Field-induced Strain Research Articles

Constructing local structure heterogeneity in AgNbO3-based antiferroelectrics: Achieving excellent anti-fatigue and energy storage properties

AgNbO3 ceramics are important candidates for developing high-property dielectric capacitors because of their unique field-induced antiferroelectric (AFE)-ferroelectric (FE) phase transformation behavior and good environmental friendliness. However, until now, they have not yet exhibited simultaneously ultrahigh recoverable energy density (Wrec) and efficiency (η), and superior electrical fatigue resistance. Herein, we design a heterovalence-doping-enabled local structure heterogeneity strategy to achieve AgNbO3-based ceramics with excellent anti-fatigue and capacitive characteristics. The replacement of A-site Ag+ with higher valence Sm3+, and the substitution of lower electronegativity Ta5+ for B-site Nb5+ decrease the [Nb/TaO6] octahedral tilting, destroy the long-range ordering of AFE domains and produce low-atom-displacement regions, as confirmed by the atomic-scale electron microscopy. These are in favor of improving AFE features, refining P-E curves, and decreasing electric field-induced strain. Consequently, an ultrahigh Wrec of 8.03 J/cm3, and a large η of 74.77 % are obtained in the (Ag0.94Sm0.02)(Nb0.75Ta0.25)O3 ceramic. More interestingly, the Wrec and η both show excellent anti-fatigue characteristics with less than 2.6 % degradation even after 106 cycles, far superior to those obtained in other AgNbO3 systems with only 104 cycle stability.

Enhancement of microstructure-based magnetic, electronic, and lattice contribution in a CoNiAl ferromagnetic shape memory alloy

In this study, a Co-Ni-Al system with nominal compositions Co42​Ni31Al27​ and Co41Ni32Al27​ was synthesized. The structural and microstructure of these confirm the presence of a non-ferromagnetic face-centered cubic (γ) phase interspersed between the grains of a ferromagnetic body-centered cubic (β) phase. Notably, γ phase is increased by 1.5 times in the Co41Ni32Al27 sample due to the 1% substitution of Co by Ni. The microstructural tuning induced a higher thermal hysteresis in the shape memory effect of Co41​Ni32Al27 with an increase in enthalpy during the phase transition (Austenitic↔Martensitic). In addition, the temperature-dependent resistivity, ρ(T) was measured to study the electron-phonon and electron-magnon scattering around the phase transition of the studied samples. The dynamic elastic properties of the studied samples were tracked by the relative change in sound velocity (δv/v) with temperature and elastic recovery was confirmed in both alloys across the 120 K to 300 K range. However, the Co41​Ni32Al27​ exhibits a high amount of lattice contribution to the shape recovery compared to the Co42​Ni31Al27​. Moreover, a larger variation in relative resistivity (Δρ/ρ) for Co41Ni32Al27 compared to Co42​Ni31Al27 during the phase transition indicates a larger shape change due to decreased Co content. Furthermore, the Co41Ni32Al27 sample shows higher temperatures of martensitic start (TMs ≈ 260K) and Austenitic finish (TAf ≈ 290K) along with high Curie temperature (Tc = 330K). Consequently, the temperature-dependent susceptibility (χ′) confirms the higher magnetoelastic recovery in the Co41Ni32Al27 sample, indicating an enhancement of magnetic field-induced strain (MFIS). Stress-induced Q−1 is lower for Co41Ni32Al27 (∼2.9×10−3) compared to Co42Ni31Al27 sample (∼5.0×10−3) signifying the enhanced mechanical strength.

