A model for 0‐3 piezoelectric composites with an interlayer

Based on the model for 0‐3 piezoelectric composites without an interlayer, a modified model for 0‐3 piezoelectric composites with an interlayer has been proposed and the expressions for this model consequently have been derived. The interlayer is supposed to act as a bridge between the ceramic and polymer matrix during the poling process. The calculated results show that the electric field strength on ceramic phase is influenced by the volume fraction of interlayer and ceramic in the composite, and dielectric constants of interlayer, ceramic, and polymer matrix. The electric field strength on ceramic phase increases with the interlayer volume fraction and dielectric constant ratio of interlayer and polymer matrix. This indicates that the ceramic polarization and piezoelectric performance of 0‐3 piezoelectric composites can be improved by design of the interlayer with appropriate dielectric constants and volume fractions into the 0‐3 piezoelectric composites. POLYM. COMPOS., 31:1922–1927, 2010. © 2010 Society of Plastics Engineers.     

Structural and piezoelectric properties of <001> textured PZT‐PZNN piezoelectric ceramics

Rhombohedral 0.69Pb(Zr_0.47Ti_0.53)‐0.31Pb(Zn_0.6Ni_0.4)NbO₃ (PZT‐PZNN) ceramics were textured using 10.0 vol. % BaTiO₃ (BT) platelets along the <001> direction at 950°C with a high Lotgering factor of 95.3%. BT platelets did not react with the PZT‐PZNN ceramics, and the textured PZT‐PZNN ceramic had a tetragonal structure. The PZT‐PZNN ceramics exhibited a strain of 0.174% with a piezoelectric strain constant (d*₃₃) of 580 pC/N at 3.0 kV/mm. The textured PZT‐PZNN ceramic showed an increased strain of 0.276% and d*₃₃ of 920 pC/N at 3.0 kV/mm, which can be explained by the domain rotation. However, the d₃₃ values of the textured specimens are smaller than those of the untextured specimens because of the small remanent polarization and relative dielectric constant of BT platelets. The textured PZT‐PZNN ceramic synthesized in this work can be used for piezoelectric multilayer actuators because of its large strain and low sintering temperature.     

Enhanced piezoelectric properties of Mn-modified Bi5Ti3FeO15 for high-temperature applications

Bi₅Ti₃FeO₁₅ (BTF) has recently attracted considerable interest as a typical multiferroic oxide, wherein ferroelectric and magnetic orders coexist. The ferroelectric order of BTF implies its piezoelectricity, because a ferroelectric must be a piezoelectric. However, no extensive studies have been carried out on the piezoelectric properties of BTF. Considering its high ferroelectric-paraelectric phase transition temperature (T_c ~ 761°C), it is necessary to analyze the piezoelectricity and thermal stabilities of BTF, a promising high-temperature piezoelectric material. In this study, lightly manganese-modified BTF polycrystalline oxides are fabricated by substituting manganese ions into Fe³⁺ sites via the conventional solid-state reaction method. X-ray diffraction and Raman spectroscopy analyses reveal that the resultant manganese-modified BTF has an Aurivillius-type structure with m = 4, and that the substitutions of Fe by Mn lead to a distortion of BO₆. The temperature-dependent dielectric properties and direct-current (DC) resistivity measurements indicate that the Mn ions can significantly reduce the dielectric loss tanδ and increase the DC resistivity. The piezoelectricity of BTF is confirmed by piezoelectric constant d₃₃ measurements; it exhibits a piezoelectric constant d₃₃ of 7 pC/N. Remarkably, BTF with 4 mol% of Mn (BTF-4Mn) exhibits a large d₃₃ of 23 pC/N, three times that of unmodified BTF, whereas the Curie temperature T_c is almost unchanged, ~765°C. The increased piezoelectric performance can be attributed to the crystal lattice distortion, decreased dielectric loss tanδ, and increased DC resistivity. Additionally, BTF-4Mn exhibits good thermal stabilities of the electromechanical coupling characteristics, which demonstrates that manganese-modified BTF oxides are promising materials for the use in high-temperature piezoelectric sensors.     

