High Piezoelectric Strain Research Articles

Nanosecond electric pulse-induced ultrafast piezoelectric responses in Co3+ substituted BiFeO3 epitaxial thin films

Understanding the ultra-fast dynamics of ferroelectric materials is essential for advancing the development of next-generation high speed electronic and photonic devices. Here, the ultrafast piezoelectric response of cobalt-substituted BiFeO3 (BiFe1-xCoxO3) with x = 0.15, consisting of morphotropic phase boundary of monoclinic MC and MA –type phases is investigated. The real-time piezoelectric response in (001)-oriented BiFe0.85Co0.15O3 (BFCO) epitaxial thin film was monitored using the time-resolved X-ray microdiffraction technique under an applied electric field with pulse widths 70 ns and 100 ns. The BFCO thin film yielded a high piezoelectric strain of approximately 0.53 % along [001] direction, with a giant c/a ratio (∼ 1.26) at an electric field of 1.3 MV/cm and a pulse width of 100 ns, with a piezoelectric coefficient of 40 pm/V. This finding is an important step towards the development of a high performance lead-free piezoelectric material for ultrafast operations in advanced technological applications.

High and temperature-stable electrostrain in lead-free environmentally friendly BiFeO3-BaTiO3 piezoelectric ceramics

Currently, environmental pollution and industrial effluents are depleting soil, water, and aquatic life and pose serious concerns to climate change. Environmentally friendly piezoelectric materials are considered potential agents for industrial applications, as they can generate clean energy by applying mechanical forces. High and temperature-insensitive piezoelectric strain is an ever-increasing demand in lead-free ceramics. In this work, a lead-free La-doped BiFeO3-BaTiO3 composition is designed at the crossover boundary of normal-relaxor ferroelectrics. The properties are optimized as a function of sintering temperature (Ts) from 960 to 1000 °C. An enhanced and thermally stable converse piezoelectric constant (d33∗) of 760 ± 23 pm/V over a wide range of 25–150 °C is achieved at an optimized TS of 980 °C. This high electrostrain response is mainly attributed to the low energy barrier for domain switching due to multiple-point crystal structure morphotropic phase boundary. Additionally, the high Curie temperature (TC) of 355 °C with excellent piezoelectric strain performance of our work are promising results for high-temperature piezoelectric actuators. The framework of chemical composition design and phase engineering of this work could inspire further development of lead-free ceramics for industrial applications.

Achieving high electromechanical response in lead-free BNT-BT ceramics through synergistic A/B-site doping

Lead-free Bi0.5Na0.5TiO3-based ceramics show great promise for achieving high unipolar strain. However, it remains challenging to implement an effective strategy for microstructural designs with high electromechanical response. Herein, a direct composition-engineering method based on A/B-sites doping is adopted to introduce a synergistic effect of reduced oxygen vacancies, lattice distortion, ferroelectric-to-relaxor phase transition, and nano-sized domains, resulting in a high piezoelectric strain coefficient d*33 of 857 pm/V at a small electric field of 4 kV/mm. Furthermore, a large room-temperature maximum polarization (Pm) of 72.4 μC/cm2 was observed at high electric field. A phase transition from coexisting rhombohedral–tetragonal to pseudocubic was engineered by finely tuning the contents of NaTaO3, leading to a decrease in both remnant polarization (Pr) and coercive field (Ec). The phase diagram of 1-x[0.935(Bi0.5Na0.5TiO3)-0.065(BaTi0.99Nb0.01O3)]-x(NaTaO3) (x = 0–0.04) is proposed, providing a roadmap for engineering high-performance piezoelectric ceramics with enhanced electrostrain responses, which may find potential applications as piezoelectric actuators.

