Showing papers on "Lead zirconate titanate published in 2021"

Electroceramics for High-Energy Density Capacitors: Current Status and Future Perspectives

Abstract: Materials exhibiting high energy/power density are currently needed to meet the growing demand of portable electronics, electric vehicles and large-scale energy storage devices. The highest energy densities are achieved for fuel cells, batteries, and supercapacitors, but conventional dielectric capacitors are receiving increased attention for pulsed power applications due to their high power density and their fast charge-discharge speed. The key to high energy density in dielectric capacitors is a large maximum but small remanent (zero in the case of linear dielectrics) polarization and a high electric breakdown strength. Polymer dielectric capacitors offer high power/energy density for applications at room temperature, but above 100 °C they are unreliable and suffer from dielectric breakdown. For high-temperature applications, therefore, dielectric ceramics are the only feasible alternative. Lead-based ceramics such as La-doped lead zirconate titanate exhibit good energy storage properties, but their toxicity raises concern over their use in consumer applications, where capacitors are exclusively lead free. Lead-free compositions with superior power density are thus required. In this paper, we introduce the fundamental principles of energy storage in dielectrics. We discuss key factors to improve energy storage properties such as the control of local structure, phase assemblage, dielectric layer thickness, microstructure, conductivity, and electrical homogeneity through the choice of base systems, dopants, and alloying additions, followed by a comprehensive review of the state-of-the-art. Finally, we comment on the future requirements for new materials in high power/energy density capacitor applications.

Airborne Piezoelectric Micromachined Ultrasonic Transducers for Long-Range Detection

Abstract: This paper presents an airborne piezoelectric micromachined ultrasonic transducers (PMUTs) operated at low frequency (40–50 kHz) for long-range detection, where the acoustic absorption loss in air is relatively low (0.8–1 dB/m). The PMUTs made with single-crystal Lead Zirconate Titanate (PZT) enables a high piezoelectric coefficient ( ${e} _{31, f} \approx ~16$ - 24 C/ $\text{m}^{{2}}$ ), and a low dielectric constant ( $\varepsilon _{\mathrm {r}}~\approx ~308$ ), achieving high PMUT transceiver efficiency. The $2\times 2$ PMUT array achieves a very high sound pressure level (SPL) output of 109.4 dB at 26 cm distance. Different from conventional PZT PMUTs, this study utilized single-crystal PZT with a low permittivity to achieve a good acoustic reception, demonstrating the sensitivity of 2 mV/Pa. This work reports the PMUT design, modeling, fabrication, characterization, enabling a long-range detection of 4.8 meters in a pulse-echo experiment, which was conducted by a pair of $2\times 2$ PMUT arrays with the matched resonances. [2020-0270]

Polarisation tuneable piezo-catalytic activity of Nb-doped PZT with low Curie temperature for efficient CO2 reduction and H2 generation

Abstract: The reduction of CO2 into useful hydrocarbon chemicals has attracted significant attention in light of the depletion in fossil resources and the global demand for sustainable sources of energy. In this paper, we demonstrate piezo-catalytic electrochemical reduction of CO2 by exploiting low Curie temperature, Tc ∼ 38 °C, Nb-doped lead zirconate titanate (PZTN) piezoelectric particulates. The large change in spontaneous polarisation of PZTN due to the acoustic pressures from to the application of ultrasound in the vicinity of the Tc creates free charges for CO2 reduction. The effect of applied acoustic power, particulate agglomeration and the impact of Tc on piezo-catalytic performance are explored. By optimization of the piezo-catalytic effect a promising piezo-catalytic CO2 reduction rate of 789 μmol g−1 h−1 is achieved, which is much larger than the those obtained from pyro-catalytic effects. This efficient and polarisation tunable piezo-catalytic route has potential to promote the development of CO2 reduction via the utilization of vibrational energy for environmental improvement.

Hardening effect in lead-free piezoelectric ceramics

Abstract: Ecologically sustainable development of piezoelectric ceramics has been the primary target of the community over the past 20 years. While the development of “soft” lead-free piezoelectric ceramics has been of high maturity, the understanding of “hard” lead-free piezoelectric ceramics is still far from satisfactory, leading to a limited chance for high-power applications. The review starts with an introduction of loss mechanisms and the hardening effect in piezoelectric ceramics, including three different models mainly developed based on the lead zirconate titanate system. Then, studies on the hardening behavior of BaTiO3-based, (Bi0.5Na0.5)TiO3-based, and (K0.5Na0.5)NbO3-based lead-free piezoelectric ceramics are summarized with emphasis on the approaches to enhance mechanical quality factor. Meanwhile, three different characterization methods of high-power performances are introduced: the constant-voltage method, constant-current method, and transient (or burst) method. Finally, the state-of-the-art lead-free ultrasonic transducer applications are highlighted. This paper concludes with the remaining challenges for the development of “hard” lead-free piezoelectric ceramics for high-power piezoelectric applications.

