Piezoelectric Coefficient Research Articles

Improved piezoelectric properties of 2–2 piezoelectric single crystal composites for acoustic transducer applications via alternating current polarization

Piezoelectric single-crystal composites with 2–2 type (2–2 PSCCs) have attracted widespread attention in acoustic transducer applications due to the higher hydroacoustic piezoelectricity and electromechanical coupling performance compared to traditional ceramic piezoelectric composites. At present, alternating current polarization (ACP) has been proven as an effective method to improve the performance of piezoelectric materials. Here, to optimize the conditions of ACP, the influence of ACP on the properties of 2–2 PSCCs with different amplitudes, frequencies, and polarization cycles of the electric field was investigated. Compared to direct current polarized (DCP) samples, the piezoelectric coefficient (d33), the relative free dielectric permittivity (ε33T/ε0), and the thickness electromechanical coupling factor (kt) of ACP samples were improved by 36%, 60%, and 3.5% respectively. Furtherly, the domain structure of DCP and ACP samples was compared, and the result demonstrates that the improvement in piezoelectric and dielectric properties is related to the grown domain size in single crystals. This work shows a simple and effective method to improve the performance of 2–2 PSCCs.

Structural, nanomechanical, and piezoelectric properties of lead-free orthorhombic and tetragonal K0.35Na 0.65Nb0.97Sb0.03O3 piezo-ceramics

Materials based on ferroelectric ceramics exhibit piezoelectric, electro-optical, acousto-optical, and nonlinear optical coefficient properties. The synthesis of the lead-free ceramic was carried out by mechanical grinding. This article aims to accurately determine the tetragonal and orthorhombic phases of a lead-free ferroelectric ceramic K0.35Na0.65Nb0.97Sb0.03O3. As well as its structural analysis by Rietveld analysis, the chemical composition of the items contained VEELS and CEELS. The characteristic peak associated with perovskite structures is observed at 950 °C. Showing behavior different for each temperature, with an apparent orthorhombic structure at 950 °C and an apparent mixture of orthorhombic-tetragonal phases up to an apparent tetragonal dominant phase at 1200 °C.The mechanical and piezoelectric properties were evaluated using nanoindentation and SS-PFM, obtaining better ferroelastic and piezoelectric properties in the tetragonal phase than in the orthorhombic phase.

A Highly Flexible Piezoelectric Ultrasonic Sensor for Wearable Bone Density Testing.

Driven by the loss of bone calcium, the elderly are prone to osteoporosis, and regular routine checks on bone status are necessary, which mainly rely on bone testing equipment. Therefore, wearable real-time healthcare devices have become a research hotspot. Herein, we designed a high-performance flexible ultrasonic bone testing system using axial transmission technology based on quantitative ultrasound theory. First, a new rare-earth-element-doped PMN-PZT piezoelectric ceramic was synthesized using a solid-state reaction, and characterized by X-ray diffraction and SEM. Both a high piezoelectric coefficient d33 = 525 pC/N and electromechanical coupling factors of k33 = 0.77, kt = 0.58 and kp = 0.63 were achieved in 1%La/Sm-doped 0.17 PMN-0.47 PZ-0.36 PT ceramics. Combining a flexible PDMS substrate with an ultrasonic array, a flexible hardware circuit was designed which includes a pulse excitation module, ultrasound array module, amplification module, filter module, digital-to-analog conversion module and wireless transmission module, showing high power transfer efficiency and power intensity with values of 35% and 55.4 mW/cm2, respectively. Finally, the humerus, femur and fibula were examined by the flexible device attached to the skin, and the bone condition was displayed in real time on the mobile client, which indicates the potential clinical application of this device in the field of wearable healthcare.

New insights into the effect of glass addition on the piezoelectric and thermal stability properties of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 Pb-free ceramic by defect engineering of MPB

