Electrostrictive Effect Research Articles

Electrostriction-enhanced giant piezoelectricity via relaxor-like secondary crystals in extended-chain ferroelectric polymers

<h2>Summary</h2> Piezoelectricity in ferroelectric polymers originates from the electrostrictive effect coupled with a remanent polarization. However, its structural origin remains controversial, and it is not clear how modifying the electrostriction can further improve piezoelectricity for polymers. Here, we report that electrostriction can be significantly enhanced in poled poly(vinylidene fluoride-<i>co</i>-trifluoroethylene) [P(VDF-TrFE)] random copolymers containing extended-chain primary crystals and relaxor-like secondary crystals in the oriented amorphous fraction (SC_OAF). As a result of the high polarizability of dipoles and ferroelectric nanodomains in the SC_OAF, the inverse piezoelectric coefficient d₃₁ reaches as high as 77 ± 5 pm/V for the P(VDF-TrFE) 55/45 copolymer at 55°C. This finding not only extends our understanding of piezoelectricity in polymers but also provides guidance for further enhancing the piezoelectricity of ferroelectric polymers in the future.

Unique beam deflection based on dynamic polarized nano-domains in Cu-doped KTN.

In this report, we successfully implement a unique cross-field beam deflector by exploiting the modulation of a one-dimensional refractive index in a copper-doped potassium tantalite niobite crystal. A theoretical model is established based on an electrostrictive effect regulated by the dynamic polarized nano-domains to explicate the mechanism of the abnormal beam deflection which is perpendicular to the applied electric field. Experimental results agree well with our theoretical deduction while validating the interactions between the dynamic polarized nano-domains and the applied electric field. Our findings will break the limitation of conventional electro-optic deflectors, paving the way to develop promising optical functional devices with a large field-of-view scanning angle and ultra-low driving voltage.

Thermo-acoustic, spectroscopic, and electrochemical investigation of sparfloxacin–ionic surfactant interactions

The rising antibiotic resistance crisis poses a severe threat in the medicinal field and thus, underlines an urgent need for developing new and more effective antibiotics to overcome this crisis. However, one of the significant challenges in developing more effective antibiotics that can diffuse passively across the biomembranes is the limited understanding of their physicochemical interactions with these membranes. There has been a recent renaissance of interest in using surfactant systems as potential model biomembranes to correlate the physicochemical interactions of pharmaceutical drugs and biomolecules with the cell membranes at the molecular level. In this study, the effect of adding a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), and an anionic surfactant, sodium dodecyl sulfate (SDS), to a solution containing sparfloxacin (SPRF), a fluoroquinolone drug, was investigated using volumetric and acoustic measurements under physiological conditions (phosphate buffer, pH 7.4) over a temperature range (298.15 to 313.15 K) at an interval of 5 K. The obtained density and sound velocity data were used to compute and interpret various volumetric and acoustic parameters based on cosphere overlap model and electrostriction effect for comprehension of solute–solute and solute–solvent interactions prevailing in these systems. The parameters, partitioning and binding coefficients of SPRF with ionic surfactants, are measured employing UV–visible spectroscopy and cyclic voltammetry. The results revealed that SPRF shows more significant partitioning and binding with SDS micelles than with DTAB micelles.

Effect of Ultrasonic Techniques on Welding Technologies

The article discusses selected physical properties of industrial ultrasonic equipment utilising the magnetostrictive or electrostrictive effect. Particular attention was paid to equipment enabling the ultrasonic welding of various metals and thermoplastics. The research involved the comparison of various designs and operation of technological equipment, taking into account selected energy, control and environmental aspects. Based on reference publications it was possible to determine and categorise general features concerning the application of ultrasonic technologies as well as to indicate factors responsible for the formation of imperfections during the ultrasonic welding process.

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.

Vector harmonic mode-locking by acoustic resonance

For an Er-doped fiber laser, for the first time, to the best of our knowledge, we demonstrate both experimentally and theoretically a novel mechanism of harmonic mode-locking based on the electrostriction effect leading to excitation of the torsional acoustic modes in the transverse section of the laser. The exited torsional acoustic modes modulate the fiber birefringence that results in synchronization of oscillations at the harmonic modes and the linewidth narrowing with the increased signal-to-noise ratio of 30 dB. By adjusting the in-cavity birefringence based on tuning the polarization controller, we enable the selection of the harmonic mode to be stabilized.

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 (&gt;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.

Interfacial, Electroviscous, and Nonlinear Dielectric Effects on Electrokinetics at Highly Charged Surfaces.

