High Electromechanical Properties Research Articles

Electrostrictive Fiber with High Electromechanical Properties Using a Styrene–Ethylene–Butylene–Styrene-Based Dielectric Elastomer

Electrostrictive Fiber with High Electromechanical Properties Using a Styrene–Ethylene–Butylene–Styrene-Based Dielectric Elastomer

Intrinsic and extrinsic contributions in the ferroelectric response of chemically synthesized BiFeO3-xPbTiO3 thin films

Multiferroic (BiFeO3)1−x-(PbTiO3)x (1−x)BF−xPT thin films exhibit very high electromechanical properties in the vicinity of the morphotropic phase boundary (MPB), making them important candidates for use in several modern device applications. However, preparing high-quality (1−x)BF−xPT thin films is challenging due to the high conductivity caused by oxygen vacancies produced during the synthesis process. This study aims to understand the effect of size and porosity density on the electrical properties of (1−x)BF−xPT thin films. A series of (1−x)BF−xPT solid solution thin films were fabricated using the spin-coating method on Pt/TiO2/SiO2/Si(100) substrates through chemical solution deposition. X-ray diffraction studies revealed a polycrystalline structure. Surface SEM images showed that the films have a uniform surface with average grain sizes ranging between 50 and 200 nm and an average film thickness of 1.5 μm. A decrease in average pore size and an increase in the number of pores were observed with the increase in PT concentration in the prepared films. Ferroelectric characterization revealed that the films exhibit room-temperature ferroelectric hysteresis loops. Sources of various contributions to polarization were extracted from hysteresis loops, including true ferroelectric switching and space charge contributions. Thin films with 0.30 < x < 0.45 show higher remanent and saturation polarization values, suggesting that these compositions exhibit the MPB. The highest remanent polarization value (PR = 16.68 μC/cm2) was observed for the thin film with x = 0.40. The correlation between the phase, composition, film morphology, and ferroelectric response is described and discussed.

Simulation and structural design of 2–2 PIMNT/epoxy piezoelectric composites

Piezoelectric materials are commonly used in transducers to convert electromechanical signals due to their energy conversion characteristics. We designed a PIMNT/epoxy 2–2 composite to take full advantage of the excellent beam-mode piezoelectric and acoustic features of PIMNT single crystals. Following the approach used for piezoelectric ceramic composites, we selected PIMNT piezoelectric single crystal and EPO-TEK301-2 epoxy resin for the composite, and combined finite element analysis with experimental preparation. We prepared, tested and analyzed 2–2 piezoelectric single crystal composites with varying volume fractions, which showed high electromechanical coupling properties ([Formula: see text]%) and low acoustic impedance ([Formula: see text][Formula: see text]MRayl). These encouraging findings suggest the possibility of devising high-performance ultrasonic transducers utilizing the PIMNT/epoxy 2–2 composite.

Robust performance for composites using silicone rubber with different prospects for wearable electronics

AbstractThe different configurations of the composites originated with machine or human motion, and their mechanical stability for wearable electronics is in focus. Here, the study highlights that these configurations are critical for wearable devices. To achieve these aspects, the electroactive and dielectric silicone rubber (SR) was used as a host matrix. This SR not only provides flexibility, twisting, or stretchability for such devices, but its lightweight makes them comfortable for robust wearable devices. The reinforcing fillers such as graphite nanoplatelets (GNP) or diatomaceous earth (DE) and their hybrids are used. The electromechanical properties of the device were performed using the universal testing machine. The output voltage generated at 15 phr filler was 0.3 mV (GNP), 0.15 mV (DE), and 0.22 mV (hybrid). Similarly, the biomechanical properties were studied with human motion joints such as thumb pressing or wrist bending. The output voltage at 15 phr was best for thumb pressing and it was 0.42 mV (GNP), 0.18 mV (DE), and 0.25 mV (hybrid). In the same way, the mechanical aspects studied in this work are compressive modulus, tensile strength, and fracture strain. For example, the compressive modulus was 1.28 MPa (control) and increased at 15 phr filler to 2.44 MPa (GNP), 3.2 MPa (DE), and 2.75 MPa (hybrid). Similarly, the mechanical stretchability of the devices was 134% (control) and changed at 15 phr filler to 128% (GNP), 78% (DE), and 109% (hybrid). Overall, the work demonstrates the method to develop a device with high mechanical, electromechanical, and biomechanical properties and their usefulness for wearable electronic devices.

