Showing papers on "Lead zirconate titanate published in 2011"
TL;DR: In this paper, the temperature-dependent dielectric permittivity of BNT-6BT was studied to disentangle the existing unclear issues over the crystallographic aspects and phase stability of the system.
Abstract: Temperature-dependent dielectric permittivity of 0.94(Bi1/2Na1/2)TiO3-0.06BaTiO3 (BNT-6BT) lead-free piezoceramics was studied to disentangle the existing unclear issues over the crystallographic aspects and phase stability of the system. Application of existing phenomenological relaxor models enabled the relaxor contribution to the entire dielectric permittivity spectra to be deconvoluted. The deconvoluted data in comparison with the temperature-dependent dielectric permittivity of a classical perovskite relaxor, La-modified lead zirconate titanate, clearly suggest that BNT-6BT belongs to the same relaxor category, which was also confirmed by a comparative study on the temperature- dependent polarization hysteresis loops of both materials. Based on these results, we propose that the low-temperature dielectric anomaly does not involve any phase transition such as ferroelectric- to-antiferroelectric. Supported by transmission electron microscopy and X-ray diffraction experiments at ambient temperature, we propose that the commonly observed two dielectric anomalies are attributed to thermal evolution of ferroelectric polar nanoregions of R3c and P4bm symmetry, which coexist nearly throughout the entire temperature range and reversibly transform into each other with temperature.
716 citations
TL;DR: In this article, the effects of frequency, temperature and microstructure (point defects, grain size and texture) on the ferroelectric properties of several Ferroelectric compositions, including BaTiO3, lead zirconate titanate (PZT), lead-free Na0.5K0.15Nd0.06FeO3.
Abstract: Triangular voltage waveform was employed to distinguish the contributions of dielectric permittivity, electric conductivity and domain switching in current-electric field curves. At the same time, it is shown how those contributions can affect the shape of the electric displacement — electric field loops (D–E loops). The effects of frequency, temperature and microstructure (point defects, grain size and texture) on the ferroelectric properties of several ferroelectric compositions is reported, including: BaTiO3; lead zirconate titanate (PZT); lead-free Na0.5K0.5NbO3; perovskite-like layer structured A2B2O7 with super high Curie point (Tc); Aurivillius phase ferroelectric Bi3.15Nd0.5Ti3O12; and multiferroic Bi0.89La0.05Tb0.06FeO3. This systematic study provides an instructive outline in the measurement of ferroelectric properties and the analysis and interpretation of experimental data.
285 citations
TL;DR: In this paper, high-resolution powder x-ray diffraction patterns reveal peak splitting in the room temperature phase that evidence the true structure as monoclinic with space group Cc.
Abstract: Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. Na0.5Bi0.5TiO3 (NBT), one of the widely studied compositions, has been assumed thus far to exhibit the rhombohedral space group R3c at room temperature. High-resolution powder x-ray diffraction patterns, however, reveal peak splitting in the room temperature phase that evidence the true structure as monoclinic with space group Cc. This peak splitting and Cc space group is only revealed in sintered powders; calcined powders are equally fit to an R3c model because microstructural contributions to peak broadening obscure the peak splitting.
268 citations
TL;DR: In this article, the authors measured a full set of elastic, piezoelectric, and dielectric properties for the MPB composition, Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 (BZT-50BCT), by using a resonance method.
Abstract: There is an urgent demand for high performance Pb-free piezoelectrics to substitute for the current workhorse, the lead zirconate titanate (PZT) family. Recently, a triple point (also tricritical point) type morphotropic phase boundary (MPB) in Pb-free Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 system has been reported that shows equally as excellent piezoelectricity as soft PZT at room temperature (Liu and Ren6). In the present study, we measured a full set of elastic, piezoelectric, and dielectric properties for the MPB composition, Ba(Zr0.2Ti0.8)O3-50(Ba0.7Ca0.3)TiO3 (BZT-50BCT), by using a resonance method. The resonant method gives piezoelectric properties d33 = 546 pC/N, g33 = 15.3 × 10−3 Vm/N, electromechanical coupling factor k33 = 65%, and the elastic constant s33E = 19.7 × 10−12 m2/N, c33E = 11.3 × 1010 N/m2, which are close to the properties of soft PZT (PZT-5A). Furthermore, the piezoelectric coefficients (k33, d33), the ferroelectric properties (coercive field, remnant polarization), and the elastic ...
