Piezoelectric Composite Films Research Articles

Fabrication of flexible piezoelectric PMN-PT based composite films for energy harvesting

Flexible piezoelectric composite films of lead magnesium niobate and lead titanate (PMN-PT) ceramic and multiwalled carbon nanotube (MW-CNT) in the matrix of polyvinyldene fluoride (PVDF) were fabricated for green energy harvesting and self-powered sensing. Compositions of PMN-PT was varied from 10-50 volume (vol. %) in PVDF matrix while a constant concentration of MW-CNT was maintained (1vol. %). Phase purity of the synthesized composites was confirm by X-ray diffraction (XRD) analysis. PMN-PT powder was found to be in single phase without the presence of any additional peak, which generally arises due to crystallization of another pyrochlore phase. Surface morphology study by scanning electron microscopy (SEM) revealed a well dispersed PMN-PT/CNT in PVDF matrix. The maximum measured output voltage and current during mechanical pressing and releasing conditions were found to be ∼ 3 volt and 30 nA, respectively in 30 vol. % PMN-PT composite.

Enhanced dielectric and piezoelectric properties of 0–3 PZT/PVDF composites

Flexible piezoelectric composite films of ([PZT/]x/[PVDF]1-x (x = 0, 0.1, 0.2, 0.3) with 0–3 connectivity were synthesized from 0.2 wt% Li2CO3 added PZT ceramic powders in the morphotropic phase boundary (MPB) and PVDF polymer by solution cast technique under optimized thermal processing conditions. It is seen that crystallinity and β phase are enhanced with the addition of Li in the composite films and as well as with the volume content of PZT ceramics in PVDF matrix, thereby resulting in superior dielectric and piezoelectric properties. It is also seen that reasonably high dielectric and piezoelectric properties are obtained for 30 % of the volume content of PZT ceramics as compared to 50 % of the volume content of ceramic in the polymer matrix as reported in literature and hence, the flexibility is better in these films.

Piezoelectric Sol-Gel Composite Film Fabrication by Stencil Printing.

Piezoelectric films using sol-gel composites could be useful as ultrasonic transducers in various industrial fields. For sol-gel composite film fabrication, the spray coating technique has been used often because of its adaptability for various substrates. However, the spray technique requires multiple spray coating processes and heating processes and this is an issue of concern, especially for on-site fabrication in controlled areas. Stencil printing has been developed to solve this issue because this method can be used to fabricate thick sol-gel composite films with one coating process. In this study, PbTiO3 (PT)/Pb(Zr,Ti)O3 (PZT) films, PZT/PZT films, and Bi4Ti3O12 (BiT)/PZT films were fabricated by stencil printing, and PT/ PZT films were also fabricated using the spray technique. After fabrication, a thermal cycle test was performed for the samples to compare their ultrasonic performance. The sensitivity and signal-to-noise-ratio (SNR) of the ultrasonic response of PT/PZT fabricated by stencil printing were equivalent to those of PT/PZT fabricated by the spray technique, and better than those of other samples between room temperature and 300°C. Therefore, PT/PZT films fabricated by stencil printing could be a good candidate for nondestructive testing (NDT) ultrasonic transducers from room temperature to 300°C.

Structural, dielectric and piezoelectric properties of 0–3 PZT/PVDF composites

Piezoelectric composite films of ([PZT]x/[PVDF]1−x) with 0–3 connectivity were prepared using a solution cast technique. The films with different volume fractions of PZT ceramics in the morphotropic phase boundary were prepared in the form of thin films for the optimized thermal processing conditions. It is seen that the increase in the content of PZT ceramic in the PVDF matrix not only increases the dielectric constant of the composites but also enhances the β phase in the PVDF polymer, thereby resulting in the overall improved dielectric and piezoelectric behavior of the system. The as-synthesized films exhibited superior dielectric and piezoelectric properties than reported in the literature.