Lead-free piezoceramics with superior piezoelectric properties don't meet the requirements of practical applications due to their lower phase transition temperature and poor thermal stability. In the present work, we report a new insight into the effect of glass phase on the piezoelectric, Curie temperature and thermal stability of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCZT) ceramic. Unlike traditional glass materials with more than 80% of B2O3 and SiO2 as glass formers, our approach is to fabricate a glass phase (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3-0.05B2O3 (abbreviate BBCZT) with the same elements and concentrations as the ceramic phase. The ceramics-doped glass samples with the composition [(1-x)BCZT-xBBCZT], where x=(0.0, 0.025, 0.05, 0.075 and 0.1 wt%), were sintered according to the glass phase content. The effect of BBCZT glass composition on the crystal structure, dielectric, ferroelectric and piezoelectric properties of BCZT was investigated in detail. X-ray diffraction revealed that the addition of glass phase causes a defect engineering of the tricritical triple point of BCZT ceramic, where the tetragonal (T) and rhombohedral (R) phases were suppressed by the addition of glass phase and the T-phase has completely vanished at x = 0.05. The maximum value of permittivity (ε = 4102) and converse piezoelectric coefficient (d*33 = 1150 Pm/V) were achieved for the 0.975BCZT-0.025BBCZT sample at ambient temperature. Furthermore, the diffusion coefficient (γ) and Curie temperature (Tc) were observed to increase beyond x = 0.025, indicating enhanced thermal stability of BCZT at high glass content. These results qualify that the addition of (BBCZT) can enhance piezoelectric properties, phase transition temperature and thermal stability of BCZT ceramic which can meet wide requirements of practical applications.

Defect engineering in barium titanate ferroelectric ceramic showing simultaneous enhancement of piezoelectric coefficient and mechanical quality factor

For high-power on-resonant piezoelectric applications, piezoelectric materials with high piezoelectric coefficient (d33) and mechanical quality factor (Qm) are in high demand. However, previous work has shown that the d33 and Qm are generally inversely proportional, implying that it is difficult to improve these properties simultaneously. Here we report the simultaneous enhancement of d33 and Qm in (Mn, Zr) co-doped BaTiO3 (BT-xMn-yZr) ceramics. Compared with pure BaTiO3 ceramics, the piezoelectric coefficient (d33) of BT-0.5%Mn-5%Zr ceramic is increased from 190 pC/N to 321 pC/N, and the Qm is increased from 290 to 513. Furthermore, the Qm of BT-1%Mn-5%Zr ceramic reaches 1470, and the d33 is 248 pC/N. When both d33 and Qm are considered, the obtained properties outperform commercial hard Pb(Zr,Ti)O3 and other typical lead-free ferroelectric ceramics. The experimental results show that the enhanced d33 and Qm of these ceramics originate from the synergistic effect of defect engineering-induced domain configuration effect and pinning effect. This work provides insights into the design of high-performance high-power lead-free ferroelectric materials.

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.

Rosen-Type Piezoelectric Transformers Based on 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 Ceramic and Doped with Sb2O3.

In this study, the characteristics in the lead-free piezoelectric ceramic 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 (0.5BZT-0.5BCT) were investigated to assess its potential for Rosen-type piezoelectric transformers. This piezoelectric ceramic has a piezoelectric charge coefficient d33 of 430 pC/N, an electromechanical coupling factor kp of 49%, a dielectric constant εr of 2836, a remnant polarization Pr of 4.98 μC/cm2, and a coercive electric field Ec of 2.41 kV/cm. Sb2O3 was soft doped with 0.05, 0.1, 0.15, and 0.2 mol%, respectively, and exhibited excellent physical properties at 0.1 mol%. Based on this, a piezoelectric transformer was fabricated and measured, and it showed better output characteristics than pure 0.5BZT-0.5BCT. The amplification ratio (Vout/Vin) was optimized based on the device geometry and properties of the piezoelectric material. Moreover, the output characteristics of the Rosen-type piezoelectric transformer were simulated with the PSpice program. Output values of the fabricated and simulated piezoelectric transformers for the r vibrational frequency were compared and analyzed. Accordingly, the step-up amplification ratios Vout/Vin of the fabricated and simulated devices at the vibrational frequency were compared as well. This piezoelectric transformer could replace silicon steel transformers and be used for the creation of black light and for laptop chargers.

Giant Piezoelectric Output and Stability Enhancement in Piezopolymer Composites with Liquid Metal Nanofillers.