Ultra-high strain in Bi0.5(Na0.41K0.09)TiO3 Pb-free piezoelectric ceramics modified by Sr(Hf0.5Sb0.4)O3

The lead-free piezoelectric ceramics used in piezoelectric actuators have attracted extensive attention owing to their substantial electric-field-induced strain. In this study, The (1-x)Bi0.5(Na0.41K0.09)TiO3-xSr(Hf0.5Sb0.4)O3 (BNKT-xSHS) piezoelectric ceramics were synthesized using the conventional solid-state reaction method. The impact of SHS substitution on the microstructure and electrical properties was systematically explored. Among them, the BNKT-0.015SHS sample, featuring ergodic relaxor states, demonstrates a high piezoelectric strain coefficient (d33*) of 785 p.m./V under a low electric field of 50 kV/cm(Strain = 0.392 %). It exhibits a repeatable strain value of 0.47 % under an 80 kV/cm electric field(d33* = 590 p.m./V). Moreover, the strain values remain around 0.4 % between room temperature and 100 °C, with variations within 90 %. The heightened repeatable strain response is considered to be linked to the electric field-induced reversible phase transition occurring within the ergodic relaxor state. The higher strain temperature stability is ascribed to the coexistence of quadrilateral polar nanoregions and rhombic polydomain nanoregions. This study provides an effective example for achieving significant strain responses, presenting a feasible candidate material for applications in piezoelectric actuators.

Large strain with broad temperature insensitivity in PZT-PNN multilayer piezoactuators

Achieving high performance in piezoactuators at extremely low temperatures is challenging and restricts the operating temperature range of devices in practical applications. In this study, 0.5Pb(Ni1/3Nb2/3)O3-(0.5−x)PbTiO3-xPbZrO3+0.1 wt% MnCO3 bulk ceramics demonstrated a high piezoelectric strain coefficient of d33* = 1095 pm/V at 1 kV/mm. Using a tape casting method, multilayer piezoactuators with a thickness of 48 μm and 32 active layers were prepared, and these devices exhibited high active strain (0.122%, 2.5 kV/mm) and total strain (0.088%, 2.5 kV/mm). The temperature-insensitive strain response was acquired at x = 0.15, with a variation of approximately 10% over the range from −100 to 110 °C, which surpassed the stability of current commercial PZT actuators. These results demonstrate that PZT-PNN multilayer piezoactuators promise to meet the requirements of high-performance devices and have potential for applications in harsh environmental conditions.

Investigations on electric properties and domain structures of Nd-doped 0.70Pb(Mg1/3Nb2/3)O3–0.30PbTiO3 relaxor ferroelectric ceramics with high piezoelectric properties

Although rare earth neodymium (Nd) doping is common in Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN–PT) single crystals, it is rarely reported in PMN–PT ceramics. To explore the effect of Nd doping on PMN–PT ceramics, PMN–30PT:xNd3+ (x = 0%, 1%, 2%, and 3%) relaxor ferroelectric ceramics were fabricated using a solid-state method via two-step sintering. An enhanced piezoelectric charge coefficient (d33) of ~870 pC/N and a high piezoelectric strain coefficient (d33⁎) of ~1025 pm/V were achieved for x = 2%. Through Rayleigh analysis of polarization–electric field (P–E) hysteresis loops under small electric fields, it was found that the dielectric property was mainly influenced by the intrinsic contribution (local lattice distortion). Furthermore, by investigating domain configurations, high piezoelectric properties were found to be associated with the domain size reduction and local structural heterogeneity. The results indicate that the PMN–30PT:xNd3+ ceramics is a promising material for electronic devices, and that rare earth Nd doping is an efficient strategy for improving the electronic performance of Pb-based relaxor ferroelectrics.

Design and development of a new lead-free BiFeO3-BaTiO3 quenched ceramics for high piezoelectric strain performance

Designing a new high-performance lead-free ceramic has become a cutting-edge research topic due to growing concerns about the toxic nature of lead-based materials. In this work, a convenient strategy of compositional design and domain engineering is applied to the lead-fee BiFeO3-BaTiO3 ceramics which provides a flexible polarization free-energy profile for domain switching. Here, simultaneously enhanced dynamic piezoelectric constant (d33* ≈ 772 pm/V) and a good thermal-stability (Δd33* ≈ 26% over the temperature of 20–180 °C) are achieved with a high Curie temperature (TC) of 432 °C. This high piezoelectric strain performance is collectively attributed to multiple effects such as thermal quenching, suppression of defect charges by donor doping, chemically induced local structure heterogeneity, and electric field-induced phase transition. Furthermore, the addition of BT content decreased octahedral tilting that reduce anisotropy for domain switching and increased in tetragonality (cT/aT) providing a wider polar length for B-site cation displacement, leading to high piezoelectric strain performance. Atomic-resolution transmission electron microscopy and piezoelectric force microscopy combined with X-ray diffraction results strongly support the origin of high piezoelectricity. The high and temperature-stable piezoelectric strain response of this work is superior to those of other lead-free ceramics. The synergistic approach of composition design and the concept present here for the origin of high strain response provides a paradigm for the development of new materials for high-temperature piezoelectric actuator applications.

