PZT Volume Fraction Research Articles

Properties of novel 0–3 PZT/silicone resin flexible piezoelectric composites for ultrasonic guided wave sensor applications

Ultrasonic guided wave (UGW) technology based on piezoelectric sensors is considered a very promising technology for aircraft structural damage detection. Traditional piezoelectric sensors are made of lead zirconate titanate (PZT) ceramics, but their brittleness and hardness make them difficult to apply to curved structure surfaces. In this study, a novel 0–3 flexible piezoelectric composite was fabricated by dispersing PZT particles in silicone resin, and its performance for potential applications in UGW sensors was studied. The effects of polarization conditions, PZT volume fraction, and PZT powder size on the performance of the composite were investigated. The influence of ambient temperature on composite performance was discussed, and temperature adaptability experiments were conducted. The results show that the optimal poling process of 0–3 PZT/silicone resin piezoelectric composite has a poling time of 25 min, a poling electric field of 4 kV/mm, and a poling temperature of 100°C. When the sensor is required to meet the test strain range of 8,000 με, the composite should be fabricated with a PZT volume fraction of 50% and a powder size of 170∼212 μm to obtain optimal sensing sensitivity. At an ambient temperature range of -55–75°C, the fabricated piezoelectric composite sensor has good flexibility and sensitivity in detecting the guide wave signals. These research results provide a new flexible piezoelectric sensing technology for aircraft structural damage detection.

Flexible Composite Films Made of EMAA-Na+ Ionomer: Evaluation of the Influence of Piezoelectric Particles on the Thermal and Mechanical Properties.

Studies that aim to produce flexible films of composite materials based on ionomers-PZT, and volume fractions lower than 10% PZT, in order to monitor damage in aeronautical structures are seldom investigated. The growing emphasis on the use of polymers capable of self-healing after damage or activation by heating has motivated the application of self-healing ionomers as polymeric matrices in composites with piezoelectric particles aiming to monitor damage. Flexible composite films were developed based on the self-healing polymer matrix Surlyn® 8940 ionomer (DuPontTM—Wilmington, DE, USA) and PZT particles (connectivity 2–3) in volume fractions of 1, 3, 5 and 7%, with thickness around 50–100 µm. The choice of PZT volume fractions followed the preliminary requirement that establishes a final density, which is lower or at least close to the density of the materials used in aeronautical structures. Since the application of composites based on epoxy resin/carbon fibers has been increasing in the aeronautical segment, this material (with density lower than 1500 kg/m3) was chosen as a reference for the present work. Thus, due to self-healing (a characteristic of the matrix Surlyn® 8940) combined with recyclability, high flexibility and low thickness, the flexible composite films showed advantages to be applied on aeronautical structures, which present complex geometries and low-density materials. The manufactured films were characterized by SEM, XRD, DMA and mechanical tensile tests. The results were discussed mainly in terms of the volume fraction of PZT. X-ray diffraction patterns showed coexistent rhombohedral and tetragonal phases in the PZT particles-dispersed composite, which can potentialize the alignment of ferroelectric domains during polarization under strong electrical field, enhancing dielectric and piezoelectric properties toward sensing applications. DMA and tensile testing results demonstrated that the addition of PZT particles did not impair either dynamic or quasi-static mechanical performance of the flexible composite films. It was concluded that the PZT volume fraction should be lower than 3% because, for higher values, the molecular mobility of the polymer would suffer significant reductions. These findings, combined with the high flexibility and low density of the ceramic particle-filled thermoplastic polymer, render the developed flexible composite film a very promising candidate for strain and damage sensing in aeronautical structures.

Influence of PZT volume fraction, composite thickness and cement matrix on the performance of d15 shear mode 1–3 connectivity cement-based piezoelectric composites

In this work, we investigated the influence of PZT volume fraction, composite thickness and cement matrix on the performance of 1–3 connectivity cement-based piezoelectric composites working in d15 shear mode. Results revealed that the piezoelectric strain coefficient d15 and the relative dielectric coefficient εr decrease with the decrease of the PZT volume fraction and increase with the increase of the composite thickness. The piezoelectric strain coefficient d15 of the composite specimens with Phosphoaluminate cement (PALC) matrix is the largest, followed by Sulfoaluminate cement (SAC) matrix and Portland cement (PC) matrix. The relative dielectric coefficient εr of the composite specimens with PC matrix is the largest, followed by PALC matrix and SAC matrix. The piezoelectric voltage factor g15 increases with the decrease of the PZT volume fraction and decreases with the increase of the composite thickness. The piezoelectric voltage factor g15 of the composite specimens with PC matrix is the smallest, and the values of specimens with SAC matrix and PALC matrix are very close.