Integrating nanomaterials into the polymer matrix is an effective strategy to optimize the performance of polymer-based piezoelectric devices. Nevertheless, the trade-off between the output enhancement and stability maintenance of piezoelectric composites usually leads to an unsatisfied overall performance for the high-strength operation of devices. Here, by setting liquid metal (LM) nanodroplets as the nanofillers in a poly(vinylidene difluoride) (PVDF) matrix, the as-formed liquid-solid/conductive-dielectric interfaces significantly promote the piezoelectric output and the reliability of this piezoelectric composite. A giant performance improvement featured is obtained with, nearly 1000% boosting on the output voltage (as high as 212V), 270% increment on the piezoelectric coefficient (d33 ∼51.1pCN-1 ) and long-term reliability on both structure and output (over 36000 cycles). The design of a novel heterogenous interface with both mechanical matching and electric coupling can be the new orientation for developing high performance piezoelectric composite-based devices.

Investigation on growth, spectral, hardness, piezoelectric, contact angle, optical stress and nonlinear optical properties of acid blue 22 dye on ADP single crystals

Reclusive single crystals of ammonium dihydrogen phosphate (ADP) and 0.1[Formula: see text]mol.% Acid Blue 22 dye-incorporated ADP were harvested by using a standard slow cooling mechanism. The skeletal framework of the anisotropic materials was analyzed by using single crystal X-ray diffraction cram. The powder X-ray diffraction examines the phase growth and incorporation of substituents in the crystalline matrices. The incorporation of additives in the system was examined by employing Fourier Transform Infrared Spectroscopy. The analysis of vibrational bands gives insights into the incorporation of additives in ADP crystal system. The transmission window of the specimen and optical bandgap of the given material were analyzed by using UV–Vis spectroscopic analysis. The incorporation of additives to parent crystals was examined by using Scanning Electron Microscope. The quantification of elements in the grown specimen was investigated by using Energy Dispersive X-ray spectroscopy. The mechanical rigidity of the material was inspected by using Vickers microhardness analysis. The piezoelectric charge coefficient of dye-incorporated ADP is higher than pristine ADP. The wettability of the material was identified by contact angle measurements. The optical stress was identified by employing photoelastic measurements. The second- and third-order nonlinear optical properties of pristine and dye-incorporated ADP crystals were investigated by using Kurtz–Perry powder technique and Z-scan technique.

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.

Effect of acceptor–donor co‐doping on the microstructure and electrical properties of BiScO3–PbTiO3‐based ceramics

AbstractDesigning BiScO3‐PbTiO3 (BS–PT) ceramics that merge high Curie temperature (TC) and large piezoelectric coefficient (d33) has always been a significant challenge for high‐temperature applications. Doping is a commonly used and effective method for enhancing the electrical performances of piezoelectric ceramics. In this study, the Li+/W6+ acceptor–donor co‐doping method was used to enhance the piezoelectric properties of 0.36BiSc1‐xLixO3–0.64PbTi1‐yWyO3 (0.36x = 0.64y) ceramics. The optimal electrical performance was observed at x = 0.01 near morphotropic phase boundaries, with a large d33 (505 pC/N), high TC (407°C), huge remnant polarization (Pr ∼ 40.9 μC/cm2), and inverse piezoelectric coefficient (d33* = 601 pm/V). Rietveld refinement and piezoelectric force microscopy results revealed that incorporating Li+/W6+ into the BS–PT ceramics decreased the T phase proportion and domain size and increased the domain wall density. The enhancement in piezoelectricity can be attributed to the lowered energy barrier resulting from the reduced T‐phase proportion and complex domain structure, which promotes polarization rotation and facilitates domain wall motion. This work demonstrates that acceptor–donor co‐doping is a promising strategy for optimizing the electrical performance of the BS–PT ceramics.

Dielectric anomaly in Bi3Ti1-x(Y0.5Sb0.5) xNbO9 piezoceramics with high Curie temperature

Bismuth layered material stand out from other piezoelectric materials due to their high Curie temperature (Tc) and are often used in high temperature piezoelectric actuators and capacitors. However, its low piezoelectric coefficient (d33) and dielectric constants (ε′) limit the scope of application of this material. The Bi3Ti0.99 (Y0.5Sb0.5) 0.01NbO9 (BTN-1YSb) ceramics by solid state sintering method show improved d33 (8.1 pC/N), dielectric constants (ε′ ∼2051), temperature stability (d33＞8 pC/N at 800 °C) and mechanical quality factor (Qm ∼ 1834). After Rietveld refinement, it was found that the oxygen element contributed the most to the spontaneous polarization (Ps) enhancement of the piezoelectric material. In addition, three dielectric anomalous peaks are observed for the first time in BTNO-4YSb BTN-3YSb ceramics, which is due to the interaction of point defects with domain walls in a wide temperature range. This advantage can be maximized by tuning the dielectric anomaly peak to provide a more stable d33 at high temperatures. This study analyzes that the contribution of each ion to the piezoelectric properties of BTN-based ceramics and provides a good example for the study of dielectric peaks.

