Showing papers on "Lead zirconate titanate published in 2010"

1.6 V Nanogenerator for Mechanical Energy Harvesting Using PZT Nanofibers

Abstract: Energy harvesting technologies that are engineered to miniature sizes, while still increasing the power delivered to wireless electronics,(1, 2) portable devices, stretchable electronics,(3) and implantable biosensors,(4, 5) are strongly desired. Piezoelectric nanowire- and nanofiber-based generators have potential uses for powering such devices through a conversion of mechanical energy into electrical energy.(6) However, the piezoelectric voltage constant of the semiconductor piezoelectric nanowires in the recently reported piezoelectric nanogenerators(7-12) is lower than that of lead zirconate titanate (PZT) nanomaterials. Here we report a piezoelectric nanogenerator based on PZT nanofibers. The PZT nanofibers, with a diameter and length of approximately 60 nm and 500 μm, were aligned on interdigitated electrodes of platinum fine wires and packaged using a soft polymer on a silicon substrate. The measured output voltage and power under periodic stress application to the soft polymer was 1.63 V and 0.03 ...

Thickness effect on the dielectric, ferroelectric, and piezoelectric properties of ferroelectric lead zirconate titanate thin films

Abstract: Lead zirconate titanate (PbZr0.52Ti0.48O3−PZT) thin films with different thicknesses were deposited on Pt(111)/Ti/SiO2/Si substrates by a sol-gel method. Single perovskite phase with (111)-texture was obtained in the thinnest films, whereas with the increase in thickness the films changed to a highly (100)-oriented state. An increase in the mean grain size as the film thickness increased was also observed. Dielectric, ferroelectric, and piezoelectric properties were analyzed as a function of the film thickness and explained based on film orientation, grain size, domain structure, domain wall motion, and nonswitching interface layers. Both serial and parallel capacitor models were used to analyze the influence of the nonswitching interface layer in the dielectric properties and the effect of substrate clamping in the microscopic piezoelectric response as the film thickness decreased. The scanning force microscopy technique was used to study the effect of thickness on the microscopic piezoresponse. Signific...

A reusable PZT transducer for monitoring initial hydration and structural health of concrete.

Abstract: During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT) transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD) is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use.

Flexural deformation in a compositionally stepped ferrite and magnetoelectric effects in a composite with piezoelectrics

Abstract: The nature of strain mediated magnetoelectric (ME) coupling is investigated in laminates of lead zirconate titanate (PZT) and compositionally stepped ferrite with grading of piezomagnetic coefficient. ME effects that could only be attributed to grading related bending strain are observed in a trilayer of ferrite and oppositely poled PZT. It is shown that in a bilayer, grading induced flexural strain counteracts bending moment due to structural asymmetry and enhances ME coupling by a factor of 2. A zero-bias field ME effect is observed in such laminates. The graded composites are of interest for self-biased magnetic field sensors.

Optimizing a spectral element for modeling PZT-induced Lamb wave propagation in thin plates

Abstract: Use of surface-mounted piezoelectric actuators to generate acoustic ultrasound has been demonstrated to be a key component of built-in nondestructive detection evaluation (NDE) techniques, which can automatically inspect and interrogate damage in hard-to-access areas in real time without disassembly of the structural parts. However, piezoelectric actuators create complex waves, which propagate through the structure. Having the capability to model piezoelectric actuator-induced wave propagation and understanding its physics are essential to developing advanced algorithms for the built-in NDE techniques. Therefore, the objective of this investigation was to develop an efficient hybrid spectral element for modeling piezoelectric actuator-induced high-frequency wave propagation in thin plates. With the hybrid element we take advantage of both a high-order spectral element in the in-plane direction and a linear finite element in the thickness direction in order to efficiently analyze Lamb wave propagation in thin plates. The hybrid spectral element out-performs other elements in terms of leading to significantly faster computation and smaller memory requirements. Use of the hybrid spectral element is proven to be an efficient technique for modeling PZT-induced (PZT: lead zirconate titanate) wave propagation in thin plates. The element enables fundamental understanding of PZT-induced wave propagation.

