Large Electric Field-induced Strain Research Articles

Large electric field-induced strain and excellent photoluminescence properties of Pr-modified 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 lead-free ferroelectric ceramics

The 0.94Bi0.5-xPrxNa0.5TiO3-0.06BaTiO3 (BNT-6BT-xPr) lead-free ceramics with doping content of x = 0, 0.01, 0.025, 0.04, 0.05, 0.075, and 0.1 were synthesized by the conventional solid-state reaction method. After doping with the Pr element, a composition-induced phase transition took place, which from the rhombohedral perovskite (R3c) and tetragonal perovskite (P4bm) phases coexisting into the pseudo-cubic phase. At the same time, the introduction of the Pr element had a beneficial effect on grain growth, and the average size of the crystal particle increased from 299 to 742 nm. The Curie temperature Tm showed no obvious change with the increasing Pr content, but the temperature TF-R of the ferroelectric-relaxor phase transition was gradually shifted toward lower temperatures. In addition, the depolarization temperature Td gradually decreased from 125 to 53 °C. In the BNT-6BT-0.025Pr ceramics, giant electric field-induced strain (Smax) and normalized piezoelectric coefficient (d33*) were obtained (Smax = 0.58%, d33* = 723 pm/V). Furthermore, a significant photoluminescence emission intensity was achieved, exhibiting a bright red color. Due to significant enhancement of the piezoelectric and the photoluminescence properties, the BNT-6BT-0.025Pr ceramics exhibited strong competitiveness in actuators and multifunctional devices, which may broaden their application fields.

Enhanced electro-strain with high electrostrictive performances of Bi0.5Na0.4K0.1TiO3 based lead-free piezoelectric ceramics by Ba(Fe0.5Nb0.5)O3

Complex piezoelectric ceramics of (1-x)[0.97(Bi0.5Na0.4K0.1)TiO3–0.03(Ba0.7Sr0.3)TiO3]-xBa(Fe0.5Nb0.5)O3 or (1-x)[0.97BNKT-0.03BST]-xBFN were investigated, where the x value was between 0 and 0.03. All compositions were synthesized via a conventional mixed oxide method. X-ray diffraction and Raman spectroscopy techniques indicated that all ceramics exhibited a coexistence of rhombohedral (R) and tetragonal (T) phases without any impurity phase. However, the T phase became dominant at higher BFN contents. The maximum temperature (Tm), the ferroelectric to ergodic relaxor phase transition temperature (TF-R), and Burn’s temperature (TB) decreased with increasing BFN content, while the dielectric constant at Tm was enhanced for the x = 0.01 ceramic. The BFN additive interrupted ferroelectric ordering, which led to constriction in the hysteresis loops as well as large electric field-induced strains (Smax = 0.42%), a normalized strain coefficient (d*33 = Smax/Emax = 846 pm/V), and an electrostrictive coefficient (Q33 = 0.0432 m4/C2) for the x = 0.01 ceramic under a moderate applied electric field of 50 kV/cm. These results indicated that this ceramic had the potential for electromechanical applications.

Ferroelectric properties and large electric field-induced strain of Eu3+-doped Na0.5Bi0.5TiO3–BaTiO3 lead-free ceramics

Eu3+-doped lead-free piezoelectric ceramics, 0.937Na0.5Bi0.5−xEuxTiO3-0.063BaTiO3 (abbreviated as NBExT-BT, where x = 0, 0.003, 0.005, 0.01, 0.013, 0.015, 0.017, and 0.02), were synthesized using a conventional solid-state synthesis method. All the component samples were crystallized in a pure perovskite structure without a secondary phase. The introduction of Eu3+ caused the evident variation of the dielectric, ferroelectric and luminescence properties. The remanent polarization and coercive field of the pure NBT-BT are Pr ∼29.24 μC/cm2, Ec∼39.33 kV/cm, respectively. The maximum of the remanent polarization Pr of ∼38.02 μC/cm2 at room temperature and the highest dielectric constant of 6899 with a frequency of 1 kHz were obtained for NBE0.003T-BT. The maximum bipolar strain Smax of ∼0.91% and the minimum of coercive field Ec ∼18.45 kV/cm were achieved by the NBE0.015T-BT, resulting from the formation of a double hysteresis loop. For all the components, Eu3+ doping stabilized the antiferroelectric phenomenon at high temperature. Furthermore, the polarized NBE0.015T-BT had the strongest fluorescence luminescence intensity as well as a fluorescence lifetime reaching 785.98 μs.

