Electric Field-induced Strain Research Articles

Temperature Dependence on Mechanical, Dielectric, and Electric Field-Induced Strain Properties of Lead-Free BNST Ceramics

In this research, temperature dependence on the phase evolution, physical, microstructure, mechanical, dielectric, and electric field-induced strain responses of the Bi0.41Na0.35Sr0.21TiO3 or BNST ceramics were investigated. The BNST ceramic was prepared by a conventional mixed oxide method and sintered at various temperatures from 1100 °C to 1175 °C in order to clarify the optimal sintering temperature for all propereties. X-ray diffraction results showed that all ceramics exhibited a single perovskite without any secondary phases. A mixed between tetragonal and rhombohedral phases were identified for all ceramics. Grain size tended to increase with increasing the sintering temperature. The mechanical improvement was related with the change in densification. The optimum relative density (95.83 %), mechanical (HV = 6.43 GPa, HK = 5.12 GPa, E = 107.57 GPa, and KIC = 2.42 MPa.m1/2), and dielectric properties (ε′ = 1752, tan δ = 0.0514, and δA = 100 K), were obtained for the ceramic sintered at 1125 - 1150 °C. In addition, the obtimum sintering temperature of 1125 - 1150 °C were also found to improve the electric field-induced strain response (Smax = 0.14 % and d*33 = 285 pm/V), and the electrostrictive coefficient (Q33 = 0.0199 m4/C2).

Low driving field-induced large strain in ternary lead-free Na0.5Bi0.5TiO3-SrTiO3-ABO3 piezoceramics

In this letter, three ternary lead-free Na0.5Bi0.5TiO3-SrTiO3-ABO3 piezoceramics (ABO3 = LiNbO3, BaZrO3, and LaFeO3) were studied. The addition of ABO3 into Na0.5Bi0.5TiO3-SrTiO3 ceramic induces a ferroelectric tetragonal-to-ergodic relaxor pseudocubic phase transition, resulting in the significant disruption of ferroelectric order with the shift of the ferroelectric-relaxor transition temperature down to below room temperature. The conventional furnace sintering and microwave sintering methods are conducted in this study to improve the electric field-induced strain properties of BNST-LN piezoceramic. Interestingly, the Na0.5Bi0.5TiO3-SrTiO3-LiNbO3 sample sintered via microwave sintering method shows an ultrahigh normalized strain of 995 pm/V at an ultralow driving field of 2 kV/mm, suggesting a potential candidate for lead-free piezoactuator applications.

Enhanced Electric Field-Induced Strain Properties in Lead-Free BF-BT-Based Piezoceramics by Local Structure Inhomogeneity

Enhanced Electric Field-Induced Strain Properties in Lead-Free BF-BT-Based Piezoceramics by Local Structure Inhomogeneity

Bi(Mg1/2Zr1/2)O3–PbZrO3–PbTiO3 relaxor ferroelectric ceramics with large and temperature-insensitive electric field-induced strain response

A large strain (0.33% at 5 kV mm−1) and high temperature stability (strain variation less than 8%) were obtained simultaneously in new BMZ-PZ-PT ternary ceramics by the substitution of BMZ for PZ in PZT ceramics.

Ferroelectric-Thermoelectric Hybrid Property in La-Doped BaTiO3 Polycrystalline Ceramics

Ceramic systems of Ba1−xLaxTiO3 with La-doping contents of x = 0, 0.005, 0.01, 0.02, 0.04, and 0.08, denoted as BT, BLT0.5, BLT1, BLT2, BLT4, and BLT8, respectively, were synthesized by the solid-state reaction route. All systems were observed the crystal structure, dielectric constant (), dielectric loss polarization and electric field-induced strain. Thermoelectric properties including electrical resistivity (), Seebeck coefficient ( S ), and power factor (PF) of all systems were also performed. The BT0.5 provided the best shot in a term of ferroelectric properties since lanthanum could well diffuse into the BT lattice and enhance the dielectric constant and polarization, while BT1 was quite good for thermoelectric aspect as ion displacement and electrical conductivity was well incorporated. The result suggests that the BT1 system has a possible potential to be further developed for high-temperature thermoelectric applications in the case of polycrystal ceramics.

