High Electric Field-induced Strain Research Articles

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.

Fine-grained high-performance Ba0.85Ca0.15 Zr0.1Ti0.9O3 piezoceramics obtained by current-controlled flash sintering of nanopowders

Due to environmental concerns, extensive research has been carried out to develop high-performance lead-free piezoceramics capable of replacing commercial lead-based materials. The lead-free (Ba0.7Ca0.3)TiO3 −Ba(Zr0.2Ti0.8)O3 system has emerged as a candidate for room temperature transducer applications because a high piezoelectric charge coefficient is achieved in this system for compositions at the morphotropic phase boundary. However, conventional ceramic processing of these eco-friendly piezoceramics demands high energy consumption because long-lasting, high-temperature heat treatments are needed, which often lead to microstructural degradation that compromises the material reliability. Field-assisted flash sintering has started to be explored since the application of an adequate electric field was shown to significantly reduce the sintering time and temperature, thereby controlling grain growth. In this work, Ba0.85Ca0.15Zr0.1Ti0.9O3 ceramics are obtained by current-controlled flash sintering of mechanosynthesized nanopowders. Exhaustive control of the sintering parameters allows tailoring of the microstructure, which allows dense fine-grained flash-sintered ceramics exhibiting a high electric field-induced strain response to be obtained.

High electric field-induced strain properties in La-doped Pb(In1/2Nb1/2)O3–PbZrO3–PbTiO3 relaxor ferroelectric ceramics

Piezoelectric ceramics with high strain response and low hysteresis are highly in demand for high-performance actuator applications. Unfortunately, the trade-off relationship between large field-induced strain and low hysteresis in piezoelectric ceramics is a key challenge for designing high-performance piezoelectric actuators. Herein, ymol%La-doped 0.10 Pb(In1/2Nb1/2)O3-xPbZrO3-(0.90–x)PbTiO3 [0.10PIN-xPZ-(0.90-x)PT: ymol%La] ternary relaxor ferroelectric ceramics were prepared by conventional solid-state reaction technique. Pb(In1/2Nb1/2)O3 (PIN) as a relaxor end member was introduced into (Pb,La) (Zr,Ti)O3 (PLZT) system to improve relaxor characteristics and strain properties. A giant strain of 0.23% was obtained in 0.10PIN-0.59PZ-0.31 PT: 8mol%La ceramic at the electric field of 20 kV/cm, with a high piezoelectric d33* of 1150 pm/V and low hysteresis Hy of 6.4%, exhibiting a potential application in high-performance piezoelectric actuators. Furthermore, the effects of La ion doping and components on the ferroelectric, dielectric and electric field-induced strain properties were investigated, and provides a new way for improve the strain properties of piezoelectric materials.

Enhanced Piezoelectric, Ferroelectric, and Electrostrictive Properties of Lead-Free (1-x)BCZT-(x)BCST Electroceramics with Energy Harvesting Capability.