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.

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.

Large Electric Field-Induced Strain Response Under a Low Electric Field in Lead-Free Bi1/2Na1/2TiO3-SrTiO3-BiAlO3 Ternary Piezoelectric Ceramics

Bismuth-based lead-free ceramics are some of the most promising candidates for actuator applications due to their large strain response. Despite the large strains in bismuth-based piezoelectric ceramics, there still remain challenges regarding their utilization in practical applications. For instance, a relatively high operating field is required to obtain the large strain properties. In this work, lead-free Bi1/2Na1/2TiO3-SrTiO3-BiAlO3 (BNT-ST-BA) ternary piezoelectric ceramics are proposed as materials that could enhance the electromechanical strain performance under low driving field. We found that the highest normalized strain d33* value of 707 pm/V was achieved at a relatively low electric field of 3 kV/mm from 2 mol.% BA-modified BNT-ST ceramics. We suggest that the naturally induced nonergodicities in the ergodic relaxor generate internal stress. This induced internal stress is responsible for the excellent strain properties of this material. We believe that the materials synthesized in this study are promising candidates for actuator applications.

Structural and large electric field-induced bipolar strain study of lead free Bi0.5Na0.5TiO3: Gd piezoceramics

In the present work, crystal structure and field-induced bipolar strain response of Pb-free (Bi1−xGdx)0.5Na0.5TiO3 (BNT:Gd) ceramics with x ≤ 0.04 were investigated systematically. Pure perovskite phase exhibited without any notable change in the crystal structure within the range of specimen studied. Structural analysis of BNT: Gd ceramics was performed through Rietveld refinement by Fullprof software. Rhombohedral structure with space group R3c had been confirmed for x ≤ 0.04. Electric field-induced strain showed a butterfly characteristic of bipolar strain hysteresis curve for the composition x ≤ 0.04 in BNT: Gd ceramics at RT. The maximum normalized piezoelectric strain coefficient d*33 of 148 pm/V was obtained in BNT: Gd systems which is approximately 4.9 times greater than static piezoelectric constant d33 (30pC/N) for the specimen x = 0.04.

Large electric field-induced strain in the novel BNKTAN-BNBLTZ lead-free ceramics

(1-x)Bi0.5(Na0.82K0.18)0.5Ti0.96(Al0.5Nb0.5)0.04O3-xBi0.46Na0.46Ba0.5La0.02Ti0.97Zr0.03O3 lead-free ceramics (abbreviated as BNKTAN-100xBNBLTZ) was prepared by the conventional solid reaction. XRD patterns and EDS spectrums revealed that a stable solid solution had been formed between BNBLTZ and BNKTAN. With the introduction of BNBLTZ anti-ferroelectric content, BNKTAN relaxor ferroelectrics exhibited the excellent field-induced-strain for x = 0.04 corresponding to electric field-induced strain S ∼ 0.505 % and normal strain d33* ∼777 pm/V at 65 kV/cm. The large strain response was attributed to the emergence of PNRs in the relaxation process. Additionally, an excellent fatigue resistance performance was obtained within 105 cycles (S = 0.505 %–0.495 % and d33* = 777–758 pm/V, 65 kV/cm). It suggested that prepared ceramics had the great potential to strain sensor and actuators.

Investigations on the electrical properties, domain structure, and local piezoelectric response in 0.3Pb(In1/2Nb1/2)–0.4Pb(Mg1/3Nb2/3)–0.3PbTiO3 single crystal

High-Curie temperature relaxor ferroelectric single crystals attracted attention recently due to the excellent global electrical properties for electromechanical devices. In this work, the electrical properties, domain structure, and local piezoelectric response of ternary 0.3Pb(In1/2Nb1/2)–0.4Pb(Mg1/3Nb2/3)–0.3PbTiO3 (0.3PIN-0.4PMN-0.3PT) single crystal was investigated. Large electric field-induced strain with little hysteresis was obtained in -oriented high-quality crystal. Nanosized fingerprint pattern domain of ~ 100–300 nm with obvious local piezoelectric response was observed. The temperature-dependent dielectric spectrum revealed a ferroelectric rhombohedral to tetragonal phase transition at 106 °C, obviously higher than that of binary 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3 single-crystal (~80 °C). The evolution of the ferroelectric property and strain response was also studied at elevated temperature. The temperature dependence of the PFM results demonstrated that the surface domain structure of the 0.3PIN–0.4PMN–0.3PT single crystals could still be detected above the Curie temperature. The local piezoelectric hysteresis loop exhibited strong dependence on the DC bias field and obvious local butterfly shape displacement curve could be induced at 180 °C under larger local DC field.

