including industrial, environmental, and medical. For use in electrical applications, nanocomposites made of polystyrene, polymethyl methacrylate, and zinc oxide have been processed to produce piezoelectric materials. Various concentrations of ZnO nanoparticles were mixed into a polymer blend composed of (PS-PMMA), with those concentrations being (0, 2, 4, 6, and 8) weight percent. Nanocomposites were investigated both in terms of their structure and their electrical properties. The direct current electrical conductivity for (PS-PMMA-ZnO) nanocomposites increases with both increase at temperature and increase in ZnO nanoparticles concentration, activation energy decreases where concentration of ZnO nanoparticles increase. When applied electric field frequency increase, A.C electrical characteristics showed that both dielectric constant (ε^') and dielectric loss (ε^'') for (PS-PMMA-ZnO) nanocomposites decreased, whereas alternating current electrical conductivity increased. When increase concentration of ZnO nanoparticles, a (PS-PMMA) polymer blend demonstrates an increase in its ε^', ε^'', and σ_(A.C). The findings from the piezoelectric application that the increase in pressure cause decrease in the electrical resistance for (PS-PMMA-ZnO) nanocomposites.

Two-dimensional Janus XWZAZ' (X = S, Se, Te; A = Si, Ge; Z, Z' = N, P, As): candidates for photocatalytic water splitting and piezoelectric materials.

Due to their extraordinary properties, particularly the presence of an inherent electric field that effectively suppresses the recombination of photogenerated carriers, Janus two-dimensional (2D) materials exhibit strong light absorption and high solar-to-hydrogen conversion efficiency, making them promising candidates for photocatalytic water splitting applications. In this study, we conducted first-principles calculations to investigate the layers XWZAZ' (X = S, Se, Te; A = Si, Ge; Z, Z' = N, P, As; Z ≠ Z'). Out of 36 possible structures, 25 were found to be stable in terms of their dynamic, thermal, and mechanical properties. Among these 25 stable structures, 22 exhibit semiconductor behavior. Notably, 9 of these semiconductor structures demonstrate excellent photocatalytic and light absorption properties. These 9 photocatalysts possess remarkable light absorption rates (∼23%), high solar-to-hydrogen energy conversion efficiencies (38.447%), ultra-high carrier mobilities (101 596.37 cm2 s-1 V-1), and spontaneous hydrogen evolution reaction (HER) capabilities. Furthermore, all 22 semiconductor structures display significant piezoelectric responses both in-plane and out-of-plane, and biaxial strain has a considerable impact on the properties of the 25 stable structures. This study not only provides potential candidate materials for photocatalytic and piezoelectric applications but also offers theoretical guidance for addressing energy crises and environmental pollution challenges.

Ultra-high piezoelectric properties and ultra-high Curie temperature of Li/Ce-doped La2Ti2O7 ceramics.

The demand for ultra-high-temperature piezoelectric sensors in industrial applications has witnessed a rapid upsurge. In this study, the piezoelectric properties of La2Ti2O7 (LTO) piezoelectric ceramics with a perovskite-like layered structure were enhanced by doping with Li/Ce ions. It was found that a remarkable 300% enhancement in the piezoelectric constant (d33) value was achieved in Li/Ce-doped LTO ceramics compared to their pristine counterparts, reaching 6.4 pC N-1 at room temperature with an ultra-high Curie temperature of 1408 °C. After annealing at 500 °C, the d33 value of the samples can be further improved to 7.4 pC N-1. Moreover, temperature-dependent resistivity measurements indicate that even at 1000 °C, the ceramics exhibit a high resistivity of 8.9 × 105 Ω cm. By combining X-ray diffraction, Raman spectra, transmission electron microscopy and piezoresponse force microscopy data, the enhanced piezoelectricity of the ceramics is attributed to local heterogeneity induced by Li/Ce doping. Our results unequivocally demonstrate the suitability of modified LTO ceramics for ultra-high-temperature piezoelectric applications.

Metal-free small molecule-based piezoelectric energy harvesters.

Organic and metal-free molecules with piezoelectric and ferroelectric properties have gained wide interest for their applications in the domain of mechanical energy harvesting due to their desirable properties such as light weight, thermal stability, mechanical flexibility, feasibility to achieve high Curie temperatures, and ease of synthesis. However, the understanding and design of these materials for piezoelectric energy harvesting applications is still in its early stages. This review paper presents a comprehensive overview of the fundamental characterization of piezoelectricity for a range of organic ferro- and piezoelectric materials and their composites. It also discusses the limitations of traditional piezoelectric materials and highlights the advantages of organic materials in this area in the introduction part. In addition, the paper provides a detailed description of peptide-based and other biomolecular piezoelectric materials as a bio-friendly alternative to current materials. This perspective aims to guide researchers in designing functional organic materials and composites for practical mechanical energy harvesting applications and to highlight current limitations and future perspectives in this emerging area of research.

