R-curves of lead zirconate titanate (PZT)

R-curves were measured for ferroelectric ceramic lead zirconate titanate (PZT) using surface cracks in flexure (SCF) in a single composition of unpoled, ferroelastic PZT. The effects of several parameters on the R-curves were experimentally determined. These included grain size, indentation load, polishing away the residual stress zone associated with the Knoop indentation, and thermal depolarization after indentation. The larger grain size resulted in a higher plateau value of the R-curve, a result consistent with the larger amount of ferroelastic switching observed in the stress/strain curve. Increasing the indentation load from 10 to 50 N resulted in larger initial crack sizes. This had some effect on the early part of the R-curve, but did not much affect the plateau value. Polishing away the residual stress zone eliminated the residual stress contribution of the Knoop indentation to the stress intensity factor. This resulted in the most accurate measurement of the intrinsic toughness (0.4 MPa m^1/2). Thermal depolarization to remove any potential ferroelastic crack tip switching zone associated with the indentation had little or no effect on the measured R-curves.     

Synthesis of spherical lead zirconate titanate (PZT) nanoparticles by electrohydrodynamic atomisation

Abstract

This paper describes the production of spherical-shaped lead zirconate titanate (PZT) nanoparticles by the electrohydrodynamic atomisation (EHDA) process in order to make inks suitable for ink jet printing applications. PZT sols with different concentrations (0·1–0·6 M) were used as starting materials. Two different heating systems, gas heating and direct heating, were used in order to remove the solvent, reduce the particle size and stabilise the PZT particles. Several aspects have been considered, such as liquid flow rate, sol concentration and heat system temperature, and their influence on the particle dimension is determined. Using optimised processing parameters of direct heating at 520°C, 0·2 M precursor sol, flow rate of 0·2 mL h^?1 and field of 3 kV cm^?1, particles of 100–300 nm in diameter were synthesised. Following stabilisation at 300°C, the particles were suspended in a PZT sol to produce an ink suitable for ink jet printing.     

Processing and electromechanical properties of lead zirconate titanate thick films by electrophoretic deposition

Electrophoretic deposition (EPD) was used for the fabrication of piezoelectric [lead zirconate titanate (PZT)] thick films on alumina substrates. The EPD was performed in constant current mode from an ethanol based suspension consisting of PZT and PbO particles. The influence of addition of ethyl cellulose (EC) and sintering temperature on the thickness, density, homogeneity and functional response of PZT thick films is studied. Results show that the highest electromechanical performance is obtained for the PZT thick films sintered at 900 or 950°C, with a thickness coupling factor k_t of 50%. The addition of EC influenced the thickness of the PZT thick films but had only minor effect on the porosity content for sintering temperatures over 900°C. Moreover, elastic constants of the thick films based on the suspension with EC were lower, which leads to lower acoustic impedance (15?MRa) while maintaining high (k_t) value. In this last case, a better acoustic matching can be expected with propagation media such as water or biological tissues for ultrasound medical imaging applications.     

Sb2O3-modified lead zirconate titanate piezoelectric ceramics with enhancing piezoelectricity and low loss

Lead zirconate titanate (PZT)–based piezoelectric ceramics as important functional materials are widely used in many electromechanical devices. The piezoelectric coefficient and mechanical quality factor are vital property parameters for piezoelectric applications. However, the piezoelectric coefficient is inversely proportional to the mechanical quality factor, resulting in a strong limitation among wide applications. Herein, piezoelectric ceramics composed of (xSb₂O₃, 0.3-wt% MnCO₃)-doped (Pb_0.92Sr_0.08)(Zr_0.533Ti_0.443Nb_0.024)O₃ ((xSb, Mn)-PSZTN) were prepared by a conventional solid-state process. The excellent piezoelectric properties d₃₃ = 554 pC/N, k_p = 0.645, and high mechanical quality factor Q_m = 540 were simultaneously obtained at x = 0.1 ceramic in the morphotropic phase boundary region. The enhancement of piezoelectric properties was mainly due to the contribution of irreversible domain wall motion. In particular, the regulation of different defect chemical reactions on the properties showed that Sb₂O₃ could play the role of both donor and acceptor dopant. This work demonstrated that (0.1Sb, Mn)-PSZTN ceramic was a good candidate material for high-power piezoelectric devices.     