Structures, dielectric properties and AC impedance characteristics of BiFeO3–BaTiO3 high-temperature lead-free piezoceramics synthesized by the hydrothermal method

Among the lead-free piezoceramics, ([Formula: see text])BiFeO[Formula: see text]BaTiO3 (BF-BT) is considered a promising candidate for high-temperature piezoelectric materials owing to its high Curie temperature ([Formula: see text]C) and good electromechanical properties. In this work, the hydrothermal synthesis method was used to prepare the precursor powders of BiFeO3 and BaTiO3, and then the mixed powder compacts with the chemical composition of 0.7BF–0.3BT were sintered under pressureless conditions. The influence of the hydrothermal reaction times (12–24[Formula: see text]h) of BiFeO3 on the structures and electric properties of the sintered ceramics was instigated. First, all the samples synthesized with the tetragonal BaTiO3 and BiFeO3 powders were identified with relatively stable dielectric properties. As the hydrothermal reaction time to synthesize BiFeO3 increased, the dielectric properties as well as the temperature stability of the 0.7BiFeO3–0.3BaTiO3 ceramics also improved. At the condition of a hydrothermal reaction time of 24[Formula: see text]h, the sample obtained possesses both the lowest temperature coefficient of dielectric constant ([Formula: see text]C between RT and [Formula: see text]C) and the highest Curie temperature ([Formula: see text]C at 100[Formula: see text]kHz). Moreover, at high temperatures, it exhibits a higher AC impedance than others. The calculating result based on the resistive constant-phase-element model (R-CPE) circuit model showed that the grain boundary of the 0.7BF–0.3BT ceramics contributes more resistance to the conductivity at high temperatures. In summary, the hydrothermal reaction proved to be a useful way that achieves the preparation of single-phase 0.7BF–0.3BT ceramics with improved electrical properties.

Synthesis of a Stable and High-Concentration BaHfxTi1−xO3 Sol–Gel for High Electromechanical Performance of Bulk Ceramics

Lead-based materials are widely used in piezoceramics due to their high electromechanical properties. However, due to environmental protection and sustainable development, the use of the toxic element lead (Pb) in electronic devices is strictly restricted, therefore requiring the rapid development of piezoelectric-based devices with lead-free ceramics. In this context, a lead-free doped barium titanate was studied with a dual objective. First, a new sol–gel method to synthesize Hf4+-doped BaHfxTi1−xO (BHT) with x = 0.05, 0.075, and 0.10 is presented. Such BHT sols were prepared at high concentrations of up to 1 M. Dilution in ethylene glycol allowed parameters (viscosity, colloid sizes, etc.) to be controlled, which ensured a time-stable sol for several months at room temperature. Second, densified bulk ceramics with attrited powders were obtained from these sols and showed very good electromechanical properties, with a thickness coupling factor of kt = 47% (BaHf0.05Ti0.95O3 sintered at 1500 °C/6 h). These results are a first step that will allow the processing of lead-free piezoelectric thick films using a sol–gel composite method for vibrational energy harvesting applications.

Origin of high comprehensive electromechanical properties of novel donor and acceptor–codoped PMN–30PT ceramics

Donor and acceptor–codoped PMN–30PT ceramics with 1–3 mol% Sm and 1 mol% Mn were fabricated via a two-step solid-state reaction. The crystal structure and electrical properties were investigated in detail. Donor Sm and acceptor Mn codoping substantially enhances the electromechanical, piezoelectric, and dielectric properties with a high piezoelectric coefficient d33 = 483–680 pC/N, a high mechanical quality factor Qm = 518–642, a high field-induced strain = 0.20%–0.24 %, and a low dielectric loss tan δ = 0.54%–0.69 %. X-ray diffraction and Raman spectra reveal the coexisting triple phase composition of the rhombohedral phase, tetragonal phase, and monoclinic polar nanoregions. Thermally stimulated depolarization current verifies the formation of various defect dipole clusters such as (MnTi″–VO··)×. With enhanced local structure heterogeneity induced by Sm, the phase composition and defect chemistry are regarded as the origin of such high comprehensive performance.

