Lead Zirconate Titanate Powders Research Articles

A statistical volume element-based procedure for the prediction of the mechanical and electrical response of an epoxy-PZT self-sensing layer for application in composite laminates

Structural Health Monitoring (SHM) techniques are being developed to continuously oversee defects in composite structures. Within this context, research is focusing on the development of new types of sensors with high sensitivity and proper integration in the laminate.In this work, the mechanical and electrical properties of a recently developed piezoelectric composite material made of a Lead Zirconate Titanate (PZT) powder embedded in an epoxy matrix are evaluated with finite element simulations of plane strain Statistical Volume Elements (SVEs). The homogenized properties are then implemented in a second finite element model of a composite specimen with the embedded self-sensing material and loaded in compression. The electrical sensitivity is evaluated as a function of the distance between the signal electrodes.The results show that the finite element models with the homogenized properties have decreasing sensitivity with increasing electrodes distance, in agreement with the experimental results from another work, in which Glass Fiber Reinforced Polymer (GFRP) laminates with the embedded piezoelectric composite are loaded in compression and tested for output signal.

Efficient energy harvesting enabled by large-area piezoelectric PVDF-based composite film enhanced by carbon nanotubes

Considerable attention has been drawn to the use of flexible piezoelectric energy harvesting devices for powering smart wearable technology. Herein, we employed a melt extrusion casting process to prepare large-area PVDF-based piezoelectric composite films and achieved continuous production. The films were prepared by adding 15 wt% lead zirconate titanate powder modified with a titanium coupling agent (PZT@UP15) and different content of carbon nanotubes (CNTs) exhibiting high conductivity into the PVDF matrix. The addition of CNTs in moderate amounts significantly enhanced the mechanical, dielectric, and piezoelectric properties of the composite films. Remarkably, the composite film containing 0.06 wt% CNTs achieved a d33 value of 28 pC/N, generated an open circuit voltage of 16.85 V, and a maximum power density of 0.46 μW/cm2 in the bending-releasing mode. Furthermore, the film exhibited relatively stable output performance even after 1500 cycles. The enhanced performances of the piezoelectric composite films can be attributed to the factors that the CNTs can effectively promote PVDF polarization by inducing dipole alignment and building an internal electric field, and further improve the piezoelectric performance and the electrostrictive performance. This work shows that the prepared piezoelectric composite film holds great potential as an energy harvesting device to provide power for wearable electronic devices.

Additive Manufacturing of Piezoelectric Niobium-Doped Lead Zirconate Titanate (PZT-N) by Binder Jetting

Binder jetting is an emerging indirect additive manufacturing technique for ceramic materials, which could be employed to produce application-oriented designed components impossible to achieve with traditional processes and featuring enhanced performances. In our study, niobium-doped lead zirconate titanate (PZT-N) powder, usually processed through the standard press-and-sinter route, was employed as the raw material. First, the powder was characterized in terms of granulometry and flowability to assess its suitability for the printing process. Then, shaping by binder jetting was studied, and the effect of three levels of binder saturation (75–90–105%) on the green bodies was assessed. Finally, the microstructure of the sintered samples was studied using SEM, to investigate the effect of thermal treatments on the grain size distribution and residual porosity (~40%). The piezoelectric properties were measured and compared to those of conventionally processed material. The piezoelectric charge and voltage constants (d33 and g33) were evaluated to determine the possible use of printed parts as porous piezoelectric components to be exploited in hydrophones in the direct mode.

On the design of a piezoelectric self-sensing smart composite laminate

The structural health monitoring of composite laminates is a rapidly emerging need in structural applications. Different real-time sensors integrated into laminates have been proposed, such as fiber Bragg gratings and piezoceramics. However, their presence negatively affects the mechanical properties of the hosting laminate.This work proposes a non-invasive method for piezoelectric functionalization of composite laminates by interleaving lead zirconate titanate micrometric powder between glass-fiber-reinforced polymer plies. The effects of different powder volume fractions on the electromechanical properties were evaluated in terms of the electrical response and laminate inherent strength. The lead zirconate titanate powder laminates demonstrated an electrical sensitivity value that was up to 439% higher compared with that of the embedded commercial disk laminate (12.4 V/kN versus 2.3 V/kN). Impact tests revealed that the resistance of the interleaved lead zirconate titanate powder laminates is comparable to that of the pristine laminates, whereas a fragile commercial disk leads to delamination. Furthermore, an analytical model was proposed to predict the piezoelectric voltage coefficient g33 as a function of the electrical properties, volumetric powder fractions, and polarization process. The model matched the experimental g33 coefficients (R2=0.97), demonstrating its capability to predict the electromechanical behavior of piezoelectric composites and define their design guidelines.

