Electrostrictive Coefficient Research Articles

Electrostrictive and Structural Properties of Poly(Vinylidene Fluoride-Hexafluoropropylene) Composite Nanofibers Filled with Polyaniline (Emeraldine Base).

Previous studies have reported that poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) copolymers can exhibit large electrostrictive strains depending on the filler. This work examines the electrostrictive and structural properties of P(VDF-HFP) nanofibers modified with conductive polymer polyaniline (PANI). The P(VDF-HFP)/PANI composite nanofibers were prepared by an electrospinning method with different PANI concentrations (0, 0.5, 1, 1.5, 3 and 5 wt.%). The average diameter, water contact angle and element were analyzed by SEM, WCA and EDX, respectively. The crystalline, phase structure and mechanical properties were investigated by XRD, FTIR and DMA, respectively. The dielectric properties and electrostrictive behavior were also studied. The results demonstrated that the composite nanofibers exhibited uniform fibers without any bead formation, and the WCA decreased with increasing amount of PANI. However, a high dielectric constant and electromechanical response were obtained. The electrostrictive coefficient, crystalline, phase structure, dielectric properties and interfacial charge distributions increased in relation to the PANI content. Moreover, this study indicates that P(VDF-HFP)/PANI composite nanofibers may represent a promising route for obtaining electrostrictive composite nanofibers for actuation applications, microelectromechanical systems and sensors based on electrostrictive phenomena.

Non‐Classical Electrostriction in Hydrated Acceptor Doped BaZrO3: Proton Trapping and Dopant Size Effect

AbstractPoint defects such as oxygen vacancies and protonic interstitials are not only essential for ionic conductivity in oxides since they also affect the mechanical and electromechanical properties. These properties of nominally dry and hydrated proton‐conducting BaZr0.85M0.15O2.925+δH2δ (M = Al, Ga, Sc, In, Y, Eu) ceramics are investigated. Doping decreases Young's modulus with increasing ionic radii difference between the dopant and the host. Nominally dry samples show consistently higher Young's moduli than hydrated samples. All samples exhibit large non‐classical electrostriction, with a negative electrostriction coefficient M33<0. M33 shows saturation with the field and a non‐ideal Debye relaxation with frequency. The low‐frequency M33 value for both dry and hydrated samples shows a similar dependence on dopant radius as Young's modulus. For the hydrated samples, the relaxation frequency increases by a factor >100 in the series Ga‐Y, emphasizing the importance of proton trapping, with Y‐doped samples having minimal trapping energy. This coincides with the fact that the saturation strain for Y‐doped samples is also the smallest. In light of these findings, it is concluded that the present data give strong evidence for the existence of defect‐related elastic dipoles in acceptor doped barium zirconate and that the non‐classical electrostriction originates in their reorientation under electric field.

Enhanced strain and electrostrictive properties in lead-free BNT-based ceramics via rare earth doping

Bi0.5Na0.5TiO3 (BNT)-based ceramics are one of the most promising lead-free ferroelectrics due to their high strain property. Compared to other chemical modifications, rare earth ions doping provides significant possibility to optimize the strain property of BNT-based ceramics. In this work, the effects of rare earth ions on phase structure, microstructure, and strain & electrostrictive properties of lead-free BNT-based ceramics were systematically investigated. Rare earth ions (i.e., La3+, Sm3+, Yb3+, Dy3+, and Nd3+) were selected as the doping ions. Introducing moderate La3+ ions can drive the ferroelectric state of BNT-based ceramics to nonergodic relaxor state or ergodic relaxor state. The enhanced strain response of ∼0.40–0.42% and high converse piezoelectric coefficient of ∼600–630 pm/V can be achieved under 60–70 kV/cm for La3+-doped ceramic with nonergodic relaxor state. Besides, the giant electrostrictive coefficient Q33 of ∼0.047 m4/C2 can be obtained for La3+-doped ceramic with ergodic relaxor state. Other rare earth ions also present the promotion effect on strain enhancement for BNT-based ceramics. This study affords a significant guidance to optimize strain and electrostrictive properties of BNT-based ceramics via rare earth ions doping.