On the origin of grain size effects in Ba(Ti0.96Sn0.04)O3 perovskite ceramics

Over the last 50 years, the study of grain size effects in ferroelectric ceramics has attracted great research interest. Although different theoretical models have been proposed to account for the variation in structure and properties of ferroelectrics with respect to the size of structural grains, the underlying mechanisms are still under debate. Here, we report the results of a study on the influence of grain size on the structural and physical properties of Ba(Ti0.96Sn0.04)O3 (BTS), a ferroelectric compound that represents a model perovskite system, where the effects of point defects, stoichiometry imbalance and phase transitions are minimized by chemical substitution. It was found that different microscopic mechanisms are responsible for the different grain size dependences observed in BTS. High permittivity is achieved in fine-grained BTS ceramics due to high domain wall density and polar nanoregions; high d33 is obtained in coarse-grained ceramics due to a high degree of domain alignment during poling; large electric field-induced strain in intermediate-grained ceramics is an outcome of a favorable interplay between constraints from grain boundaries and reversible reorientation of non-180° domains and polar nanoregions. These paradigms can be regarded as general guidelines for the optimization of specific properties of ferroelectric ceramics through grain size control.

Large electric field-induced strain in ternary Bi0.5Na0.5TiO3-BaTiO3-Sr2MnSbO6 lead-free ceramics

The large electric-field-induced strain of Bi0.5Na0.5TiO3-BaTiO3 based ceramic make it a potential replacement for lead-based ferroelectrics in actuator applications. Herein, a ternary system (1-x)(Bi0.5Na0.5)0.935Ba0.065TiO3-xSr2MnSbO6 (BNBT6.5-xSMS) ceramic was fabricated using conventional solid-state reaction. It was found that the ferroelectric to relaxor phase transition temperature TF-R gradually shifted to lower temperature by increasing SMS contents. The ferroelectricity and piezoelectricity of BNBT6.5 were highly affected by trace amount of SMS doping. For composition BNBT6.5-0.003SMS, where TF-R was near room temperature, a large electric-field-induced unipolar strain of ~0.4% with high normalized strain (Smax/Emax) of 728 pm/V, which is comparable to lead-based ferroelectric/antiferroelectric ceramics, was achieved owing to the reversible electric-field-induced phase transition between a non-polar relaxor phase to a polar phase with long-range ferroelectric order.

Enhanced piezoelectric, electrocaloric and energy storage properties at high temperature in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics

The piezoelectric, electrocaloric and energy storage properties were systemically investigated in lead-free Bi0.5(Na1-xKx)0.5TiO3 ceramics from room temperature to high temperature region. These ceramics can be poled completely to obtain large piezoelectric coefficient (104–153 pC/N) at low electric field of ~30 kV/cm. The piezoelectric property shows good thermal stability due to high depolarization temperature (Td). For BNKT20, a large low electric field-induced strain of 0.36% is obtained at 120 °C under 50 kV/cm, the corresponding normalized strain coefficient is up to 720 pm/V, which is larger than other BNT-based ceramics at high temperature region. The electrocaloric properties of these ceramics are studied via indirect and direct methods. Large EC value (~1.08 K) in BNKT20 ceramic is obtained at 50 kV/cm using indirect calculation. Above 100 °C, the dielectric energy storage density and efficiency of BNKT20 is still up to ~0.85 J/cm3 and 0.75, respectively. The BNKTx ceramics may become promising candidates in the fields of actuators, electrocaloric cooling and energy storage at high temperature region.

Large field-induced strain, giant strain memory effect, and high thermal stability energy storage in (Pb,La)(Zr,Sn,Ti)O3 antiferroelectric single crystal

(Pb,La)(Zr,Sn,Ti)O3 (PLZST) tetragonal antiferroeletric single crystals have been grown by conventional flux method. Phase structure, domain evolution, electric field-induced strain and energy storage properties of the as-grown PLZST crystals with [100] crystallographic orientation have been investigated systematically. A large electric field-induced strain up to 0.76% at 110 °C and a giant memory strain of 0.51% at 100 °C have been realized in the PLZST crystals. This field-induced strain has a nonlinear relationship with the square polarization, which simultaneously stems from the quadratic and higher order electrostrictions. Furthermore, a good thermal stability of energy storage performance with the recoverable energy variation less than 5% in a wide temperature window (105 °C) has been achieved. The combination of high strain and good thermal stability of energy storage wound make the PLZST crystals one of the most important candidates for high temperature electromechanical coupling and high reliability energy-storage devices.