Fabrication and Testing of PDMS Micropump Actuated by Piezoelectric Polymer Composite

Appropriate technological solutions to healthcare can cause huge impact on medical processes and practices leading to sustainable future. Prevalence of diabetes and other chronic diseases has been steadily increasing for which self-attention and healthcare procedure is a logical solution. This paper proposes a piezoelectric polymer composite based micropump that is biocompatible and inexpensive. Lead Zirconate Titanate (PZT) powder is dispersed in polyvinyledene difluoride (PVDF) to form a novel PZT/PVDF composite material. The PZT/PVDF composite material is sonicated, cast, and cured to form a film which is used as the actuator. The polydimethylsiloxane (PDMS) based micropump is designed and fabricated using soft lithography technique. Once the master mold is prepared in clean room, other fabrication steps can be accomplished in a normal environment and multiple PDMS replicas can be prepared with ease. The proposed processing and fabrication steps are simple and inexpensive leading to substantial reduction in the device cost. The piezoelectric polymer based valveless micropump thus fabricated is subjected to performance testing. The micropump is found to deliver fluid in small quantities in a controlled manner and sufficient back pressure and flow rate can be achieved at low applied voltage and frequency.

A plantar wearable pressure sensor based on hybrid lead zirconate-titanate/microfibrillated cellulose piezoelectric composite films for human health monitoring.

Flexible and wearable electronic sensors hold great promise for improving the quality of life, especially in the field of healthcare monitoring, owing to their low cost, flexibility, high electromechanical coupling performance, high sensitivity, and biocompatibility. To achieve high piezoelectric performance similar to that of rigid materials while satisfying the flexible requirements for wearable sensors, we propose novel hybrid films based on lead zirconate titanate powder and microfibrillated cellulose (PZT/MFC) for plantar pressure measurements. The flexible films made using the polarization process are tested. It was found that the maximum piezoelectric coefficient was 31 pC N-1 and the maximum tensile force of the flexible films was 26 N. A wide range of bending angles between 15° and 180° proves the flexibility capability of the films. In addition, the charge density shows a proportional relation with the applied mechanical force, and it could sense stress of 1 kPa. Finally, plantar pressure sensors are arranged and packaged with a film array followed by connection with the detection module. Then, the pressure curves of each point on the plantar are obtained. Through analysis of the curve, several parameters of human body motions that are important in the rehabilitation of diabetic patients and the detection of sports injury can be performed, including stride frequency, length and speed. Overall, the proposed PZT/MFC wearable plantar pressure sensor has broad application prospects in the field of sports injury detection and medical rehabilitation training.

Calibration of powder constitutive model using digital image correlation validated for hollow hemisphere of lead zirconate titanate

This paper presents the application of digital image correlation to uniaxial and diametral compression tests to identify the Drucker-Prager/cap shear failure and the elastic parameters of a lead zirconate titanate powder (PZT). The calibrated parameters were validated through finite element simulation of the cold isostatic pressing of a hollow hemisphere used in piezoelectric transducers. The results showed that the dilatancy stresses were 50–65% lower than the fracture stresses, demonstrating that adopting the fracture stress may overestimate material cohesion. The simulation using the calibrated model achieved an excellent agreement with the measured geometry, with a difference of only 1.1% in the dimension and 2.0% in the average density. The results highlight how digital image correlation can obtain more accurate parameters with fewer tests. The proposed methodology can be used to calibrate other powder materials, especially those in which dilatancy plays a key role.