Epitaxial piezoelectric MEMS on silicon

Abstract: This paper reports on the microfabrication and characterization of piezoelectric MEMS structures based on epitaxial Pb(Zr02Ti08)O3 (PZT) thin films grown on silicon wafers Membranes and cantilevers are realized using a sequence of microfabrication processes optimized for epitaxial oxide layers Different issues related to the choice of materials and to the influence of the fabrication processes on the properties of the piezoelectric films are addressed These epitaxial PZT transducers can generate relatively large deflections at low bias voltages in the static mode Estimations of the piezoelectric coefficient d31 of the epitaxial PZT thin film (100 nm) yield 130 pm V−1 In the dynamic mode, the performance of the epitaxial PZT transducers in terms of the resonant frequency, modal shape and quality factor are examined An epitaxial PZT/Si cantilever (1000 × 2500 × 40 µm3) resonating in air and in vacuum exhibits a deflection of several microns with quality factors of 169 and 284, respectively For a 1500 µm diameter membrane, the quality factor is 50 at atmospheric pressure, and this rises to 323 at a pressure of 01 mbar These results indicate the high potential of epitaxial piezoelectric MEMS, which can impact a variety of technological applications

Lamb wave tuning curve calibration for surface-bonded piezoelectric transducers

Abstract: Surface-bonded lead zirconate titanate (PZT) transducers have been widely used for guided wave generation and measurement. For selective actuation and sensing of Lamb wave modes, the sizes of the transducers and the driving frequency of the input waveform should be tuned. For this purpose, a theoretical Lamb wave tuning curve (LWTC) of a specific transducer size is generally obtained. Here, the LWTC plots each Lamb wave mode' amplitude as a function of the driving frequency. However, a discrepancy between experimental and existing theoretical LWTCs has been observed due to little consideration of the bonding layer and the energy distribution between Lamb wave modes. In this study, calibration techniques for theoretical LWTCs are proposed. First, a theoretical LWTC is developed when circular PZT transducers are used for both Lamb wave excitation and sensing. Then, the LWTC is calibrated by estimating the effective PZT size with PZT admittance measurement. Finally, the energy distributions among symmetric and antisymmetric modes are taken into account for better prediction of the relative amplitudes between Lamb wave modes. The effectiveness of the proposed calibration techniques is examined through numerical simulations and experimental estimation of the LWTC using the circular PZT transducers instrumented on an aluminum plate.

The Development of Piezoelectric Materials and the New Perspective

Abstract: Certain materials produce electric charges on their surfaces as a consequence of applying mechanical stress. The induced charges are proportional to the mechanical stress. This is called the direct piezoelectric effect and was discovered in quartz by Pierre and Jacques Curie in 1880. Materials showing have a geometric strain proportional to an applied electric field. This is the converse piezoelectric effect, discovered by Gabriel Lippmann in 1881. This article first reviews the historical episodes of piezoelectric materials in the sequence of quartz, Rochelle salt, barium titanate, PZT, lithium niobate/tantalate, relaxor ferroelectrics, PVDF, Pb-free piezoelectrics, and composites. Then, the detailed performances are described in the following section, which serves as the introduction to each chapter in this book. Third, since piezoelectricity is utilized extensively in the fabrication of various devices such as transducers, sensors, actuators, surface acoustic wave devices, frequency control, etc., applications of piezoelectric materials are introduced briefly in conjunction with materials. The author hopes that the reader can ‘learn the history aiming at creating a new perspective for the future of piezoelectric materials’.