Next-generation electronics and energy technologies can now be developed as a result of the design, discovery, and development of novel, environmental friendly lead (Pb)-free ferroelectric materials with improved characteristics and performance. However, there have only been a few reports of such complex materials' design with multi-phase interfacial chemistry, which can facilitate enhanced properties and performance. In this context, herein, novel lead-free piezoelectric materials (1-x)Ba0.95 Ca0.05 Ti0.95 Zr0.05 O3 -(x)Ba0.95 Ca0.05 Ti0.95 Sn0.05 O3 , are reported, which are represented as (1-x)BCZT-(x)BCST, with demonstrated excellent properties and energy harvesting performance. The (1-x)BCZT-(x)BCST materials are synthesized by high-temperature solid-state ceramic reaction method by varying x in the full range (x = 0.00-1.00). In-depth exploration research is performed on the structural, dielectric, ferroelectric, and electro-mechanical properties of (1-x)BCZT-(x)BCST ceramics. The formation of perovskite structure for all ceramics without the presence of any impurity phases is confirmed by X-ray diffraction (XRD) analyses, which also reveals that the Ca2+ , Zr4+ , and Sn4+ are well dispersed within the BaTiO3 lattice. For all (1-x)BCZT-(x)BCST ceramics, thorough investigation of phase formation and phase-stability using XRD, Rietveld refinement, Raman spectroscopy, high-resolution transmission electron microscopy (HRTEM), and temperature-dependent dielectric measurements provide conclusive evidence for the coexistence of orthorhombic + tetragonal (Amm2 + P4mm) phases at room temperature. The steady transition of Amm2 crystal symmetry to P4mm crystal symmetry with increasing x content is also demonstrated by Rietveld refinement data and related analyses. The phase transition temperatures, rhombohedral-orthorhombic (TR-O ), orthorhombic- tetragonal (TO-T ), and tetragonal-cubic (TC ), gradually shift toward lower temperature with increasing x content. For (1-x)BCZT-(x)BCST ceramics, significantly improved dielectric and ferroelectric properties are observed, including relatively high dielectric constant εr ≈ 1900-3300 (near room temperature), εr ≈ 8800-12900 (near Curie temperature), dielectric loss, tan δ ≈ 0.01-0.02, remanent polarization Pr ≈ 9.4-14 µC cm-2 , coercive electric field Ec ≈ 2.5-3.6kV cm-1 . Further, high electric field-induced strain S ≈ 0.12-0.175%, piezoelectric charge coefficient d33 ≈ 296-360 pC N-1 , converse piezoelectric coefficient ≈ 240-340 pm V-1 , planar electromechanical coupling coefficient kp ≈ 0.34-0.45, and electrostrictive coefficient (Q33 )avg ≈ 0.026-0.038 m4 C-2 are attained. Output performance with respect to mechanical energy demonstrates that the (0.6)BCZT-(0.4)BCST composition (x = 0.4) displays better efficiency for generating electrical energy and, thus, the synthesized lead-free piezoelectric (1-x)BCZT-(x)BCST samples are suitable for energy harvesting applications. The results and analyses point to the outcome that the (1-x)BCZT-(x)BCST ceramics as a potentially strong contender within the family of Pb-free piezoelectric materials for future electronics and energy harvesting device technologies.

Large strain and reduced hysteresis of BiFeO3-xBaTiO3 lead-free ceramic via multiphase coexistence and relaxor behaviors

Ferroelectric ceramics with large strain response, low hysteresis and high Curie temperature (TC) are required for contemporary displacement actuator. In this work, (1-x)BiFeO3-xBaTiO3 ceramics were synthesized using traditional solid sintering technique. A high electric field-induced strain (0.25%), a relatively low hysteresis (22.5%) and a high Curie temperature (415 °C) were achieved in BiFeO3-0.35BaTiO3 ceramic. Meanwhile, the ceramics exhibited apparent relaxor behavior owing to the local structural heterogeneity. Aberration-corrected scanning transmission electron microscopy revealed that polar nano-regions with multiphase coexistence occur in the material, which is the microstructure origin of the enhanced strain and low hysteresis in BiFeO3-0.35BaTiO3 ceramics. This work indicates that BiFeO3–BaTiO3-based ceramics are good high-temperature ferroelectric materials and are promising candidates for high-precision actuator.

0.4% Electrostrain at Low Field in Lead-Free Bi-Based Relaxor Piezoceramics by La Doping

This work investigates the effects of lanthanum doping on the crystal structure, surface morphology, dielectric properties, ferroelectric properties, piezoelectric properties, and electromechanical strain properties of lead-free (Bi0.47Na0.47Ba0.06)1−xLaxTiO3 piezoelectric ceramics. All specimens were fabricated by a traditional solid-state reaction method. The results of crystal structure and dielectric properties categorize all specimens as relaxor materials. The results of dielectric properties and ferroelectric properties confirm the nonergodic-to-ergodic transformation as a function of La content. At the phase transition point, the material shows a high electric field-induced strain of 0.4% under an applied electric field of 5 kV/mm. The large electromechanical strain response at low applied field in the 0.02 mol La specimen may contribute to the two synergistic effects. First, the electric field induced the reversible ergodic-ferroelectric phase transition, which can generate the large strain. Second, the nonergodic and ergodic phases coexist at the phase transformation point, which can reduce the driving field by facilitating the growth of ferroelectric domains.