Flexible piezoelectric energy harvesters with graphene oxide nanosheets and PZT-incorporated P(VDF-TrFE) matrix for mechanical energy harvesting

Flexible piezoelectric energy harvesters (PEHs) have attracted extensive interest because of their ability to transform mechanical energy into electric power. Here, PEHs were fabricated using P(VDF-TrFE)-based piezoelectric composite films containing lead zirconate titanate (PZT) powder and –OH-functionalized graphene (HOG) nanosheets (HOG-P/P). Among all composites, a high open-circuit voltage (Voc) of approximately 50 Vp-p and a maximum power density of 1.4 μW/cm2 were obtained from a HOG-P/P PEH with 0.10 wt% HOG nanosheets and 15 wt% PZT under bending–releasing mode. Moreover, the PEH exhibited a stable voltage output after 3000 bending–releasing cycles. In addition, the PEH harvested mechanical energy from human body movements and generated an output voltage and current of 60 V and 8 μA during the finger bending–releasing process, lighting up 30 commercial white LEDs. The enhanced piezoelectric performance can be attributed to the introduction of HOG nanosheets and PZT powder. This work provides an effective strategy for improving the output performance of P(VDF-TrFE)-based PEHs.

Thermal analysis of the crystallization kinetics of lead zirconate titanate powders prepared via sol–gel route

The crystallization evolution of lead zirconate titanate (PZT) powders processed from two organic gel systems with nominal composition was investigated. The crystallization of the perovskite PZT form initiated as the calcining temperature reached 400 °C. The formation of PbO phase constituted seeding grains for PZT crystallization at such low temperature. The formation of lead-deficient fluorite or pyrochlore phases was completely avoided under judicious processing conditions. TGA/DTA analysis was carried out to evaluate the activation energy associated with the perovskite phase formation. The kinetic parameters of the PZT crystallization toward perovskite formation were followed by employing Kissinger and JMAK isoconversional kinetic models. The results revealed that the crystallization mechanism is related to the powder precursor system. The value of the activation energy for the perovskite formation was about 77 kJ mol−1 irrespective of the precursor system when the Kissinger model was applied.

Hydrothermal synthesis and characteristics of lanthanumdoped Pb(Zr₀.₆₅Ti ₀.₃₅)O₃ ceramics

Lanthanum-doped lead zirconate titanate (PLZT) powders were synthesized using thehydrothermal method. The influence of pH, reaction temperature and time, lanthanum concentration on the formation and characteristics of PLZT were investigated. Obtained powders were investigated using X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) techniques and a dielectric analyzer. The results showed that Pb1-xLax(Zr0.65Ti0.35)O3 with x= 0.0 – 0.1 were well formed under conditions: pH≥13, reaction time of 12hrs, reaction temperature of 180oC. Dielectric constant of PLZT is higher than PZT. The grain size of the PLZT is found to be 1–3.5 µm.

PZT/PZT and PZT/BiT Composite Piezo-Sensors in Aerospace SHM Applications: Photochemical Metal Organic + Infiltration Deposition and Characterization.

The composition of fine-ground lead zirconate-titanate powder Pb(Zr0.52Ti0.48)O3, suspended in PZT and bismuth titanate (BiT) solutions, is deposited on the curved surface of IN718 and IN738 nickel-based supper alloy substrates up to 100 µm thickness. Photochemical metal organic and infiltration techniques are implemented to produce smooth, semi-dense, and crack-free random orientated thick piezoelectric films as piezo-sensors, free of any dopants or thickening polymers. Every single layer of the deposited films is heated at 200 °C with 10 wt.% excess PbO, irradiated by ultraviolet lamp (365 nm, 6 watt) for 10 min, pyrolyzed at 400 °C, and subsequently annealed at 700 °C for one hour. This process is repeated successively until reaching the desired thickness. Au and Pt thin films are deposited as the bottom and top electrodes using evaporation and sputtering methods, respectively. PZT/PZT and PZT/BiT composite films are then characterized and compared to similar PZT and BiT thick films deposited on the similar substrates. The effect of the composition and deposition process is also investigated on the crystalline phase development and microstructure morphology as well as the dielectric, ferroelectric, and piezoelectric properties of piezo-films. The maximum remnant polarization of Pr = 22.37 ± 0.01, 30.01 ± 0.01 µC/cm2, the permittivity of εr = 298 ± 3, 566 ± 5, and piezoelectric charge coefficient of d33 = 126, 148 m/V were measured versus the minimum coercive field of Ec = 50, 20 kV/cm for the PZT/PZT and PZT/BiT thick films, respectively. The thick film piezo-sensors are developed to be potentially used at frequency bandwidth of 1–5 MHz for rotary structural health monitoring and also in other industrial or medical applications as a transceiver.