Enhancing Electrostrictive Actuation via Strong Electrostatic Repulsion among Field-Induced Nanodomains in a Relaxor Ferroelectric Poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) Random Terpolymer

Electrostrictive polymers having a large strain are desirable for actuation, sensing, and energy harvesting in wearable electronics and soft robotics. However, a high electric field (>100 MV/m) is usually required for current electrostrictive polymers. To realize large electrostriction at reduced electric fields, the fundamental electrostriction mechanism needs to be better understood. In response to this need, the structure and electrostrictive properties of relaxor ferroelectric (RFE) poly(vinylidene fluoride-co-trifluoroethylene-co-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] random terpolymers films with different thermal annealing histories were studied in this work. First, the semicrystalline structure of the P(VDF-TrFE-CTFE) terpolymer films was studied by combined small-angle X-ray scattering and wide-angle X-ray diffraction analyses. A three-phase model was employed, namely, crystals and oriented and isotropic amorphous fractions (OAF and IAF). The bulky CTFE units generated taut-tie molecules (TTM) in the crystalline lamella, dividing it into many nanosized crystals (∼1.3 nm thick). It is this unique crystalline structure with nanocrystals and mobile TTM/OAF that enabled the RFE behavior for the P(VDF-TrFE)-based terpolymers. Through electrostriction measurements and nonlinear dielectric analysis, an inverse correlation was observed between the ferroelectric nonlinearity and the electrostrictive coefficient under a high poling electric field (>100 MV/m). This suggested that higher electrostriction performance could be achieved by decreasing the ferroelectric nonlinearity of the RFE terpolymer. Indeed, above the Curie temperature, the paraelectric terpolymer films achieved a high electrostrictive performance with the transverse strain being ∼5% at 200 MV/m. This was attributed to the strong electrostatic repulsion among electric field-induced ferroelectric nanodomains. The finding from this work provides a viable way to design new electrostrictive polymers with higher performance at low driving fields.

Role of polar nanoregions in the enhancement of the recoverable energy storage density and electrostrictive coefficient in the lead free Na0.25K0.25Bi0.5TiO3

The electrostrictive materials are gaining attention for the actuating application because of their positive strain irrespective to the electric field direction and low hysteresis loss. In this work, the room temperature electrostrictive effect of lead free ferroelectrics Na0.3K0.2Bi0.5TiO3 and Na0.25K0.25Bi0.5TiO3 are studied. Due to the relaxor nature of Na0.25K0.25Bi0.5TiO3, sprout shape strain (S) and pinched polarization (P) loops are noticed as a function of electric field (E), which are beneficial for high electrostrictive coefficient and recoverable energy storage density, respectively. The reversible transformation of the polar nanoregion into the ferroelectric domain with electric field is the reason behind the sprout shape S-E loop. This composition shows the dielectric constant of ≈4000 and strain of 0.30% without any Sneg (negative value of strain). The obtained value of the electrostrictive coefficient from the S vs. P2 graph of Na0.25K0.25Bi0.5TiO3 is ≈0.022 m4/C2, which is comparable to 0.93Na0.5Bi0.5TiO3-0.07BaTiO3 composition and other Na0.5−xKxBi0.5TiO3-based binary solid solutions.

Phase and Structure Behavior vs. Electromechanical Performance of Electrostrictive P(VDF-HFP)/ZnO Composite Nanofibers

In this work, we improved the electromechanical properties, electrostrictive behavior and energy-harvesting performance of poly(vinylidenefluoridene-hexafluoropropylene) P(VDF-HFP)/zinc oxide (ZnO) composite nanofibers. The main factor in increasing their electromechanical performance and harvesting power based on electrostrictive behavior is an improved coefficient with a modified crystallinity phase and tuning the polarizability of material. These blends were fabricated by using a simple electrospinning method with varied ZnO contents (0, 5, 10, 15 and 20 wt%). The effects of the ZnO nanoparticle size and content on the phase transformation, dielectric permittivity, strain response and vibration energy harvesting were investigated. The characteristics of these structures were evaluated utilizing SEM, EDX, XRD, FT-IR and DMA. The electrical properties of the fabrication samples were examined by LCR meter as a function of the concentration of the ZnO and frequency. The strain response from the electric field was observed by the photonic displacement apparatus and lock-in amplifier along the thickness direction at a low frequency of 1 Hz. Moreover, the energy conversion behavior was determined by an energy-harvesting setup measuring the current induced in the composite nanofibers. The results showed that the ZnO nanoparticles’ component effectively achieves a strain response and the energy-harvesting capabilities of these P(VDF-HFP)/ZnO composites nanofibers. The electrostriction coefficient tended to increase with a higher ZnO content and an increasing dielectric constant. The generated current increased with the ZnO content when the external electric field was applied at a vibration of 20 Hz. Consequently, the ZnO nanoparticles dispersed into electrostrictive P(VDF-HFP) nanofibers, which offer a large power density and excellent efficiency of energy harvesting.