Fine scale 2-2 connectivity PZT/epoxy piezoelectric fiber composite for high frequency ultrasonic application

High frequency piezoelectric fiber composites have extensive application in fields of biomedical imaging, ultrasonic inspection, underwater acoustic imaging and so forth. In this paper, fine scale 2-2 connectivity PZT/epoxy piezoelectric fiber composites were tailored by using the dicing-filling-pressing method with poled ferroelectric ceramic (PZT) and epoxy resin, respectively. The effects of thickness and volume fraction of PZT ceramic on piezoelectric, dielectric, and acoustic properties of the composites were discussed. The results showed that the piezoelectric strain constant, relative permittivity (ε33T), thickness electromechanical coupling coefficient (kt), mechanical quality factor (Qm) and acoustic impedance of the composites exhibit an increasing trend with the increase of the volume fraction of the PZT ceramics, while the piezoelectric voltage constant (g33) showed a decreasing trend. In the low frequency range of 60−90 kHz, the planar resonance peaks can be observed in the impedance-frequency spectra, while in the high frequency range of 2−6 MHz, there only exist clear thickness resonance peaks. With increasing the PZT volume fraction, the bandwidth of the thickness vibration mode of the piezoelectric fiber composites under the same thickness increases gradually. When the PZT volume fraction keep unchanged, the thickness resonance frequency of the composites increases with decreasing the thickness as well as the bandwidth of the thickness vibration mode, which is conducive for improving the frequency response range of the ultrasonic transducer made of the proposed piezoelectric fiber composites.

PZT volume fraction’s impact on electrical and thermal characterization of the piezoelectric composite PU/PZT

Lead zirconate titanate (PZT) is a well-known ceramic for his mechanical-electrical conversion since he has the larger piezoelectric coefficients. It is also known as a pyroelectric material. Nonetheless, this piezoelectric material is rigid and firm and cannot be used in flexible applications. The polyurethane (PU) which is an electrostrictive polymer known as a low electromechanical converter is the base matrix that can be loaded by the PZT as composite. This mixture was made to combine between the flexibility of PU and the larger piezoelectric coefficient of PZT. These studies involved its dielectric and mechanical characterization, but its thermal characterization is rarely found. This work proposes to elaborate PU with different fraction of PZT, to investigate the electrical and the thermal characterization of this composite, and to figure out the impact of PZT volume fraction on its thermal parameters. The electrical characterization involves the dielectric constant and the electrical conductivity of each sample. While the thermal characterization focuses on measuring the thermal conductivity using both, an indirect and a direct measurement technique. The indirect one uses Flash method to figure out thermal diffusivity and DSC to measure the specific heat capacity. As for the direct method, it consists on placing the sample between two heat sources where the heat flux is imposed and the temperatures are measured.

An experimental model for predicting the piezo and dielectric constant of PVDF-PZT nanocomposite fibers with 0–3 and 1–3 connectivity

Energy harvesting from mechanical energy around ambient by flexible nanogenerators is one of the most efficient ways to generate green and renewable energy. Lead zirconate titanate (PZT) particles were embedded into a polyvinylidene fluoride (PVDF) polymer matrix to prepare mixed 0–3 and 1–3 connectivity nanocomposite fibers by electrospinning method. Various theoretical models of Maxwell-Garnett, Rayleigh, and Tinga etc were presented at two different Classes to predict the dielectric constant of PVDF-PZT nanocomposite fibers and compared the predicted results with the experimental results. Also, the piezoelectric properties like the piezoelectric coefficient (d33) and piezoelectric voltage coefficient (g33) were predicted by the Furukawa model and the predicted values were compared with the experimental values. Finally, the experimental model was derived to predict the dielectric constant of binary composites with mixed 0–3 and 1–3 connectivity. Compared to well-known models, the proposed experimental model accurately predicted the dielectric constant of PVDF-PZT nanocomposite fibers. The highest and lowest difference between the theoretical and the experimental results were obtained 12.24% and 0.12% for PZT volume fractions 1.1 and 17, respectively. Also, due to the linear relationship between the dielectric constant and piezoelectric coefficients, this model was generalized to predict the piezoelectric coefficients.