Synchronous improvement of piezoelectric property and temperature stability in PSN-PMN-PT ceramics by forming composites with ZnO

Relaxor ferroelectric materials with high piezoelectric properties always suffer from low phase transition temperature, making them difficult to satisfy the demands for high-temperature environment applications. In this work, we proposed a composite approach to improve the piezoelectricity and temperature stability of PSN-PMN-PT ceramics at the same time. The ZnO nanoparticles as a second phase were introduced into the PSN-PMN-PT matrix to form composite ceramics. When the ZnO content reaches 5 mol%, the piezoelectric constant d₃₃ increases from 529 pC/N for pure PSN-PMN-PT ceramic to 590 pC/N. Meanwhile, the retained d₃₃ after annealing at 200 °C keeps 92% of the value before annealing, indicating the thermal depolarization behavior is suppressed by the composite method. The synchronous improvement of the d₃₃ and thermal depolarization behavior for PSN-PMN-PT/ZnO composite ceramics is related to the local electric field and stress field caused by the addition of ZnO particles. Our results pave a simple and effective way to develop next-generation PT-based relaxor ferroelectric ceramics.     

Electrospinning of poly(γ‐benzyl–α,L‐glutamate) microfibers for piezoelectric polymer applications

One of the latest developments in the field of piezoelectric polymers is the use of poly(γ‐benzyl‐α,L‐glutamate) (PBLG), a poly(amino acid) that can be poled along its α‐helical axis and fabricated into thermally stable piezoelectric microfibers via electrospinning. This study demonstrates a method for improving the piezoelectricity of electrospun PBLG microfibers by controlling the orientation of fibers using a method based on a concentrated electric field. The piezoelectricity is verified via customized quasi‐static and dynamic measurement methods, while the correlation between fiber alignment and the piezoelectric constant, d₃₃, in the longitudinal mode of the electrospun PBLG fibers is investigated. When the level of alignment was varied from 50% to 90%, the piezoelectric constant increased linearly, showing a maximum d₃₃ of 27 pC N^?1 and a maximum force sensitivity of 65 mV N^?1 at peak alignment. A fabricated flexible prototype based on electrospun PBLG fibers provides a new solution for the use of PBLG fibers in wearable energy harvesters or composites based on piezoelectric polymer fibers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46440.     

Lead-free LiNbO3 nanowire-based nanocomposite for piezoelectric power generation

In a flexible nanocomposite-based nanogenerator, in which piezoelectric nanostructures are mixed with polymers, important parameters to increase the output power include using long nanowires with high piezoelectricity and decreasing the dielectric constant of the nanocomposite. Here, we report on piezoelectric power generation from a lead-free LiNbO₃ nanowire-based nanocomposite. Through ion exchange of ultra-long Na₂Nb₂O₆-H₂O nanowires, we synthesized long (approximately 50 μm in length) single-crystalline LiNbO₃ nanowires having a high piezoelectric coefficient (d₃₃ approximately 25 pmV^-1). By blending LiNbO₃ nanowires with poly(dimethylsiloxane) (PDMS) polymer (volume ratio 1:100), we fabricated a flexible nanocomposite nanogenerator having a low dielectric constant (approximately 2.7). The nanogenerator generated stable electric power, even under excessive strain conditions (approximately 10⁵ cycles). The different piezoelectric coefficients of d₃₃ and d₃₁ for LiNbO₃ may have resulted in generated voltage and current for the e₃₃ geometry that were 20 and 100 times larger than those for the e₃₁ geometry, respectively. This study suggests the importance of the blending ratio and strain geometry for higher output-power generation in a piezoelectric nanocomposite-based nanogenerator.

PACS

77.65.-j; 77.84.-s; 73.21.Hb     

Microstructure,dielectric and piezoelectric properties of 0–3 lead free barium zirconate titanate ceramic-Portland fly ash cement composites

Piezoelectric ceramic – Portland cement composites have been developed for sensor application in concrete structures to overcome the acoustic matching problem that may occur for piezoelectric ceramic or polymers with concrete. Pozzolanic materials such as fly ash are commonly used in concrete to enhance durability. The objectives of this research were to investigate the effects of fly ash addition on the physical properties, dielectric properties and piezoelectric properties of 0–3 barium zirconate titanate ceramic– Portland cement composites. The results showed that the dielectric constant of these composites decreased when the fly ash content in the composite increases. However, the piezoelectric coefficient (d₃₃) value of BZT–PC composite with fly ash 10% by volume was found to be similar to that of BZT–PC composites.     