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.

Enhanced Electrostrictive Coefficient and Suppressive Hysteresis in Lead-Free Ba(1−x)SrxTiO3 Piezoelectric Ceramics with High Strain

Lead-free piezoelectric ceramics with both low hysteresis and superior electrostrictive coefficient features are crucial toward providing desired performance for intelligent electrical devices, especially in high-precision displacement actuators. In this work, we propose a novel scenario, which is to design the phase transition around ambient temperature to enhance electrostrictive effect and inhibit hysteresis. In other words, the dense ceramics with cubic phases (C) and tetragonal phases (T) coexisting at RT (room temperature) were designed. According to this scenario, the Ba(1−x)SrxTiO3 (abbreviated as BT-100xST) ceramics were fabricated by the conventional solid-state reaction method. The relaxor behavior, ferroelectric properties, crystal structure and microstructure of BT-100xST ceramics have been investigated in detail. As a result, the BT-100xST ceramics with x = 0.20–0.40 present relaxor behavior which was indicated by dielectric constant as a function of temperature and (polarization–electric field) P–E hysteresis loops. The BT-30ST ceramics exhibit enhanced electrostrictive coefficient Q33 (>0.034 m4/C2), and the electrostrictive strain and low hysteresis achieves 0.11% and 2%, respectively. The BT-100xST ceramics are considered as a prospective option for application in displacement actuators with high sensitivity and high precision.

High-temperature and long-term stability in Co/Sb-codoped (Bi0.5Na0.5)TiO3-based electrostrictive ceramics

In this study, we report lead-free Co/Sb-codoped (Bi0.5Na0.5)TiO3-based ceramics with enhanced electrostrictive properties and high-temperature and long-term stability. The effect of Co/Sb codoping on the phase structure, electrical properties, and thermal stability of (Bi0.5Na0.5)TiO3-based ceramics was studied. The Co/Sb codoping induced the phase transition from the coexisting rhombohedral (R) − tetragonal (T) phase to the single pseudocubic (Pc) symmetry and the disruption of the long-range ferroelectric order of the ceramics, yielding enhanced electrostrictive properties. A large electrostrictive response was obtained in the sample with 0.02 Co/Sb content, with electrostrictive coefficients Q33 of 0.022–0.024 m4/C2 and electro-strains of 0.35–0.46% under different strengths of the electric field. The electrostrictive material exhibited temperature-insensitive and fatigue-free behavior after up to 105 cycles from room temperature to 120 °C, rendering it a promising material for high-temperature and long-term stability actuator applications.

Poling effect on the electrostrictive and piezoelectric response in CH3NH3PbI3 single crystals

Methylammonium lead triiodide perovskites (MAPbI3) have demonstrated a large electrostrictive strain up to 1%, which was theoretically proved to be related to the additional defects under applied bias voltages. However, as this effect was detected only at a low frequency, we explored the electrostrictive response at a higher frequency (4 kHz) by using ac poling at 1 Hz. In such conditions, the electrostrictive coefficient was evaluated at –45.7 nm2 V−2, i.e., quite larger than the results under dc poling or in unpoled samples. The occurrence of a high-frequency electrostrictive effect may be correlated with the defects that rise in the ac poled samples from the ion migration under reverse bias as it was also demonstrated from the shift of the dielectric loss peak in the considered systems. In parallel to the electrostrictive effect, the piezoelectric response shows a drastic increase after the ac and dc poling due to the lattice distortion induced by the applied electric field. Based on the above approach, the achieved electrostrictive and piezoelectric responses at 4 kHz in MAPbI3 may open opportunities in the area of actuators, energy-harvesting, and micro-electromechanical systems.