Phase Structure and Electrical Properties of 0.28PIN-0.32PZN–(0.4-x) PT-xPZ Piezoelectric Ceramics

Piezoelectric constant and Curie temperature are two important parameters of piezoelectric materials, but currently most piezoelectric materials have the problem of obtaining both high piezoelectric coefficient and Curie temperature. In this work, quaternary piezoelectric ceramics of 0.28Pb(In1/2Nb1/2)O3-0.32Pb(Zn1/3Nb2/3)O3–(0.4-x)PbTiO3-xPbZrO3 (x = 0~0.25) were designed and prepared by a solid-phase method, and the phase structure, dielectric, piezoelectric and ferroelectric properties of 0.28PIN-0.32PZN-(0.4-x)PT-xPZ piezoelectric ceramics were investigated by regulating the Zr/Ti ratio. The results show that the selected compositions are located in the MPB region, and the ceramic samples of each component display high density, the piezoelectric constant (d33) and the electromechanical coupling coefficient (kp) increase and then decrease with the increase of x. The optimum piezoelectric properties are found in compositions at x = 0.1, which showed a high piezoelectric coefficient d33 of 450 pC/N and high Curie temperature Tc of 272 °C. It is promising for use in high-temperature piezoelectric transducers.

Achieving ultrahigh electromechanical properties with high TC in PNN-PZT textured ceramics

<001> textured Pb(Ni1/3Nb2/3)O3-PbZrO3-PbTiO3 (PNN-PZT) ceramics were prepared by templated grain growth (TGG) technique using 0.36PNN-xPZ-(0.64-x)PT (x = 0.23, 0.25 and 0.27) powder matrix. Optimum template content was derived to achieve the best electromechanical properties of textured ceramics. The piezoelectric coefficient d33 = 1165 pC/N, Curie temperature TC = 197 °C, longitudinal mode electromechanical coupling factor k33 = 0.86 and a very large effective piezoelectric strain coefficient d33* = 2041 pm/V were simultaneously achieved at the morphotropic phase boundary (MPB) composition (x = 0.25) with 3 vol.% BaTiO3 (BT) templates. Domain structures of textured ceramics were analyzed in detail to reveal the origin of these high piezoelectric and electromechanical properties.

Strong piezoelectricity of the nm-thick flexible Hf0.5Zr0.5O2 ferroelectric film

Integrated nanoelectromechanical systems (NEMS) exhibit enormous potential for replacing current microelectromechanical systems in various fields, such as 5G/6G wireless communication, in the future. However, their advancement is impeded by the challenge of achieving nanometer-thick ferroelectric oxide films with a high piezoelectric coefficient of d33. Herein, the nm-thick flexible Hf0.5Zr0.5O2 (HZO) films were deposited on mica substrates, and they exhibited a remnant polarization of ≥ 8.1 μC/cm2 at 25–320 °C and a high d33 value of 37.8 pC/N at 25 °C. After the HZO films with inter-digitated electrodes were fully polarized, the flexible HZO film with a dynamic bending strain of 0.102 % at 4 Hz produced an open-circuit voltage of 1.1 V. This HZO film with strong piezoelectricity can promote the development of novel NEMS and flexible piezoelectric sensors.

Improvement of the piezoelectric response of AlN thin films through the evaluation of the contact surface potential by piezoresponse force microscopy

Sputtered aluminum nitride (AlN) thin films were characterized by Piezoresponse Force Microscopy (PFM) technique using a methodology to decrease the contribution of the electrostatic forces to obtain a pure piezoelectric response. Our method is based on the sweeping of the DC voltage applied to the Atomic Force Microscope (AFM) tip under a fixed AC field to evaluate the contact surface potential difference (VCPD) between the tip and the sample used to measure the proper AlN piezoelectric coefficient (d33,eff), minimizing the electrostatic contribution. Kelvin probe Force Microscopy (KPFM) was employed as reference standard technique to measure the surface potential, confirming the reliability of the proposed experimental procedure on ceramic piezoelectric films, and simultaneously overcoming the disadvantages of the KPFM technique. The capability to tune surface potential of materials over a wide range of values opens new perspectives for the design of devices with changeable surface potential.