Expanding the application space for piezoelectric materials

Abstract: The long history of innovation in the field of piezoelectric devices has, over the last 65 years, been predominantly rooted in a single material, the Pb(Zr, Ti)O3 ceramic, known as lead zirconate titanate (PZT). Despite enormous resources being dedicated in the last 20 years to identifying lead-free alternatives to PZT and developing a thriving, but limited, market in PbTiO3-relaxor single crystals, most device developments are still PZT based. However, more recently, solid solutions based on BiFeO3 have opened up new applications for active piezoelectric devices at high temperatures (to 600 °C) and under high stress (exceeding 250 MPa), with applications in industrial ultrasound, aerospace, automotive, and micro-actuators. This perspective article examines how new materials are expanding the application space for piezoelectric materials.

Pyroelectric and photovoltaic properties of Nb-doped PZT thin films

Abstract: Nb-doped lead zirconate titanate (PZT) films with up to 12 at. % of Nb were co-sputtered from oxide PZT and metallic Nb targets at a substrate temperature of 600 °C. Up to 4 at. % of Nb was doped into the perovskite structure with the formation of B-site cation vacancies for charge compensation. The preferential (111) PZT orientation decreased with Nb-doping within the solid solution region. The ferroelectric response of the films was affected by the large values of the internal field present in the samples (e.g., −84.3 kV cm−1 in 12 at. % Nd doped films). As-deposited unpoled films showed large values of the pyroelectric coefficient due to self-poling. The pyroelectric coefficient increased with Nb-doping and showed a complex dependence on the applied bias. The photovoltaic effect was observed in the films. The value of the photocurrent increased with the A/B ratio. The combined photovoltaic–pyroelectric effect increased the values of the measured current by up to 47% upon light illumination.

Comprehensive study of magnetostriction-based MEMS magnetic sensor of a FeGa/PZT cantilever

Abstract: This research comprehensively studies a magnetostriction-based cantilever resonator magnetic sensor of Iron Gallium (FeGa) coupled to a piezoelectric material of lead zirconate titanate (PZT) is performed. The study is meant to explore its magnetic sensing mechanism, reaction to magnetic field direction, the separate effect of magnetic force, and the advantage of miniaturization. The FeGa/PZT cantilever is sensitive to magnetic field direction when objected to a static DC magnetic field in the perpendicular direction with 5.47 Hz/mT sensitivity. It is also concluded that the FeGa/PZT cantilever is also sensitive to magnetic force with a different reaction to a static magnetic field. The sensitivity to magnetic force is in the value of 1.77 Hz/mT. Both sensitivities are calculated from the slope of the resonance frequency shift and magnetic field graph divided by its resonance frequency. The Allan variance method's minimum detectable magnetic field is determined with a frequency noise of 0.02 Hz, equal to 3.66 μT. The minimum detectable magnetic field can be improved by reducing the thermal noise through structure modification by designing a narrow, thin, and long cantilever with a high Q factor with complementary material. The magnetostriction-based magnetic sensor can be applied in either direct magnetic field measurement or a magnetic resonance system such as micro NMR or micro ESR.

Synthesis, Microstructure and Properties of Magnetron Sputtered Lead Zirconate Titanate (PZT) Thin Film Coatings

Abstract: Compared to aluminum nitride (AlN) with simple stoichiometry, lead zirconate titanate thin films (PZT) are the other promising candidate in advanced micro-electro-mechanical system (MEMS) devices due to their excellent piezoelectric and dielectric properties. The fabrication of PZT thin films with a large area is challenging but in urgent demand. Therefore, it is necessary to establish the relationships between synthesis parameters and specific properties. Compared to sol-gel and pulsed laser deposition techniques, this review highlights a magnetron sputtering technique owing to its high feasibility and controllability. In this review, we survey the microstructural characteristics of PZT thin films, as well as synthesis parameters (such as substrate, deposition temperature, gas atmosphere, and annealing temperature, etc.) and functional proper-ties (such as dielectric, piezoelectric, and ferroelectric, etc). The dependence of these influential factors is particularly emphasized in this review, which could provide experimental guidance for researchers to acquire PZT thin films with expected properties by a magnetron sputtering technique.