Mn-doped 0.15Pb(Yb1/2Nb1/2)O3–0.48Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 piezoelectric ceramics for high performance high-power transducers

For high-power transducer applications, the piezoelectric materials should fulfill specific requirements of a high mechanical quality factor (Qm), a high piezoelectric strain coefficient (dij), and a high Curie phase transition temperature (Tc). In this study, we present an investigation of the structural, piezoelectric, and high-power characteristics of Mn-doped 0.15Pb(Yb1/2Nb1/2)O3–0.48Pb(Mg1/3Nb2/3)O3–0.37PbTiO3 (0.15PYN–0.48PMN–0.37PT) ceramics. The introduction of Mn dopants led to an increase in the tetragonal phase fraction within the 0.15PYN–0.48PMN–0.37 PT ceramics and the formation of oxygen vacancies, consequently significantly enhancing Qm due to their synergistic effect. Despite the hardening effect, the high value of the piezoelectric coefficient (d33) was maintained due to the increase in grain size. Particularly, the specimen doped with 3 mol% of Mn exhibited excellent piezoelectric properties of d33 = 345 pC/N, Qm = 1159, and Tc = 207°C. This specimen displayed a high vibration velocity of 0.6 m/s under the condition of equilibrium ΔT < 20°C (temperature rise from initial temperature), thereby confirming its immense potential for high-power transducer applications.

Fatigue-free dielectric and piezoelectric response in single-crystal BaTiO3 tuned by dislocation imprint

Dislocations have recently been imprinted into barium titanate single crystals to provide local domain wall pinning sites. Here, we assess the cycling stability under unipolar loading for the interaction between dislocations with [001] line vector and engineered ferroelectric domain walls. We find that a high large-signal piezoelectric strain coefficient (∼2100 pm/V) and dielectric permittivity (20 800) can be obtained without degradation if the topological interaction between domain wall and dislocation line is well chosen to utilize transient and permanent pinning sites. Our findings demonstrate the potential of dislocation engineering for the manipulation of the mobility of domain walls in bulk ferroelectrics.

Design and Fabrication of 15-MHz Ultrasonic Transducers Based on a Textured Pb(Mg1/3Nb2/3)O3-Pb(Zr, Ti)O3 Ceramic.

Ultrasound medical imaging is an entrenched and powerful tool for medical diagnosis. Image quality in ultrasound is mainly dependent on performance of piezoelectric transducer elements, which is further related to the electromechanical performance of the constituent piezoelectric materials. With rising need for piezoelectric materials with better performance and low cost, a highly 〈001〉 textured piezo ceramic, Pb(Mg1/3Nb2/3)O3-Pb(Zr, Ti)O3, has been developed. Recently, textured ceramic materials can be produced at low cost and exhibit high piezoelectric strain constants and large electromechanical coupling coefficients. In this work, 15-MHz ultrasonic transducers with an effective aperture of 2.5 mm in diameter based on these highly 〈001〉 textured ceramics have been successfully fabricated. The fabricated transducers achieved a central frequency of 15 MHz, a fractional bandwidth of 67% (at -6 dB), a high effective electromechanical coupling coefficient [Formula: see text] of 0.55, and a low insertion loss (IL) of 21 dB. Ex vivo ultrasonic imaging of a porcine eyeball was used to assess the tomography quality of the transducer. The results show that utilized textured ceramic has a great potential in developing ultrasonic devices for biomedical imaging purposes.