Modified sepiolite/PVDF-HFP composite film with enhanced piezoelectric and dielectric properties

Flexible film with both piezoelectric and dielectric properties is considered to be a potential candidate for the energy conversion and storage devices. In this study, the Li⁺ and H₂O modified sepiolite/poly(vinylidene fluoride-co-hexafluoropropylene) (LiSEP-H₂O/PVDF-HFP) composite films with both good piezoelectric and dielectric properties were prepared by traditional coating process. When the H₂O content was 13 wt %, the LiSEP-H₂O/PVDF-HFP composite exhibited high d₃₃ of 32 and dielectric constant of 48. Moreover, the effects of the Li⁺ and adsorbed H₂O on the d₃₃, F(β), dielectric constant, short-circuit currents were discussed. The adsorbed H₂O enhanced the β-phase by the hydrogen bonds and Li⁺ improved the polarization to realize the composite film with increased piezoelectric and dielectric properties respectively. We expected the common modification to lead other clay minerals realizing the future applications in the adjustment of composites' electric properties. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48412.     

Phase transformation mechanisms and piezoelectric properties of poly(vinylidene fluoride)/montmorillonite composite

Poly(vinylidene fluoride) (PVDF)/montmorillonite (MMT) composite with different MMT contents were prepared by solutions‐casting method. The effects of MMT on crystalline structure, morphology, dielectric property, piezoelectric property and phase transformation mechanism were studied. The results showed that acted as effective nucleation agents, the orientation of MMT were almost parallel to the surface of the film. The beta phase in the PVDF matrix was increased and the alpha phase was decreased. Relative dielectric constant and loss of the composite were increased with the increasing of MMT. The d₃₃ was also increased with MMT, which reached a maximum (5.8pC/N) with 2.0 wt % MMT. The mechanisms of changes in phase transformation and piezoelectric property were proposed based on experiment results. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Enhanced piezoelectric properties in BF-BT based lead-free ferroelectric ceramics for high-temperature devices

Due to the high Curie temperature (T_C), BiFeO₃–BaTiO₃ (BF-BT) ceramics have been broadly investigated in high-temperature piezoelectric devices. The piezoelectric constant is one of the most significant factors in determining the sensitivity and reliability of piezoelectric functional components. However, the poor piezoelectric constant (d₃₃) of BF-BT ceramic has prevented the practical application of the material. In this work, we innovatively introduce the 0.93Bi_0.5Na_0.5TiO₃-0.07BaTiO₃ (0.93NBT-0.07BT) component to 0.7BF-0.3BT ceramic, to build a morphotropic phase boundary (MPB) for enhancing d₃₃. The XRD analysis shows that the (0.7BF-0.3BT)-x(0.93NBT-0.07BT) ceramics are still in the MPB region with R–PC phases coexistence, and exhibits a homogeneous solid solution. Moreover, the introduction of 0.93NBT-0.07BT ceramic suppresses the generation of defects and facilitates grain growth, thus enhancing piezoelectric property. In consequence, an optimum piezoelectricity d₃₃ = 213 pC/N along with T_c～450 °C was obtained in (0.7BF-0.3BT)-0.01(0.93NBT-0.07BT). This research provides a new idea for the application of BF-BT ceramics in high-temperature piezoelectric devices.     

Fabrication and Characterization of the Piezoelectric Ceramic–Polymer Composites

The modified sol–gel method was used to synthesize lead zirconate titanate nanoparticles, and the lead zirconate titanate nanoparticles and polyvinylidene fluoride were used to prepare piezoelectric nano‐ceramic–polymer composites with 0–3 connectivity type. The composites were successfully prepared by cold‐pressing and curing‐molding methods. X‐ray diffraction and scanning electron microscopy were adopted to characterize the microstructure of the obtained lead zirconate titanate nanoparticles and composites. The normal vibration modes of the lead zirconate titanate nanoparticles were investigated by Fourier transform infrared spectroscopy. The dielectric and piezoelectric properties of the composites were analyzed in detail with respect to different volume fractions of the lead zirconate titanate nanoparticles. It demonstrated that the values of d₃₃ and ε increased with the increase in the content of lead zirconate titanate. The results here pointed to potential and simple methods to fabricate the lead zirconate titanate nanoparticles and the piezoelectric ceramic–polymer composites for piezoelectric applications.     