Cold sintering and electrical characterization of lead zirconate titanate piezoelectric ceramics

This paper describes a cold sintering process for Pb(Zr,Ti)O3 ceramics and the associated processing-property relations. Pb(Zr,Ti)O3 has a very small, incongruent solubility that is a challenge during cold sintering. To circumvent this, a Pb(NO3)2 solution was used as the transient liquid phase. A bimodal lead zirconate titanate powder was densified to a relative density of 89% by cold sintering at 300 °C and 500 MPa. After the cold sintering step, the permittivity was 200, and the dielectric loss was 2.0%. A second heat-treatment involving a 3 h anneal at 900 °C increased the relative density to 99%; the resulting relative dielectric permittivity was 1300 at room temperature and 100 kHz. The samples showed well-defined ferroelectric hysteresis loops, having a remanent polarization of 28 μC/cm2. On poling, the piezoelectric coefficient d33 was ∼200 pC/N. With a 700 °C 3 h post-annealing, samples show a lower room temperature relative permittivity (950 at 100 kHz), but a 24 h hold time at 700 °C produces ceramics where there is an improved relative dielectric constant (1050 at 100 kHz).

Crystal structure of lead zirconate titanate ceramics prepared using ultrasonic processing

We have studied how the duration of ultrasonic processing of presynthesized lead zirconate titanate powders influences the crystal structure and physical properties of ceramics produced from such powders. The effect of the ultrasonication time on the sintering temperature, the formation of crystalline phases in the ceramics, and their Curie temperature has been assessed.

Photoluminescence of sol–gel synthesized PZT powders

A wide band of photoluminescence (PL) emission in structurally disordered lead zirconate titanate (PZT) powders, prepared by sol–gel route, was observed at room temperature excited with a laser line (488nm). Powders with PbZr0.53Ti0.47O3 nominal composition annealed at different temperatures were studied by X-ray diffraction, Raman spectroscopy, Luminescence, Diffuse Reflectance and Electronic Paramagnetic Resonance Spectroscopy (EPR). Our results indicate that the PL response can be associated to order–disorder degree in the perovskite structure, with the exception of samples annealed at low temperature, where a mixture of oxides precursors׳ phases was observed. Furthermore, in quasi-crystalline ordered samples (95% of crystallinity) a small generation of PL remains. In these experiments, the band gap increases with the formation of crystalline structure. EPR experiments were conducted in order to follow the evolution of paramagnetic species with thermal treatment from the mixture of oxides precursors to the perovskite phase and paramagnetic point defects were identified (Pb+3 and Ti+3). EPR data suggest the presence of order–disorder within the lattice network. Paramagnetic species are similar in samples treated at 700 and 800°C, nevertheless the emission intensity decreases by a factor of 6, indicating that the defects associated with PL are not paramagnetic at both temperatures.

Dielectric characterization of microwave sintered lead zirconate titanate ceramics

Highly reactive lead zirconate titanate powders (PZT) with different compositions were successfully synthesized by the oxidant-peroxo method (OPM) and used to prepare dense ceramic samples with composition near to the morphotropic phase boundary (MPB) sintered at 1000°C for 2h using a tubular conventional oven and a commercial microwave system. Crystalline phases were identified in the powder and ceramic samples by X-ray powder diffraction and FT-Raman spectroscopy at room temperature. The fractured surface of the ceramic sample showed a high degree of densification with fairly uniform grain sizes. Dielectric constants measured in the range from 30 to 500°C at different frequencies (1, 10 and 100kHz) indicated a normal ferroelectric behavior regardless of the sintering method. Samples sintered by a microwave radiation (MW) method and composition near to the MPB region showed a maximum dielectric constant of 17.911 and an anomalous high Curie temperature of 465°C.

Microwave sintering of sol–gel composite films using a domestic microwave oven

Feasibility study of sol–gel composite microwave sintering using a domestic microwave oven was carried out. Two kinds of lead zirconate titanate (PZT) powders were mixed with PZT sol–gel solution and the mixture was sprayed onto 3-mm-thick titanium substrate. The films were sintered by 700 W domestic oven for 10 min. Ultrasonic measurement was carried out in pulse–echo mode and clear multiple echoes were confirmed. It would be suitable method to fabricate high frequency broadband focused ultrasonic transducers. Further research is required to improve sintering degree.