Orientation-dependent, field-induced phase transitions in soft lead zirconate titanate piezoceramics

Abstract: In situ high-energy X-ray diffraction (XRD) was performed on lead-zirconate-titanate-based ferroelectric materials with composition near the morphotropic phase boundary (MPB) The utilization of the two-dimensional area detector in in situ field-dependent experiments enables the complete analysis of the material response with respect to all azimuthal angles at each field amplitude The studies reveal that the field-induced phase transition from tetragonal to rhombohedral is dependent on crystal orientation in Nb-doped PbZr053Ti047O3 that is in close compositional proximity to the MPB However, only domain wall motion is activated in Nb-doped PbZr050Ti050O3, which is further in composition from the MPB This synchrotron-based XRD characterization approach illustrates the importance in evaluating the orientation-dependence of phase transitions in piezoelectric and ferroelectric polycrystalline materials

How to Make Porous Piezoelectrics? Review on Processing Strategies

Abstract: Ferroelectric ceramics are a technologically important class of materials that are currently exploited in actuators, sensors, transducers, and memory devices The introduction of porosity into these materials has been proved to be an effective tool for tuning functional properties for specific applications, such as piezoelectric and pyroelectric devices and energy harvesters In this review, a comprehensive description of the most widely used processing techniques able to produce porous ferroelectric ceramics is reported In particular, the state-of-the-art production strategies including replica technique, direct foaming, sacrificial template method, and additive manufacturing used up to now for the realization of porous piezoelectric lead zirconate titanate (PZT)-based structures are critically reviewed and rationalized Moreover, this work aims to give concrete indications on the more effective and actual production strategies that should be exploited for the development of porous PZT-based materials for the specific applications Finally, two case studies are reported to remark the critical importance of material–processing–microstructure correlations on the functional properties of the designed devices

Ceramic-Based Piezoelectric Material for Energy Harvesting Using Hybrid Excitation.

Abstract: This paper analyzes the energy efficiency of a Micro Fiber Composite (MFC) piezoelectric system. It is based on a smart Lead Zirconate Titanate material that consists of a monolithic PZT (piezoelectric ceramic) wafer, which is a ceramic-based piezoelectric material. An experimental test rig consisting of a wind tunnel and a developed measurement system was used to conduct the experiment. The developed test rig allowed changing the air velocity around the tested bluff body and the frequency of forced vibrations as well as recording the output voltage signal and linear acceleration of the tested object. The mechanical vibrations and the air flow were used to find the optimal performance of the piezoelectric energy harvesting system. The performance of the proposed piezoelectric wind energy harvester was tested for the same design, but of different masses. The geometry of the hybrid bluff body is a combination of cuboid and cylindrical shapes. The results of testing five bluff bodies for a range of wind tunnel air flow velocities from 4 to 15 m/s with additional vibration excitation frequencies from 0 to 10 Hz are presented. The conducted tests revealed the areas of the highest voltage output under specific excitation conditions that enable supplying low-power sensors with harvested energy.

Toward low-temperature processing of lead zirconate titanate thin films: Advances, strategies, and applications

Abstract: Lead zirconate titanate (PZT) thin films stand for a prominent technological brick in the field of microsystems. The recent improvements of their manufacturability combined with excellent piezoelectric properties have enabled their introduction in industrial clean rooms all around the world. These films require annealing temperatures beyond 600 °C to crystallize in the desired perovskite phase, which exhibits outstanding piezoelectric coefficients. This temperature requirement forbids large application fields such as flexible electronics, smart glass but also system-on-chip approaches. Decreasing the annealing temperature of PZT films would therefore spread further their potential usage to other applications. The purpose of this paper is to provide the reader with a comprehensive review of the different techniques available in the literature to process piezoelectric PZT thin films at temperatures compatible with semiconductors (450 °C), smart glass (400 °C), or flexible electronics (350 °C). We first present the typical ferroelectric and piezoelectric properties of PZT films. The different deposition techniques and growth mechanisms of these films are then reviewed with a focus on thermodynamics. Then, all the low temperature processes are detailed, such as seeding effects, the modification of deposition parameters in vapor-phase deposition, special annealing technologies assisted with UV, lasers, flash lamps, microwave radiations or high-pressure, a focus on the hydrothermal method, and finally what is called solution chemistry design with notably combustion synthesis. Transfer processing is also detailed, as an alternative way to this low temperature approach. An outlook of future applications enabled by these innovative techniques is finally provided.

