Electrostrictive Behavior Research Articles

Electrostriction of Dielectric Elastomer Based on Natural Rubber/Graphene Composites for Actuator Applications

The combination of elastic natural rubber (NR) and conductive graphene were assessed for such improved electromechanical properties that are promising material in an actuator applications. For this work, dielectric elastomer composite films were prepared with varied graphene contents. These films were fabricated by solution casting method. The morphology along with electrical and mechanical properties, and specifically the electrostrictive coefficient, were studied. The electrostrictive behavior was determined from electric field induced strain, observed with a photonic displacement apparatus in the film thickness direction. It is shown that the electrostrictive coefficient for the NR/Graphene composite has already raised over 3.7 times compared to the neat natural rubber by the reason of an interfacial polarization. The surface between NR matrix and graphene filler generates the larger permittivity. Meanwhile, the Young's modulus was quite invariant. Consequently, the enlarging of the electrostrictive coefficient under low electric field of the NR/Graphene composites is representing a potentially good actuation response base on the electrostriction phenomena.

High electromechanical performance of modified electrostrictive polyurethane three-phase composites

In order to enhance the electrostrictive polymer, the polyurethane has been modified with conductive fillers that are promising for actuator applications, energy conversion, and sensors. The polyurethane (PU) matrix and the conductive fillers such as graphene nanosheets (GRN) and polyaniline nanopowder (PANI) were prepared to gain films by solution casting method. The morphology, structure and thermal behavior of PU three-phase composite were observed by SEM imaging, FTIR, and DSC techniques. In addition, the electrical and mechanical properties of polyurethane filled with both composites were investigated by an LCR meter and strain gauge setup. In order to study the electrostriction behavior, the electric field induced strain of PU three-phase composite films was monitored via lock-in amplifier at a low frequency of 1 Hz. A greater electrostriction effect of the PU three-phase composites at low electric field significantly related with contribute to conduction and interfacial polarization base on space charges distribution, filler-filler network and microstructure on crystallinity in the HS domain of PU matrix. Therefore, electrostriction behavior in the PU three-phase composites has been discussion. It was known that why the three-phase composites can provide high electromechanical performance for actuator applications.

Large electrostrictive effect in lead-free (Bi.5Na.5)TiO3-based composite piezoceramics

The quadratic electrostrictive effect possesses several unique advantages over the piezoelectric effect, including a fast response speed, temperature stability, hysteresis-free characteristic. In this regards, we report a 0–3 type 0.92(Bi.5Na.5)TiO3−0.06BaTiO3−0.02(K.5Na.5)NbO3:6 wt% Bi4Ti3O12 (BNT-BT-KNN: BiT) composite ceramics to achieve the competent electrostrictive effect at room temperature. The electrostrictive behavior of composite ceramics was systematacially explored with respect to driving field, temperature, frequency and cycles. The manufactured composite ceramic is featured by not only large room-temperature electrostrictive coefficient Q33 of 0.0327 m4 C−2 but also superior thermal stability in the temperature range from 25 °C to 120 °C. Simultaneously, the gained electrostrictive response exhibited relatively good frequency-dependent and fatigue character. It is demonstrated that construct of a 0–3 type connectivity composite provides a highly effective path to tailor electrostrictive characteristic of BNT-based ceramics. The current study shows a significant advancement in the area of lead-free electrostrictive materials and can inspire potential interest in search for novel BNT-based ceramics with promising electrostrictive effect.

Modulation of electrostriction and strain response in bismuth sodium titanate‐based ceramics

AbstractThe electrostriction and strain response of lead‐free Bi0.5Na0.5TiO3–BaTiO3 piezoceramics with La and Nb [(Bi0.47Na0.47Ba0.06)1−xLaxTi1−yNbyO3] were modified by optimizing the depolarization temperature. The influences of La and Nb on their phase structure and electrical properties were systematically investigated. All the ceramics exhibited a pseudocubic phase, which is independent of the addition of La and Nb. The strain values increased gradually with the addition of La, and a high strain of ~0.5% (80 kV/cm) was attained without any remnant strain when the compositions had a value of x = 0.015. Instead, the piezoelectric constant d33 dropped down ~20 pC/N due to the shift of the Td (or Tf−r) to room temperature. Interestingly, by establishing the relationship between Td and strain values, it should be feasible to optimize the strain property of Bi0.5Na0.5TiO3 (BNT)‐based ceramics by regulating Td to ambient temperature. In addition, a very high electrostriction coefficient Q33 of ~0.0758 m4 C−2 can be found under high temperatures of 125 and 150°C. We believe that the strain and electrostriction behavior of BNT‐based ceramics can be well modified by the modulation of depolarization temperature.