Development of piezoelectric thick-film sensors to be embedded into adhesively bonded joints

Techniques have been developed for making a unique type of piezoelectric thick-film strain sensor in the form of a ‘piezoelectric adhesive’ to be embedded into a bonded joint. Lead zirconate titanate (PZT) powder is used as the active ingredient of the piezoelectric composite and epoxy resin as the matrix. The sensors have been fully characterised (i.e. type of piezoelectric powder, the surface area of the sensor, its thickness, weight fraction and the poling field) through an extensive testing programme in order to determine the optimum formulation for enhancing the sensitivity of the sensor. One of the main challenges was to effectively incorporate those sensors into the adhesive layer of a lap joint without greatly affecting the joint's mechanical properties. This application would allow the direct measurement of the stress field in a joint along the bond area, aiming at the optimisation of the adhesively bonded joint design as well as serving as an in-service structural health monitoring device. In the present work, the sensors were tested using the dynamic four-point bending test and preliminary results demonstrate the feasibility of this approach, achieving a satisfactory performance of the piezoelectric sensors applied on a metal substrate.

New synthesis route for lead zirconate titanate powder

Phase pure lead zirconate titanate (PZT) powder was produced via a new aqueous coprecipitation method. A suite of characterization techniques, including FTIR, Raman, X-ray diffraction, SEM as well as nitrogen sorption were employed to investigate the structural evolution of the synthesized and calcined powder. The dried precipitate formed in aqueous phase yielded approximately 80wt% final product after calcination. The PZT perovskite structure was obtained after calcination at 550°C for 3h. Milling of the calcined powder reduced the mean particle size from approximately 10µm to 2µm. With increasing calcination temperature from 550°C to 700°C, both surface area and pore volume decreased while pore size increased from 3.4nm to 9.8nm. The bulk density of pelletized samples increased from 4.83 to 7.57g/cm3 with increasing sintering temperature from 800°C to 1200°C. Powder processing using this aqueous route is simple and reproducible leading to a method that is readily scalable for industrial applications.

Processing method and property study for cement-based piezoelectric composites and sensors

The cement-based piezoelectric composite is developed to fabricate smart sensors in real-time structural health monitoring. The cement-based piezoelectric sensor is suitable for applications in civil engineering because of its good compatibility in acoustic impedance. The 0–3 cement-based piezoelectric composites were fabricated by mixing the cement particles and lead zirconate titanate powders under high pressure in this paper. The parameters including the piezoelectric factors, relative dielectric constant ɛr, thickness and planar electromechanical coupling coefficients of cement-based composites with different lead zirconate titanate ceramic contents were measured to characterise the electromechanical coupling properties. Further, the acoustic impedance was detected to test acoustic compatibility with concrete materials. Laboratory tests show that the voltage output of the sensor is linearly proportional to the applied pressure. The cement-based piezoelectric sensors have better mechanical–electrical conversion property than pure ceramic sensors. The findings indicate that the 0–3 cement-based piezoelectric sensor meets all requirements of application in construction engineering, and is feasible to be utilised in concrete structures.

Lead zirconate titanate-based thick films for high-frequency focused ultrasound transducers prepared by electrophoretic deposition

An electrophoretic deposition (EPD) process with high deposition rate was used to fabricate a curved piezoelectric thick film devoted to high-frequency transducers for medical imaging. Niobium-doped lead zirconate titanate (PZTNb) powder was stabilized in ethanol to prepare a suspension with high zeta potential and low conductivity. A gold layer, pad-printed and fired on a curved porous PZT substrate, was used as the working electrode for the deposition of the PZTNb thick film. This substrate was chosen because it has the required properties (acoustic impedance and attenuation) to be used directly as a backing for the high-frequency transducer, leading to a simplified process for transducer assembly with this integrated structure. PZT-Nb thick films were also deposited by EPD on flat gold-coated alumina substrates as a reference. The thickness of the films was between 20 and 35 μm, and their electromechanical performance was comparable to standard PZT bulk ceramics with a thickness coupling factor of 48%. For the curved thick film, the thickness coupling factor was slightly lower. The corresponding integrated structure was used to fabricate a transducer with a center frequency of 40 MHz and an f-number of 2.8. It was integrated into a realtime ultrasound scanner and used to image human forearm skin; the resulting images showed, for the first time, the efficacy of the EPD process for these imaging applications.