Mechanical properties and connectivity evaluation of a conductive coated piezoceramic/polymer composite

In the present work, piezoelectric composite films made of Polyaniline (PAni) coated Lead Zirconate Titanate (PZT) particles immersed into polyvinylidene fluoride (PVDF) matrix were characterized by mechanical tests, and the connectivity of the composite sample was determined using dielectric measurements and applying the Poon–Shin model. The composite was considered a binary system with coated PZT particles as one phase and the polymer matrix the other one. To support the result obtained from theoretical analysis, scanning electron microscopy of the composites were done. It was observed a decrease up to 85% on the mechanical resistance when the ceramic volume fraction increases from 0% to 40%. Furthermore, the composite film no longer can be considered with 0–3 connectivity when the ceramic content is 30 vol.% or over.

Superior piezoelectric composite films: taking advantage of carbon nanomaterials

Piezoelectric composites comprising an active phase of ferroelectric ceramic and a polymer matrix have recently found numerous sensory applications. However, it remains a major challenge to further improve their electromechanical response for advanced applications such as precision control and monitoring systems. We here investigated the incorporation of graphene platelets (GnPs) and multi-walled carbon nanotubes (MWNTs), each with various weight fractions, into PZT (lead zirconate titanate)/epoxy composites to produce three-phase nanocomposites. The nanocomposite films show markedly improved piezoelectric coefficients and electromechanical responses (50%) besides an enhancement of ∼200% in stiffness. The carbon nanomaterials strengthened the impact of electric field on the PZT particles by appropriately raising the electrical conductivity of the epoxy. GnPs have been proved to be far more promising in improving the poling behavior and dynamic response than MWNTs. The superior dynamic sensitivity of GnP-reinforced composite may be caused by the GnPs’ high load transfer efficiency arising from their two-dimensional geometry and good compatibility with the matrix. The reduced acoustic impedance mismatch resulting from the improved thermal conductance may also contribute to the higher sensitivity of GnP-reinforced composite. This research pointed out the potential of employing GnPs to develop highly sensitive piezoelectric composites for sensing applications.

Development of Acoustic Emission Sensor Based on the 0-3 PZT/P(VDF-TFE) Piezoelectric Composite

In this paper, we produced the 0-3 PZT/P(VDF-TFE) piezoelectric composite film with 80μm thickness using PZT piezoelectric ceramics and fluorine resin P(VDF-TFE) by weight 85/15 ingredients through the hot rolling machine and corona-discharge method. A sensor with 4cm×1.3cm area is designed and produced by using this film. We have carried out the breaking of a pencil lead pressed against an aluminum plate acoustic emission testing. The result shown that the sensor is with fast response and high sensitivity advantage, the sensor can be used as acoustic emission sensor. Meanwhile the sensor is very easy to use due to it is a soft film sensor.

Development of Stretchable PZT/PDMS Nanocomposite Film with CNT Electrode

The piezoelectric composite film of ferroelectric PZT ceramic (PbZrxTi1-xO3) and polymer (PDMS, Polydimethylsiloxane) was prepared to improve the flexibility of piezoelectric material. The bar coating method was applied to fabricate flexible nanocomposite film with large surface area by low cost process. In the case of using metal electrode on the composite film, although there is no problem by bending process, the electrode is usually broken away from the film by stretching process. However, the well-attached, flexible CNT electrode on PZT/PDMS film improved flexibility, especially stretchability. PZT particles was usually settled down into polymer matrix due to gravity of the weighty particle, so to improve the dispersion of PZT powder in polymer matrix, small amount of additives (CNT powder, Carbon nanotube powder) was physically mixed with the matrix. By stretching the film, an output voltage of PZT(70 wt%)/PDMS with CNT (0.5 wt%) was measured.