Utilisation of smart polymers and ceramic based piezoelectric materials for scavenging wasted energy

Abstract: Piezoelectric smart polymer and ceramic materials can be deployed as a mechanism to transform mechanical energy into electrical energy that can be stored and used to power portable devices. This paper focuses on the development and comparison of a micropower based harvesting generator using piezoelectric PZT (lead zirconate titanate) ceramic, PVDF (polyvinylidene fluoride) membrane and PP (polypropylene) foam polymer with the intention of establishing power output from temperature fluctuations. Unimorph and bimorph strips of various sizes were prepared and subjected to vibration and impact experiments in order to directly compare the voltage output. The effect of the ceramic fibre diameter, laminate thickness, impact area, weight of the free falling mass, vibration frequency and temperature on the voltage output were studied. Experiments are outlined detailing the performance characteristics of such piezoelectric fibre laminates. Results show voltage outputs of nearly 40 V which is considered sufficient for potential applications in powering microsystems.

Single Crystal Study of Competing Rhombohedral and Monoclinic Order in Lead Zirconate Titanate

Abstract: Neutron diffraction data obtained on single crystals of PbZr(1-x)Ti(x)O3 with x=0.325 and x=0.460, which lie on the pseudorhombohedral side of the morphotropic phase boundary, suggest a coexistence of rhombohedral (R3m/R3c) and monoclinic (Cm) domains and that monoclinic order is enhanced by Ti substitution. A monoclinic phase with a doubled unit cell (Cc) is ruled out as the ground state.

Identification of elastic, dielectric, and piezoelectric constants in piezoceramic disks

Abstract: Three-dimensional modeling of piezoelectric devices requires a precise knowledge of piezoelectric material parameters. The commonly used piezoelectric materials belong to the 6mm symmetry class, which have ten independent constants. In this work, a methodology to obtain precise material constants over a wide frequency band through finite element analysis of a piezoceramic disk is presented. Given an experimental electrical impedance curve and a first estimate for the piezoelectric material properties, the objective is to find the material properties that minimize the difference between the electrical impedance calculated by the finite element method and that obtained experimentally by an electrical impedance analyzer. The methodology consists of four basic steps: experimental measurement, identification of vibration modes and their sensitivity to material constants, a preliminary identification algorithm, and final refinement of the material constants using an optimization algorithm. The application of the methodology is exemplified using a hard lead zirconate titanate piezoceramic. The same methodology is applied to a soft piezoceramic. The errors in the identification of each parameter are statistically estimated in both cases, and are less than 0.6% for elastic constants, and less than 6.3% for dielectric and piezoelectric constants.

Experimental and theoretical investigation on polarization reversal in unfatigued lead-zirconate-titanate ceramic

Abstract: The dynamics of polarization switching in a soft lead-zirconate-titanate ceramic has been studied over a broad time window ranging from 10−6–106 for applied fields between 0.5 and 2.5 kV/mm. The classical Kolmogorov–Avrami–Ishibashi model of the polarization reversal was not able to satisfactory explain the obtained results. Therefore, a new concept for the polarization dynamics of ferroelectric ceramics has been suggested, which is based on two principal assumptions, (1) a strong dependence of the polarization switching time on the local electric field and (2) a random distribution of the local switching times caused by an intrinsic randomness in the field distribution within the system. Thereby the switching volume is composed as an ensemble of many regions with independent dynamics governed by local field exclusively. Such random field distribution could be well adjusted by a Gaussian distribution around the mean value of the field applied. A total polarization dependence on time and applied field was obtained in explicit form with only three fitting parameters which enabled a good description of the experimental results on polarization reversal in the whole time-field domain.

In situ 24 kHz coherent imaging of morphology change in laser percussion drilling

Abstract: We observe sample morphology changes in real time (24 kHz) during and between percussion drilling pulses by integrating a low-coherence microscope into a laser micromachining platform. Nonuniform cut speed and sidewall evolution in stainless steel are observed to strongly depend on assist gas. Interpulse morphology relaxation such as hole refill is directly imaged, showing dramatic differences in the material removal process dependent on pulse duration/peak power (micros/0.1 kW, ps/20 MW) and material (steel, lead zirconate titanate PZT). Blind hole depth precision is improved by over 1 order of magnitude using in situ feedback from the imaging system.