Enhancement of electrostrictive and magnetic performance with high energy storage efficiency in Fe2O3 nanoparticles-modified Ba(Zr0.07Ti0.93)O3 multiferroic ceramics

Lead-free Ba(Zr0.07Ti0.93)O3/xFe2O3 (93BZT/xFe2O3, x = 0-1.0 mol%) ceramics were prepared using a conventional mixed oxide method. The Fe2O3 nanoparticles additive disturbed the long-range ferroelectric order of the ceramics by changing the normal P-E hysteresis loop for the unmodified ceramic into a constricted loop for the 0.5 mol % Fe2O3 ceramic thereby resulting in an enhancement of the electric field-induced strain and electrostrictive coefficient at this composition. The 1.0 mol% Fe2O3 ceramic showed the highest energy storage efficiency (98%). The M-H hysteresis loop and the magnetocapacitance value were improved by the Fe2O3 nanoparticles additive. Results indicated that the magnetic and electrical performances of Ba(Zr0.07Ti0.93)O3 modified by the Fe2O3 nanoparticle could be remarkably improved, thereby suggesting that this ceramic system has potentials for multifunction device applications.

Giant electric field-induced strain with low hysteresis in Bi0.5Na0.5TiO3-xSr0.7Ca0.3TiO3 lead-free piezoceramics

Giant electric field-induced strain with low hysteresis in Bi0.5Na0.5TiO3-xSr0.7Ca0.3TiO3 lead-free piezoceramics

Highly enhanced discharged energy density and superior cyclic stability of Bi0.5Na0.5TiO3-based ceramics by introducing Sr0.7Ca0.3TiO3 component

The composition-induced phase transition from ferroelectric to relaxor and cycling stability is critical for energy storage application of Bi0.5Na0.5TiO3 (BNT) ceramics. The paraelectric Sr0.7Ca0.3TiO3 (SCT) component is selected to modify the ferroelectric phases of BNT ceramics and improve its energy storage properties. A tiny amount of manganese is used to reduce leakage current. High breakdown field of 210 kV/cm, large recoverable energy density of 2.64 J/cm3, and high power density of 61.89 MW/cm3 are achieved simultaneously in the SCT modified BNT ceramics. Meanwhile, an improved discharged energy density for practical application is obtained within the temperature range of 20–120 °C. By deviating from the critical composition with giant strain, the discharged energy density of 1.11 J/cm3 with excellent stability of cycling performance after 7100 cycles can be achieved. Therefore, the as-proposed solution can solve the ceramic cracking originating from high electric field-induced giant strain, and promote the practical capacitor application.

One simple approach, two remarkable enhancements: Manipulating defect dipoles and local stress of (K, Na)NbO3-based ceramics

Although the composition-driven multi-phase coexistence strategy has been widely used to modify the piezoelectric properties of potassium sodium niobate ((K, Na)NbO3, KNN) based ceramics, the trade-off between long-range ferroelectric ordering and chemical additives-induced disorder hinders the further improvement of piezoelectricity and makes the electric field-induced strain temperature-dependent. Herein, to resolve two issues, we proposed a new concept, that is, manipulating defect dipoles and local stress of a pre-constructed multi-phase coexistence through controlling zirconium (Zr) content. We validated the new concept by designing 0.96(K0.4Na0.6)Nb0.955Sb0.045O3-0.04(Bi0.5Na0.5)Zr(1+x)O3 ceramics. In samples with Zr deficiency (i.e., x=-0.1), we obtained high retention of 91% in normalized unipolar strain (Suni) over the temperature range of 30-160 °C, even under low electric fields of 10-20 kV/cm, superior to those of other representative KNN-based ceramics. In samples with slight Zr excess (i.e., x=0.07), we achieved an increase in direct piezoelectric coefficient (d33) and converse piezoelectric coefficient (d33*) by 12% and 25%, respectively, in comparison with that at x=0. The enhanced temperature stability stems from the released domain walls that are pinned by defect dipoles, and the increased d33 (and d33*) originates from the synergetic contributions of the multi-phase coexistence, increased grain size, and stabilization of the ZrO2 secondary phase. Therefore, our new concept would benefit the composition design and performance improvement of KNN-based ceramics in the future.