Large strain under low electric field in NBT-KBT-BT ceramics synthesized by Sol–Gel approach

In this paper, the (1-4x)(Na0.5Bi0.5)TiO3-3x(K0.5Bi0.5)TiO3-xBaTiO3 ((1-4x)NBT-3xKBT-xBT) ceramics with x = 0.020, 0.034, 0.040, and 0.050 were synthesized by Sol–Gel flame synthetic approach. Decreased ferroelectric-to-relaxor transition temperature and abrupt decrease of piezoelectric constant reveal that the long-range ferroelectric order would be destroyed when x ≥ 0.040, and a composition boundary between ferroelectric (FE) and relaxor phase (RE) is constructed around x = 0.040. As a result, a large strain of 0.30% under a significantly lower external field of 50 kV/cm was achieved for the critical composition at x = 0.040 due to a reversible RE/FE phase transformation, resulting in a large normalized strains Smax/Emax of 600 pm/V accordingly. Meanwhile, high electrostrictive coefficient of 0.0311 m4/C2 with relatively large strain response of 0.22% was obtained at x = 0.050. The findings may pave a way for obtaining large strain under low electric field and high electrostrictive effect in NBT-based system through the appropriate compositional design and optimized preparation technology.

Giant electrostrictive coefficient in rapidly cooled nanodisordered KTa1−xNbxO3 lead-free single crystals

The temperature dependent electrostrictive effect, with respect to increasing the cooling rate to a cooling temperature, was quantitatively investigated in potassium tantalate niobate (KTN) lead-free single crystals above and near Curie temperature (TC). High work-function Pt electrodes are used to minimize the effect of charge injection, and the electric field induced displacement was measured with Michelson interferometry. It was found that a giant electrostrictive coefficient of 696 × 10−16 m2/V2 could be obtained at a high cooling rate of 0.75 °C/s to a temperature of TC + 4.5 °C due to the evolution of polar nano-regions, which is one order of magnitude larger than the previously reported value in KTN crystals. This strengthens the realization of replacing toxic lead-based electrostrictive materials with environmentally friendly KTN materials in real world applications.

Large Electrostrictive Coefficient in a Two-Dimensional Hybrid Perovskite Ferroelectric.

Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) are attracting tremendous interest for their great scientific and technological potential in photovoltaics and optoelectronics. Although the ferroelectricity in 2D HOIPs has been greatly developed, however, to date no phosphonium-based 2D HOIP ferroelectrics have yet been found. Meanwhile, electrostriction plays an important role in the electromechanical behavior of ferroelectrics, while it has never been reported for 2D HOIP ferroelectrics. Here, we present the first phosphonium-based 2D HOIP ferroelectric (EATMP)PbBr4 (EATMP = (2-aminoethyl)trimethylphosphanium) with a direct bandgap of 2.84 eV. Notably, (EATMP)PbBr4 possesses a high Curie temperature of 534 K, which is the highest among all reported 2D HOIP ferroelectrics. Moreover, it exhibits a large electrostrictive coefficient of about 3.96 m4 C-2 as well, far exceeding those of PVDF (1.3 m4 C-2) and inorganic ones (∼0.034-0.096 m4 C-2). With excellent ferroelectric and piezoelectric properties and the merit of easy fabrication, (EATMP)PbBr4 shows great potential in applications for future smart devices of actuators, transducers, and sensors.

Temperature independent fatigue-free behavior in sodium bismuth titanate-based lead-free ceramics

In this work, excellent electrostrictive properties with a giant electrostrain of 0.46% and a large electrostriction coefficient of 0.028 m4/C2 were achieved in Ni/Mn-modified (Bi0.5Na0.5)0.935Ba0.065TiO3 ceramics. For high-temperature performance, an interesting finding is that the temperature stability of electrostrain is strongly dependent on the applied electric field strengths, that is, the lower the electric field is, the higher the temperature stability will be. A model of the electric-field-induced phase transition was introduced to find the causes of the different stability behaviors at various electric field strengths. The Ni/Mn-modified sample exhibited a fatigue-free behavior that was insensitive to temperature, which can be related to the reversible field-induced ergodic relaxor-ferroelectric phase transition. In addition, the fine-grained microstructure of the ceramics could also provide a high resistance to field cycling and thus improve the fatigue resistance. The current materials show great potential for actuator applications that require good cycling reliability.