The influence of processing parameters on piezoelectric and dielectric properties of dome-shaped composite PZT-epoxy actuators

Thick film dome-shaped composite PZT-epoxy structures have been fabricated using a modified sol gel and spin coating technique. Processing parameters and polarization technique (Corona versus contact polarization) have been studied to elucidate their influence on piezoelectric and dielectric properties. The volume fraction of PZT was varied from 0.0 to 0.7 and the highest values for the longitudinal piezoelectric coefficient, effective dielectric constant (@1kHz) and dielectric loss (@1kHz), were 11.1 pC/N, 28.7 and 0.004 respectively for the PZT volume fraction equal to 0.7. The piezoelectric strain coefficient for this dome structure was 7 times higher than previously reported values for a composite PZT-epoxy dome structure of similar structure and composition. The sample morphology was examined with the aid of scanning electron microscopy (SEM) images. The piezoelectric strain coefficients, capacitance, and effective dielectric constant increased with increasing PZT volume fraction, in addition to the surface roughness. Samples that were Corona poled facilitated higher polarization voltages (45 kV/mm and 70 kV/mm) and resulted in higher values of piezoelectric strain coefficients. Investigation of composite structures such as these will advance the development of curved and hemispherical piezoelectric actuators with enhanced displacement and mechanical properties.

A flexible piezoelectric pressure sensor based on PVDF nanocomposite fibers doped with PZT particles for energy harvesting applications

Flexible piezoelectric energy harvesters are a suitable choice for scavenging wasted mechanical energy because of the high demand for sustainable power sources. Flexible pressure sensors based on PVDF-PZT nanocomposite with different PZT volume fractions (0.011, 0.041, 0.096, 0.17, 0.3, and 0.37) were prepared in the form of fibers through an electrospinning method for piezoelectric energy harvesting application. According to the results, dielectric constant and piezoelectric coefficients (e.g. piezoelectric coefficient, and figure of merit) gradually increased with the doping of PZT particles into PVDF fibers. Dielectric constant (ϵ), piezoelectric coefficient (d), and figure of merit (d × g) for PVDF-PZT nanocomposite with 0.011 PZT volume fraction were 37.29, 10.51 pCN−1, and 33.46 × 10−16 m2/N, respectively, and increased to 104.81, 22.93 pCN−1, and 56.68 × 10−16 m2/N for PVDF-PZT nanocomposite fibers with a volume fraction of 0.37. As piezoelectric energy harvesters, piezoelectric sensitivity of PVDF-PZT nanocomposite fibers rose with increasing the PZT volume fraction. The generated output voltage was 184 mV under an applied force of 2.125 N with the piezoelectric sensitivity calculated as 173.507mV/Nμm for PVDF-PZT nanocomposite fibers with 0.37 PZT volume fractions which increased compared to pristine PVDF fibers (generated output voltage = 22 mV under applied force 2.4 N, piezoelectric sensitivity = 29.49 mV/Nμm). The achieved output power density of PVDF-PZT nanocomposite fibers with 0.37 PZT volume fractions was obtained 30.69μW cm−2 higher than PVDF-PZT nanocomposite fibers with 0.011 PZT volume fractions (18.44μW cm−2).

Piezoelectric and Dielectric Characterization of MWCNT-Based Nanocomposite Flexible Films

PZT-epoxy-multiwalled carbon nanotube (MWCNT) flexible thick film actuators were fabricated using a sol-gel and spin coat and deposition process. Films were characterized in terms of their piezoelectric and dielectric properties as a function of MWCNT volume fraction and polarization process. Correlations between surface treatment of the MWCNTs and composite performance were made. The surface morphology and filler distribution were observed with the aid of SEM and TEM images. The volume fraction of PZT was held constant at 30%, and the volume fraction of MWCNTs varied from 1% to 10%. Two forms of dielectric polarization were compared. Corona discharge polarization induced enhanced piezoelectric and dielectric properties by a factor of 10 in comparison to the parallel-plate contact method (piezoelectric strain coefficient and dielectric constant were 0.59 pC/N and 61.81, respectively, for the parallel-plate contact method and 9.22 pC/N and 103.59 for the corona polarization method, respectively). The percolation threshold range was observed to occur at a MWCNT volume fraction range between 5% and 6%.