Electric field control of the reversible magnetocaloric effect in strain-mediated Ni37.5Co12.5Mn35Ti15/PMN-PT composite

In this study, the martensite transformation of Ni37.5Co12.5Mn35Ti15 ribbon was studied and regulated by the electric field-induced strain in the PMN-PT substrate. The reversible magnetocaloric effect in the Ni37.5Co12.5Mn35Ti15/PMN-PT composite was enhanced by manipulating transition paths under the coupling of magnetic field and electric field, which is significantly important for applications in solid-state refrigeration. With the assistance of E = +8 kV/cm, the reversible entropy change increased from 19.5 to 25.7 J/kgK at 294.5 K. Meanwhile, the reversible cooling temperature span was also enlarged. Hence, the reversible refrigerant capacity was enhanced from 83 to 131 J/kg, and the increase ratio reached 58%. On this basis, an active magnetic regenerating cycle facilitated by an electric field was designed. This work provides an effective method for enhancing reversible caloric effects in first-order phase transition materials via electric fields.

An investigation of structural, electrical and optical properties of lead-free barium zirconium titanate (BZT)-based ceramic compounds

ABSTRACT The present work is a demonstration of improved electrical and optical properties of barium zirconium titanate ceramic modified by the addition of Europium, i.e. Ba(1–x)Eu2x/3Zr0.05Ti0.95O3 (x = 0.01, 0.02, 0.03, 0.04). The Rietveld refinement studies confirmed the formation of tetragonal phase in the samples. The scanning electron microscopy (SEM) images revealed a decrease in grain size with increasing Eu concentration. The dielectric constant, dielectric loss and TCC plots are drawn to study temperature and frequency dependence of the samples. The electric field-induced strain behavior has been studied for all the compositions of the synthesized ceramic at room temperature. Conduction mechanism in the samples as a function of frequency and temperature was studied with the help of AC conductivity data. Also, the effect of grain and grain boundaries are studied in term of Cole–Cole plots. Photoluminescence (PL) emission spectra were recorded upon excitation with a wavelength of 360 nm.

Proposing a phase diagram for BNT-BKT-KNN and finding a new MPB and large strain region in the system

Detailed investigation on “1-x-yBNT-xBKT-yKNN” was done for better understanding of its phase diagram which is crucial for estimating a useful composition range for actuation applications. A phase diagram is proposed along with a MPB between “rhombohedral ferroelectric and tetragonal ferroelectric” phases in the range x = 0.05 (0.04 ≤ y < 0.08) and x = 0.10 (0.02 ≤ y < 0.06). However addition of KNN above the critical value y ≥ 0.12 is observed to drive the system toward cubic structure. A region having large “electric field induced strain (EFIS)” value (∼0.45%) is also identified in the phase diagram.

Enhanced electric field-induced strain and electrostrictive response of lead-free BaTiO3-modified Bi0.5(Na0.80K0.20)0.5TiO3 piezoelectric ceramics

ABSTRACT Lead-free (1-x)Bi0.5(Na0.80K0.20)0.5TiO3-xBaTiO3 or (1-x)BNKT-xBT (x = 0 – 0.15 mol fraction) piezoelectric ceramics have been investigated. The optimum density was found for the ceramic sintered at 1125°C, corresponding 98 – 99% of their theoretical values. All ceramics had a single perovskite structure. The coexisting mixed tetragonal-rhombohedral phases all over the entire compositional range with tetragonal phase becoming superior at higher BT. The diffuse phase transition was promoted by the addition of BT. With increasing BT content, the Tm and Td values were found to decrease. Phase transition from ferroelectric (FE) phase to ergodic relaxor (ER) phase was also induced by the changes in BT content. These changes significantly suspended long-range ferroelectric order, then correspondingly reducing the Pr and Ec , resulting in an improvement of electrostrictive and electric field-induced strain responses. A significant increasing of electric field-induced strain response (Smax = 0.37% and d*33 = 630 pm/V) is noted for the x = 0.05 ceramic. Furthermore, high electrostrictive coefficient (Q33 ) of 0.0421 m4/C2 is observed for this composition, which was more than ~ 2 times (~108%) as compared to the pure BNKT ceramic. The studied results indicated these ceramics can be considered promising candidates for actuator applications.