Hydrothermal synthesis of lead titanate and lead zirconate titanate electroceramic particles

Hydrothermal synthesis of two lead-based perovskite powder systems, lead titanate and lead zirconate titanate, was investigated. Phase-pure perovskite lead titanate and lead zirconate titanate with various morphologies have been synthesized by hydrothermal methods at 150° and 175°C, respectively. Solution pH should be greater than 14 to obtain the phase-pure perovskite phases in a reasonable time. In addition, the KOH concentration and the stirring rate significantly influence particle morphology of the hydrothermally derived PT and PZT. Therefore, these parameters can be used to tailor particle size and morphology.     

Dielectric and piezoelectric performance of gadolinium‐doped lead lanthanum zirconate titanate

In this article, polycrystalline samples of Gd³⁺ ion‐modified lead lanthanum zirconate titanate PLGZT: (Pb_0.94‐xGd_xLa_0.06)(Zr_0.52Ti_0.48)O₃; x = 0, 2, 4, 6, and 8% have been prepared by the sol‐gel autocombustion strategy. The structural properties of the prepared samples were analyzed by X‐ray diffraction profile (XRD), Fourier transform infrared spectra (FT‐IR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The samples were assigned to pure PZT perovskite tetragonal structure. Ag electrodes were made on both sides of the disks for measurements of electrical and dielectric properties at different temperatures ranging from 30 to 500°C at various frequencies. The maximum dielectric constant, Curie temperature (T_C), dielectric loss at T_C, and the piezoelectric charge coefficient d₃₃ ranges of the investigated samples were found to be 1850 to 2420, 350 to 399°C, 0.023 to 0.026, and 299 to 532 pC/N, respectively. Higher coefficients were reached for the 4 % Gd substitution. Finally, the obtained results indicate that these materials can be good candidates for ultrasonic transducers.     

Effect of heat treatment on the electrical properties of lead zirconate titanate/poly (vinylidene fluoride) composites

Ceramic/polymer composites are attracting increasing interest in materials research and practical applications due to the combination of excellent electric properties of piezoelectric ceramics and good flexibility of polymer matrices. In this case, the crystallization of the polymer has a significant effect on the electric properties of ceramic/polymer composites. Based on different heat treatment methods, the crystallization of poly(vinylidene fluoride) (PVDF) in composites of lead zirconate titanate (PZT) and PVDF can be controlled effectively. PZT/PVDF composites with various PVDF crystallizations exhibit distinctive dielectric and piezoelectric properties. When the crystallization of PVDF is 21%, the PZT/PVDF composites show a high dielectric constant (ε) of 165 and a low dielectric loss (tan δ) of 0.03 at 10³ Hz, and when the crystallization of PVDF reaches 34%, the piezoelectric coefficient (d₃₃) of PZT/PVDF composites can be up to ca 100 pC N^?1. By controlling the crystallization of PVDF, PZT/PVDF composites with excellent dielectric and piezoelectric properties were obtained, which can be employed as promising candidates in high‐efficiency capacitors and as novel piezoelectric materials. Copyright © 2010 Society of Chemical Industry     

Electrical fatigue behavior of lead zirconate titanate ceramic under elevated temperatures

The electrical fatigue behavior of lead zirconate titanate (PZT) ceramics is investigated under different temperatures. A bipolar triangular electric field with the amplitude of ±1.5 kV/mm and the frequency of 50 Hz is applied to samples up to 1 × 10⁶ cycles. The fatigue rate is found to be temperature dependent, and the fatigue degradation is represented by the loss of remnant polarization, dielectric constant, and piezoelectric constant increased with loading cycle numbers. The degradation, involving surface damage and crack propagation, is more pronounced in samples cycled at lower temperatures, and increases with increasing number of cycles. The temperature effect on fatigue degradation of the properties is described based on the field shielding effect caused by surface damage and fatigue-induced cracks. The effect is more dominant in case of higher cycling numbers and lower temperature fatigue due to higher strain mismatch between switchable and non-switchable domains. Moreover, Raman spectroscopy is used to determine the influence of fatigue on the ferroelectric domains in different areas of the specimens.     