Relaxor-ferroelectric BaLnZT (Ln = La, Nd, Sm, Eu, and Sc) ceramics for actuator and energy storage application

Lead free ceramics Ba1−xLn2x/3Zr0.3Ti0.7O3 (Ln = La, Nd, Sm, Eu and Sc), x = 0.02–0.10 are investigated for electrostrictive effect and energy storage properties in the proximity of relaxor-paraelectric phase boundary. Relaxor phase evidence from slim hysteresis loop and low remnant polarization are the key parameters responsible for improve the electrostrictive effect and energy storage properties simultaneously. With increase in rare earth content negative strain disappeared and almost hysteresis free strain is achieved. Strain-hysteresis profile in term of S–E, S–E2 and S–P2 is used to analyze the electrostrictive behavior of these ceramics. An average strain (S%) ∼ 0.03%, is accomplished at initial concentrations of x = 0.02–0.04 and electrostrictive coefficients (Q11, and M11) as well as the energy storage density is improved by a factor of 1.2 and 2.6 respectively when compare with pure (x = 0.0) ceramic. Above x ≥ 0.06, all compositions show a stable behavior which suggested the possibilities of these relaxor ceramics towards high precision actuators and energy storage application.

Partial molar volumes and compressibilities of metformin hydrochloride in aqueous-NaCl/sucrose solutions at 30 °C

Present article reports the partial molar volumes (V2, φo) and compressibilities (κS, 2, φ0) calculated from measured ultrasonic velocity (u) and density (ρ) data of antidiabetic drug metformin hydrochloride + {aqueous-cosolutes (NaCl/sucrose)} solutions at 30°C. The isentropic compressibilities (κs) and other acoustic parameters were calculated and discussed. In addition to this, the refractive indices (n) and relative viscosities (ηr) along with Jones-Dole parameters have been measured and reported. Results have been discussed in terms of effect of cosolutes NaCl/sucrose on electrostriction and hydration behavior of the drug.

Electromechanical properties of Na0.5Bi0.5TiO3-SrTiO3-PbTiO3 solid solutions

Thorough studies of electric field-induced strain are presented in 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3 (NBT-ST-PT) ternary solid solutions. The increase of concentration of lead x induces crossover from relaxor to ferroelectric. Strain in a relaxor state can be described by electrostrictive behavior. The electrostrictive coefficients correspond to other well-known relaxor ferroelectrics. The concentration region with a stable ferroelectric phase revealed that the polarization dependence of strain does not exhibit nonlinearity, although they are inherent to the electric field dependence of strain. In this case, electric field dependence of strain is described in terms of the Rayleigh law and the role of domain wall contribution is extracted. Finally, the character of strain at the electric field-induced phase transition between the nonpolar and the ferroelectric states is studied. The data shows that in the vicinity of the electric field induced phase transition the strain vs. electric field displays electrostrictive character.

Relaxation and saturation of electrostriction in 10 mol% Gd-doped ceria ceramics

10 mol% Gd-doped ceria (10GDC) ceramics, with grain size in the single micron range, display electrostrictive behavior under ambient conditions of temperature and pressure. In weak, quasi-static electric fields, i.e. <1 kV/cm, frequency <1 Hz, the longitudinal strain is measured to be proportional to the square of the applied electric field, albeit with the corresponding electrostrictive strain coefficient (M33) displaying large variability between samples: −(2-20)·10−17 (m/V)2. Nevertheless, |M33| of all samples exceeds the values expected on the basis of the classical (Newnham) electrostriction scaling law by up to two orders of magnitude. A systematic study reveals the functional dependence of M33 on frequency: above 10 Hz, |M33| decreases to ≈10−18 (m/V)2, which may be characterized as non-Debye relaxation with non-ideality factor 0.35–1.13. For frequencies ≤1.5 Hz, increasing the field strength beyond 1 kV/cm results in an exponential decrease in |M33|: the longitudinal strain saturates at 1-4 ppm. Dielectric impedance spectra suggest that partitioning of the applied voltage between grain boundaries and grain cores may be a factor contributing both to the large variability in the electrostriction parameters, and to the strong dependence on electric field amplitude. The frequency dependence may have two sources: the slow electric field-driven reorganization of the Ce-containing active complexes in the electrostrictive medium as well as the influence of the grain boundaries. 10GDC ceramics may therefore be added to the list of non-classical electrostrictors which includes reduced and Gd-doped ceria thin films and (Nb,Y)-doped bismuth oxide ceramics.