The dielectric constant and the viscosity of water at the interface of hydrophilic surfaces differ from their bulk values, and it has been proposed that the deviation is caused by the strong electric field and the high ion concentration in the interfacial layer. We calculate the dependence of the dielectric constant and the viscosity of bulk electrolytes on the electric field and the salt concentration. Incorporating the concentration and field-dependent dielectric constant and viscosity in the extended Poisson–Boltzmann and Stokes equations, we calculate the electro-osmotic mobility. We compare the results to literature experimental data and explicit molecular dynamics simulations of OH-terminated surfaces and show that it is necessary to additionally include the presence of a subnanometer wide interfacial water layer, the properties of which are drastically transformed by the sheer presence of the interface. We conclude that the origin of the anomalous behavior of aqueous interfacial layers cannot be found in electrostriction or electroviscous effects caused by the interfacial electric field and ion concentration. Instead, it is primarily caused by the intrinsic ordering and orientation of the interfacial water layer.

Electrostrictive Effect of Materials under High Pressure Revealed by Electrochemical Impedance Spectroscopy

Because electrostrictive materials are completely sealed and confined in a diamond anvil cell (DAC), their strain and atomic displacement excited by electric field cannot be in situ measured by gen...

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.

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

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

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.

Non-linear Conductance, Rectification, and Mechanosensitive Channel Formation of Lipid Membranes.

There is mounting evidence that lipid bilayers display conductive properties. However, when interpreting the electrical response of biological membranes to voltage changes, they are commonly considered as inert insulators. Lipid bilayers under voltage-clamp conditions display current traces with discrete conduction-steps, which are indistinguishable from those attributed to the presence of protein channels. In current-voltage (I-V) plots they may also display outward rectification, i.e., voltage-gating. Surprisingly, this has even been observed in chemically symmetric lipid bilayers. Here, we investigate this phenomenon using a theoretical framework that models the electrostrictive effect of voltage on lipid membranes in the presence of a spontaneous polarization, which can be recognized by a voltage offset in electrical measurements. It can arise from an asymmetry of the membrane, for example from a non-zero spontaneous curvature of the membrane. This curvature can be caused by voltage via the flexoelectric effect, or by hydrostatic pressure differences across the membrane. Here, we describe I-V relations for lipid membranes formed at the tip of patch pipettes situated close to an aqueous surface. We measured at different depths relative to air/water surface, resulting in different pressure gradients across the membrane. Both linear and non-linear I-V profiles were observed. Non-linear conduction consistently takes the form of outward rectified currents. We explain the conductance properties by two mechanisms: One leak current with constant conductance without pores, and a second process that is due to voltage-gated pore opening correlating with the appearance of channel-like conduction steps. In some instances, these non-linear I-V relations display a voltage regime in which dI/dV is negative. This has also been previously observed in the presence of sodium channels. Experiments at different depths reveal channel formation that depends on pressure gradients. Therefore, we find that the channels in the lipid membrane are both voltage-gated and mechanosensitive. We also report measurements on black lipid membranes that also display rectification. In contrast to the patch experiments they are always symmetric and do not display a voltage offset.

Towards Poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene)-Based Soft Actuators: Films and Electrospun Aligned Nanofiber Mats

In the pursuit of designing a linear soft actuator with a high force-to-weight ratio and a stiffening behavior, this paper analyzes the electrostrictive effect of the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) polymer in the form of film and aligned electrospun nanofiber mat. An experimental setup is realized to evaluate the electrostrictive effect of the specimens disjointly from the Maxwell stress. In particular, an uniaxial load test is designed to evaluate the specimens’ forces produced by their axial contraction (i.e., the electrostrictive effect) when an external electric field is applied, while an uniaxial tensile load test is designed to show the specimens’ stiffening properties. This electro-mechanical analysis demonstrates that both the film and the nanofiber mat are electrostrictive, and that the nanofiber mat exhibits a force-to-weight ratio ∼65% higher than the film and, therefore, a larger electrostrictive effect. Moreover, both the film and the nanofiber mat show a stiffening behavior, which is more evident for the nanofiber mat than the film and is proportional to the weight of the material. This study concludes that, thanks to its electro-mechanical properties, the poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene), especially in the form of aligned electrospun nanofiber mat, has high potential to be used as electro-active polymer for soft actuators in biomedical and biorobotics applications.