Large electric field-induced strain in AgNbO3-modified 0.76Bi0.5Na0.5TiO3-0.24SrTiO3 lead-free piezoceramics

Bi0.5Na0.5TiO3-based lead-free piezoceramics with large strain output are of great importance in the application of piezoelectric actuators. AgNbO3-modified 0.76Bi0.5Na0.5TiO3-0.24SrTiO3 (BNT-24ST) lead-free piezoceramics were synthesized by conventional solid-state reaction method. The effects of AgNbO3 on the structures, dielectric, ferroelectric and piezoelectric properties were carefully investigated. A large electrostrain and normalized strain (d33* = Smax/Emax) of 0.27% and 700 pm/V, were obtained respectively at low electric field (40 kV/cm) for 1 mol.% AgNbO3-doped BNT-24ST. AgNbO3 doping modified the phase composition which contained moderate amounts of tetragonal and rhombohedral phase by shifting its TF-R to below room temperature. Moreover, the reversible field-induced phase transition between relaxor and ferroelectric made contributions to its large strain related properties. This work has confirmed that the actuating performance of BNT-ST-based piezoceramics can be further improved by an easy and cost-effective composition engineering method and showed it a promising candidate for lead-free actuator material.

Large electric field-induced strain and large improvement in energy density of bismuth sodium potassium titanate-based piezoelectric ceramics

Ceramic solid solutions based on (1-x)Bi0.5(Na0.84K0.16)0.5TiO3-xBa(Nb0.01Ti0.99)O3 or (1-x)BNKT-xBNbT) (where x = 0, 0.01, 0.03, 0.05 and 0.07 mol fraction) were investigated to demonstrate the improvement of electrical properties as compared to the unmodified BNKT ceramic. The dielectric, ferroelectric, piezoelectric and electric field-induced strain properties were investigated as a function of composition and temperature. All ceramics presented a single phase perovskite structure. X-ray diffraction analysis revealed a transition from co-existing rhombohedral-tetragonal phases to a single tetragonal phase for compositions with x > 0.03. The maximum dielectric constant tended to increase with increasing BNbT content and the dielectric spectra for all compositions exhibited a broad maximum around Td and Tm. The polarization hysteresis measurement indicated a disruption in the long range ferroelectric order at the critical composition of x = 0.03 along with a significant enhancement in the electric field-induced strains (Smax = 0.41%) with a large normalized strain coefficient (d*33 = Smax/Emax) of 683 pm/V. The x = 0.03 composition also presented a high energy density (0.67 J/cm3) as compared with the unmodified BNKT composition (0.25 J/cm3). These results suggest that the (1-x)BNKT-xBNbT solid solution is a promising lead-free piezoelectric material candidate.

Giant strain response in 2 mol% Nb-doped (Bi0.5Na0.4K0.1)TiO3 lead-free ceramics

A series of Nb-doped (Bi0.5Na0.4K0.1)TiO3 lead-free piezoelectric ceramics were fabricated by a conventional solid-state reaction method. The X-ray diffraction patterns reveal a pure perovskite structure for all the samples. A giant strain of 0.34% is achieved at 2 mol% Nb-doping concentration, and the corresponding normalized strain $$d_{33}^*$$ reaches 625 pm V−1, which is one of the best results of the BNT-based ceramics. Complex ac impedance data indicate that only the bulk effect contributes to the resistivity. The compositionally induced disruption of long-range ferroelectric order and relaxor transition contributed to the pinched polarization loops as well as the large electric field-induced strain. The results indicate that appropriate Nb-dopant content can remarkably enhance the strain level of (Bi0.5Na0.4K0.1)TiO3 ceramics, making it a promising candidate for actuator applications.