Ultra-low hysteresis electric field-induced strain with high electrostrictive coefficient in lead-free Ba(ZrxTi1-x)O3 ferroelectrics

From the application point of view, high electric field-induced strain with ultra-low hysteresis or hysteresis-free characteristic is highly desired in high-precision displacement actuators. In this work, lead-free Ba(ZrxTi1-x)O3 (BZT) ferroelectrics with x in the range between 0.02 and 0.1 were fabricated by a conventional solid state reaction method. The structural evolution and electrical properties were investigated systematically with an emphasis on electrostrictive effect. As x increases from 0.02 to 0.1, the crystal lattice parameters (a and c axes) increase while the tetragonality (c/a-1) goes down. In addition, the Curie temperature (TC) of BZT decreases gradually, while the temperatures corresponding to tetragonal-to-orthorhombic (T-O) and orthorhombic-to-rhombohedral (O-R) phase transitions increase. Ultra-low hysteresis (<8%) and high electric field-induced strains (>0.15% at 60 kV/cm) are observed in all studied compositions. Most importantly, a high longitudinal electrostrictive coefficient Q33 (0.0453 m4/C2) was also identified in x = 0.1 composition. This work not only reports high electric field-induced strains with ultra-low hysteresis and high Q33 in lead-free BZT ferroelectrics, but also indicates a potential application for BZT ceramics in high-precision displacement actuators.

High dielectric permittivity and electrostrictive strain in a wide temperature range in relaxor ferroelectric (1-x)[Pb(Mg1/3Nb2/3)O3-PbTiO3]-xBa(Zn1/3Nb2/3)O3 solid solutions

High electric field-induced strain with ultralow hysteresis, which is often generated based on electrostrictive effects in ferroelectric materials, is highly desired due to its potential applications in high-precision displacement actuators. In this paper, (1-x)[Pb(Mg1/3Nb2/3)O3-PbTiO3]-xBa(Zn1/3Nb2/3)O3 [(1-x)(PMN-PT)-xBZN] ceramics were fabricated by a solid-state reaction method. The effect of Ba(Zn1/3Nb2/3)O3 (BZN) content on dielectric and electrostrictive properties in relaxor ferroelectric PMN-PT solid solutions was investigated in detail by dielectric spectra, polarization-electric field (P-E) hysteresis loops and strain-electric field (S-E) curves. With an increasing BZN content, the temperature stability of the dielectric permittivity of (1-x)(PMN-PT)-xBZN is improved due to the formation of two coexistent phases. A high electrostrictive strain (~0.17% at 60 kV/cm) with an ultralow hysteresis (<10%) characteristic is obtained in a composition where x = 0.1725. The strain versus polarization (S-P) curves measured from 30 °C to 130 °C can be well fitted based on a quadratic relation, suggesting the dominating role of the electrostrictive effect. The longitudinal electrostrictive coefficient Q33 for this system ranges from 0.0254 m4/C2 to 0.0318 m4/C2. Our results suggest that (1-x)(PMN-PT)-xBZN ferroelectric ceramics are potential candidates for applications in capacitors and high-precision displacement actuators.

High thermal stability of electric field-induced strain in (1−x)(Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 lead-free ferroelectrics

In ferroelectric materials high electric field-induced strain (EFIS) with good thermal stability is of much interest from both fundamental research and potential applications. Here we propose a strategy to achieve high thermally stable EFIS based on electrostrictive effect and thermal stability of polarization. According to this strategy, we synthesized (1−x)(Bi0.5Na0.5)TiO3-xBa0.85Ca0.15Ti0.9Zr0.1O3 (BNT-xBCZT) ferroelectric ceramics in order to tailor the thermal stability of dielectric permittivity, polarization and EFIS. A dielectric platform with a wide temperature region is induced by increasing x from 0.24 to 0.36 gradually. From 30 °C to 150 °C, a variation of 20% polarization results in a change of 36% EFIS, suggesting a good thermal stability as expect. Temperature-insensitive electrostrictive coefficient Q33 ranges from 0.0264 m4/C2 to 0.0314 m4/C2. These results not only prove the effectiveness of this strategy, but also suggest that this strategy can be applied to other ferroelectric materials to improve the thermal stability.