Grain-orientated lead-free BNT-based piezoceramics with giant electrostrictive effect

In this study, we propose an effective approach to gain prominent electrostrictive behavior by taking advantage of texture construction in lead-free (Bi0.5Na0.5)TiO3(BNT)-based piezoceramics for actuator applications. The electrostrictive effect was explored systematically in <00l> textured 0.90(0.83Bi0.5Na0.5TiO3-0.17Bi0.5K0.5TiO3)-0.10NaNbO3(BNT-BKT-NN) ceramics with respect to grain orientation, temperature and electric fields. It was found that the electrostrctive coefficient Q33 and recoverable strain increase monotonously with the grain orientation increasing. At the optimized microstructure (F00l=92%), a giant Q33 with nearly purely electrostrictive characteristics was detected to be around ~0.0354m4C−2, which was far larger than the reported values of Pb(Mg1/3Nb2/3)O3 (PMN) and the existing BNT-based electrostrictive materials. Meanwhile, the acquired Q33 was found to exhibit excellent stability for the highly textured sample under different temperature or electric field conditions. Our achievement demonstrates that the giant electrostrictive properties with superior temperature and electric field stability for <00l> textured BNT-BKT-NN ceramic are of great significance in replacing traditional PMN ceramics for actuator applications.

Ultra-High Tunability of &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\text{Ba}_{(2/3)}\text{Sr}_{(1/3)}\text{TiO}_{3}$&lt;/tex-math&gt; &lt;/inline-formula&gt;-Based Capacitors Under Low Electric Fields

We report the high-frequency electrical characterization of $\text{Ba}_{2/3}\text{Sr}_{1/3}\text{TiO}_{3}$ (BST) thin films exhibiting a very high dielectric tunability with low losses at 2.45 GHz under very low applied electrical fields. BST layers were integrated in out-of-plane Metal-Insulator-Metal (MIM) devices with optimized Ir/MgO(100) bottom electrodes. The high frequency properties of BST films with thicknesses of 200 nm, 450 nm and 1450 nm were thoroughly investigated in the 100 MHz–10 GHz domain and exhibit extremely high capacitance tuning abilities of 82%, 81% and 70% respectively, under applied voltages as low as 10 V. MIM devices responses show the onset of acoustic resonances associated with the BST electrostrictive behavior under an electric field. By combining high tunability with low resistive losses under low applied voltages, these devices are opening promising avenues for their integration in high-performance tunable devices in the microwave domain and particularly at 2.45 GHz, corresponding to the widely used ISM (industrial, scientific and medical) frequency band.

Actuation Behavior of Polylactic Acid Fiber Films Prepared by Electrospinning.

A poly-DL-lactide (PLA) fiber film was prepared using the electrospinning method. This film consisted of randomly oriented PLA nanofibers. Consequently, it had sponge-like structure and was quite soft compared to PLA films prepared by spin coating. The average diameter of the fibers and the density of the film were 730 nm and 20%, respectively. By applying a voltage, the PLA film was subjected to electric-field-induced strain: expansion and compression in the thickness direction. When a voltage of -200 V was applied to the film, its thickness shrank from 13.5 µm to 10.0 µm (a 26% reduction). Electric-field-induced strain can occur via two different mechanisms: The first is electrostrictive behavior. That. is, in a highly electric field region, a change of film thickness occurs (compression only) from the electrostatic force between electrodes. The second mechanism is piezoelectric-like behavior that occurs in racemic PLA, wherein a PLA nanofiber is expanded and compressed by applying positive and negative voltage. Such piezoelectric-like behavior was not observed in spin-coated PLA films.

Enhanced strain response and energy harvesting capabilities of electrostrictive polyurethane composites filled with conducting polyaniline

The aim of this work was to study electrostrictive behavior and vibration energy harvesting performance of conductive polyaniline (PANI)/polyurethane (PU) composites at low percolation threshold. Polyurethane composites with various PANI contents (0–2 wt%) were fabricated by solution casting. AFM, TGA and DSC techniques were used to investigate the topography, intermolecular interactions and dispersion effects in these composites. Moreover, dielectric and mechanical properties were determined to characterize electrostriction and energy conversion behaviors. The experimental results indicated that the PANI filler in PU matrix improved the electromechanical coupling, which is related to the interfacial charges between these phases. When an external electric field was applied to the electrodes, the generated current increased with the PANI content. Theoretical power analysis supported the experimental results, demonstrating that 2 wt% PANI in PU gave the maximum output power in a low electric field at 20 Hz mechanical frequency. Consequently, conductive PANI dispersed into electrostrictive PU can provide high power density and good efficiency of electromechanical conversion.