238 citations
TL;DR: A strategy for integrating nanoribbons of one of the most widely used ferroelectric ceramics, lead zirconate titanate, in "wavy" geometries, on soft, elastomeric supports to achieve reversible, linear elastic responses to large strain deformations, without any loss in ferro electric or piezoelectric properties is reported.
Abstract: Applications of ferroelectric ceramics, ranging from components for sensors, memory devices, microelectromechanical systems, and energy convertors, all involve planar and rigid layouts. The brittle nature of such materials and their high-temperature processing requirements limit applications to devices that involve only very small mechanical deformations and narrow classes of substrates. Here, we report a strategy for integrating nanoribbons of one of the most widely used ferroelectric ceramics, lead zirconate titanate, in “wavy” geometries, on soft, elastomeric supports to achieve reversible, linear elastic responses to large strain deformations (i.e., stretchable properties), without any loss in ferroelectric or piezoelectric properties. Theoretical and computational analysis of the mechanics account for these characteristics and also show that the amplitudes of the waves can be continuously tuned with an applied electric field, to achieve a vertical (normal) displacement range that is near 1000 times l...
194 citations
TL;DR: The results indicate that higher aspect ratio fillers show promising potential to improve the energy density of nanocomposites, leading to the development of advanced capacitors with high energy density.
Abstract: High energy storage plays an important role in the modern electric industry. Herein, we investigated the role of filler aspect ratio in nanocomposites for energy storage. Nanocomposites were synthesized using lead zirconate titanate (PZT) with two different aspect ratio (nanowires, nanorods) fillers at various volume fractions dispersed in a polyvinylidene fluoride (PVDF) matrix. The permittivity constants of composites containing nanowires (NWs) were higher than those with nanorods (NRs) at the same inclusion volume fraction. It was also indicated that the high frequency loss tangent of samples with PZT nanowires was smaller than for those with nanorods, demonstrating the high electrical energy storage efficiency of the PZT NW nanocomposite. The high aspect ratio PZT NWs showed a 77.8% increase in energy density over the lower aspect ratio PZT NRs, under an electric field of 15 kV mm − 1 and 50% volume fraction. The breakdown strength was found to decrease with the increasing volume fraction of PZT NWs, but to only change slightly from a volume fraction of around 20%–50%. The maximum calculated energy density of nanocomposites is as high as 1.158 J cm − 3 at 50% PZT NWs in PVDF. Since the breakdown strength is lower compared to a PVDF copolymer such as poly(vinylidene fluoride-tertrifluoroethylene-terchlorotrifluoroethylene) P(VDF-TreEE-CTFE) and poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP), the energy density of the nanocomposite could be significantly increased through the use of PZT NWs and a polymer with greater breakdown strength. These results indicate that higher aspect ratio fillers show promising potential to improve the energy density of nanocomposites, leading to the development of advanced capacitors with high energy density.
185 citations
TL;DR: In this paper, a polyvinylidene fluoride/lead zirconate titanate nanocomposite thin films (PVDF/PZT-NPs) were successfully prepared by mixing fine Pb(Zr 0.52,Ti 0.48 )O 3 nanoparticles into a PVDF solution under ultrasonication.
131 citations
TL;DR: The microscopic origin of the macroscopic ferro- and piezoelectric properties of the most widely used ferroelectric material, lead zirconate titanate, is described.
Abstract: An in situ structural description of the origin of the ferroelectric properties as a function of the applied electric field E was obtained by synchrotron x-ray diffraction. A setup was used to average the effects of the preferred orientation induced by the strong piezoelectric strain and solve in situ the crystal structure as a function of the applied electric field. Hence, we were able to describe the microscopic origin of the macroscopic ferro- and piezoelectric properties of the most widely used ferroelectric material, lead zirconate titanate.
126 citations
TL;DR: In this paper, a PZT patch covered with asphalt lacquers is embedded into one of concrete cubes to measure the compressive strength gain of concrete since the conventional nondestructive detection techniques have many limitations.
113 citations
TL;DR: In this paper, a single-phase, low-loss, room-temperature multiferroic with magnetoelectric coupling was proposed, which combines x-ray scattering, magnetic and polarization hysteresis in both phases, plus a second-order dielectric divergence for an unambiguous assignment as a C2v-C4v (Pmm2-P4mm) transition.