Comparison of different sintering aids in cold sinter-assisted densification of lead zirconate titanate

Ceramics such as lead zirconate titanate (PZT) tend to dissolve incongruently, and thus pose a challenge in the cold sintering process. Moist lead nitrate has previously been shown to enable a cold sinter-assisted densification of PZT by a viscous phase sintering mechanism. In this paper, lead acetate trihydrate is demonstrated to lower the required temperature of the cold sintering step to 200°C. This densification process was described as a two-step process: cold sintering of PZT with lead acetate trihydrate and post-annealing the as-cold sintered PZT ceramics. Unlike in the case of lead nitrate, PZT densification with lead acetate trihydrate occurs by a liquid phase assisted sintering mechanism, leading to an as-cold sintered relative density of 84% at 200°C. After performing a post-anneal step at 900°C, >97% relative densities were achieved in samples that were cold sintered with lead acetate trihydrate. This step not only densified PZT but also refined the grain boundaries. In the post-annealed samples, the room-temperature relative permittivity at 100 Hz was ~1600, slightly higher than that reported in samples that used lead nitrate as a sintering aid; the loss tangent was about 3.8%. For measurements at 10 Hz, the remanent polarization in both cases was ~28 µC/cm². Both Rayleigh analysis and aging studies showed that a higher irreversible contribution to the permittivity exists in samples that used lead nitrate as a cold sintering aid.     

Thermal and dielectric behavior of flexible polycarbonate/lead zirconate titanate composite system

Polycarbonate (PC)/Lead Zirconate Titanate (PZT) composites were prepared using solution mixing method followed by hot pressing. The volume fraction of PZT particles was varied from 0 to 27.5%. SEM showed good dispersion of PZT in the PC matrix. XRD confirmed the perovskite structure of PZT and amorphous structure of polycarbonate. The dielectric constant of the composites measured at 1 kHz, increased ～3.5‐fold compared with pure PC. The modified Lichtenecker equation agreed well with the experimental data. There was no dispersion in the dielectric constant of the composites for the frequency range of 1 kHz to 10 MHz. However, at frequencies higher than 10 MHz significant drop in dielectric constant was observed. The dissipation factor of the composites was found below 0.02. However, above 1 MHz, an abrupt increment in the dissipation factor was observed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39913.     

Novel forming of columnar lead zirconate titanate structures

The present study is focused on the processing of columnar lead zirconate titanate (PZT) structures on Ti/Pt-coated silicon substrates using electrohydrodynamic deposition. It was found that the as-deposited PZT structure is highly dependent on the concentration of the sprayed precursor, which is believed to be the characteristic of electrohydrodynamic deposition. 0.01, 0.03, 0.06, 0.12, 0.3 and 0.6 M PZT sols were used to prepare as-deposited structures. Columnar PZT structures, which are important for the processing of 1-3 composites, were obtained with the 0.6 M sol. As-deposited and heat-treated columnar PZT structures were investigated using scanning electron microscopy and X-ray diffraction. The development of the PZT columns was studied by observing the cross-section of the structures deposited over different time sprays, revealing a three-stage growth process for these structures. The affect of substrate temperature on the columnar structure was also analysed by studying the density of the columns. Finally, a 1-3 composite was produced by infiltrating photoresists into the columnar PZT structures and the relative permittivity and dissipation factor of such composite were measured as 105 and 0.021. Modelling the structures as a PZT and a polymer capacitor connected in parallel in the PZT/polymer composite suggests that the relative permittivity of PZT columnar material is approximately 154.     