Achieving ultrahigh electrostrain with giant piezoelectric strain coefficient in (Bi0.5Na0.5)TiO3-based ceramics via integrating NER/ER boundary and defect engineering

Ferroelectric ceramics with high electrostrain have been widely applied in actuators and sensors for their rapid response and precision. However, the current bottleneck is the inability to obtain superior electrostrain values along with high piezoelectric strain coefficient (d33*), limiting the practical applications. Herein, we report a remarkable enhancement of electrostrain values and d33* simultaneously in (Bi0.5Na0.5)0.93Ba0.07Ti1-x(Nb0.5Ga0.5)xO3 (BNBT-xNG, 0 ≤ x ≤ 0.06) ceramics with the integration of nonergodic/ergodic relaxor (NER/ER) boundary and defect engineering at room temperature. This strategy by combining NER/ER boundary and defect engineering allow for highly asymmetric strain-electric field (S-E) loops with an ultrahigh and temperature-insensitive electrostrain of 0.73% as well as giant piezoelectric strain coefficient of 913 pm/V simultaneously. The electrostrain value is greater than most of the reported lead-free ceramics and even exceeds those of conventional lead-based materials. This work suggests an effective method for developing new lead-free ceramics to achieve high piezoelectric response.

Enhancing the Temperature Stability of 0.42PNN-0.21PZ-0.37PT Ceramics through Texture Engineering.

Although the MPB composition 0.42PNN-0.21PZ-0.37PT ceramic has high piezoelectric properties, its temperature stability at room temperature is rather poor due to the low phase-transition temperature. By texture engineering using BaTiO3 (BT) as the template, the temperature stability of this material can be greatly improved. In the temperature range from room temperature up to 140 °C, the high effective piezoelectric strain constant d33* of 0.42PNN-0.21PZ-0.37PT-3BT only changed by 4.9% from 1278 to 1215 pm/V, while the d33* of the nontextured counterpart changed by 46.7% from the room temperature value of 920 pm/V with the maximum deviation to 1350 pm/V at 80 °C. In addition, the textured ceramic has higher piezoelectric properties, lower dielectric loss, and slightly higher coercive field. The room-temperature figure-of-merit d33 × g33 for PNN-PZT-2BT is increased by as much as 42% compared with the nontextured counterpart. Our results demonstrated that texture engineering is an effective way to improve the temperature stability of the MPB composition piezoceramics.

Effect of Point Defects on Electronic Structure of Monolayer GeS.

Using density functional theory calculations, atomic and electronic structure of defects in monolayer GeS were investigated by focusing on the effects of vacancies and substitutional atoms. We chose group IV or chalcogen elements as substitutional ones, which substitute for Ge or S in GeS. It was found that the bandgap of GeS with substitutional atoms is close to that of pristine GeS, while the bandgap of GeS with Ge or S vacancies was smaller than that of pristine GeS. In terms of formation energy, monolayer GeS with Ge vacancies is more stable than that with S vacancies, and notably GeS with Ge substituted with Sn is most favorable within the range of chemical potential considered. Defects affect the piezoelectric properties depending on vacancies or substitutional atoms. Especially, GeS with substitutional atoms has almost the same piezoelectric stress coefficients as pristine GeS while having lower piezoelectric strain coefficients but still much higher than other 2D materials. It is therefore concluded that Sn can effectively heal Ge vacancy in GeS, keeping high piezoelectric strain coefficients.

Temperature-insensitive PMN-PZ-PT ferroelectric ceramics for actuator applications

Piezoelectric actuators are essential for numerous electromechanical applications, because of their advantages of high resolution, large generated forces, no friction, low heat dissipation and fast response. The design of the next-generation piezoelectric actuators is desired to meet the complex needs of advanced machines and instruments, where the high-performance and stable output under the combined thermal and mechanical loads are expected. However, simultaneously achieving high-performance and good temperature stability of piezoelectric actuators is a challenge, which hinders the use temperature range in practical applications. Here, in the studied Sm-doped Pb(Mg1/3Nb2/3)O3-PbZrO3-PbTiO3 system, the high piezoelectric strain coefficient d33* = 870 pm/V with superior temperature stability (below 7% variation over the temperature of 20°C to 280°C), together with negligible property degradation up to 106 cycles was successfully achieved. The outstanding blocking stress of 37.2 MPa and mechanical work of 6.4 kJ/m3 were obtained under the driving electric field of 15 kV/cm. This work provides a paradigm to achieve high piezoelectric strain properties with good temperature stability, where the studied materials are expected to greatly benefit the development of high temperature piezoelectric actuator applications.