Enhanced Electromechanical Performance in Lead-free (Na,K)NbO3-Based Piezoceramics via the Synergistic Design of Texture Engineering and Sm-Modification.

Next-generation electromechanical conversion devices have a significant demand for high-performance lead-free piezoelectric materials to meet environmentally friendly requirements. However, the low electromechanical properties of lead-free piezoceramics limit their application in high-end transducer applications. In this work, a 0.96K0.48Na0.52Nb0.96Sb0.04O3-0.04(Bi0.5-xSmx)Na0.5ZrO3 (abbreviated as T-NKN-xSm) ceramic was designed through phase regulation and texture engineering, which is expected to solve this difficulty. Through our research, we successfully demonstrated the enhanced electromechanical performance of lead-free textured ceramics with a highly oriented [001]c orientation. Notably, the T-NKN-xSm textured ceramics doped with 0.05 mol % Sm exhibited the optimal electromechanical performance: piezoelectric coefficient d33 ≈ 710 pC N-1, longitudinal electromechanical coupling k33 ≈ 0.88, planar electromechanical coupling kp ≈ 0.80, and Curie temperature Tc ≈ 244 °C. Finally, we conducted a detailed investigation into the phase and domain structures of the T-NKN-Sm ceramics, providing valuable insights for achieving high electromechanical properties in NKN-based ceramics. This research serves as a crucial reference for the development of advanced electromechanical devices by facilitating the utilization of lead-free piezoelectric materials with superior performance and environmental benefits.

Achieving ultrahigh electromechanical properties with high TC in PNN-PZT textured ceramics

<001> textured Pb(Ni1/3Nb2/3)O3-PbZrO3-PbTiO3 (PNN-PZT) ceramics were prepared by templated grain growth (TGG) technique using 0.36PNN-xPZ-(0.64-x)PT (x = 0.23, 0.25 and 0.27) powder matrix. Optimum template content was derived to achieve the best electromechanical properties of textured ceramics. The piezoelectric coefficient d33 = 1165 pC/N, Curie temperature TC = 197 °C, longitudinal mode electromechanical coupling factor k33 = 0.86 and a very large effective piezoelectric strain coefficient d33* = 2041 pm/V were simultaneously achieved at the morphotropic phase boundary (MPB) composition (x = 0.25) with 3 vol.% BaTiO3 (BT) templates. Domain structures of textured ceramics were analyzed in detail to reveal the origin of these high piezoelectric and electromechanical properties.

Design and analysis of a broadband class VII flextensional transducer with the third-generation crystal, Mn:PIN-PMN-PT

For designing flextensional transducers (FTs), driving material is an important innovation direction to improve performance. The third-generation single crystal: manganese-modified Pb(In 1/2 Nb 1/2 )O 3 -Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 (Mn:PIN-PMN-PT) has superior piezoelectric and electromechanical properties. However, up to date, Mn:PIN-PMN-PT single crystals applied to practical FTs haven’t been reported in the literature. In this paper, a broadband class VII FT based on [001] C poled Mn:PIN-PMN-PT is proposed. To fully utilize the excellent properties of Mn:PIN-PMN-PT, the structural parameters of the transducer were designed and optimized using the finite element method (FEM). Prototypes were fabricated and measured. Compared with the PZT-4 class VII FT, the bandwidth of the Mn:PIN-PMN-PT FT increased by 27.8%, and the transmitting voltage response (TVR) was 6.3 dB higher. This work verifies that Mn:PIN-PMN-PT single crystals have great potential as the driving material for broadband high-power FTs. • This paper proposes a broadband class VII flextensional transducer based on Mn:PIN-PMN-PT single crystals. • We fully utilize the high piezoelectric and electromechanical properties of the third-generation crystal, Mn:PIN-PMN-PT. • The acoustic performance of the Mn:PIN-PMN-PT flextensional transducer is significantly improved. • Mn:PIN-PMN-PT has great potential as the driving material for broadband high-power flextensional transducers.