Electric field-induced strain response of lead-free Fe 2 O 3 nanoparticles-modified Bi 0.5 (Na 0.80 K 0.20 ) 0.5 TiO 3 -0.03(Ba 0.70 Sr 0.03 )TiO 3 piezoelectric ceramics

Abstract In this research, the effects of Fe 2 O 3 nanoparticles additive on the phase evolution, dielectric, ferroelectric, piezoelectric and electric field-induced strain responses of BNKT-based piezoelectric ceramics were systematically investigated. The Bi 0.5 (Na 0.80 K 0.20 ) 0.5 TiO 3 -0.03(Ba 0.70 Sr 0.03 )TiO 3 or BNKT-0.03BSrT piezoelectric ceramics with the addition of 0–2 vol% Fe 2 O 3 nanoparticles were prepared by a solid-state reaction method. Optimum sintering temperature was found to be 1125 °C for 2 h at which all compositions had high densities of 5.73–5.80 g/cm 3 . All compositions exhibited a perovskite structure with no impurity. The XRD result showed coexisting rhombohedral and tetragonal phases throughout the entire compositional range with the rhombohedral phase becoming dominant at higher Fe 2 O 3 content. The addition of Fe 2 O 3 promoted the diffuse phase transition in the system that is characteristic of a relaxor-like mechanism and interrupted the polarization which leads to a reduction in the remanent polarization and coercive field. However, the destabilization of the ferroelectric order is accompanied by a significant increase in electric field-induced strain response for the studied system. A large electric field-induced strains ( S max ) of 0.38% and a normalized strain coefficient ( d * 33 = S max / E max ) of 760 pm/V were obtained for the 1 vol% Fe 2 O 3 ceramic. The obtained results indicate that the addition of Fe 2 O 3 significantly enhances the field-induced strain in BNKT-0.03BST ceramics, and the studied material is considered as a promising candidate for lead-free electromechanical actuator applications.

Large electric field-induced strain and piezoelectric responses of lead-free Bi0.5(Na0.80K0.20)0.5TiO3-Ba(Ti0.90Sn0.10)O3 ceramics near morphotropic phase boundary

Lead-free piezoelectric ceramics with compositions belonging to family of compositions (1−x)Bi0.5(Na0.80K0.20)0.5TiO3-xBa(Ti0.90Sn0.10)O3 or (1−x) BNKT-xBTS (when x = 0.05 − 0.15 mol fraction) near the morphotropic phase boundary (MPB) were fabricated by a conventional mixed oxide method. Sintered samples had relative densities greater than 98% of their theoretical values. X-ray diffraction data revealed that the MPB region consisted of coexisting rhombohedral and tetragonal phases in the BNKT-BTS system was identified over the entire compositional range. A large electric field-induced strain (Smax) of 0.36% and a normalized strain coefficient (d*33) of 649 pm/V were observed in the BNKT-0.05BTS sample. The sample close to the MPB composition (BNKT-0.11BTS) exhibited the maximum dielectric constant (er = 1770), temperature of maximum permittivity (Tm = 333C°) and low-field piezoelectric coefficient (d33 = 227 pC/N), along with reasonable ferroelectric properties (Pr = 20.6 mC/cm2, Rsq = 0.88) and strain properties (d*33 = 445 pm/V and Smax = 0.24%).

Evolution of phase structure and giant strain at low driving fields in Bi-based lead-free incipient piezoelectrics

Abstract Lead-free 0.99[(Bi0.5Na0.5)0.935Ba0.065Ti(1–x)NbxO3]–0.01SrZrO3 (BNBTNb100x–SZ, with Nb100x = 0–1) ceramics were prepared by the conventional mixed oxide route. X-ray diffraction and Raman scattering was utilized for the structural evolution of Nb-modified BNBT–SZ ceramics at average and short-scale localized structure. Temperature dependent dielectric properties showed ferroelectric–ergodic relaxor (FE–ER) transition in Nb-modified BNBT–SZ ceramics by producing a significant disruption of the long-range FE order. A giant normalized strain of 825 pm/V at 4 kV/mm was achieved at Nb1.0. Interestingly, at a relatively low applied field of 3 kV/mm, the Nb0.75 sample displayed a large electric field-induced strain (EFIS) response of 0.20%, which is highest value obtained in non-textured lead-free BNT-based ceramics at such low driving field. The structural distortion induced by doping and electric poling is correlated with the dielectric, ferroelectric and EFIS response, and the evolution of giant strain was ascribed to reversible field induced phase transition from ER–FE phase.

Enhancement of electric field-induced strain in BaTiO3ceramics through grain size optimization

The effect of grain size on electric field-induced strain in BaTiO3 ceramics was explored. The unipolar strain first increases and then decreases with increasing grain size with a peak of 0.28% around 4.5 µm. Small grains have more recoverable non-180° domains, but also more restriction from grain boundaries, while coarse grains have less restriction from grain boundaries, but less recoverable non-180° domains. Thus, only ceramics with intermediate grain size can show large electric field-induced strain at electrical loading regime conditions.