Emergence of reentrant relaxor behavior with enhanced electromechanical and electrocaloric effect in Ba0.95Ca0.05Sn0.09Ti0.91O3 ceramic

Both A- and B-site-substituted BaTiO3 ceramics are promising alternative relaxor materials to replace lead zirconium titanate as an actuator. With a motivation to improve electromechanical properties, a lead-free Ba0.95Ca0.05Sn0.09Ti0.91O3 (BCST) ceramic close to the polymorphic phase boundary composition is synthesized by solid-state reaction. X-ray diffraction and Raman spectroscopy confirm the coexistence of orthorhombic (Amm2) and tetragonal (P4 mm) phases at room temperature. Our low-temperature dielectric study reveals the appearance of a reentrant relaxor state from the ferroelectric state near ∼150 K and is attributed to the coexistence of short and long ferroelectric ordered regions and slowing down of domain dynamics in the smaller regions, similar to the reentrant spin glass state observed in the system Fe-xAu. This feature is confirmed through glass model fitting parameters [ωo = 2.66(±0.28) × 108 Hz, Tg = 110(±1) K, zv = 4.5(±0.3)], and Mydosh parameter (“K” ∼ 0.05). The field-induced polarization (P–E) and strain (S–E) curves show well-defined slim ferroelectric and “butterfly-like” loops with a large value of maximum strain of ∼0.12%, an electromechanical coefficient of d*33 ∼ 1113 pm/V, and an electrostrictive coefficient of Q11 ∼ 0.048 m4/C2 at room temperature.

Large electrostrictive coefficient with high electro‐strain dominated by modified ergodic state in BNT‐based solid solutions

AbstractFor ferroelectric electrostrictors, shifting their Curie temperature TC to the ambient temperature is an effective way to enhance their electrostrictive effect. However, the enhanced electrostrictive coefficient Q33 in this way is often accompanied with an inferior electro‐strain. In this work, by introducing CaZrO3/BaZrO3 as the special kind of solid solution, with an effective regulation on the ergodic state, we simultaneously realize a larger room‐temperature electrostrictive coefficient Q33 (~0.04337 m4/C2) with a superior electro‐strain (~0.41%) in Bi0.5Na0.5TiO3‐based relaxor ferroelectric ceramics. The ions substitution with larger radius in either A‐site or B‐site of perovskite structure tends to facilitate the evolution from ferroelectric tetragonal phase P4mm to relaxor tetragonal phase P4bm along with the decrease in polarity in crystal, thereby shifting the transition temperature TF‐R below room temperature. As a result of the effective regulation on the ergodic state, a large electro‐strain with low hysteresis, just like electrostrictors, is successfully realized in BNT‐based ferroelectric ceramics. Our investigation provides an effective way to simultaneously enhance the electrostrictive coefficient Q33 and electro‐strain for practical applications in precisely controlled displacement.

Piezoresponse amplitude and phase quantified for electromechanical characterization

Piezoresponse force microscopy (PFM) is a powerful characterization technique to readily image and manipulate the ferroelectric domains. PFM gives an insight into the strength of local piezoelectric coupling and polarization direction through PFM amplitude and phase, respectively. Converting measured arbitrary units into units of effective piezoelectric constant remains a challenge, and insufficient methods are often used. While most quantification efforts have been spent on quantifying the PFM amplitude signal, little attention has been given to the PFM phase, which is often arbitrarily adjusted to fit expectations. This is problematic when investigating materials with unknown or negative sign of the probed effective electrostrictive coefficient or strong frequency dispersion of electromechanical responses, because assumptions about the PFM phase cannot be reliably made. The PFM phase can, however, provide important information on the polarization orientation and the sign of the effective electrostrictive coefficient probed by PFM. Most notably, the orientation of the PFM hysteresis loop is determined by the PFM phase. Moreover, when presenting PFM data as a combined signal, the resulting response can be artificially lowered or asymmetric if the phase data have not been correctly processed. Here, we explain the PFM amplitude quantification process and demonstrate a path to identify the phase offset required to extract correct meaning from the PFM phase data. We explore different sources of phase offsets including the experimental setup, instrumental contributions, and data analysis. We discuss the physical working principles of PFM and develop a strategy to extract physical meaning from the PFM amplitude and phase.