Achieving both high electromechanical properties and temperature stability in textured PMN‐PT ceramics

AbstractTextured piezoelectric ceramics, such as textured Pb(Mg1/3Nb2/3)O3‐PbTiO3 (PMN‐PT) ceramics, have attracted considerable attention from both academia and industry, as they possess crystal‐like piezoelectric properties, high composition homogeneity, and low manufacturing cost. However, the main difficulty with the textured piezoelectric ceramics is the presence of BaTiO3 (BT) templates, which greatly reduces their piezoelectricity and phase transition temperature. Thus, it is highly recommended to fabricate textured piezoelectric ceramics using as few templates as possible. Here, we successfully fabricated high‐quality &lt;001&gt;‐textured PMN‐28PT ceramics (texturing degree of 99%) by using an extremely small amount of BT templates (1 vol.%) with the help of CuO/B2O3 sintering aids. The textured PMN‐28PT ceramic exhibits 80% piezoelectric coefficient (d33 ∼ 1200 pC/N), 96% electromechanical coefficient (k33 ∼ 88%) and the same temperature stability (Trt ∼ 100, Tc ∼ 150°C) when compared to its single crystal counterpart. In addition, by using an alternating current electric field poling (AC‐poling), the piezoelectric coefficient d33 and dielectric permittivity ε33 of the textured PMN‐28PT ceramics were further enhanced around 5–8%. It is believed that the advantages of high electromechanical properties, low cost, and easy mass production of textured PMN‐28PT ceramic will make it a promising candidate for advanced electromechanical devices.

High temperature 0.63BiFeO3-0.37BaTiO3 based ceramics with large electromechanical properties by simple A-site K+ doping

Designing high temperature piezoelectric ceramics with large electromechanical properties is key to the actuators application in harsh environment. BiFeO3-BaTiO3 based piezoelectric ceramics are the promising candidates due to their high electromechanical properties and high Curie temperature. Here, the simple A-site single K+ doped 0.63Bi1−xKxFeO3-0.37BaTiO3 (abbreviated as 0.63B1−xKxF-0.37BT) ceramics with positive temperature dependent electromechanical properties were fabricated via conventional solid phase method. The electromechanical properties in the 0.63B1−xKxF-0.37BT ceramics are closely related to the content of K+ doping. The excellent electromechanical properties of S= 0.26% and d33*=861 pm/V under low electric field of 30 kV/cm at 105 ℃ are achieved in the 0.63B0.9975K0.0025F-0.37BT ceramic, which is conducive to their application at high temperature. Combined with the microstructure and PFM, the optimized electromechanical properties in 0.63B0.9975K0.0025F-0.37BT ceramic are mainly due to more nanodomains switching facilitated by the large grain size and local structural heterogeneity. The site engineering of A-site single ion doping is an efficient and simple strategy for BF-BT based piezoelectric ceramics to achieving excellent electromechanical properties under low electric field at high temperature.

Poly(thioether)-b-polysiloxane-b-poly(thioether) triblock copolymer towards homogeneous dielectric elastomer with high dielectric performance

Dielectric elastomers (DEs) have drawn much attention owing to their application prospects in artificial muscles and soft robotics, it is still a big challenge to prepare DEs with high electromechanical performances. This work reports a highly stretchable poly(thioether)-b-polysiloxane-b-poly(thioether) triblock copolymer based homogenous DEs with high electromechanical properties. The triblock copolymer (PSiPGE) was synthesized through the ring-opening polymerization (ROP) of phenyl glycidyl ether (PGE) and carbonyl sulfide (COS) catalyzed by silicon alkoxides. The dipoles (benzene rings) on the side groups of PSiPGE improved the dipole polarizations and the phase separation structure of this triblock copolymer enhanced the interfacial polarizations between poly(thioether) and polysiloxane, and thus improving the dielectric constant (ε’, up to 5.8). In addition, the PSiPGE exhibited low elastic modulus (Y, 0.04 MPa), and thus possessed high electromechanical sensitivity (β, ∼145 MPa−1) which is much higher than that of most homogenous DEs. This work provides a new strategy to construct homogenous DEs with excellent electromechanical performances, leading to a greater application aspect in the actuated devices.