Flash sintering of lead zirconate titanate (PZT) ceramics: Influence of electrical field and current limit on densification and grain growth

Flash sintering of lead zirconate titanate ceramics were investigated under DC electric fields ranging from 300 to 600?V/cm. The onset temperature for flash sintering significantly decreased with the electrical field to a lower limit of furnace temperature of 538?°C at 600?V/cm. The retardation of grain growth was observed, and the grain size decreased with increasing the electrical field. The current limit had a great influence on the density and grain size of specimen. During the flash sintering process, power dissipation first rose abruptly to a maximum value, then declined sharply to a steady state. Meanwhile, optical glow of specimen was observed. Using black body radiation model, the actual specimen temperature was estimated, which was too low to obtain the full dense ceramics in 30?s. It was suggested that Joule heating, ultra-high heating rate and high concentrations of defects were responsible for flash sintering of PZT ceramics.     

Effect of lead content on the performance of niobium‐doped {100} textured lead zirconate titanate films

Niobium‐doped, {100} textured, gradient‐free, lead zirconate titanate (PZT) films were fabricated from solutions with different lead contents. Film lead content was controlled through changes in the average solution lead excess from 14.7% to 17 at.%. The low field dielectric response as well as the polarization‐electric field hysteresis loops were not a strong function of lead content. However, films with lower lead contents in the precursor tended to withstand higher poling fields than films prepared from more lead‐rich precursors. Although no residual PbO was observed at the grain boundaries, films prepared from more lead‐rich solutions had higher levels of grain‐boundary porosity, lower breakdown strengths, and lower threshold electric fields at which cracking was observed.     

Hydrothermal synthesis of lead zirconium titanate (PZT) powders and their characteristics

The combined influences of KOH initial concentration and initial lead precursor excess on the characteristics (morphology, powder density, specific surface area, crystalline structure and powder chemical composition) and sintering behaviour of hydrothermally synthesised powders, have been investigated. Optimised conditions (low KOH concentration and presence of lead excess in the feedstock) have been determined that lead to fine deagglomerated and reactive PZT powders densifying at about 850°C. A Pb-rich surface layer has been identified over the grains, that is responsible for this low sintering temperature. Despite the large excess of lead, the core of powders remains lead deficient. But by lowering [KOH]_o, it is possible to keep the lead deficiency within a few percent.     

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 2 h 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 100 kHz) 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.     

Low-temperature preparation of hydrothermal lead zirconate titanate thin films

In preparing lead zirconate titanate thin films under hydrothermal conditions, we investigated the effects of concentrations of nutrient and mineralizer, reaction time and reaction temperature on crystallinity, grain size and shape. Experiments were performed in the ranges of 0.1-1.0M Pb(NO₃)₂, and 0-6.0M KOH with varying reaction time from 0 to 48 hours at 60-200 °C. In the experiment, lead zirconate titanate thin film of homogeneous crystalline grain was obtained through a 24 hour reaction with 0.4M Pb(NO₃)₂ and 5.0M KOH at 140 °C. The thickness of the film was 0.9-1.6 μm, and it exhibited a saturation polarization (Ps) of 18.3 μC/cm², remnant polarization (Pr) of 7.4 μC/ cm₂ and coercive field (Ec) of 0.41 kV/cm. The dielectric constant and loss (δ) measured at 1 kHz were approximately 1020 and 0.15, respectively.     

Transparent lead lanthanum zirconate titanate (PLZT) ceramic fibers for high-frequency ultrasonic transducer applications

This paper presents fabrication of transparent lanthanum zirconate titanate (PLZT) fibers using extrusion technique. The diameter of the sintered PLZT fiber is about 400-μm, and the fibers exhibit very good transparency. Measured dielectric constant, remnant polarization and coercive field of PLZT fiber were found to be 2340, 22.5-μC/cm², and 9.8-kV/cm, respectively. The transparent piezoelectric materials may exhibit great potential for Photoacoustic (PA) imaging and hybrid intravascular imaging combining OCT and ultrasound imaging by using the transparent fiber as the path of light propagation and ultrasonic transducer material. In our study, these transparent PLZT fibers were designed to fabricate two types of high-frequency ultrasonic transducers: small aperture single PLZT fiber/epoxy composite and large aperture 1–3 PLZT fiber/epoxy composite ultrasonic transducers. Besides, a 20-μm tungsten wire phantom and the cornea of the porcine eye were also imaged with the 1–3 PLZT fiber/epoxy composite ultrasonic transducer to demonstrate its imaging capability.     