Synthesis, Structural, Optical and Dielectric Properties of Nanostructured 0-3 PZT/PVDF Composite Films.

Nanostructured PbZr0.52Ti0.48O3 (PZT) powder was synthesized at 500 °C-800 °C using sol-gel route. X-ray diffraction and Rietveld analysis confirmed the formation of perovskite structure. The sample heat treated at 800 °C alone showed the formation of morphotropic phase boundary with coexistence of tetragonal and rhombohedral phase. The PZT powder and PVDF were used in 0-3 connectivity to form the PZT/PVDF composite film using solvent casting method. The composite films containing 10%, 50%, 70% and 80% volume fraction of PZT in PVDF were fabricated. The XRD spectra validated that the PZT structure remains unaltered in the composites and was not affected by the presence of PVDF. The scanning electron microscopy images show good degree of dispersion of PZT in PVDF matrix and the formation of pores at higher PZT loading. The quantitative analysis of elements and their composition were confirmed from energy dispersive X-ray analysis. The optical band gap of the PVDF film is 3.3 eV and the band gap decreased with increase in volume fraction of PZT fillers. The FTIR spectra showed the bands corresponding to different phases of PVDF (α, β, γ) and perovskite phase of PZT. The thermogravimetric analysis showed that PZT/PVDF composite films showed better thermal stability than the pure PVDF film and hydrophobicity. The dielectric constant was measured at frequency ranging from 1 Hz to 6 MHz and for temperature ranging from room temperature to 150 °C. The composite with 50% PZT filler loading shows the maximum dielectric constant at the studied frequency and temperature range with flexibility.

Effect of structural parameters and stability of constituent materials on the performance of 1–3 spherical crown piezocomposite and transducer

Transducer is the main instrument for signal transmitting and receiving. As the core component of the transducer, the preparation and performance of piezocomposite directly affect the efficiency of the transducer. The novel 1–3 spherical crown piezocomposites with resonance frequency higher than 320 kHz was prepared via arrangement-casting technique. And the effect of structure parameters on properties of piezocomposite was studied in this paper. The results showed that PZT aspect ratio had a significant effect on the resonance frequency of the piezocomposite. Resonance frequency varied from 322 kHz to 457 kHz as the PZT aspect ratio increased from 0.57 to 0.74. While resonance frequency slightly increased from 347 kHz to 368 kHz as the PZT volume fraction varied from 27.0% to 70.6%. Resonance frequency of piezocomposites were merely dependent on the temperature varying from −20 °C to 60 °C, revealing a great thermal stability. The -3 dB opening angle of the transducer was respectively 42° and 39° in horizontal and vertical directions. And the increasing PZT volume fraction was beneficial for enhancing the peak value of transmitting voltage response from 157 dB to 164 dB with -3 dB bandwidth of 42 kHz.

Effects of conductive carbon black on PZT/PVDF composites

ABSTRACTIn this paper, the hot-pressing method is selected to prepare piezoelectric vibrator. The effects of different volume ratio of PZT on the dielectric, piezoelectric and mechanical properties of the composites are studied. With the increase of PZT volume fraction in a certain range, the density of the composites, the dielectric constant (ɛ), the dielectric loss (tanδ) and the piezoelectric strain constant (d33) are all increased, while the piezoelectric voltage constant (g33) tends to change smoothly, however, the deformation and compressive yield strength are decreased. The mechanical and piezoelectric properties of the composites are improved after the addition of conductive carbon black particles. The results show that the conductive carbon black can make the structure more compacted and improve the conductivity (σ) of PZT/PVDF composites.