Development of dual PZT transducers for reference-free crack detection in thin plate structures

Abstract: A new Lamb-wave-based nondestructive testing (NDT) technique, which does not rely on previously stored baseline data, is developed for crack monitoring in plate structures. Commonly, the presence of damage is identified by comparing "current data" measured from a potentially damaged stage of a structure with "baseline data" previously obtained at the intact condition of the structure. In practice, structural defects typically take place long after collection of the baseline data, and the baseline data can be also affected by external loading, temperature variations, and changing boundary conditions. To eliminate the dependence on the baseline data comparison, the authors previously developed a reference-free NDT technique using 2 pairs of collocated lead zirconate titanate (PZT) transducers placed on both sides of a plate. This reference-free technique is further advanced in the present study by the necessity of attaching transducers only on a single surface of a structure for certain applications such as aircraft. To achieve this goal, a new design of PZT transducers called dual PZT transducers is proposed. Crack formation creates Lamb wave mode conversion due to a sudden thickness change of the structure. This crack appearance is instantly detected from the measured Lamb wave signals using the dual PZT transducers. This study also suggests a reference-free statistical approach that enables damage classification using only the currently measured data set. Numerical simulations and experiments were conducted using an aluminum plate with uniform thickness and fundamental Lamb waves modes to demonstrate the applicability of the proposed technique to reference-free crack detection.

Fatigue failure characteristics of lead zirconate titanate piezoelectric ceramics

Abstract: Mechanical properties and fatigue failure characteristics of lead zirconate titanate piezoelectric ceramic (PZT) have been investigated. Bending and fatigue strengths of PZT ceramic are directly attributed to the electrode status. Material hardening occurs in the PZT ceramic during the cyclic loading, which is influenced by domain switching occurring anywhere in the grains. The domain structure is clearly detected by electron back scatter diffraction analysis and etching techniques. It also appears that the poling direction causes the change of failure characteristics due to different domain and domain wall orientation. The domain orientation changes alternately from domain to domain by 90°. Moreover, the domain wall orientation is well regulated in the grains perpendicular to the poling direction. An acceleration of fatigue crack growth occurs as the crack propagates along the domain wall.

Piezoelectric PZT / PVDF-copolymer 0-3 composites: aspects on film preparation and electrical poling

Abstract: Composite films of lead zirconate titanate (PZT) and different (non-polar and polar) polyvinylidene fluoride (PVDF) copolymers are prepared as 30 to 150 μm thick freestanding, relatively flexible films. For low ceramic-volume fractions the ceramic fillers are homogeneous distributed within the polymer matrix as indicated by scanning electron microscopy studies. Ceramic-volume fractions higher than approximately 0.5 lead to porous composite films which became brittle. The brittle films are difficult to polarize and not suitable as piezoelectric transducers. The permittivities of non-porous composite films follow the Bruggeman model for dielectric mixtures. Different procedures are presented and verified in order to polarize the ferroelectric PZT particles and the ferroelectric polymer matrix. In detail, the overall polarization is discussed by taking into account the polarities of the applied poling voltage and of the measured piezoelectric signals. In summary, for composites with high ceramic-volume fractions piezoelectric coefficients of up to 8.6 pC/N and 22.1 pC/N (for PZT / P(VDFTrFE) composites) and up to 11.3 pC/N and 24.8 pC/N (for PZT / P(VDF-HFP) composites) are reached after short-term, room-temperature and long-term, high-temperature poling, respectively.