스프레이 코팅법으로 제조된 CNT/PVDF 압전 복합막의 자기분극 메커니즘

Carbon nanotubes (CNT) / polyvinylidene fluoride (PVDF) piezoelectric composite films for nanogenerator devices were fabricated by spray coating method. When the CNT/PVDF mixture solution passes through the spray nozzle with small diameter by the compressed nitrogen gas, electric charges are generated in the liquid by a triboelectric effect. Then randomly distributed <TEX>${\beta}$</TEX> phase PVDF film could be re-oriented by the electric field resulting from the accumulated electrical charges, and might be resulted in extremely one-directionally aligned <TEX>${\beta}$</TEX> phase PVDF film without additional electric field for poling. X-ray diffraction patterns were used to investigate crystal structure of the CNT/PVDF composite films. It was confirmed that they revealed extremely large portion of the <TEX>${\beta}$</TEX> phase PVDF crystalline in the film. Therefore we could obtain the poled CNT/PVDF piezoelectric composite films by the spray coating method without additional poling process.

Cu-particle-dispersed (K0.5Na0.5)NbO3 composite thin films derived from sol–gel processing

Sol–gel processing of Cu-particle-dispersed (K0.5Na0.5)NbO3 (Cu/KNN) thin films was studied in an attempt to develop a method producing piezoelectric composite films with good mechanical performance. The Cu/KNN films were prepared via crystallization annealing at 650–750 °C for 1 min in air, followed by reduction annealing at 400–500 °C for 1–2 h in a 5% H2 and 95% Ar gas mixture. The resultant composite films consisted of perovskite KNN, metallic Cu, and Cu4O3. This suggests that the decomposition of Cu sources takes two different ways in this study. The Cu/KNN composite films containing Cu4O3 phases were produced by the crystallization annealing at 700 °C for 1 min followed by the reduction annealing at 500 °C for 1 h. Surface morphology observations reveal that these films have dense KNN matrix with a grain size of ~200 nm and uniformly dispersed Cu or Cu4O3 particles with a size of <500 nm.

Flexible ultrasonic transducer arrays for health monitoring of an aircraft component

The damage detection capability of a flexible ultrasonic transducer (FUT) array bonded onto a planar and a curved surface are presented. The piezoelectric lead zirconate titanate composite (PZT-c) film FUT arrays are fabricated on a 75 μm titanium membrane substrate using a sol-gel spray technique. The test article was a complex aluminium component that is representative of aircraft structural complexity. Room temperature curable adhesive is used as the bonding material and ultrasonic couplant between the FUT and the test article. The glue has been successfully tested in the temperature range of -80°C to 100°C, which covers the sensor operating temperatures commonly required for aircraft structures. For a planar surface, the selected FUT arrays were able to detect the fasteners and the 2.54 mm-long electrical discharge machining (EDM) notch up to a distance of 176 mm with sufficient signal-to-noise ratio. The pulse-echo measurements obtained by the FUT array were compared with those of a commercial 10 MHz ultrasonic transducer (UT). The results showed that the performance of the FUT array was as good as the commercial UT. Another FUT array was bonded onto a curved surface of the test article using the same adhesive. No measurement using commercial UTs was taken on the curved surface because restricted access around this area did not allow such measurement. The pulse-echo measurements confirmed the detection of EDM notches of 2.54 mm and 1.27 mm in length. The experimental results demonstrated the potential of FUT arrays for aircraft structural health monitoring.

Engine Oil Condition Monitoring Using High Temperature Integrated Ultrasonic Transducers

The present work contains two parts. In the first part, high temperature integrated ultrasonic transducers (IUTs) made of thick piezoelectric composite films, were coated directly onto lubricant oil supply and sump lines of a modified CF700 turbojet engine. These piezoelectric films were fabricated using a sol-gel spray technology. By operating these IUTs in transmission mode, the amplitude and velocity of transmitted ultrasonic waves across the flow channel of the lubricant oil in supply and sump lines were measured during engine operation. Results have shown that the amplitude of the ultrasonic waves is sensitive to the presence of air bubbles in the oil and that the ultrasound velocity is linearly dependent on oil temperature. In the second part of the work, the sensitivity of ultrasound to engine lubricant oil degradation was investigated by using an ultrasonically equipped and thermally-controlled laboratory test cell and lubricant oils of different grades. The results have shown that at a given temperature, ultrasound velocity decreases with a decrease in oil viscosity. Based on the results obtained in both parts of the study, ultrasound velocity measurement is proposed for monitoring oil degradation and transient oil temperature variation, whereas ultrasound amplitude measurement is proposed for monitoring air bubble content.