Optimized strain properties with small hysteresis in BNT-based ceramics with ergodic relaxor state

Electric field-induced high strain with small hysteresis and good temperature stability is necessary for piezoactuators devices. Most of previous works focus on the giant strain achieved in Bi0.5Na0.5TiO3 (BNT)-based ceramics through electric field-induced transition from nonergodic relaxor to ferroelectric state, while the high remnant strain or/and large hysteresis are always accompanying. In this work, through enhancing the local polarization by rare earth ions doping (e.g., La3+), we propose to improve the strain properties of BNT-based lead-free ceramics with ergodic relaxor state which displays the near zero remnant strain, small hysteresis, high temperature stability but the low strain value. The addition of La3+ would not change the ergodic relaxor state, but can improve the short-range correlation of local polar nanoregions, cut down the critical electric field of transition between relaxor and ferroelectric states, and elevate the electrostrictive effect of ceramics. Finally, high strain of ∼0.3 % with low hysteresis of ∼8−30 % was obtained in the broad temperature range from room temperature to 100 °C, which is superior to previous BNT-based ceramics and other lead-based/lead-free ceramics. This work affords a paradigm to regulate the ergodic relaxor state to optimize the strain properties, which give the significant guide for strain developments.

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.

Manganese-doping enhanced local heterogeneity and piezoelectric properties in potassium tantalate niobate single crystals.

Ion doping, an effective way to modify the nature of materials, is beneficial for the improvement of material properties. Mn doping exhibits gain of piezoelectric properties in KTa1-x Nb x O3 (KTN). However, the impact mechanism of Mn ions on properties remains unclear. Here, the effects of Mn doping on local heterogeneity and piezoelectric properties in KTN are studied. The electric field-induced strain of Mn-doped KTN is ∼0.25% at 10 kV cm-1, 118% higher than that of pristine KTN. Meanwhile, as a result of Mn doping, the dielectric permittivity was tripled and the ferroelectricity was modified. The changes in A1(2TO), B1 + E(3TO) and E(4TO) vibrations characterized by Raman spectra indicate increased local polarization, weak correlation of dipoles and distorted lattices in Mn-doped KTN, respectively. First-principles calculations demonstrate stronger local heterogeneity introduced by Mn dopants, which weakens the dipole correlations and reduces domain sizes. As a result, the decreased domain sizes, combined with the larger ratio of lattice parameters c and a of the Mn-contained portion, are responsible for the higher piezoelectricity. This work reveals the impact on properties of KTN from Mn dopants and the prominent role of local heterogeneity in improving piezoelectricity, being valuable for the optimization and design of material properties.

Na0.5Bi0.5TiO3-based ferroelectric relaxor with high thermal stability and anti-fatigue for charge-discharge properties

Apart from discharge energy density (Wr) and discharging time (t0.9), thermal stability and anti-fatigue for charge-discharge performance are also the important performance indexes for dielectric pulsed capacitor. Na0.5Bi0.5TiO3 based ceramics are usually accompanied by huge electric field-induced strain when appling electric field, resulting in the fatigue phenomenon and thermal accumulation effect in the cycling process. In this work, Na0.5Bi0.5TiO3-xNaNbO3 (NBT-xNN) ferroelectric relaxor ceramic has been prepared by the solid state reaction process. The effect of NaNbO3 content on microstructures, impedance spectroscopy, electric-field-induced strain and charge-discharge performance of NBT-xNN ceramics have been investigated systematically. Results indicate the proper percent of NaNbO3 could favor the formation of polar nanoregions (PNRs), which leads to the diffusion of phase transition and the diminution of electromechanical strain. Therefore, the high thermal stability and anti-fatigue for charge-discharge property has been achieved in NBT-xNN ceramics. An enhanced discharging energy density of 2.44 J cm−3 along with discharge time of 0.31 μs could be obtained in the NBT-xNN with x = 0.3, and a very stable discharge energy density of 2.06 J cm−3 concomitantly with discharge time less than 0.37 μs could be gained in a wide temperature range of 20–150 °C with a fluctuation of ±4% after 104 charge/discharge cycles. This work would contribute to the development of charge-discharge system, especially dielectric capacitor, for green pulsed power devices.