Abstract: Mixing 60-70% lead zirconate titanate with 40-30% lead iron tantalate produces a single-phase, low-loss, room-temperature multiferroic with magnetoelectric coupling: (PbZr0.53Ti0.47O3) (1-x)- (PbFe0.5Ta0.5O3)x. The present study combines x-ray scattering, magnetic and polarization hysteresis in both phases, plus a second-order dielectric divergence (to epsilon = 6000 at 475 K for 0.4 PFT; to 4000 at 520 K for 0.3 PFT) for an unambiguous assignment as a C2v-C4v (Pmm2-P4mm) transition. The material exhibits square saturated magnetic hysteresis loops with 0.1 emu/g at 295 K and saturation polarization Pr = 25 μC/cm2, which actually increases (to 40 μC/cm2) in the high-T tetragonal phase, representing an exciting new room temperature oxide multiferroic to compete with BiFeO3. Additional transitions at high temperatures (cubic at T>1300 K) and low temperatures (rhombohedral or monoclinic at T<250 K) are found. These are the lowest-loss room-temperature multiferroics known, which is a great advantage for magnetoelectric devices.
97 citations
TL;DR: In this article, a range of ceramics were prepared by substituting 0.5-2 at.% of Fe or Mn for TiO 3 and it was found that a low dopant concentration (0.5 at.%) increases the depolarization temperature (T d ) with a minimal loss in room temperature d 33, allowing for high piezoelectric coefficients at elevated temperatures.
Abstract: Bismuth-based ferroelectric ceramics are currently under intense investigation for their potential as Pb-free alternatives to lead zirconate titanate-based piezoelectrics. The present work evaluated the thermal depoling behavior of various compositions of Na 0.5 Bi 0.5 TiO 3 (NBT), one of the Bi-based materials of broad interest, through in situ and ex situ measurements of the piezoelectric constant (d 33 ). A range of ceramics was prepared by substituting 0.5-2 at.% of Fe or Mn for Ti. It was found that a low dopant concentration (0.5 at.%) increases the depolarization temperature (T d ) with a minimal loss in room temperature d 33 , allowing for high piezoelectric coefficients at elevated temperatures. For example, 0.5 at.% Fe substitution leads to an enhanced piezoelectric coefficient of d 33 of 133 pm/V at an elevated temperature of 180°C. However, with further increase of dopant concentration, T d decreases in both Mn- and Fe-doped NBT. The in situ depoling measurements of 0.5 at.% Fe- and Mn-doped NBT in the present work exhibit the potential for higher temperature applications.
01 Jul 2011
TL;DR: In this paper, a large-scale density functional theory (DFT) investigation of the ABO3 chemical space in the perovskite crystal structure is presented, with the aim of identifying those that are relevant for forming piezoelectric materials.
Abstract: We present a large-scale density functional theory (DFT) investigation of the ABO3 chemical space in the perovskite crystal structure, with the aim of identifying those that are relevant for forming piezoelectric materials. Screening criteria on the DFT results are used to select 49 compositions, which can be seen as the fundamental building blocks from which to create alloys with potentially good piezoelectric performance. This screening finds all the alloy end points used in three well-known high-performance piezoelectrics. The energy differences between different structural distortions, deformation, coupling between the displacement of the A and B sites, spontaneous polarization, Born effective charges, and stability is analyzed in each composition. We discuss the features that cause the high piezoelectric performance of the well-known piezoelectric lead zirconate titanate (PZT), and investigate to what extent these features occur in other compositions. We demonstrate how our results can be useful in the design of isovalent alloys with high piezoelectric performance.
TL;DR: A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme that uses radiation heating and natural cooling such that the temperature varies between hot and cold regions.
Abstract: A method of continuously harvesting energy from pyroelectric materials is demonstrated using an innovative cyclic heating scheme. In traditional pyroelectric energy harvesting methods, static heating sources are used, and most of the available energy has to be harvested at once. A cyclic heating system is developed such that the temperature varies between hot and cold regions. Although the energy harvested during each period of the heating cycle is small, the accumulated total energy over time may exceed traditional methods. Three materials are studied: a commonly available soft lead zirconate titanate (PZT), a pre-stressed PZT composite, and single-crystal PMN-30PT. Radiation heating and natural cooling are used such that, at smaller cyclic frequencies, the temporal rate of change in temperature is large enough to produce high power densities. The maximum power density of 8.64 μW/cm3 is generated with a PMN-30PT single crystal at an angular velocity of 0.64 rad/s with a rate of 8.5°C/s. The pre-stressed PZT composite generated a power density of 6.31 μW/cm3, which is 40% larger than the density of 4.48 μW/cm3 obtained from standard PZT.