Deformation on segment-structure of electrostrictive polyurethane/polyaniline blends

Blends of elastic polyurethane (PU) and conductive polyaniline (PANI) were assessed for such improved electromechanical properties that are promising for further application in actuators, sensors and energy conversion. For the experiments, electrostrictive polyurethane blends were prepared with varied PANI contents. These blends were prepared with two alternative solvents, namely N,N-dimethylformamide (DMF) and 1-methyl-2-pyrrolidone (NMP), and were fabricated by solution casting. The morphology along with electrical and mechanical properties, and specifically the electrostrictive coefficient were studied. The electrostrictive behavior was determined from electric field induced strain, observed with a photonic displacement apparatus in the film thickness direction. The results suggest that the PANI component in NMP solvent effectively enhanced the electrostriction of these PU/PANI polymer blends. The solvent effects during film forming on the film's electrostriction were likely related to the hard interfacial domains between the dispersed PANI and the PU matrix that could increase the electrostriction coefficient.

Phase diagram and electrostrictive effect in BNT-based ceramics

In this work, phase diagram for the (Bi0.5Na0.5)TiO3–KNbO3–SrTiO3 ternary system has been constructed and analyzed based on macroscopic properties and structure analysis and pseudocubic (0.92−x)BNT–0.08KN–xST (0≤x≤0.07) ceramics have been fabricated and investigated. A morphotropic phase boundary between the ferroelectric rhombohedral and relaxor pseudocubic phases at around critical composition was proposed, resulting in large strain response. The polarization hysteresis loops, strain hysteresis loops and S–P2 curves demonstrate electrostrictive behavior of all studied samples. A very high electrostrictive strain (~0.148%) with a high electrostrictive coefficient Q11 of 0.0236m4C−2 is obtained for the 0.90BNT–0.08KN–0.02ST composition, which was entirely comparable to the well-known electrostrictive material Pb(Mg1/3Nb2/3 )O3 and attributed to the formation of relaxor pseudocubic phase developed by the SrTiO3 substitution. Meanwhile, the electrostrictive coefficient exhibited a highly temperature-insensitive behavior, indicating that the investigated system is suitable for high-precision positioning devices and solid-state actuators.

Variation of Piezoelectric properties and mechanisms across the relaxor-like/Ferroelectric continuum in BiFeO3- (K0.5Bi0.5)TiO3-PbTiO3 ceramics.

1- x - y)BiFeO3-x(K0.5Bi0.5)TiO3-yPbTiO3 (BFKBT- PT) piezoelectric ceramics were investigated across the compositional space and contrasted against the xBiFeO3- (1-x)(K0.5Bi0.5)TiO3 (BF-KBT) system, whereby a range of relaxor-like/ferroelectric behavior was observed. Structural and piezoelectric properties were closely related to the PbTiO3 concentration; below a critical concentration, relaxor-like behavior was identified. The mechanisms governing the piezoelectric behavior were investigated with structural, electrical, and imaging techniques. X-ray diffraction established that longrange non-centrosymmetric crystallographic order was evident above a critical PbTiO3 concentration, y > 0.1125. Commensurate with the structural analysis, electric-field-induced strain responses showed electrostrictive behavior in the PbTiO3-reduced compositions, with increased piezoelectric switching in PbTiO3-rich compositions. Positive-up-negative-down (PUND) analysis was used to confirm electric-field-induced polarization measurements, elucidating that the addition of PbTiO3 increased the switchable polarization and ferroelectric ordering. Piezoresponse force microscopy (PFM) of the BF-KBT-PT system exhibited typical domain patterns above a critical PbTiO3 threshold, with no ferroelectric domains observed in the BF-KBT system in the pseudocubic region. Doping of BiFeO3-PbTiO3 has been unsuccessful in the search for hightemperature materials that offer satisfactory piezoelectric properties; however, this system demonstrates that the partial substitution of alternative end-members can be an effective method. The partial substitution of PbTiO3 into BF-KBT enables long-range non-centrosymmetric crystallographic order, resulting in increased polar order and TC, compared with the pseudocubic region. The search for novel high-temperature piezoelectric ceramics can therefore exploit the accommodating nature of the perovskite family, which allows significant variance in chemical and physical characters in the exploration of new solid-solutions.