Enhanced structural,dielectric, ferroelectric,and piezoelectric properties of (1−x)Ba0.9Sr0.1TiO3–(x)Ba0.7Ca0.3TiO3 ceramics derived using mechano‐chemical activation technique

The effect of Ba_0.7Ca_0.3TiO₃ (BCT) substitution on the structural, dielectric, ferroelectric, and piezoelectric properties of mechano‐chemically synthesized lead‐free (1?x)Ba_0.9Sr_0.1TiO₃‐(x)Ba_0.7Ca_0.3TiO₃ (x=0.0, 0.10, 0.20, 0.35, and 0.50) ceramics have been investigated. XRD patterns confirms the formation of tetragonal phase with P4mm space group. The results indicate a strong influence of BCT substitution on the structural and electrical properties of Ba_0.9Sr_0.1TiO₃ (BST) ceramic. BST–BCT ceramic for x=0.35 have shown high dielectric constant ε_m~21 800, high remnant polarization P_r~10.16 μC/cm², large piezoelectric charge constant D₃₃~293 pC/N, large piezoelectric voltage constant g₃₃~5.80 mV·m/N, and highest dielectric breakdown strength E_bd~224 kV/cm among the five synthesized samples. The correlation between structural, dielectric, ferroelectric, and piezoelectric properties of the BST ceramic with increasing BCT content have been systematically described on the basis of domain wall motion and grain size effect.     

Electric field-induced piezoelectricity in polymer film

An apparatus is devised for measuring the real and imaginary components of the piezoelectric strain constant d = d′ ? id″ for polymer films with a d.c. bias field. Electric fieldinduced piezoelectricity is observed for films of several types of polymer. The ratio of the piezoelectric constant to the d.c. bias field gives (? + κ)/G where ? is the dielectric constant, κ is the electrostriction constant, and G is the elastic constant. The temperature dependence of the field-induced piezoelectricity gives, therefore, combined information of dielectric and elastic properties of polymers. After heating to about 95°C followed by cooling to room temperature, maintaining a constant d.c. basis on a poly(vinyl chloride) film, piezoelectricity is observed at null d.c. field, which suggests the introduction of a residual polarization in the films.     

Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) composites

Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (ε) of 165 and a low dielectric loss (tan δ) of 0.03 at 10³ Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d₃₃) of PZT/PVDF composites can be up to ca 100 pC N^?1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high‐efficiency capacitors and as novel piezoelectric materials. Copyright © 2010 Society of Chemical Industry     

Dielectric and mechanical optimization properties of porous poly(ethylene‐co‐vinyl acetate) copolymer films for pseudo‐piezoelectric effect

In this article, the authors present a porous copolymer film with pseudo‐piezoelectric effects as a new candidate material for sensing applications. Porous films of poly(ethylene‐co‐vinyl acetate) (EVA) with a thicknesses ranging from 160 to 310 μm are fabricated by a coextrusion chemical foaming process and charged using a high‐voltage contact charging process. Output performances (piezoelectric constant and relative permittivity) with related thermal/mechanical stability are specifically studied as a function of the film porosity and of the electrical charging process. The piezoelectric constant d₃₃ increases with the cell porosity and an interesting piezoelectric constant close to 5.1 pC/N is achieved with a porous EVA film containing 65% of porosity. Actual results are then discussed using a theoretical solid–gas multilayer model to describe and predict the pseudo‐piezoelectric effect of porous polymer materials. The originality of this work lies in the fact that all the steps leading to optimize pseudo piezoelectric films are included, and also in the use of EVA which is not a standard piezoelectric material. Therefore, this work is a contribution in the development of low‐cost piezoelectric materials with potential applications as sensor in different fields such as medical, security, environment, sport, and transport. POLYM. ENG. SCI., 59:1455–1461 2019. © 2019 Society of Plastics Engineers     

Achieving large piezoelectric response and ultrahigh electrostriction in [001] textured BiScO3-PbTiO3 high-temperature piezoelectric ceramics