Study of impedance parameters of cerium modified lead zirconate titanate ceramics

Abstract: A high-temperature solid-state reaction technique was used to prepare the polycrystalline samples of cerium (Ce) modified lead zirconate titanate with Zr/Ti ratio 65:35 (i.e., Pb(Zr0.65-xCexTi0.35)O3 (PZCT)). Preliminary X-ray structural analysis exhibits the formation of the new compositions of PZT. In order to study the compositional effects on the electrical properties (complex impedance Z*, complex modulus M*, electrical conductivity and relaxation mechanisms) of PZCT, a nondestructive experimental technique (i.e., complex impedance spectroscopy) was used. The complex impedance analysis with Nyquist plots shows that the impedance parameters of all the PZCT samples contain bulk effect. The presence of single arc in the complex modulus spectra of PZCT confirms the single phase of PZCT with high relaxation time. The asymmetric behaviour of semi-circular arcs and shifting of peaks suggest the existence of non-Debye (Cole-Cole) type of relaxation mechanism in the PZCT systems.

Comparison of the Temperature-Dependent Ferroelastic Behavior of Hard and Soft Lead Zirconate Titanate Ceramics

Abstract: The ferroelastic properties of a hard acceptor-doped lead zirconate titanate (PZT) ceramic are investigated between room temperature and 300°C. Comparison with a soft PZT shows that acceptor doping has a stronger influence on mechanically induced domain switching than on switching caused by electric fields. A quantitative analysis of spontaneous and remanent strain and polarization indicates that poling in the soft material is dominated by 180° domain processes, while non-180° processes dominate the strain behavior. If the mechanical load exceeds a threshold level, the “hardening” effect of the acceptor doping vanishes, and hard and soft materials behave identically. The results are discussed based on the defect dipole model and the charge drift model for hardening and aging in acceptor-doped ferroelectric ceramics.

Lattice dynamics and dielectric response of undoped, soft and hard PbZr0.42Ti0.58O3

Abstract: In this study, ceramic samples of lead zirconate titanate Pb(Zr0.42Ti0.58)O3 (PZT 42/58) doped with Fe (hard) and Nb (soft) were studied by Raman, infrared (IR) and THz spectroscopy in the temperature range from 900 to 20 K. From the evaluation of the IR and Raman phonons in undoped ceramics, we conclude that tetragonal PZT ceramics undergo a low-temperature phase transition to a tilted phase, revealed by anomalies in phonon parameters and the appearance of new modes. Doped samples also presented similar behaviour. The main differences between undoped and doped ceramics lie in the dielectric behaviour below phonon frequency range, where several mechanisms appear: a soft central mode (CM) located near 1 THz and two relaxations in the GHz range. Both types of doping raise the permittivity values below the phonon frequencies, not only increasing the dielectric contribution of the CM, but also modifying the dielectric response near the GHz range. Soft ceramics show higher permittivity with logarithmic increas...

Optimal Frequency Range Selection for PZT Transducers in Impedance-Based SHM Systems

Abstract: Piezoelectric transducers of PZT (lead zirconate titanate) have been widely used in structural health monitoring (SHM) systems based on the electromechanical (E/M) impedance technique. In this technique, damages in the structure are identified by measuring the electrical impedance of the transducer in an appropriate frequency range. Usually, the selection of the correct frequency range to detect and evaluate damage is obtained by trial and error methods. In this paper, it is proposed a formal procedure to determine the frequency ranges in which the PZT transducers are more sensitive for damage detection. Tests were carried out on specimens with different sizes and there was a good match between the theoretical and practical results.

Time Reversal Based Piezoelectric Transducer Self-diagnosis Under Varying Temperature

Abstract: Conventional structural health monitoring (SHM) studies using surface-mountable wafer-type piezoelectric transducers such as Lead Zirconate Titanate (PZT) mainly have focused on structural damage identification, but not so much on functionality of the PZT transducers although the transducers themselves could be often the weakest link in the entire system. In this study, piezoelectric transducer self-diagnosis schemes are developed based on a time reversal process and explicitly considering temperature effects. Several transducer self-diagnosis indices are proposed so that debonded and cracked PZT conditions can be identified and distinguished from temperature variation. First, the proposed self-diagnosis schemes are theoretically formulated, and then the effectiveness of the proposed schemes under varying temperature is verified through numerical simulations and experimental tests.