Two-dimensional Janus SeMoZAZ′ (A = Si, Ge; Z = N, P, As; Z ≠ Z′): multifunctional properties for electronic, piezoelectric and photocatalytic applications

2D Janus SeMoZAZ′ monolayers exhibit excellent photocatalytic and piezoelectric properties.

Recent advances in MXene-based composites for piezoelectric sensors.

Piezoelectric sensors are crucial in medical, industrial, and consumer electronics applications, yet their performance and sensitivity often fall short due to the limitations in current piezoelectric materials. To address these deficiencies, significant research has been directed towards developing composite materials that enhance piezoelectric properties by integrating piezoelectric materials with various fillers. MXenes, a novel class of 2D transition metal carbides/nitrides, exhibit remarkable properties such as high electrical conductivity, mechanical strength, and chemical stability. These characteristics, along with a high surface area and hydrophilicity, make MXenes an ideal additive for preparing piezoelectric composites with improved properties. Despite existing reviews on MXenes in sensor applications, only a few have systematically explored their role in piezoelectric sensors. This review provides a comprehensive analysis of MXene-based piezoelectric sensors, examining the impact of different composites on piezoelectric properties, synthesis methods, structural designs, and application areas. While promising, challenges such as scalability, reproducibility, and environmental stability must be addressed to fully realize the potential of MXene-based composites. This comprehensive analysis highlights the advancements, opportunities for further development, and the transformative potential of MXenes in the next generation of high-performance, multifunctional piezoelectric sensors.

Investigation on the growth aspects and properties of rubidium hydrogen succinate hydrate single crystal for NLO applications.

A novel semiorganic nonlinear optical single crystal of rubidium hydrogen succinate hydrate (RbHSH) was grown at room temperature using the slow evaporation solution growth technique (SEST) with water as a solvent for nonlinear optical applications. The grown crystal is a triclinic system with a centrosymmetric space group of P1̄ and the compound is stabilized by intramolecular O-H-O and C-H-O bonding. FTIR spectral studies were used to determine the various functional groups present in the material. The optical transmission spectra of the grown crystal demonstrated that a transparency of 89%, with a low cut off wavelength of 240 nm and an energy band gap of 5.21 eV, which is beneficial to developing advanced photonic and optoelectronic devices in the solar blind UV area. The grown crystal is thermally stable upto 174 °C. The electrical properties of RbHSH crystal exhibit low dielectric loss and a low dielectric constant at high frequencies tends to have good optical characteristics. Mechanical analysis demonstrated that the grown crystal shows the normal indentation size effect (ISE) and falls into the hard material category with n = 1.4. Photoconductivity measurements revealed negative photoconductivity. Photoluminescence studies showed that RbHSH emits blue light with a wavelength of 484 nm. Hirshfeld surface analysis was used to analyze intermolecular interactions in the RbHSH crystal. The grown RbHSH crystal piezoelectric charge coefficient have been calculated (d33 = 13 pC N-1) and it is suitable for piezoelectric device applications. Under continuous-wave laser excitation, the third order nonlinear refractive index (n2), absorption coefficient (β), and susceptibility (χ(3)) of the RbHSH crystal were found to be 1.6639 × 10-12 (cm2 W-1), 1.1739 × 10-5 (cm W-1) and 4.86331 × 10-9 esu, respectively.

Well-balanced performance achieved in PZT piezoceramics via a multiscale regulation strategy.

Emerging high-power piezoelectric applications demand the development of piezoelectric materials featuring both a high mechanical quality factor (Qm) and a large piezoelectric coefficient (d33). However, it is widely accepted that an increase in d33 is usually accompanied with a decrease in Qm, and vice versa. Herein, a multiscale regulation strategy is proposed to improve Qm and d33 simultaneously from the perspectives of phase structure, ferroelectric domains, and lattice defects. A well-balanced combination of electromechanical performances with Qm = 726, d33 = 502 pC N-1, kp = 0.69, tan δ = 0.0024, and TC = 267 °C was obtained. Through structural characterization, it was observed that the morphotropic phase boundary and enhanced dispersion behavior lead to a lowered energy barrier, which contributes to polarization rotation and enhances piezoelectric performance. At the same time, the excellent piezoelectric performances also benefit from the highly oriented domain structure and small domain size after high-temperature poling. Furthermore, the segregation of Ba2+ causes A-site defects in the crystal lattice, accompanied with an increase in oxygen vacancies, which maintains the hardening effect of the ceramics. This study proposes a multiscale regulation strategy, providing insights for the design of high-power piezoelectric ceramics with high d33 and Qm.