Low hysteresis in composites ceramics achieved by building polarization field and restoring force

Large strain hysteresis and remnant strain are one of the vital reasons for the absence of BiFeO3-BaTiO3-based ceramics in commercial actuator fields. Here, we elaborately propose a strategy, preparing 0–3 type composite ceramics, to reduce the hysteresis and remnant strain, and the target is successfully achieved by building restoring force and polarization field. Normal strain constant and electric field-induced strain in 0–3 composites have enhanced by 260% and 196% compared to those of non-composite ceramics, respectively. Also, hysteresis and remnant strain in 0–3 composites have decreased by 35.9% and 50.6% in contrast to those of non-composites. Superior electrostrain properties under the low electric field are attributed to the construction of polarization field, restoring force, and micro-capacitance, coinciding with phase field simulation, and the strategy will pave a useful way to optimize the hysteresis and remnant strain in BiFeO3-BaTiO3-based high-temperature ceramics.

Time-dependent relaxation dynamics of remanent strain in textured PMN–PZ–PT and PMN–PIN–PT piezoceramics

Crystallographically textured lead-based piezoceramics, particularly Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 (PMN–PZ–PT) and Pb(Mg1/3Nb2/3)O3–Pb(In1/2Nb1/2)O3–PbTiO3 (PMN–PIN–PT), play a pivotal role in electromechanical applications due to their enhanced field-induced strain responses. However, challenges in precision positioning arise from heightened remanent strain (Sr) caused by embedded templates in the textured grains, impacting strain cycle consistency due to increased time delay for Sr relaxation. This study investigates the time-dependent relaxation dynamics of Sr in textured PMN–PZ–PT and PMN–PIN–PT piezoceramics, focusing on experimentally determining relaxation time between cycles required for complete Sr relaxation. Our findings reveal that the relaxation time in textured piezoceramics is notably longer than that in their non-textured counterparts, primarily due to pinning of domain walls by embedded templates. This work provides insights into the strain relaxation characteristics of piezoceramics and underscores the importance of time delay in designing precision positioning systems for improved reliability.

Improving piezoelectric performance in PMN-0.26 PT single crystal via low frequency AC poling

In this experiment, the alternating current poling (ACP) was applied to the 0.74 Pb(Mg1/3Nb2/3)O3-0.26PbTiO3 (PMN-0.26 PT) single crystal to explore the impact of low frequency (0.1 Hz) ACP on electrical performance. When the poling condition is loading 5 cycles at 14 kV/cm, high piezoelectric coefficient d33 of 1780 pC/N and giant dielectric constant of 5881 are obtained for the ACP treatment sample, enhanced 42.4 % and 14.3 % by contrast with the conventional direct current poling (DCP), respectively. The values of coercive field, maximum strain, and converse piezoelectric constant d33∗ vary considerably around the ferroelectric phase transition detected by polarization-electric field, as well as bipolar and unipolar electric field-induced strain hysteresis loops. In addition, the domain configuration of the ACP sample presents a more periodic stripe-like structure with narrower width and relatively more uniformity after three months aging as compared with the DCP sample, showing the importance of domain engineering in enhancing electrical performance of ferroelectric single crystals.

Field-induced strain of Pb0.97La0.02(Zr0.72-xSn0.17+xTi0.11)O3 antiferroelectric ceramics near the MPB

Antiferroelectric (AFE) materials have great potential for applications in large-strain actuators due to their unique field-induced phase transition properties. In particular, AFE ceramics that exhibit a high level of field-induced strain with reversible and “on/off” features at low electric fields are well suited for use in reliable actuators. In this study, we designed Pb0.97La0.02(Zr0.72-xSn0.17+xTi0.11)O3 (x = 0, 0.03, 0.06, 0.09, 0.12, 0.15) AFE ceramics with the components close to the morphotropic phase boundary (MPB). The polarized Pb0.97La0.02(Zr0.60Sn0.29Ti0.11)O3 AFE ceramics exhibit an excellent field-induced strain of 1.21 % at a low electric field (60 kV/cm). This phenomenon can be attributed to the more miniaturized and disordered domain structure, which provides an important contribution to its field-induced strain beyond the AFE-FE phase transition. This work not only provides an AFE ceramic candidate for actuators but also explains the origin of the excellent field-induced strain properties of AFE ceramics with components close to the MPB.