Effect of multi-armed chain extender on microphase morphology, stress-strain behavior and electromechanical properties of polyurethane elastomers

High dielectric constant and low modulus of thermoplastic polyurethane elastomers (PUEs) are required for various applications in actuators, sensors and energy harvestings. In this work, we controlled the microphase separated morphology of PUEs by regulation of the content of hydroxyl-terminated four-armed polycaprolactone (4amPCL) chain extender to achieve J-shaped stress-strain curve with low modulus and high electromechanical properties. Our results showed that the hydrogen bonding between hard segments (HSs) and crystallization of soft segment (SS) are significantly impeded by long-chain branched structure when added lower molar fraction (<20% of chain extenders) of 4amPCL as chain extender, whereas the branched long-chains are embedded in microphase separated hard and soft domains (HD and SD) to form strip shaped interconnected hard domain (HD) rich regions when added higher molar fraction (>20% of chain extenders) of 4amPCL as chain extender. The PUE with 29% of 4amPCL (PU-4amPCL-0.29) showed lower modulus (1.5 MPa), higher tensile strength (17.5 MPa) at 1048% of elongation, and 3.9% of actuation strain at 20 kV/mm, and higher contribution (48.1%) of Maxwell stress on actuation strain at 20 kV/mm. We found that the microphase separation of branched long-chains induced semi-interpenetration polymer network like structure of PUEs played an important role in exhibiting J-shaped stress-strain behavior. Our results can provide new insight on fabrication of high electromechanical performance of dielectric polyurethane elastomers.

Printable dielectric elastomers of high electromechanical properties based on SEBS ink incorporated with polyphenols modified dielectric particles

In this work, a recently developed 3D additive processing technology termed electrohydrodynamic (EHD) printing was employed to fabricate dielectric elastomer (DE) films by using styrene-ethylene-butylene-styrene (SEBS) inks with the addition of high dielectric titanium dioxide (TiO2) nanoparticles. In order to improve the dispersibility of TiO2 in the SEBS matrix, extracted walnut polyphenols were utilized for surface modification of TiO2 nanoparticles labelled wp-TiO2. The effect of the applied voltage on the ink jet morphology of the obtained SEBS based inks during EHD printing was analyzed. The prepared films had precision patterned shapes and their morphology was studied. It revealed that the dispersibility of TiO2 nanoparticles in the SEBS matrix and their compatibility were greatly improved using this procedure. Furthermore, the printed DE films were found to have excellent mechanical, dielectric and electromechanical properties. For the range of DEs fabricated, the SEBS/10%wp-TiO2 composite exhibited the maximum actuated area strain of 21.5% at an electric field of about 34.0 V/μm without degradation of other properties.

Superior actuation performance and healability achieved in a transparent, highly stretchable dielectric elastomer film

A transparent, stretchable, and self-healable dielectric elastomer with high electromechanical properties is tolerant to various operating environments, which provides a promising strategy for fabricating multifunctional soft materials.

Ultralow dielectric loss of BiScO3-PbTiO3 ceramics by Bi(Mn1/2Zr1/2)O3 modification

BiScO3-PbTiO3 ceramics are attractive for high-temperature piezoelectric applications while their high dielectric loss has to be substantially reduced. In this paper, a ternary perovskite system of xBi(Mn1/2Zr1/2)O3-(1-x-y)BiScO3-yPbTiO3 (abbreviated as xBMZ-BS-yPT) with x = 0.02, 0.04 and y = 0.62–0.67 were fabricated by conventional solid-phase method, and their ceramics were systematically studied with regards to phase structure, microstructure, dielectric and piezoelectric properties. X-ray diffraction results indicate a gradual change from rhombohedral to tetragonal phase with increasing PT composition. Morphotropic phase boundary (MPB) is revealed for the system with x = 0.02, y = 0.64, at which ultralow dielectric loss factor (0.58 %), almost unchanged Curie temperature (449 °C), high electromechanical properties (d33 = 360 pC/N, kp = 0.53), and stable strain output below 200 °C are observed. With such excellent piezoelectric properties and high-temperature stability, BMZ modified BS-PT ceramics are promising candidates for power electromechanical devices, especially operating in high-temperature environments.