[001] textured 0.40BiScO₃-0.60PbTiO₃-0.125 mol%Nb⁵⁺ (BS-60PT-0.125Nb) high-temperature piezoelectric ceramics were synthesized using templated grain growth process. A high texture degree F₀₀₁ of 99% was obtained using 2 vol% BaTiO₃ (BT) templates. The piezoelectric charge constant d₃₃ and the unipolar strain under 40 kV cm⁻¹ at room temperature for the textured ceramics are 646 pC N⁻¹ and 0.36%, respectively, which is over two times as those for untextured ceramics (∼243 pC N⁻¹ and 0.17%). The electrostriction Q₃₃ value of the textured sample remarkably increased from 0.034 m⁴ C⁻² to 0.068 m⁴ C⁻² under 30 kV cm⁻¹, showing a twice higher than untextured. Compared with random ceramics, the improvement piezoelectric response of the textured ceramics is primarily attributed to the increase of the dielectric constant ε_r and electrostriction coefficient Q₃₃ along [001] orientation, which is originating from the anisotropy of piezoelectricity. The BS-60PT-0.125Nb textured ceramics have large piezoelectric response and ultrahigh electrostriction with high temperature stability (high depolarization temperature T_d of ∼360°C and high Curie temperature T_c of 421°C), showing great potential for the piezoelectric applications at high temperatures.     

CNT loaded PVDF-KNN nanocomposite films with enhanced piezoelectric properties

The emerging smart PVDF-based composites can compensate for the intrinsic property deficiencies in either of their components. The properties of the composite are determined by the properties of the constituents and its fabrication method. In this research, a lead-free piezoelectric ceramic, potassium sodium niobate (KNN), was used as the primary reinforcement, and MWCNTs were added to improve the electrical properties. Solution casting was used to prepare PVDF-KNN-CNT composite films. After phase and structure identification of composites using SEM, XRD, FTIR, and TGA methods, the dielectric, piezoelectric and ferroelectric properties of the products were investigated. The obtained results indicated a strong dependency of dielectric, piezoelectric, and ferroelectric properties of composites on KNN content. Samples with the highest KNN content rendered ε_r, d₃₃ and g₃₃ values of 156, 28 pC/N, and 20.32 mV m/N, respectively. Introducing a small amount of conductive CNT to primary PVDF-KNN composites can drastically affect the electrical properties by severely interfering in the charge distribution within the sample. While the dielectric constant was enhanced by increasing CNT content, both piezoelectric and ferroelectric properties showed their best behavior at a critical CNT loading. Beyond this limit, a percolation path formed, which is responsible for power consumption. At the optimum CNT amount, d₃₃ and g₃₃ reached 50 pC/N and 31.93 mV m/N, respectively. The presence of conducting CNTs gave rise to the formation of more round polarization curves with higher remnant polarization. The present findings give a prospective understanding of smart piezoelectric polymer-based composites that can be used as sensors and energy harvesters.     

Piezoelectric properties and microstructure of ceramicrete-based piezoelectric composites

Inorganic piezoelectric ceramic composite is the potential sensing element for long-term structural health monitoring due to its excellent durability and compatibility. In this study, a Ceramicrete-based piezoelectric composite is proposed preliminarily, in which the magnesium potassium phosphate cement is used as the matrix and the lead zirconate titanate particle is utilized as the functional phase. Piezoelectric properties test and microstructure analysis are performed to evaluate the testing samples. Results show that the piezoelectric performance of the composite increase with the increase of piezoelectric ceramic particle size. The value of the piezoelectric strain factor (d₃₃) can reach 83.8 pC/N, while the corresponding piezoelectric voltage factor (g₃₃) is 50.1 × 10^-3 V•m/N at the 50th day after polarization. Microstructure analysis illustrates that the interfacial transition zone (ITZ) between the matrix and the particles is dense. Moreover, the influence of aging on the composite is attributed to the continuous hydration after polarization. It indicates that the composites have a higher piezoelectric performance, which can be regarded as a promising sensing element material.     

Piezoelectric and Dielectric Properties of Acrylonitrile Butadiene Rubber/Lead Magnesio-Niobate Piezoelectric Ceram

A new composite with special piezoelectric property was prepared by using lead magnesio-niobate piezoelectric ceram powders (PMN) as dispersing phase in acrylonitrile butadiene rubber (NBR) matrix. The dielectric and piezoelectric properties of the composite were studied. The result shows that the particle size of 80% of PMN ceram powders was 0.5–2 µm. The piezoelectric constant (d₃₃) of the composite increased with increasing volume fraction of PMN, and the max piezoelectric constant is 33 when the PMN volume fraction is 85%. Appropriate delay of polarizing time with increasing polarizing voltage could be helpful to improve the d₃₃ value. The optional polarizing condition is 25 min, 7–8 kv/mm, and 80°C. The dielectric constant increased with the increasing of the PMN volume fraction. Polarized time, polarized voltage, and polarized temperature have no effect on the dielectric constant.