Theoretical modeling and experimental characterization of rate and temperature dependent electromechanical behavior of piezocomposites

Abstract The rate-dependent piezoelectric behavior of 1–3 piezocomposite under thermal environment is presented. Thermo-electromechanical effective properties of 1–3 piezocomposites are evaluated based on the Finite Element (FE) resonant model. The experimentally measured vibration modes for Length Extensional (LE) and Thickness Extensional (TE) resonator model are compared with the simulated results for model validation. A 3D finite element model to predict the non-linear rate-dependent behavior of 1–3 piezocomposite under elevated temperature is proposed. In the present work, the internal variables are considered to be the function of loading rate, to simulate the rate-dependent behavior. The predicted thermo-electromechanical effective properties from the resonant model are used as an input to the proposed non-linear model. The simulation is carried out for various combinations of PZT volume fractions, loading rates, temperatures and compressive prestresses under cyclic electrical loading and validated with the experimental measurements.

Super-Cell Piezoelectric Composite With 1-3 Connectivity.

The standard fabrication method for 1-3 piezocomposites for ultrasound transducers is the "dice and fill" method (DFM) in which lateral periodicity is introduced. This contributes to the appearance of spurious modes that can drastically affect the performance of the device if they appear near its thickness mode frequency, thus limiting the effective frequency range. A new 1-3 piezocomposite fabricated with a super-cell structure [1-3 super cell (13SC)] was designed in order to overcome these limitations. It consists of the merging of several periodic cells with 47% PZT volume fraction and epoxy resin as the matrix. Two lateral periodicities in one direction are defined as well as two different kerfs. The chosen cell shape is composed of five nonaligned square section rods ( 1 ×1 mm 2 ). For comparison of performance, two regular 1-3 piezocomposites (the same materials and equivalent periodicities) were fabricated by DFM. Electroacoustic responses in water were measured for the three composites being considered as transducers. Successive regular thinnings (from 2.8 to 1.1 mm) were carried out for each sample to increase the operating frequency (from around 0.4 to 1.3 MHz) and study the evolution of the characteristics (bandwidth and sensitivity). The experimental results confirmed the behavior of those obtained with numerical simulations, showing that the 13SC composite can be used in this entire frequency range, unlike regular composites.

Piezoelectric and dielectric characterization of corona and contact poled PZT-epoxy-MWCNT bulk composites

Three-phase lead zirconate titanate (PZT, PbZr0.52Ti0.48O3)-epoxy-multi-walled carbon nanotube (MWCNT) bulk composites were prepared, where the volume fraction of PZT was held constant at 30%, while the volume fraction of the MWCNTs was varied from 1.0%–10%. The samples were poled using either a parallel plate contact or contactless (corona) poling technique. The piezoelectric strain coefficient (d33), dielectric constant (ε), and dielectric loss tangent (tan δ) of the samples were measured at 110 Hz, and compared as a function of poling technique and volume fraction of MWCNTs. The highest values for dielectric constant and piezoelectric strain coefficients were 465.82 and 18.87 pC/N for MWCNT volume fractions of 10% and 6%, respectively. These values were obtained for samples that were poled using the corona contactless method. The impedance and dielectric spectra of the composites were recorded over a frequency range of 100 Hz–20 MHz. The impedance values observed for parallel-plate contact poled samples are higher than that of corona poled composites. The fractured surface morphology and distribution of the PZT particles and MWCNTs were observed with the aid of electron dispersion spectroscopy and a scanning electron microscope. The surface morphology of the MWCNTs was observed with the aid of a field emission transmission electron microscope.

Reduced leakage current and improved multiferroic properties of 0.5((1−x)BLPFO-xPZT)-0.5PVDF composite films

0.5((1−x)Bi0.8La0.1Pr0.2FeO3 (BLPFO)-xPb(Zr0.52Ti0.48)O3 (PZT))-0.5Polyvinylidene difluoride (PVDF) composite films with x variations 0.25, 0.40 and 0.50 were synthesized using two step mixing, followed by hot pressing. The structural, microstructural, dielectric, magnetic, ferroelectric and magnetodielectric properties of composite films have been systematically investigated. The measurement of the dielectric properties at 1kHz shows that the dielectric loss (tanδ) decreases with increasing the volume fraction of PZT. The value of maximum room temperature εr ~78 and low tanδ ~0.061 for 0.5((1−x)BLPFO-xPZT)-0.5PVDF composite film with x=0.50 suggests its usefulness for capacitor applications. For predictions of effective dielectric constant of composite films experimental data were fitted with Lichtenecker model. Among all the composite films, the film with x=0.50 was found to exhibit smallest leakage current density ~7×10−8A/cm2 and hence improved electrical resistivity. The variation of magnetization with temperature indicates the presence of spin glass behavior along with the ferromagnetic component at 5K. The value of remnant polarization (2Pr) is found to increase with increase of PZT content in composite films. In the present composite films a significant dependence of dielectric constant on magnetic field has been observed, and highest value of magnetodielectric response of 2.85% is observed for composite film with x=0.50.