Molten salt synthesis of PZT powder for direct write inks

Abstract: The preparation of lead zirconate titanate (PZT) powder by molten salt synthesis (MSS) is described and a mechanism proposed. The effect of process parameters, such as reaction time and temperature and heating rate, on particle size and shape was investigated. A reaction mechanism for the synthesis of PZT by molten salt method is proposed, where dissolved Pb initially reacts with insoluble TiO2 to form intermediate PbTiO3. Subsequently Zr diffuses into and reacts with PbTiO3 to form PZT. Spherical particles, ∼340 nm in size, were obtained, using a NaCl/KCl salt, by heating the starting materials at 850 °C for 60 min, with a ramp rate of 3.3 °C min−1.

Porous PZT Ceramics with High Hydrostatic Figure of Merit and Low Acoustic Impedance by TBA‐Based Gel‐Casting Process

Abstract: Porous lead zirconate titanate (PZT) ceramics with three-dimensionally interconnected pores were prepared using a novel tert-butyl alcohol-based gel-casting process, an unconventional technique in acquiring high-porosity ceramics. In the present work, PZT ceramics with porosity ranging from 31.3% to 58.6% were fabricated by adjusting the initial solid loading and sintering temperature. The fabricated samples were characterized in terms of both porous structure and functional properties to clarify the underlying correlation. With the increase of porosity, relative permittivity (er) decreased to a significantly low value compared with dense PZT ceramics while the longitude piezoelectric coefficient (d33) exhibited a moderate decline, which could be attributed to the unique structure with homogeneous pore distribution. As a result, the resultant samples possessed a high value of hydrostatic figure of merit, 4100 times higher than that of dense materials. The acoustic impedance (Z) showed a linear dependence on porosity with the lowest magnitude reaching 3.0 MRayls (10 6 kg . (m 2 . s) –1 ), hopefully leading to enhanced coupling with biological tissue or water.

Determination of reversible and irreversible contributions to the polarization and strain response of soft PZT using the partial unloading method

Abstract: Experimental work is aimed at systematically investigating the non-linear ferroelectric and ferroelastic behavior of a commercially available soft lead zirconate titanate (PZT) material. The fast partial unloading method is used to measure the material properties of unpoled soft PZT under pure electric field and of initially pre-poled soft PZT under compressive stress loading. In the first experiment using unpoled PZT, the evolution of piezoelectric constants and dielectric permittivity is determined as a function of electric field. It is found that the piezoelectric constants and dielectric permittivity depend on the electric field history. The results are used to separate the reversible strain and polarization from the irreversible ones caused by domain switching. In the second experiment using initially pre-poled PZT, it is found that the strain response is significantly dependent on the stress loading rate. The elastic moduli and piezoelectric coefficients are evaluated with respect to the compressive stress history. The measured longitudinal and transverse irreversible strains change significantly during both loading and unloading processes. An attempt is made to discuss the use of irreversible strain and irreversible polarization as internal variables for constitutive modeling. This investigation provides valuable information for modeling to predict the performance and for improving the reliability of piezoelectric devices.

Direct laser processing of bulk lead zirconate titanate ceramics

Abstract: Laser Engineered Net Shaping (LENS™) has been used to fabricate dense, net shape melt-cast structures of lead zirconate titanate (PZT), in a single step, directly on a metallic substrate by complete melting and resolidification of PZT powders. From our results, it appears that reasonable dielectric properties can be obtained in LENS™ processed PZT structures without post-fabrication heat treatments. Our results also demonstrate potential application of LENS™ towards direct fabrication of PZT based embedded sensors and transducers on structural components.

Fabrication and characterization of the multiferroic birelaxor lead-iron-tungstate/lead-zirconate-titanate

Abstract: We compare chemical solution deposition (CSD) and pulsed laser deposition (PLD), specimens of the room temperature, single-phase, multiferroic magnetoelectric, [PbFe0.67W0.33O3]x[PbZr0.53Ti0.47O3]1−x (PZTFWx∼0.40