Structural evolution and electromechanical properties of SrTiO3-modified Bi0.5Na0.5TiO3–BaTiO3 ceramics prepared by sol-gel and hydrothermal methods

This article reports structural evolution and electromechanical properties of lead-free (1-x)(0.965Bi0.5Na0.5TiO3-0.035BaTiO3)-xSrTiO3 (BNTBT-100xST with x = 0.00–0.30) ceramics synthesized by sol-gel and hydrothermal methods. The crystal structure investigation shows a compositionally-driven phase transition from the dominant rhombohedral (R) phase to the tetragonal (T) phase. However, the physical properties revealed that BNTBT converts from normal ferroelectric to relaxor ferroelectric due to the disruption of long-range ferroelectric order with ST modifications. Highest electric field-induced strain coefficient (d33* = 320 pm/V) for the optimum composition was attributed to the crystal structure morphotropic phase boundary of the R and T phases. A phenomenological explanation from the ferroelectric properties strongly supports the argument of the high piezoelectric strain response. A phase diagram was developed based on the crystal structure, dielectric, ferroelectric and piezoelectric properties that provide a systemic correlation and better elucidation of the BNTBT-100xST ceramic system.

Lead-Free BiFeO3-BaTiO3 Ceramics with High Curie Temperature: Fine Compositional Tuning across the Phase Boundary for High Piezoelectric Charge and Strain Coefficients

BiFeO3-BaTiO3 is a promising high-temperature piezoelectric ceramic that possesses both good electromechanical properties and a Curie temperature (TC). Here, the piezoelectric charge constants (d33) and strain coefficients (d*33) of (1 - x)BiFeO3-xBaTiO3 (BF-xBT; 0.20 ≤ x ≤ 0.50) lead-free piezoelectrics were investigated at room temperature. The results showed a maximum d33 of 225 pC/N in the BF-0.30BT ceramic and a maximum d*33 of 405 pm/V in the BF-0.35BT ceramic, with TCs of 503 and 415 °C, respectively. To better understand the performance enhancement mechanisms, a phase diagram was established using the results of XRD, piezoresponse force microscopy, TEM, and electrical property measurements. The superb d33 of the BF-0.30BT ceramic arose because of its location in the optimum point in the morphotropic phase boundary, low oxygen vacancy (VO··) concentration, and domain heterogeneity. The superior d*33 of the BF-0.35BT ceramic was attributed to a weak relaxor behavior between coexisting macrodomains and polar nanoregions. The presented strategy provides guidelines for designing high-temperature BF-BT ceramics for different applications.

First-principles discovery of stable two-dimensional materials with high-level piezoelectric response

The rational design of two-dimensional (2D) piezoelectric materials has recently garnered great interest due to their increasing use in technological applications, including sensor technology, actuating devices, energy harvesting, and medical applications. Several materials possessing high piezoelectric response have been reported so far, but a high-throughput first-principles approach to estimate the piezoelectric potential of layered materials has not been performed yet. In this study, we systematically investigated the piezoelectric (e 11, d 11) and elastic (C11 and C12) properties of 128 thermodynamically stable 2D semiconductor materials by employing first-principle methods. Our high-throughput approach demonstrates that the materials containing Group-V elements produce significantly high piezoelectric strain constants, d 11 > 40 pm V−1, and 49 of the materials considered have the e 11 coefficient higher than MoS2 insomuch as BrSSb has one of the largest d 11 with a value of 373.0 pm V−1. Moreover, we established a simple empirical model in order to estimate the d 11 coefficients by utilizing the relative ionic motion in the unit cell and the polarizability of the individual elements in the compounds.