High electric field-induced strain with ultra-low hysteresis and giant electrostrictive coefficient in barium strontium titanate lead-free ferroelectrics

Ferroelectrics with high electrostrictive properties are of great interest in fundamental researches and industrial applications. In this work, the phase structural evolution, dielectric properties as well as electrostrictive properties in barium strontium titanate [(Ba1-xSrx)TiO3, BST] lead-free ferroelectrics with x from 0.05 to 0.4 were investigated in details. High electric field-induced strain (∼0.2%) at 60 kV/cm are obtained in x = 0.05 and 0.1 compositions. More importantly, almost purely positive strains with ultra-low hysteresis (<8%) determined from bipolar strain-electric field curves are observed in compositions with x from 0.05 to 0.3, suggesting the dominating role of electrostrictive effect. Temperature-insensitive and composition-insensitive longitudinal electrostrictive coefficient Q33 for BST ceramics with giant values from 0.0409 m4/C2 to 0.0479 m4/C2 is identified. These features suggest that BST ceramics not only possess high electric field-induced strain with ultra-low hysteresis and giant Q33, but also are good candidates for potential application in high-precision actuator devices.

A strategy for obtaining high electrostrictive properties and its application in barium stannate titanate lead-free ferroelectrics

Recently electrostrictive effect in ferroelectrics has attracted much attention, since the electric field-induced strain based on such an effect possesses an ultra-low hysteresis, which is of special interest to both fundamental research and potential application in high-precision actuators. In this paper, we propose a strategy to obtain high electrostrictive properties in ABO3 perovskite structure BaTiO3 (BT)-based ferroelectric ceramics by means of doping. The doping element, amount, valence as well as position are specified according to this strategy. It is suggested that B-site Sn4+-doped BT, i.e., Ba(Ti1-xSnx)O3 (BTS), would possess superior electrostrictive properties. The structural evolution and electrical properties of BTS ferroelectric ceramics were investigated in detail in order to verify this deduction. Besides the ferroelectric-to-relaxor transition with respect to the increase of x from 0.06 to 0.11, expected and high electric field-induced strain (> 0.08% at 40 kV/cm) with a very ultra-low hysteresis (< 8%) is obtained in x = 0.10–0.11 compositions. High longitudinal electrostrictive coefficient Q33 ranges from to 0.0398 m4/C2 to 0.0515 m4/C2 accompanying with temperature- and composition-insensitive characteristics. These results not only prove the effectiveness of this strategy, but also pave a way to search for novel kinds of electrostrictive systems in ferroelectrics.

High thermal stability of energy storage density and large strain improvement of lead-free Bi0.5(Na0.40K0.10)TiO3 piezoelectric ceramics doped with La and Zr

Properties of lead-free Bi0.5-xLaxNa0.40K0.10Ti0.98Zr0.02O3 (x = 0.000–0.040) ceramics were investigated. All ceramics have a pure perovskite structure. A high energy storage density (∼1.00 J/cm3) at room temperature (RT) is noted for the x = 0.030 sample, while x = 0.020 and 0.040 samples have very high thermal stability of energy storage density of ∼3% (at 75–150 °C). Furthermore, the x = 0.030 and 0.040 samples have the highest energy storage efficiency (η) value of 94% at 125 °C with high thermal stability (η = 84–95% at 25–150 °C). The x = 0.005 sample has high electric field-induced strain (Smax = 0.42%) and high normalized strain coefficient (d*33 = Smax/Emax = 700 pm/V) with large improvements (∼200% and 163% for Smax and d*33, respectively), as compared to the based composition. This ceramic system has potentials for piezoelectric and/or energy storage density applications.

Electrical properties of holmium doped (K,Na)(Nb,Sb)O3-(Bi,Na)HfO3 ceramics with wide sintering and poling temperature range