Large electric field-induced strain in BiFeO3-based ceramics by tuning defect dipoles and phase structure

High-performance lead-free piezoelectric materials with high Curie temperature can be used as substitutes for lead-based piezoelectric components to address serious environmental issues. In our works, 0.7Bi1.05Fe+3(1−x)Fe2+xO3−δ– 0.3BaTiO3 (BF–BT–xFe2+) ceramics, which demonstrate outstanding large-signal piezoelectric coefficient of d33* = 510 p.m./V and electric field-induced bipolar strain of Δsp−p = 0.34% (peak-to-peak) at 50 kV/cm. Meanwhile, optimal remanent polarization of Pr = 55.8 μC/cm2, piezoelectric coefficient of d33 = 178 pC/N, and Curie temperature of Tc = 485 °C are achieved at x = 0.07. Of particular interesting the preferred strain is observed in BF–BT–xFe2+ ceramics with major pseudo-cubic phase. Results showed that prior electric properties are derived from synergistic effect of defect dipoles and phase structure together with non-180° domain switch. The defect dipole builds an internal electric field that favors ferroelectric domain formation and polarization. In addition, the formation of defect breaks the geometry symmetry of cubic structure.

Residual Stress and Ferroelastic Domain Reorientation in Declamped {001} Pb(Zr0.3Ti0.7)O3 Films.

Ferroelectric films are often constrained by their substrates and subject to scaling effects, including suppressed dielectric permittivity. In this work, the thickness dependence of intrinsic and extrinsic contributions to the dielectric properties was elucidated. A novel approach to quantitatively deconstruct the relative permittivity into three contributions (intrinsic, reversible extrinsic, and irreversible extrinsic) was developed using a combination of X-ray diffraction (XRD) and Rayleigh analysis. In situ synchrotron XRD was used to understand the influence of residual stress and substrate clamping on the domain state, ferroelastic domain reorientation, and electric field-induced strain. For tetragonal {001} textured Pb0.99(Zr0.3Ti0.7)0.98Nb0.02O3 thin films clamped to an Si substrate, a thickness-dependent in-plane tensile stress developed during processing, which dictates the domain distribution over a thickness range of 0.27- [Formula: see text]. However, after the films were partially declamped from the substrate and annealed, the residual stress was alleviated. As a result, the thickness dependence of the volume fraction of c -domains largely disappeared, and the out-of-plane lattice spacings ( d ) for both a - and c -domains increased. The volume fraction of c -domains was used to calculate the intrinsic relative permittivity. The reversible Rayleigh coefficient was then used to separate the intrinsic and reversible extrinsic contributions. The reversible extrinsic response accounted for ~50% of the overall relative permittivity (measured at 50 Hz and alternating current (ac) field of 0.5·Ec ) and was thickness dependent even after poling and upon release.

Enhanced Piezoelectric Properties From the Electric Field-Induced Ferroelectric Transition at the MPB of BiGaO₃-Substitued Na1/2Bi1/2TiO₃-BaTiO₃(NBT-BT)

A ternary solid solution of lead-free Na1/2Bi1/2TiO3-BaTiO3 and BiGaO3 (NBT-BT-BG) was prepared using conventional, solid-state synthesis. Compositions were prepared near the morphotropic phase boundary (MPB) of ( 1- x )NBT- x BT, located near x = 0.04 -0.09 , and then systematically substituted with 2-5 mol% BG to investigate the effect of the compositional change on the accompanying properties. Dielectric, ferroelectric (FE), and piezoelectric properties were analyzed and compared for all prepared compositions. The FE to ergodic (ER) relaxor transition temperature ( [Formula: see text]) and the reversible electric field-induced relaxor to FE transition were investigated to determine their effects on the strain response. It was found that the MPB composition of 0.93NBT-0.07BT required the least amount of the tertiary phase, 3 mol% BG, to reach a disordered, ER state while also requiring the largest electric fields to induce an FE phase compared with similarly substituted NBT- x BT samples. This led to a maximum unipolar strain of 0.53% (d33* = 866 pm/V) for the 0.93NBT-0.07BT-0.04BG composition. The largest strains for each system occurred in compositions that were in the ER region at room temperature. These results demonstrate that the addition of BG most effectively destabilizes the long-range dipole order near the MPB composition of NBT-BT, which results in an enhanced electric field-induced strain.