Tailoring nanomechanical properties of hard and soft PZT piezoceramics via domain engineering by selective annealing

Abstract: The nanomechanical properties of polycrystalline “hard” and “soft” lead zirconate titanate (PZT) (abbreviated as PZT-H and PZT-S, respectively) are measured on samples having different ferroelectric domain configurations. The ferroelectric domain configurations are varied by selectively annealing the as poled samples below and above the curie temperature, Tc. The ferroelectric domain configurations characterized using piezoresponse force microscopy reveal that the degree of randomization of ferroelectric domains increases with increasing annealing temperature. Nanoindentation experiments reveal that the above Tc annealed samples exhibit the highest hardness, H among all the samples. All the samples, exhibit strong indentation size effect where H decreases with increasing in indentation load. The possible reasons for enhancement in Hin annealed samples is attributed to the differences in ferroelectric domain configurations, defect dipoles, and oxygen vacancies. The results provide insights about designing piezoelectric materials with good combination of mechanical and piezoelectric properties.

Influence of tensile vs. compressive stress on fatigue of lead zirconate titanate thin films

Abstract: Novel applications of ferroelectric films require a variety of different substrates, which exert different mechanical stress on the film. This raises the question of reliability of differently stressed films. This work compares the cycling-induced fatigue of the polarization hysteresis of PZT films in different stress states. A tensile stress of +270 MPa, for PZT on fused silica glass, causes gradual degradation, while degradation sets in abruptly under compressive stress of −100 MPa, for PZT on sapphire. The main fatigue mechanism is domain wall pinning on charged defects. Reversible and irreversible domain wall processes in the small- and large-signal permittivity reveal that the fatigue behavior results from a variation of the ferroelectric domain structure. Films under tensile stress contain more 90° domain walls, which get pinned continuously on isolated defects. Compressive stress creates more 180° domain walls, which require formation of defect agglomerates during a certain threshold cycle number for pinning.

Actuating Performance Analysis of a New Smart Aggregate Using Piezoceramic Stack

Abstract: A new type of smart aggregate using piezoceramic stack (SAPS) was developed for improved output, as compared with a conventional smart aggregate with a single piezoceramic patch. Due to the better output, the proposed smart aggregate is preferred where the attenuating effect is strong. In this research, lead zirconate titanate (PZT) material in the form of discs was used due to its strong piezoelectric performance. For analysis, the proposed SAPS was simplified to a one-dimensional axial model to investigate its electromechanical and displacement output characteristics, and an experimental setup was designed to verify the simplified model. Moreover, the influence of the structural parameters, including the number of the PZT discs, the dimensions of the PZT disc, protective shell, and copper lids, and the elastic modulus of the epoxy on the electromechanical and displacement output performance of SAPSs, were numerically studied by using the one-dimensional axial model. The numerical analysis results indicate that the structural dimension of the PZT discs has a greater effect on the electromechanical performance of SAPSs than that of the protective shell and copper lids. Moreover, the results show that the number of the PZT discs and the outer diameter of the protective shell have a much greater influence on the displacement output of SAPSs than other parameters. The analysis results of SAPSs with different elastic moduli of the epoxy demonstrate that the SAPSs’ first resonance frequency, first electromechanical coupling factor, and displacement output change less than 1.79% when the epoxy’s elastic modulus changes from 1.28 GPa to 5.12 GPa, which indicates that the elastic modulus of the epoxy has a limited influence on the property of SAPSs, and it will be helpful for their fabrication. This study provides an approach to increasing the output of SAPS and also develops a method to design the structure of SAPSs.

Structural Integrity Assessment of Composites Plates with Embedded PZT Transducers for Structural Health Monitoring

Abstract: Active sensing using ultrasonic guided waves (UGW) is widely investigated for monitoring possible damages in composite structures. Recently, a novel diagnosed film based on a circuit-printed technique with piezoelectric lead zirconate titanate (PZT) transducers has been developed. The diagnostic film is a replacement for the traditional cable connection to PZT sensors and has been shown to significantly reduce the weight of the host structure. In this work, the diagnosed films were embedded into composite structures during manufacturing using a novel edge cut-out method during lay-up, which allowed for edge trimming after curing. In this paper, the effect of fatigue loading on the integrity of PZT transducers is initially investigated. The electro-mechanical impedance (EMI) properties at different fatigue loading cycles were used as the diagnostic measure for the performance of the sensors. At the same time, the behaviours of UGW were investigated at different fatigue loading cycles. It was found that the EMI properties and active sensing behaviours remained stable up to 1 million cycles for the force ranges of 0.5~5 kN and 1~10 kN. Next, the effect of embedding the diagnosed film on the mechanical properties of the host composite structure was investigated. Tensile and compressive tests were conducted and the elastic modulus of composite coupons with and without embedded PZT diagnosed films were compared. The elastic modulus of composite coupons with PZT diagnosed films embedded across the entire coupon reduced by as much as 20% for tensile tests and just over 10% for compressive tests compared to the coupons without embedded sensors. These reductions are considered the worst-case scenario, as in real structures the film would only be embedded in a relatively small area of the structure.