Here the electrical properties can be modified by the chemical compositions {0.965K0.45Na0.55Nb(1-x)SbxO3-0.035Bi0.5Na0.5HfO3, KNNSx-BNH}, and moreover its temperature (i.e., sintering or poling temperatures) sensitivity of piezoelectricity can be further weakened by doping rare earth (i.e., Ho), which is beneficial to reproduction. Rhombohedral-tetragonal (R-T) phase boundary can be formed in the ceramics with a wide composition range of x = 0.04–0.08 by simultaneously increasing rhombohedral-orthorhombic (R-O) phase transition temperature (TR-O) and decreasing orthorhombic-tetrahedral (O-T) phase transition temperature (TO-T). The R-T phase boundary warrants a large piezoelectric coefficient (d33) of ∼418 pC/N as well as a high Curie temperature (TC) of ∼242 °C in the ceramics with x = 0.04, and a high electric field-induced strain of ∼0.33% (Smax/Emax = 983 pm V−1) as well as a large d33 (∼408 pC/N) can be attained in the ceramics with x = 0.07. Especially, a high recoverable energy density (Wrec∼0.54 J/cm3) can be gained in the ceramics with x = 0.10 under a low breakdown strength (∼129 kV/cm). The piezoelectricity sensitive to sintering or poling temperatures can be weakened by introducing Ho element, that is, a high d33 of 400–458 pC/N can be attained in a wide range of sintering temperatures (1070–1120 °C) and poling temperatures (13–120 °C). We believe that this investigation can be a significant promotion on the development of practical applications in (K, Na)NbO3-based ceramics.

Giant piezoelectric effect and high strain response in (1−x)(K0.45Na0.55)(Nb1−ySby)O3 -xBi0.5Na0.5Zr1−zHfzO3 lead-free ceramics

Here, we reported a high electric field-induced strain value of 0.34% (Smax/Emax=901pmV−1) under a low electric field of 3.7kV/mm as well as a large d33 (∼418pC/N) in the (1−x)(K0.45Na0.55)(Nb1−ySby)O3 -xBi0.5Na0.5Zr1−zHfzO3 ceramics with x=0.035, y=0.04, and z=0.75, which is mainly ascribed to the involvement of R-T phase boundary as well as optimized compositions (Hf/Zr). We investigated the relationships among composition, phase boundary, and electrical properties through (1−x)(K0.45Na0.55)(Nb1−ySby)O3 -xBi0.5Na0.5Zr1−zHfzO3 ceramics. The R-T phase boundary is constructed in the ceramics with 0.035≤x≤0.05, 0.04≤y≤0.08, and 0≤z≤1.0. Meanwhile, the highest piezoelectric coefficient of d33∼442 pC/N were obtained for x=0.0375, y=0.04, and z=0.15 due to the coexistence of R and T phases. Both dielectric constant and remanent polarization can gain the most excellent values for R-T, which is responsible for the enhanced piezoelectricity. We believe that such an investigation can promote the electrical properties of (K, Na)NbO3-based ceramics and then provide practical applications.

High strain in (K0.40Na0.60)(Nb0.955Sb0.045)O3–Bi0.50Na0.50ZrO3lead-free ceramics with large piezoelectricity

We have attained both large piezoelectricity and high strain in (1 − x)(K0.40Na0.60)(Nb0.955Sb0.045)O3–xBi0.50Na0.50ZrO3 [(1 − x)KNNS–xBNZ] lead-free ceramics by forming a rhombohedral (R) and tetragonal (T) phase boundary. The ceramics with 0.035 < x < 0.05 possess R and T phases' coexistence. A large d33 value of ∼450 pC N−1 has been attained when the x value reached 0.04 owing to the involved R–T phase boundary, which is higher with respect to d33 ∼ 416 pC N−1 of textured (K,Na,Li)(Nb,Ta,Sb)O3 ceramics reported by Saito et al. [Nature, 2004, 432, 84]. In addition, it is worth noting that such a ceramic simultaneously possesses a high electric field-induced strain (0.2%) under a low driving electric field of ∼2 kV mm−1, and its Smax/Emax value is equal to be 1071 pm V−1. As a result, we can believe that the (1 − x)KNNS–xBNZ ceramics will become one of the promising material systems in the practical applications of electrical devices.

Lead-Free Relaxor-Like 0.75Bi0.5K0.5TiO3 – 0.25BiFeO3 Ceramics with Large Electric Field-Induced Strain

Dense and phase-pure ferroelectric ceramics of 75 mol.% Bi0.5K0.5TiO3 – 25 mol.% BiFeO3 are prepared by the conventional solid state reaction method. Their crystal structure is analyzed and discussed. The dielectric and piezoelectric properties of the ceramics are investigated at various temperatures. The ceramics exhibit relaxor-like dielectric properties and high electric field-induced strain (equivalent to 250-300 pm/V at 25-75°C), not previously reported for this composition, making it a promising lead-free alternative for actuator applications.