Preparation and characterization of PZT thick film enhanced by ZnO nanowhiskers for MEMS piezoelectric generators

A hybrid sol-gel route which was used to fabricate PZT thick film for MEMS piezoelectric generators was investigated. (100)-oriented Pb(Zr0.52Ti0.48)O3 thick films enhanced by ZnO nanowhiskers (ZnOw) were successfully prepared on Pt/Cr/SiO2/Si substrates via spin-coating ZnOw suspension and PZT sol. The influences of film thickness on the microstructure and electrical properties of composite thick film were investigated. XRD results show that PZT composite thick films have (100)-oriented perovskite structure. SEM results show that, the surface of as-prepared (100)-oriented PZT piezoelectric composite thick film is smooth, compact and crack-free, and the cross section is clear. The composite thick films exhibit good ferroelectric, dielectric and piezoelectric properties. 2 μm-thick (100)-oriented PZT piezoelectric composite thick film has the remnant polarization intensity and coercive field of 6.7 μC/cm2 and 92.5 kV/cm, the dielectric constant and dielectric dissipation of 1 431 and 0.44, respectively, and piezoelectric constant d33 is calculated to be 151.0 pC/N. The composite thick film is good to meet the use of MEMS piezoelectric generators.

Preparation and characterization of piezoelectric ceramic–polymer composite thick films by aerosol deposition for sensor application

Lead zirconate titanate (PZT)-based piezoelectric ceramic and polyvinylidene fluoride (PVDF) organic composite thick films (∼20 μm in thickness) were deposited on a 4-in. diameter Pt/Ti/SiO 2/Si substrate and a 2-in. diameter Ag–Pd/sapphire substrate by aerosol deposition using a single 4-in. size nozzle for use as a tactile-sensor device. The PVDF content was varied from 3 to 10 vol% and the films deposited on silicon and sapphire were annealed at 700 and 900 °C, respectively. The annealed films showed a relatively high density, even at a 10 vol% of PVDF-piezoelectric ceramic composition, as well as good adhesion to the substrate after annealing. The relative dielectric constant of the composite film decreased sharply with increasing PVDF content, while the piezoelectric d 33 coefficient was conserved at a relatively high value. Therefore, the g 33 coefficient increased and showed the highest value at 3 vol% PVDF. The g 33 values of the as-deposited, 700 °C annealed and 900 °C annealed piezoelectric ceramic-PVDF composite films were 7.77, 16.3 and 41.5 (10 −3 m 2/N), respectively.

Fabrication and measurement of polypeptide‐based piezoelectric composite polymer film.

A new class of polymer composite piezoelectric materials based on piezoactive biopolymer, poly(‐benzyl,L‐glutamate) (PBLG), and a matrix polymer, poly(methylmethacrylate) (PMMA), is presented. The composite polymer offers the possibility of decoupling the electrical and mechanical properties, therefore improving the overall system efficiency. By simultaneously poling and curing (at ambient conditions) PBLG and methylmethacrylate (MMA) mixture solutions, we fabricated a flexible composite film with a significant portion of the PBLG molecules oriented normal to the film surface. This film exhibited moderate piezoelectricity (d33=20 pC/N), and its mechanical characteristics were similar to those of low molecular weight PMMA. Present samples are about 40 μm thick with tensile strength of 13 MPa and Young’s modules of 450 MPa. The frequency response is ± 3 dB from 0.1 to 7 kHz and at 1 kHz is linear with acceleration more than a 10 dB range.