Leakage current characteristics of polycrystalline BiFeO3 thin films affected by thickness-dependent domain wall currents

Polycrystalline BiFeO3 (BFO) thin films with a mixed crystallinity of c-oriented crystallinity and a-oriented crystallinity were deposited on a (200) Pt/TiO2/SiO2/Si substrate to have a thickness of 50, 100, and 150 nm. The ferroelectric domains observed with vertical piezoresponse force microscope (VPFM) and lateral PFM (LPFM) showed a mixed domain structure of c-domains and a-domains, and the ratio of a-domains increased as the thickness increased. The domain wall currents at the a-domains and c-domain boundaries of the BFO thin films were measured by conduction atomic force microscopy (CAFM) experiments and they were larger than those at the c-domains boundaries. In particular, the leakage currents, ferroelectric polarizations, and piezoelectric coefficients of the BFO thin films according to their thickness were significantly affected by the formation of the a-domains.

Hard piezoelectric properties of lead‐free BiFeO3–BaTiO3 ceramics

AbstractHard piezoelectric properties are investigated in lead‐free BiFeO3–BaTiO3 (BF–BT) ceramics. Rhombohedral (R) phase ceramics of (1 – x)BF–xBT (x = 0.20–0.30) were prepared using a conventional solid‐state reaction and water‐quenching process. The R structure is observed in x = 0.20–0.275, and the R and tetragonal phases coexist at x = 0.30. The piezoelectric charge sensor coefficient (d33) and electromechanical planar coupling factor (kp) increase with increasing BT content, whereas the mechanical quality factor (Qm) decreases. The x = 0.20 ceramic shows the best hard piezoelectric properties: the highest Qm = 403 and the highest TC = 607°C. In contrast, x = 0.30 ceramic shows soft piezoelectric properties: d33 = 301 pC/N and kp = 0.33 with TC = 510°C. These results show that the BF–BT system in R‐phase‐rich region has good hard piezoelectric properties for transducer applications.

Analysis of amplitude and frequency-dependent scaling behavior of dynamic hysteresis loop and thermal properties of BaZr0.05Ti0.95O3 ceramic

In this work, single-phase BaZr0.05Ti0.95O3 (BZT) ceramic was prepared through a conventional solid-state reaction route. The structural identity was analyzed by X-ray diffraction (XRD) and Rietveld refinement, which reveals the single-phase perovskite structure of the synthesized sample having an orthorhombic structure and space group Amm2. Scanning electron microscope (SEM) study gives an idea about the well-dense grains with clear grain boundaries of the BZT sample. Frequency and amplitude-dependent Polarization-Electric field (P-E) and Strain-Electric field (S-E) loops were studied. The parameters like remnant polarization (Ec), coercive field (Pr), loop area (<A>), energy storage efficiency (η), field-induced maximum strain (Smax) and inverse piezoelectric coefficient (d33*) were calculated. The scaling behavior of the hysteresis loops area as a function of frequency and field strength is studied. The thermal conductivity and thermal diffusivity as a function of temperature were investigated.

Ultra-high d31 anti-chiral negative Poisson’s ratio BaTiO3 ceramics fabricated by vat photopolymerization 3D printing

In this study, the anti-chiral negative Poisson's ratio structure BaTiO3 piezoelectric ceramics were fabricated by vat photopolymerization 3D printing technology, which obtained an ultra-high transverse piezoelectric coefficient d31. Here, we performed uniaxial compressive load simulations and electric field-driven lattice in-plane strain response simulations, which showed an in-plane negative Poisson's ratio of −1 for the BaTiO3 ceramics. Its strain amplification is about 10 times that of BaTiO3 bulk material. Using the principle of positive and negative piezoelectric effects, we measured effective transverse piezoelectric coefficients d31 for different dimensional parameters. The effective transverse piezoelectric coefficient d31 with a maximum of 599 pm/V was detected at a ligament aspect ratio of 3.6 for the negative Poisson's ratio BaTiO3 piezoelectric ceramics, which is 7.7 times higher than that of the bulk material. For the prepared hydrophone, test results show that the effective hydrostatic strain constant dh and Hydrostatic Figure of Merit (HFOM) of BaTiO3 piezoelectric ceramics with a negative Poisson's ratio structure are 29.6 and 808 times higher than those of bulk BaTiO3.