Temperature-insensitive piezoelectric properties of lead-free BiFeO3–BaTiO3 ceramics with high Curie temperature

Temperature-insensitive high piezoelectric strain and low strain hysteresis (Hs) with high Curie temperature (TC) are desirable for piezoelectric actuator applications. The excellent room-temperature piezoelectric performance (d33 = 309 pC/N and d33∗ = 458 pm/V) with very high TC = 482 °C have achieved in 0.67Bi1.03FeO3-0.33Ba1-xLaxTiO3 ceramics. Furthermore, a small variation in the piezoelectric strain (ΔST = 13%) in the temperature range of 25 °C–125 °C with low strain hysteresis (Hs = 12%) and a large average electrostrictive coefficient (Q33 = 0.03 m2/C4) leads to a high figure of merit for piezoelectric actuators. The structural origin of the high piezoelectric performance is related to the crystal structure morphotropic phase boundary and maximum crystal structure lattice distortion (90° ̶ αR = 0.12° and cT/aT = 1.008). While the physical origin is mainly attributed to the soft ferroelectric effect by La3+ as donor doping on Ba2+-site that significantly reduces the coercive field and makes it easy to switch ferroelectric polarization under the applied electric field. We believe that this breakthrough in lead-free ceramics opens a new development window for temperature-insensitive piezoelectric properties for the high-temperature commercial applications.

Phase diagram for Bi-site La-doped BiFeO3[sbnd]BaTiO3 lead-free piezoelectric ceramics

Three different series of lead-free ceramics, i.e., (1-y)Bi1.03(1-x)LaxFeO3–yBaTiO3 (y = 0.27, x = 0.00–0.12), (y = 0.30, x = 0.00–0.10), and (y = 0.33, x = 0.00–0.08) are prepared via a conventional solid-state reaction with water quenching. From X-ray diffraction and electrical property measurements, two morphotropic phase boundaries (MPBs) are discovered in all three ceramic systems. The first MPB (MPB-I) appeared between rhombohedral and tetragonal phases, whereas the second MPB (MPB-II) appeared between tetragonal and cubic-like phases. The highest direct piezoelectric coefficients (d33 = 201, 274, and 268 pC/N) are mainly attributed to the typical MPB-I of the rhombohedral and tetragonal phases. However, the highest converse piezoelectric coefficients (d33∗ = 490, 500, and 570 pm/V with Curie temperature > 330 °C) are obtained for compositions near to the MPB-II. A significant enhancement in the dielectric constant at low temperature is associated with the local structural heterogeneity by La3+ doping, which serves as an origin for a high piezoelectric strain response. Based on the crystal structure as well as on the dielectric, ferroelectric, and piezoelectric properties, a phase diagram is constructed for La-doped BiFeO3BaTiO3 ceramics. This phase diagram reveals the relationship between piezoelectric performance and crystal structure.

Thermally Stable Poly(vinylidene fluoride) for High-Performance Printable Piezoelectric Devices.

Piezoelectric polymers, such as poly(vinylidene fluoride) (PVDF) and its copolymers, can achieve large strains and high work density under external electrical fields. These materials are highly desirable in the development of electronic devices and intelligent structures. Here, we demonstrate that dehydrofluorination (DHF) can provide a versatile chemical modification of the PVDF homopolymer that yields thermally stable ferroelectricity. The DHF process significantly increases the fraction of planar chain conformation in the PVDF and results in higher piezoelectric coupling with a wider processing temperature range, compared to traditionally processed PVDF. The efficacy of DHF in promoting planar chain conformation is demonstrated through molecular simulation and further proven by experimental characterization. The induced piezoelectric phases by DHF were able to be preserved through high temperature treatments up to 200 °C. The dehydrofluorinated PVDF exhibits improved electromechanical coupling with a high piezoelectric strain coefficient of d31 = 25.12 ± 1.13 pC/N, which can be further improved to 35.12 ± 0.69 pC/N by common mechanical drawing. This high piezoelectric voltage coefficient leads to an excellent actuation and energy harvesting behavior with a power density of 21.96 mW/cm3 in a flexible undrawn PVDF energy harvester, which is 3.13 times higher than conventionally drawn PVDF. The versatile and scalable method for preparing PVDF polymers with high piezoelectric coupling will enable new manufacturing processes not currently compatible with PVDF homopolymers.