Piezo and dielectric properties of PHB–PZT composite

AbstractFlexible piezoelectric composite films made of poly(3‐hydroxybutyrate) (PHB) in powder form and lead zirconate titanate (PZT) ceramic powder were obtained by mixing both powders and pressing at 180°C. The effect of PZT on PHB crystallization was investigated using differential scanning calorimetry (DSC). The relative dielectric constant and dielectric loss factor were analyzed by dielectric spectroscopy and the α‐relaxation of amorphous phase of PHB was observed. After suitable polarization, the composite film displayed piezoelectric activity indicating the possibility of using that material as a sensor. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Micromachined ultrasonic transducers and arrays based on piezoelectric thick film

This paper reports on the design, fabrication, and characterization of diaphragm-type piezoelectric micromachined ultrasonic transducer (pMUT) and arrays. A combination of piezoelectric composite thick film techniques and silicon micromachining has been proven to be a promising approach for a batch production of pMUTs, especially pMUT transmitter arrays for ultrasound radiation. In this paper, some important issues related to the pMUT element design and micromachining processes are addressed. Thanks to the well-developed processing technology, pMUTs and arrays operating at different resonance frequencies by dimension variation have been successfully fabricated with a high yield for possible mass manufacturing. The characterization of piezoelectric composite thick film will be briefly reported. The performance of the prototype devices has been characterized in terms of vibration modes, dependency of the resonance frequency on bias voltage, nonlinearity, electromechanical coupling efficiency, equivalent circuit, output sound pressure level and directivity of a two-dimensional pMUT array.

Improvement electrical properties of sol–gel derived lead zirconate titanate thick films for ultrasonic transducer application

In this work, a fabrication process of piezoelectric PZT [Pb(Zr0.52Ti0.48)O3] thick films up to 60 μm deposited on silicon and aluminum substrates is reported. Crystalline spherical modified PZT powder about 300 nm in diameter was used as filler. PZT polymeric precursor produced by Chemat Inc. was used as the matrix material. Spinning films were annealed at 700 °C for one hour in the furnace in air. The thickness of the thick films was measured using a scanning electron microscope (SEM). Compared with previous piezoelectric PZT composite films, the modified piezoelectric thick films exhibit better dielectric properties. The dielectric constant is over 780 and dielectric loss is 0.04 at 1 KHz. Using a PiezoCAD model, the high frequency transducer was designed and fabricated. It showed a bandwidth of 75% at 40 MHz.

PREPARATION OF 1-3 CONNECTIVITY COMPOSITE FILMS OF WELL-ALIGNED ZnO WHISKER ARRAYS WITH AN ORGANIC RESIN

Zinc oxide whisker arrays well-aligned along [0001] direction have been grown on the substrates of glass and single crystal silicon by atmospheric metal organic chemical vapor deposition method (MOCVD). The SEM observation indicated that the whiskers were quite uniform in length and diameter. The whisker arrays were very dense, and the gap among the whiskers was less than 1 μm. The array materials were proposed as the component to prepare 1-3 piezoelectric composite film in-situ. Epoxy resin was used as the matrix materials. The key points to prepare the composites are how to make the resin enter the array and control a suitable thickness of the resin films. Several approaches were studied. The results showed that the best was the vertical sucking method. The SEM observations indicated that the thickness was well controlled as almost same as the length of the whiskers, and the resin perfectly entered the array without pore. The 1-3 piezoelectric composite film has great potential applications in micro sensor and actuator arrays.

Flexible ultrasonic transducers

Flexible ultrasonic transducers (UTs) consisting of a metal foil, a piezoelectric ceramic film, and a top electrode have been developed. The flexibility is realized owing to the porosity of piezoelectric film and the thinness of metal foil. In this paper, the stainless steel (SS), lead-zirconate-titanate (PZT)/PZT composite and silver paste were chosen as metal foil, piezoelectric film, and top electrode materials, respectively. The SS foil serves as both substrate and bottom electrode. The PZT/PZT piezoelectric composite film is made by the sol-gel spray technique. PZT/PZT films of thicknesses from 40 to 70 microm were fabricated onto SS foils. The capability of these flexible sensors operated in the pulse-echo mode for nondestructive testing on flat and curved surfaces of different materials at room temperature and 160 degrees C has been demonstrated. Numerical simulations of the effects of the metal foil thickness on the ultrasonic performance of flexible UTs also were carried out, and the results are in reasonable agreement with experimental data. In addition, a PZT/PZT flexible transducer showed a signal strength comparable with that obtained by a commercial room temperature broad bandwidth transducer.