Initiation of nanosecond-pulsed discharge in water: Electrostriction effect

Underwater nanosecond-pulsed discharges have been widely utilized in numerous industrial applications. The initial stage of nanosecond-pulsed discharge in water contains extremely abundant physical processes, however, it is still difficult to reveal the details of charge transportation and multiplicative process in liquid within several nanoseconds by currently existing experimental diagnostic techniques. Up to now, the initiation mechanism of underwater nanosecond discharge has been still a puzzle. In this paper, we develop a two-dimensional axially symmetric underwater discharge model of pin-to-plane, and numerically investigate the electrostriction process, cavitation process, and ionization process in water, induced by nanosecond-pulsed voltage. The negative pressure in water caused by tensile ponderomotive force is calculated. The creation of nanoscale cavities (so-called nanopores) in liquid due to negative pressure is modeled by classical nucleation theory with modified nucleation energy barrier. When estimating the temporal development of nanopore radius, a varying hydrostatic pressure is considered to restrain the unlimited expansion of nanopores. We estimate the electron generation rate by the product of the generation rate of incident electrons and the number density of nanopores. The simulation results show that cavitation occurs in liquid within several microns from pin electrode due to the electrostriction, which results in the formation of a large number of nanopores. The expansion of nanopore, caused by electrostrictive pressure on nanopore surface, provides a sufficient acceleration distance for electrons. The impact ionization of water molecules can be triggered by energetic electrons, leading the local liquid to be ionized rapidly. The effects of nanopores on rapid electron generation in water are discussed. Once nanopores are formed, the electrons can be generated in the following ways: 1) Field ionization of water molecules on the nanopore wall continuously provides seed electrons; 2) the seed electrons accelerated in nanopores enter into the liquid and collide with water molecules, resulting in the rapid increase of electrons. It can be inferred that the randomly scattered nanopores act as micro-sources of charges that contribute to the continuing ionization of liquid water in cavitation region near pin electrode. Electrostriction mechanism provides a new perspective for understanding the initiation of nanosecond-pulsed discharge in water.

Interfacial Regulation of Dielectric Properties in Ferroelectric Hf0.5Zr0.5O2 Thin Films

The discovery of ferroelectricity in hafnium zirconium oxide (HZO) thin films has attracted wide attention from academia to industry due to the application in ferroelectric non-volatile random access memories (FeRAM) with prominent performance in scalability and CMOS process compatibility. Dielectric behavior of ferroelectric HZO thin films is a key factor affecting the dynamic effect, piezoelectric and electrostrictive effect. Interface between HZO and capping electrodes plays an important role in regulating the dielectric properties. In this paper, the impedance frequency response and dielectric spectrum of ferroelectric HZO thin films were analyzed. Parameters of the interface were extracted to analyze the regulating effect on the dielectric properties based on an impedance model with constant phase element (CPE). Besides, dielectric spectrums at elevated temperatures were identified to verify this analysis.

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.

Deformable polyvinyl chloride gel for fabrication of varifocal microlens array

Limitations in further miniaturization of lenses and arrays to achieve varifocal capabilities in compact 2D/3D switchable imaging devices have spurred investigations into the use of alternative materials. To this end, we fabricated a new deformable microlens array (MLA) utilizing polyvinyl chloride (PVC) gel, containing 67–90 wt.% of dibutyl adipate (DBA), sandwiched between an anode with apertures, 20–300 μm in diameter, and a cathode made of a transparent conductive film. The effects of applied voltage and DBA content on the protrusion of the PVC gel were studied and the protrusion mechanism was investigated. The gel was deformed from a flat shape in the absence of voltage to a lens shape at 100–600 V. When a voltage was applied, the negatively charged PVC chains accumulated near the anode and induced deformation of the PVC gel, which rose along the aperture walls and protruded from the apertures. Furthermore, the protrusion level of the PVC gel increased with DBA content, which lowered its elastic modulus and increased the negative charge density. Thus, the deformation of the PVC gel was mainly governed by the effects of electrostriction and PVC chain dynamics. Additionally, aperture diameter was found to influence the shape of the lens. The protrusion profile was concave at aperture diameters of 50 and 100 μm but became convex at 20 μm. At an applied voltage of 600 V, the focal length of the MLA was −0.20 mm at aperture diameters of 50 and 100 μm, representing a concave lens, but +0.05 mm at 20 μm, representing a convex lens. The MLA functioned more as a deformable lens, which transformed from a flat shape into a lens shape, than as a variable lens whose focal length changed continuously. The roles of plasticizer content, PVC chain dynamics, and aperture diameter in achieving greater control over lens curvature merit further investigation.

Amplification of the electrostriction mechanism of photoacoustic conversion in layered media

In this work we have performed an analysis of an electrostriction mechanism of optical-to-acoustical energy conversion on the interface of two materials with low optical absorption. We compared this method of conversion with the widely used thermal conversion based on thin metal film. It was shown that the contribution of the electrostriction mechanism is significantly lower in the case of the homogeneous medium. We demonstrated the possibility to amplify the generated acoustic signal by excitation of the guided modes, for which the energy is localized in a thin dielectric layer (of about 200–400 nm in thickness). Due to the high electromagnetic field energy concentration in the structure, local values of intensity increase by more than two orders of magnitude in comparison to the intensity of the incident light, which also allows an increase in the amplitude of the pressure correspondingly. Thus, in this project, we propose the novel layered dielectric structures, in which the electrostriction effect occurs due to the excitation of the guided modes.