TL;DR: Ferroelectric lead-free thin films were successfully deposited by pulsed laser deposition on PZT substrates using a ceramic BCZT target prepared by conventional solid state reaction.
Abstract: Ferroelectric lead-free thin films of 05(Ba07Ca03TiO3) – 05[Ba(Zr02Ti08)O3] (BCZT) were successfully deposited by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates using a ceramic BCZT target prepared by conventional solid state reaction The in (111) direction orientated 600 nm thick films shows a clamped piezoelectric response of approximately d33,f = 80 pm/V and a dielectric coefficient of about ɛr = 1010; these are close to values obtained for lead zirconate titanate (PZT) films
TL;DR: In this paper, the behavior of two sets of woven fiberglass/epoxy specimens, one with embedded and one with surface-mounted piezoelectric wafer transducers (lead zirconate titanate), were tested under axial tensile fatigue at high stress ratio, and the transducers were interrogated in pitch-catch mode at different stages of the specimens' life, while they were subjected to the mean test load (the testing machine is paused).
Abstract: The need to understand and monitor the integrity of structural components made of composite materials is becoming critical, due to an increase of the use of composites in aerospace, civil, wind energy, and transportation engineering. Off-the-shelf piezoelectric transducers embedded inside the composites or bonded onto the structure surface are a pos- sible solution for on-line structural health monitoring and non-destructive evaluation: they can be used to generate Lamb waves, which are able to detect damage. This article focuses on the behavior of two sets of woven fiberglass/epoxy specimens, one with embedded, one with surface-mounted piezoelectric wafer transducers (lead zirconate titanate). The specimens are tested under axial tensile fatigue at high stress ratio, and the transducers are interrogated in pitch-catch mode at different stages of the specimens' life, while they are subjected to the mean test load (the testing machine is paused). A novel signal processing technique based on wavelet thresholding/denoising and Gabor wavelet transform is discussed. This technique identifies changes in boundary conditions, loading/unloading prior to damage and during damage. It appears to correlate the contour area changes with the so-called characteristic damage state observed in the literature in composite laminates under tensile fatigue.
TL;DR: A comprehensive review of porosity origin, microstructure peculiarities, fabrication methods, and mathematical models, as well as systematic experimental data for different porous piezoceramics with 3-0/3-3 connectivity is presented.
Abstract: A comprehensive review of porosity origin, microstructure peculiarities, fabrication methods, and mathematical models, as well as systematic experimental data for different porous piezoceramics with 3-0/3-3 connectivity is presented. New families of porous piezoceramics based on lead zirconate titanate (PZT), lead titanate, lead metaniobate, and sodium-potassium niobate compositions, with properties combining better parameters of PZT, PN-type ceramics, and 1-3 composites are introduced. Piezoelectric resonance analysis methods for automatic iterative evaluation of complex material parameters and the full sets of complex constants for different porous piezoceramics are presented. Numerical FEM calculations were critically compared with the results of various approximated formulas, unit cell models, and experimental data for different porous piezoceramics. Microstructural and physical mechanisms of losses and dispersion in porous piezoceramics, as well as technological aspects of their large-scale manufacture and application in ultrasonic devices were considered. The results of SEM microstructure analysis and microstructure-properties interrelations were discussed. Recent advances in fabrication methods for nano- and microporous piezoceramics and ceramic piezocomposites were discussed.
TL;DR: In this article, the strain mediated magnetoelectric (ME) coupling was studied in bilayers of lead zirconate titanate (PZT) and a ferromagnetic layer that is functionally stepped.