Contribution of Electrostriction in Polyurethane/Polyaniline Blends

In this work, we present a series of electrostrictive polymer blend that can potentially be used as actuators for a variety of applications. This polymer blend combines an electrostrictive polyurethane with a conductivity polyaniline polymer. The effect of filler content has been investigated. The structures of the blends, the electrical and mechanical properties which affect electrostrictive behavior were studied. The results showed that both dielectric constant and glass transition temperature of the blends increase with increasing polyaniline contents. Moreover, it was noted that space charges distribution and hard-segment domain formation significantly related with electrostrictive coefficient of polymer blend. Therefore, electrostriction behavior in the polymer blends has been demonstrated, and optimal microstructure for electrostriction enhancement has been identified.

Tunable and high quality factor SrTiO3 surface acoustic wave resonator

We fabricated a tunable surface acoustic wave resonator in the 2 GHz-frequency range by depositing and patterning 2 μm-wide pitch inter-digitated Al electrodes on SrTiO3 (STO) paraelectric substrate. We took advantage of the electrostrictive behavior of STO, whose properties are nonlinear with respect to the applied electric field, to induce tunability of the resonance frequency. The obtained frequency tunability reaches 0.7% at 0.5 MV/cm. Besides, the main advantage of this device is its high acoustic quality factor Q reaching 2450 at 2 GHz, thanks to the single-crystal nature of STO. This is one order of magnitude larger than the typical quality factor of its tunable bulk acoustic wave resonators counterparts.

Optical Interferometric Technique for Induced Strain Ferroelectric Loop Study at Low Frequency

Michelson interferometric technique was modified in the setup and used to measure very small changes in optical path length for electric field induced-strain phenomena. Induced-strain is established in the sample when the beam of light propagating through the sample surface undergoes a shift in phase, which in turn leads to a change in the intensity of the interference pattern formed where the reference and probing beams recombine. In this work the electric field induced-strain was measured as a function of electric field (s-E loop) and polarization (s-P loop) of PbMg1/3Nb2/3O3(PMN) and 0.7PbMg1/3Nb2/3O3-0.3PbZr0.52Ti0.48O3(0.7PMN-0.3PZT) ceramics, which showed electrostrictive (quadratic shape curve) and piezoelectric (butterfly shape curve) behavior at various frequency (0.01-1Hz).

Electrostriction study for single-walled carbon nanotubes-based composite

This paper proposes a 3D finite element method procedure to study the electrostrictive property of the single-walled carbon nanotube (SWCNT)-based composite. The numerical model in nanoscale is developed to investigate the electrostrictive behavior of the SWCNT and the polyvinylidene fluoride and trifluoroethylene P(VDF-TrFE) composite. A bond electrical contact model is adopted to reproduce the coupled electromechanical effects of the interface between SWCNT and P(VDP-TrFE). According to the model proposed, the mechanism of the enhanced electrostriction in SWCNT/P(VDP-TrFE) composite is intuitively demonstrated. Numerical results show that aside from the variation of electric field, the electrostriction of the SWCNT/P(VDP-TrFE) composite is greatly depend on the volume fraction of SWCNT and the difference of dielectric constant between SWCNT and P(VDP-TrFE) copolymer. While the dielectric constant of SWCNT is mainly depend on the chirality of SWCNT, which means that the electrostriction of the SWCNT/P(VDP-TrFE) composite is also largely depend on the chirality of SWCNT.

Electrostriction of Natural Rubber Latex/Carbon Black Nanocomposites

The purpose of this paper is to investigate an electrostrictive behavior of natural rubber (NR) and NR composites filled with carbon black (CB) nanopowders below percolation threshold. These NR elastomers present advantageous features such as a high productivity, elasticity, and ease of processing. In addition, such materials also exhibit the high induced strain and low young modulus for electrostrictive materials that can be used as actuators and energy harvesting. The NR and all composites were prepared by using solution casting method. The electrostrictive property of the composites was evaluated at low electric field (E 5 MV/m) by measuring the electric field induced strain Sz with the photonic displacement apparatus. The surface morphology of the samples was observed by the atomic force microscopy (AFM) and their electrical properties were analyzed as function of concentration and frequency in a range of 102105 Hz. The results show that the dielectric constant and the dielectric loss decrease when the frequency was increased. Moreover, the dielectric constant and the electrical conductivity strongly increase with increasing the CB contents, relate to interfacial charge distribution. While the dielectric loss slightly increases with increasing filler concentration. The electrostriction coefficient tended to increase with a higher CB loading. In comparison at CB 1 wt%, it was found that the electrostriction coefficient of NR composites is approximately 7 times larger than the pure NR. The NR nanocomposites thus seem to be very attractive for low frequency electromechanical applications.