PU/PZT composites for vibratory energy harvesting

Piezoelectric composites of PU/PZT with 0–3 connectivity were prepared in the film form. Homogeneous dispersion of the ceramic PZT in polyurethane matrix has been obtained and has been verified by SEM analysis. Dielectric properties reveal that under an electrical field of 1000 V the remnant polarization increased from 1.9 to 4 µC/cm−2 when the volume fraction of PZT increased from 50 to 80 %. Modeling and vibratory energy harvesting tests has been realized. At very low frequency and deformation, and without application of any static electric field, 1.15 µW of power has been obtained. The results obtained in this work contribute to demonstrate the ability of the incorporation of PZT particles in the polymer matrix to improve the conversion efficiency of the vibratory energy into electrical energy for the development of µ-generators.

Piezo, ferro and dielectric properties of ceramic-polymer composites of 0-3 connectivity

ABSTRACTFerroelectric PZT-PVDF composites (0–3 connectivity) of specific dimensions were made utilizing a hot press technique. Linear variation in the experimental density of the pellets made from 0.1 to 0.8 PZT volume fraction was observed. The surface morphology of the composite has been micro-graphed using SEM. The variation of the dielectric properties of the composites on PZT volume fractions is reported and analyzed. It is observed that there was an increment in dielectric constant (ϵr) with an increase in temperature and volume fractions. The piezoelectric strain coefficient (d33) increases with an increase in the volume fraction and voltage coefficient (g33) were calculated. Comparisons were made with the Furukawa model to ϵr and d33. The remnant polarization and coercive field were analyzed from the hysteresis plots.

Synthesis and magnetoelectric effect of composites with CoFe2O4-epoxy embedded in 3–1 type porous PZT ceramics

Three-phase magnetoelectric (ME) composites of lead zirconate titanate (PZT)/cobalt ferrite CoFe2O4 (CFO)/epoxy were synthesized in sequence by a tert-butyl alcohol (TBA)-based freeze-casting technique, a chemical solution deposition method, and an impregnation process. The novel pseudo 3–0–1 type composite structure with a high content of CFO was examined using SEM and XRD. The composites showed not only stable and excellent dielectric behavior in a wide frequency range, but also good ferroelectricity and ferromagneticity at the same time, as can be seen from the typical electrical and magnetic hysteresis loops. The ME effect of the resultant 3–0–1 type ferroelectric/ferromagnet/polymer composites was found to be significantly dependent on the content of PZT and CFO. The maximum ME coefficient of 2.2mV/cmOe was observed when the PZT volume fraction is 0.5 and CFO mass fraction is 0.2. This synthesis route we proposed provides a new connectivity type of ME composite and shows potential applications in sensors and transducers.

An Active Functionally Graded Piezocomposite Plate Subjected to a Stochastic Pressure

Abstract In the paper the analysis of random vibration of an actively damped laminated plate with functionally graded piezoelectric actuator layers is presented. The simply supported plate is subjected to stochastic loading represented by a uniformly distributed pressure. The random input is assumed as a Gaussian sta- tionary and ergodic process. The actuators are regarded as a multi-layer structure arranged of piezofiber composite sub-layers. The sub-layers differ each other with amount of PZT (lead-zirconate-titanate) fibers and are stacked to achieve a desired change of the PZT volume fraction through the actuator thickness. The gradation scheme of constituents and material properties are estimated by parabolic and power functions. Numerical simulations are performed to recognize the influence of the applied random excita- tions and the actuator properties gradations on the characteristics of the stochastic field of active plate deflection i.e. power spectral density, autocorrelation function and variance