Structure and properties of Er3+- modified (Bi0.5Na0.5)0.945Ba0.055TiO3-based lead-free ferroelectric ceramics

Er3+-modified (Bi0.5Na0.5)0.945Ba0.055Ti0.98(Fe0.5Sb0.5)0.02O3 (BNBT-FS) lead-free ferroelectric ceramics with large electrostrain and electrostrictive response were fabricated in our work. Results showed that Er3+-doping induced the destruction of ferroelectric order and significantly enhanced the field-induced strain. For 0.2 mol% modified sample, the unipolar strain reached 0.463 % under the electric field of 80 kV/cm, yielding a large normalized strain d33* (Smax/Emax) of 579 pm/V. For 0.4 mol% modified sample, high electrostrictive effect with temperature-insensitive electrostrictive coefficient Q33 (0.022–0.026 m4/C2 in the temperature range of 25–100°C) was obtained. The large electrostrain and electrostrictive response in the present materials show the great potential of the materials for nonlinear actuators applications.

Origin of the ultrahigh field-induced strain in the Gd-doped 0.854Bi0.5Na0.5TiO3-0.12Bi0.5K0.5TiO3-0.026BaTiO3 ternary ceramic system

This study focused on analyzing the ferroelectric, piezoelectric, and dielectric properties of lead-free Bi0.487Na0.427K0.06Ba0.026TiO3 (0.854BNT-0.12BKT-0.026BT) ternary ceramic system by systematically doping 0.001, 0.01, 0.1, 0.5, and 1.0 mol% Gd2O3. The specific composition that was investigated is located at the tetragonal side of the rhombohedral-tetragonal morphotropic phase boundary (MPB) region. Undoped and Gd-doped BNT-BKT-BT ceramics were produced by the conventional solid-state reaction method. Ferroelectric, piezoelectric, and dielectric properties of ceramics were analyzed by carrying out electrical measurements from sintered samples. An ultrahigh field-induced unipolar strain of 0.52% at 65 kV cm−1, with a converse piezoelectric coefficient d33* of up to 795 pm V−1, was achieved with 0.5 mol% Gd doping. This was attributed to the Gd dopant disrupting the normal ferroelectric order and leading to the formation of a nonpolar relaxor phase. The field-induced transition from the nonpolar relaxor phase to the normal ferroelectric phase resulted in relatively large field-induced strain values in the 0.5 mol% Gd-doped ceramics. These results suggest that Gd-doped BNT-BKT-BT ceramics hold promise for digital actuator applications.

Preparation and Properties of Nb5+-Doped BCZT-Based Ceramic Thick Films by Scraping Process.

A bottleneck characterized by high strain and low hysteresis has constantly existed in the design process of piezoelectric actuators. In order to solve the problem that actuator materials cannot simultaneously exhibit large strain and low hysteresis under relatively high electric fields, Nb5+-doped 0.975(Ba0.85Ca0.15)[(Zr0.1Ti0.9)0.999Nb0.001]O3-0.025(Bi0.5Na0.5)ZrO3 (BCZTNb0.001-0.025BiNZ) ceramic thick films were prepared by a film scraping process combined with a solid-state twin crystal method, and the influence of sintering temperature was studied systematically. All BCZTNb0.001-0.025BiNZ ceramic thick films sintered at different sintering temperatures have a pure perovskite structure with multiphase coexistence, dense microstructure and typical dielectric relaxation behavior. The conduction mechanism of all samples at high temperatures is dominated by oxygen vacancies confirmed by linear fitting using the Arrhenius law. As the sintering temperature elevates, the grain size increases, inducing the improvement of dielectric, ferroelectric and field-induced strain performance. The 1325 °C sintered BCZTNb0.001-0.025BiNZ ceramic thick film has the lowest hysteresis (1.34%) and relatively large unipolar strain (0.104%) at 60 kV/cm, showing relatively large strain and nearly zero strain hysteresis compared with most previously reported lead-free piezoelectric ceramics and presenting favorable application prospects in the actuator field.