Energy storage density and piezoelectric performances of barium strontium titanate modified bimuth sodium lanthanum titanate lead-free ceramics

Lead-free (1-x)(Bi0.487Na0.487La0.017)TiO3-x(Ba0.7Sr0.3)TiO3 or (1-x)BNLT-xBSrT ceramics were fabricated by a solid state reaction and sintered at 1050–1200 °C for 2 h. All sintered samples had a relative density > 97% of their theoretical values. With increasing BSrT, the transition from BNLT rhombohedral to BSrT tetragonal was observed. The addition of BSrT inhibited grain growth which resulted in the improvement of the densification of the BNLT ceramic. The changes in the BSrT content also induced a phase transition from the ferroelectric (FE) phase to the ergodic relaxor (ER) phase. These changes significantly disrupted long-range ferroelectric order, thereby correspondingly reducing the Pr and Ec values and resulting in the enhancement of the electric field-induced strain and electrostrictive response. A large Smax = 0.41%, d*33 = 788 pm/V and electrostrictive coefficient (Q33 = 0.04119 m4/C2) were observed for the x = 0.08 sample. In addition, the x = 0.15 sample showed good energy storage density (W = 0.66 J/cm3) and energy storage efficiency (η = 82.7%) @ 150 °C. Overall, these results indicated that these ceramics had the potential of becoming one of the promising lead-free piezoelectric candidates for piezoelectric applications.

Influence of Field-Induced Phase Transition on Poly(Vinylidene Fluoride-Trifluoroethylene-Chlorotrifluoroethylene) Strain

This work is focused on understanding the reasons behind the large electrostrictive strain of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) terpolymer. Although a few explanations have been proposed in the literature, it remains largely unclear. Here, the role of an electrically induced phase transition is investigated. The strain in the crystalline part of the polymer is monitored using XRD while an electric field is applied onto the sample. Three regions of interest are clearly evidenced and, of particular interest, we observe a change in crystal symmetry located on the 30--70 V \textmu{}${\mathrm{m}}^{\ensuremath{-}1}$ range. In that region, the lattice progressively loses its hexagonal symmetry and moves toward the phase usually observed at lower temperature, with a higher polar order. In parallel, we conduct macroscopic strain measurements to compare to the XRD data. Three different regimes are also observed with a sudden increase in electrostrictive coefficient on the 30--70 V \textmu{}${\mathrm{m}}^{\ensuremath{-}1}$ interval, going from 19 to 33 ${\mathrm{m}}^{4}\phantom{\rule{0.25em}{0ex}}{\mathrm{C}}^{\ensuremath{-}1}$. This corresponds to a 1% strain, i.e., 25% of the total deformation measured at 100 V \textmu{}${\mathrm{m}}^{\ensuremath{-}1}$. By thoroughly comparing macroscopic strain and x-ray measurements, we are able to single out and quantify the impact of this field-induced phase transition in the polymer overall strain.

Observation of enhanced electrostrictive strain in (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3 lead-free ceramics

Herein, the author reports the observation of composition dependent piezoelectric and electrostrictive behaviour in lead free (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: NBT-BT-BAO [x = 0.01, 0.03, 0.05, 0.07, 0.09] ceramics synthesized through standard solid state reaction route. X-ray diffraction analysis of the samples confirms existence of structural phase transition from monoclinic to pseudocubic with increase of BT and BAO concentration supported by Raman spectroscopic analysis. A flipping from piezoelectric (x≤ 0.03) to near-electrostrictive (x≥ 0.05) characteristics has been realized from strain vs electric field measurements. Especially, (1-2x)Na0.5Bi0.5TiO3-xBaTiO3-xBiAlO3: x = 0.05 showed an enhanced strain of 0.33 %, Smax/Emax of 425 pm/V and an electrostrictive co-efficient (Q33) of 0.034 m4C−2 could be attributed to the presence of MPB by the co-existence of monoclinic and pseudocubic phases. Further, minimal temperature dependence of the electrostrictive strain is inferred from temperature dependent polarization and strain measurements.