A Study on the Relationship Between Grain Size and Electrical Properties in (K,Na)NbO3‐Based Lead‐Free Piezoelectric Ceramics

AbstractThe 0.5 wt% MnO2‐doped 0.95(K0.5Na0.5)(Nb0.965Sb0.035)O3‐0.01CaZrO3‐0.04(Bi0.5K0.5)(Hf0.98Ti0.02)O3 (95KNNS‐1CZ‐4BKHT) lead‐free ceramics with grain size from 0.31 to 3.83 µm are fabricated by hot‐press sintering (HPS), microwave sintering (MS), conventional sintering (CS), two‐step sintering (TSS), and a combination of two of the above‐mentioned methods. Then, the grain size effects on the phase transition, electrical properties, domain structure, and temperature stability of the ceramics are investigated. The phase structure evolves from single rhombohedral (R) phase to coexisted rhombohedral‐tetragonal (R‐T) phases around 1 µm. The electromechanical properties are strongly grain size dependent. The values of piezoelectric coefficient (d33) and planar electromechanical coupling factor (kp) first rise sharply when the grain size is less than 1 µm, and then increase mildly in the grain size range from 2.55 to 3.04 µm and finally almost remain a constant (≈450 pC N−1 and 54%) when the grain size is larger than 3.31 µm. The R‐T phase coexistence and strip‐like nanodomain structure characterized by an easier switching feature contribute to the high piezoelectric and electromechanical properties of coarse‐grained samples. This work not only clarifies the relationship between grain size and electrical properties in KNN‐based ceramics, but also provides a novel strategy for developing high‐performance lead‐free piezoceramics.

Thermally stable electrostrain in BiFeO3-BaTiO3-based high temperature lead-free piezoceramics

BiFeO3-BaTiO3 ceramics possess both high electromechanical properties and a high Curie temperature, which are promising high temperature lead-free piezoactuator materials. However, the poor thermal stability of electrostrain limits their practical exploration. Here, we report a temperature stable electrostrain of 0.18% at 6 kV/mm, with a variation of 13% from 25 °C to 175 °C for (1-x)(0.67BiFeO3-0.33BaTiO3)-xSr0.8Bi0.1◻0.1TiO2.95 solid solutions with x = 0.04. The addition of a relaxor ferroelectric Sr0.8Bi0.1◻0.1TiO2.95 (SBT) breaks the long range ferroelectric order of BiFeO3-BaTiO3 (BFBT) ceramics. More importantly, the combined effect of the negative temperature dependent electrostrain for relaxors and the positive one for the parent BFBT contributes to the superior temperature stability of the electrostrain. This work provides an effective method for designing piezoelectric materials with an enhanced temperature stability for high temperature actuator applications.

Electrical conduction mechanisms and effect of atmosphere annealing on the electrical properties of BiFeO3-BaTiO3 ceramics

BiFeO3-BaTiO3 (BFBT) is a promising high temperature piezoelectric ceramic system, as it possesses both high electromechanical properties and high Curie temperature. However, pure BFBT commonly exhibits large electrical conductivity at high temperatures, and there is considerable disagreement on its electrical conduction mechanism. Here we investigated the electrical conduction mechanisms of 0.70BiFeO3-0.30BaTiO3 and 0.67BiFeO3-0.33BaTiO3 ceramics by systematic impedance spectroscopy measurements as a function of oxygen partial pressure and temperature. Both ceramics exhibit higher electrical conductivity with an increase of oxygen partial pressure, consistent with p-type semiconductor behaviors. Particularly, reduced conductivity and improved ferroelectric remanent polarization can be obtained in BFBT when annealed in inert atmosphere. This study provides fundamental basis for preparing insulating and high performance BFBT ceramics.