The structural evolution and electric field-induced strain performance of Bi0.5(Na0.41K0.09)TiO3–Ba(Fe0.5Sb0.5)O3 lead-free piezoelectric ceramics

In recent years, lead-free Bi0.5Na0.5TiO3 (BNT) based piezoelectric ceramics with excellent strain properties have gained widespread recognition for their application in high-precision displacement actuators. The (1-x)(0.82Bi0.5Na0.5TiO3-0.18K0.5Bi0.5TiO3)-xBa(Fe0.5Sb0.5)O3 ceramics were fabricated through the die-pressing method in this work. The effect of BFS introduction on the dielectric, ferroelectric and microstructure characteristics of BNKT ceramics was systematically investigated. Among these compositions, the BNKT-0.015BFS ceramics exhibited a piezoelectric strain coefficient (d33*) of 658 pm/V at an electric field of 55 kV/cm, while achieving a strain response of 0.51 % at 85 kV/cm. The observed improvement in strain performance can be attributed to the evolution from non-ergodic relaxor state to ergodic relaxor state caused by BFS substitution. Furthermore, transmission electron microscopy (TEM) explicitly confirmed coexistence of rhombohedral and tetragonal phase and revealed the morphology of nanosized domains. This study adds to a deeper comprehension of the characteristics of strain response enhancement in BNT-based ceramics, opening up avenues for designing novel lead-free piezoelectric ceramics with outstanding electromechanical performance.

Enhancing Short-Range Interactions to Broaden the Temperature Range for Coexistence of Antiferroelectricity and Ferroelasticity.

Antiferroelectric (AFE) materials, characterized by double electric hysteresis loops, can be transformed to the ferroelectric (FE) phase under an external electric field, making them promising candidates for electronic energy storage and solid-state refrigeration. Additionally, the field-induced strain in AFE materials is contingent upon the direction of the electric field, rendering it with a switching characteristic. Although AFE materials have made progress in the field of energy storage and negative electrocaloric effect, the coexistence of AFE and ferroelasticity is still rarely reported. Here, two isomorphic organic-inorganic hybrid perovskites, HDAEPbCl4 and HDAEPbBr4 (HDAE is [2-(hydroxydimethylammonio)ethan-1-aminium]), exhibiting FE-AFE-PE (PE is paraelectric) phase transitions, are presented. Remarkably, the temperature range where AFE and ferroelasticity coexist is significantly broadened from 59.9 K to 115.1 K by strengthening short-range forces via halogen substitution. This discovery extends the family of FE, AFE, and ferroelastic materials, contributing to the development of multifunctional materials and advancing multifunctional material development.

Structural phase transition, relaxor behavior, and ultra-low strain hysteresis in BaTiO3 ceramics modified by BiYO3

In this study, the structural properties, phase transition, relaxor behavior, and strain properties of (1−x)BaTiO3‒xBiYO3 (x= 0.02‒0.15 mol) ceramics were investigated. The room temperature x-ray diffraction and Raman spectroscopy results reveal that (1−x)BaTiO3‒xBiYO3 ceramics undergo phase transition from tetragonal to pseudo-cubic structure with x increasing. The curves of dielectric constant and loss tangent as a function of temperature and frequency show that the dielectric constant was changing from being dependent on temperature to being independent of it upon increasing BiYO3 amount, which is induced obvious dielectric relaxation behavior. Slimmer polarization–electric field (P–E) loops and lower remnant polarization (Pr ) were observed for samples with x ⩾ 0.08. The transition between the ferroelectric and relaxor states leads to the narrow strain–electric field (S–E) loops, which exhibit a high electric field-induced strain of 0.192% and an ultra-low strain hysteresis of 10.4% at an electric field of 70 kV cm−1 for x= 0.04. This excellent performance indicates that 0.96BaTiO3‒0.04BiYO3 ceramic may be promising lead-free materials for high-precision displacement actuators applications.