Mechanical and fracture behavior of an artificially ultraviolet‐irradiated poly(ethylene‐carbon monoxide) copolymer

In this work, 1 wt % carbon monoxide (CO) poly(ethylene‐carbon monoxide) (ECO) copolymer sheets were artificially exposed to ultraviolet (UV) light with a power density of 3 mW/cm² for up to 130 h. A thorough mechanical characterization of the irradiated material was conducted, in which both the stress–strain data and the values of the quasistatic crack initiation and growth toughness were measured and correlated with companion uniaxial tensile tests and single‐edge‐notched fracture tests. Average values of the elastic modulus, failure strain, and failure stress were determined from the tensile tests. The full‐field optical technique of digital image correlation was used to quantify in‐plane deformation (displacements and displacement gradients) during the fracture experiments and to extract values of the crack initiation and growth fracture toughness. The elastic modulus increased monotonically with UV irradiation for the exposure times used in this investigation. In addition, for low irradiation times of less than 5 h, both the failure strain and failure stress of ECO decreased, and this caused a corresponding decrease in the crack initiation and growth toughness. However, for longer irradiation times, the failure strain remained almost invariable, whereas the failure stress increased by about 25% over that of unirradiated ECO. As a result, for longer irradiation times (>5 h), 1 wt % CO ECO became not only stiffer but also stronger and tougher, as quantified by companion fracture experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 139–148, 2004     

Highly tailorable electromechanical properties of auxetic piezoelectric ceramics with ultra-low porosity

Conventional porous piezoelectric ceramics can possess superior figures of merit only at very high values of porosity, leading to bad fragileness, small stiffness, low toughness, and the difficulty of polarization. To this end, this study for the first time shows that it is possible that the piezoelectric ceramic with ultra-low porosity is capable of superior figures of merit based on the concept of auxetic piezoelectric ceramics. Owing to the ultra-low porosity and auxetic effect, the auxetic piezoelectric ceramic shall also possess larger stiffness, higher toughness, and is more easily polarized. First, the auxetic piezoelectric ceramic with ultra-low porosity is proposed to achieve highly tunable electromechanical properties on the basis of the rotating square mechanism. Then, using a multiscale finite element method, the effects of geometric architecture and polarization directions on the electromechanical properties including Poisson's ratios, elastic coefficients, piezoelectric stress coefficients, dielectric coefficients, and figures of merit in the auxetic piezoelectric ceramics are investigated in detail. Furthermore, the stress fields in conventional and proposed porous piezoelectric ceramics subjected to mechanical and electrical loads are compared and discussed. Finally, it can be concluded that the auxetic piezoelectric ceramic exhibits (a) giant negative Poisson's ratios (smaller than ), (b) negative elastic coefficients, (c) more extensible, higher piezoelectric sensitivity, lower acoustic impedance, stronger crack resistance than conventional porous piezoelectric ceramics with the same porosity, and (d) larger stiffness than conventional porous piezoelectric ceramics with similar figures of merit.     

Cr-doped lead lanthanum zirconate titanate (PLZT) ceramics for pyroelectric and energy harvesting device applications

Cr-doped PLZT ceramic compositions (Pb_0.94La_0.06)(Zr_0.57Ti_0.43)O₃ + X mol% of Cr₂O₃, (X = 0.00, 0.05, 0.11 and 0.16) prepared by solid state reaction have been characterized for their structural and pyroelectric properties. Rietveld refinement of X-ray diffraction (XRD) data reveals tetragonal structure with space group P4mm, and the tetragonality ratio c/a increases with increasing Cr content. Raman spectroscopy reveals the coexistence of both rhombohedral and tetragonal phases in the system suggesting a polymorphic character providing easy rotation of polarization and improved pyroelectric response. Figures of merit (FOM) useful for device design have been estimated using the measured material properties such as pyroelectric current, density, specific heat, polarization, dielectric constant and loss. A specific Cr₂O₃ content of X = 0.11 in PLZT is found to exhibit optimum performance characteristics for pyroelectric and thermal energy harvesting applications.