Effects of B- and A/B-sites Codoping on lattice distortion and defect concentration for high electromechanical response of lead-free piezoelectrics

Effects of different thermal conditions on lead-free (Bi0.65Ba0.35)(Fe0.65Ti0.35)O3 ceramics were studied to reduce secondary phase formation, regulate bismuth vacancies and resulting oxygen vacancies, and Fe ions valence transition during the heat treatment process. The optimal thermal conditions led to a higher d33 = 200 pC/N and a d33* = 420 pm/V. A/B-sites ions replacement in BF35BT, BF35BT-Zr, and BF35BTSZ ceramics were prepared to reveal the effects of different Zr or Sr-Zr-contents. A maximum tetragonality (cT/aT) was estimated for the single doping (Zr) and co-doping (Sr and Zr) cases. For Zr = 0.02, the electric field-induced strain reached its maximum value of d33* = 562 pm/V. Similarly, a strain of d33* = 701 pm/V was observed for Sr-Zr = 0.02. Additionally, the d33* improved to 870 pm/V (90 °C) in Zr = 0.02 and 1130 pm/V (120 °C) in Sr-Zr=0.02. The presence of local structural heterogeneity causes the domain size to decrease as it moves from the micro to the nanoscale. The results demonstrate that improved performance can be associated with reduced concentration of oxygen vacancies, nanodomains by local structural heterogeneity, high lattice anisotropy, higher relative density, and appropriate grain size.

Giant field-induced strain with excellent fatigue performance in (Al0.5Nb0.5)4+-modified 0.85Bi0.5Na0.5TiO3-0.11Bi0.5K0.5TiO3-0.04BaTiO3 piezoelectric ceramics

Utilizing a conventional solid-state reaction procedure, (Al0.5Nb0.5)4+-modified 0.85Bi0.5Na0.5TiO3-0.11Bi0.5K0.5TiO3-0.04BaTiO3 (BNKT-BT) samples were synthesized. The impact of (Al0.5Nb0.5)4+ on the crystal structure, ferroelectric, dielectric, and AC impedance properties was systematically investigated. The XRD patterns demonstrate that the crystal structures of all samples exhibit typical pseudo-cubic features. According to the XPS, the doping of (Al0.5Nb0.5)4+ reduces the concentration of oxygen vacancies inside the ceramics, which significantly affects the relaxation properties. This substitution successfully triggers a change from a non-ergodic relaxor (NR) state to an ergodic relaxor (ER) state, which is ascribed to the weakening of the pinning effect of the oxygen vacancies on the polar nanoregions (PNRs). The ceramics exhibit an enormous monopolar strain of 0.468 % under 60 kV/cm, accompanied by an inverse piezoelectric coefficient (d33*) of 780 pm/V, surpassing the performance of numerous other BNT-based piezoelectric ceramics. After 1×104 switching cycles, the strain value changes slightly, indicating excellent fatigue performance. The considerable strain arises from a reversible transformation of the ER phase to the ferroelectric phase induced by an electric field. This research suggests that (Al0.5Nb0.5)4+-doped BNKT-BT ceramics have good prospects for application in actuators and sensors.

Enhancement of electromechanical response in curved antiferroelectric AgNbO3 ceramics by flexoelectric effect

AgNbO3 is a typical antiferroelectric ceramic with weak ferroelectricity at room temperature. Due to this feature, AgNbO3 has received a lot of attention in electromechanical applications, but most of these studies have focused on the doping of other elements in AgNbO3. In this study, curved AgNbO3 ceramics were fabricated using a gravity-driven annealing process, and the field-induced strains were investigated. The curved ceramic exhibited a significantly higher field-induced nominal strain compared to a flat ceramic. Experimental results revealed that the curved AgNbO3 sample exhibited a maximum nominal strain of 1.22%, significantly surpassing the theoretical value of 0.13%. Analysis of various characterizations confirmed the presence of flexoelectricity, and flexoelectricity played an important role in the ultrahigh electromechanical response of curved AgNbO3 ceramics. Additionally, we demonstrated that curved AgNbO3 ceramics can enhance the flexoelectric coefficient. These findings suggest that curved antiferroelectric ceramics can enhance their displacement output, meeting the requirements for applications in large-strain actuators.

Enhanced electric field-induced strain performance in 0–3 composite ceramics by strain and polarization coupling

Inferior electric field-induced strain and large hysteresis in the high-temperature (1-x)BiFeO3-xBaTiO3-based piezoceramics under low driving electric field, which restricts their practical applications, are dramatically technical bottlenecks. Herein, we successfully prepare the 0–3 type composite piezoceramics with super strain properties under a small electric field. Electric field-induced strain and normalized strain coefficient in the 0–3 composite piezoceramics have been severally increased by 161% and 215% than those of non-composite piezoceramics, and the hysteresis and remnant strain in the 0–3 composite piezoceramics have been decreased by 230% and 165% compared with non-composite piezoceramics. Superior electric field-induced strain properties originate from strain and polarization couple, promoting domain switching at low driving electric field, and the novel strategy will accelerate the development and practical applications of lead-free piezoelectric ceramics.

Critical character of the field dependence of giant values of converse piezoelectric moduli in polycrystalline relaxor ferroelectric 0.675Pb(Mg1/3Nb2/3)O3–0.325PbTiO3

Temperature and field dependences of dielectric permittivity ε and unipolar electric field-induced strain S of the 0.675Pb(Mg1/3Nb2/3)O3−0.325PbTiO3 ceramics have been studied in the 25…200 °C range. Temperature dependences of both dielectric permittivity and converse piezoelectric modulus d*33 show anomalies corresponding to phase transitions between rhombohedral (monoclinic), tetragonal, and cubic phases. Based on the data of dielectric and field-induced strain studies, the E,T-phase diagram is plotted. The possible critical behavior of converse piezoelectric modulus d*33 and its correlation with the position of the known critical point in the E,T-phase diagram of PMN-xPT system are discussed.

Investigation of the large-signal electromechanical behavior of ferroelectric HfO2–CeO2 thin films prepared by chemical solution deposition

Investigation of the large-signal electromechanical behavior of ferroelectric HfO2–CeO2 thin films prepared by chemical solution deposition

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.

Achieving giant field-induced strain in BS-modified BNKT lead-free ferroelectric ceramics

Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNT-BKT) binary systems with the morphotropic phase boundary (MPB) are promising candidates for piezoelectric actuators. However, pure BNT-BKT ceramics commonly exhibit unfavorable electric field-induced strain, which is insufficient to meet the requirements for actuator applications. Rare earth-containing dopants have been extensively explored to modify various materials due to their unique optical, magnetic, and electronic properties. Here, by introducing rare earth ion-containing dopants BiScO3 (BS), the electrical properties of Bi0.5(Na0.84K0.16)0.5TiO3 (BNKT) lead-free ferroelectric ceramics have been modified. X-ray diffraction (XRD) and scanning electron microscopy (SEM) results suggest that the introduction of BS results in an increase in tetragonal (T) phases, reduced grain sizes, and uniform morphologies. Ferroelectric measurements demonstrate that the BS-containing ceramics show slimmer hysteresis loops. The BNKT-2BS ceramics show a noteworthy improvement in electric field-induced strain, with bipolar and monopolar strains of 0.58% and 0.68%, respectively, which are almost 4 times and 6 times higher than those of pure BNKT ceramics. Furthermore, the corresponding normalized strain (d33*) also achieves high values of 967 pm/V and 1133 pm/V, respectively. Temperature-dependent dielectric measurements reveal that BS-containing ceramics exhibit good relaxor characteristics with frequency dispersion and diffuse phase transitions. This study presents a sufficient and feasible strategy for the optimization of strain performance in large displacement actuator applications.