Abstract: The strain mediated magnetoelectric (ME) coupling is studied in bilayers of lead zirconate titanate (PZT) and a ferromagnetic layer that is functionally stepped. Nickel with negative piezomagnetic coefficient $q$ and Metglas with positive $q$ are bonded to achieve the desired step in $q$ for the ferromagnetic phase. Samples of PZT-Ni-Metglas and PZT-Metglas-Ni are used for measurements of ME voltage coefficient (MEVC) at low frequencies and at frequencies corresponding to bending resonance. It is shown that at low frequencies the bending moment due to stepped-$q$ counteracts the asymmetry-related flexural strain in the sample and enhances the strength of ME coupling. The MEVC is found to be as high as in symmetric trilayers in which flexural deformation is absent, and it ranges from 0.4 to 3.4 V/cm Oe depending on the grading scheme and the thickness of Metglas. A resonance enhancement of the MEVC to 40--220 V/cm Oe is measured at bending modes for samples clamped at one end. Samples of PZT-Ni-Metglas show a higher MEVC than for PZT-Metglas-Ni both at low frequencies and at bending resonance. The $q$-stepped composites are of importance for ultra-sensitive magnetic field sensors.
TL;DR: In this paper, a piezoelectrically actuated high-fill-factor tip-tilt-piston (TTP) micromirror with small tilt and lateral shift during scanning is presented.
Abstract: This paper presents the design, fabrication and characterization of a piezoelectrically actuated high-fill-factor tip-tilt-piston (TTP) micromirror with small tilt and lateral shift during scanning. The piezoelectric material is a sol–gel lead zirconate titanate (PZT) thin film with a Zr/Ti ratio of 53/47. The small initial tilt and lateral-shift-free (LSF) of the mirror plate is achieved by a folded, three-segment piezoelectric unimorph actuator design. The piezoelectric unimorph actuation beams consist of Pt/Ti/PZT/Pt/Ti/SiO 2 multilayers, which are released via undercutting the substrate silicon. The fabricated piezoelectric micromirror can be actuated about two rotational axes in the mirror plane and for translational vertical scan (piston actuation). The resonant frequencies of the piston and rotation modes are 316 Hz and 582 Hz, respectively. At their respective resonant frequencies, the maximum piston magnitude at resonant driving is 32 μm, and the two-dimensional rotating scan ranges are about 5°, both measured at a 2V pp sinusoidal driving voltage.
TL;DR: In this article, a magnetic field sensor based on the nonlinear nature of the magnetostrictive response of a magneto-electric (ME) heterostructure has two orders of magnitude improvement in sensitivity and signal to noise ratio compared with a conventional dc-biased configuration.
Abstract: A magnetic field sensor based on the nonlinear nature of the magnetostrictive response of a magneto-electric (ME) heterostructure has two orders of magnitude improvement in sensitivity and signal-to-noise ratio compared with a conventional dc-biased configuration. The sensor consists of a longitudinally magnetized and transversely poled lamination of iron-cobalt-boron (Metglas) and lead zirconate titanate (PZT). The ac-modulated sensor has enhanced environmental noise immunity and does not require a dc magnetic bias field. Combined, these advantages hold promise for the development of miniature ME sensor elements for applications with size and weight limitations.
TL;DR: In this paper, the temperature dependence of the lowfrequency vibrations, related to Pb atoms, was analyzed in terms of two overdamped modes-a soft mode and an anharmonic hopping central mode-in the cubic and high-temperature ferroelectric phase with the doubled unit cell.
Abstract: Infrared (IR) reflectivity spectra of nominally pure Pb(Zr1-xTix)O-3 ceramics with different Ti/Zr concentration (x = 0.42-0.58) were measured and evaluated, along with the time-domain terahertz transmittance spectra in the temperature range 10 K-900 K. The temperature dependence of the low-frequency vibrations, related to Pb atoms, was analyzed in terms of two overdamped modes-a soft mode and an anharmonic hopping central mode-in the cubic and high-temperature ferroelectric phase and three main vibrations in the low-temperature ferroelectric phase with the doubled unit cell: two E-symmetry modes (the soft mode and a mode corresponding to antiphase vibrations of neighboring Pb atoms in the terahertz range) and the antiferrodistortive mode producing the antiphase tilts of the oxygen octahedra. The last bare mode is not IR active, but it becomes activated by coupling with the soft mode. As predicted by theory, the intrinsic permittivity of Pb(Zr1-xTix)O-3 has a maximum at the morphotropic phase boundary, although this represents just a small percentage of the total permittivity at lower frequencies. Its maximum is linked to the softening of the anharmonic vibrations of Pb ions, perpendicular to the polarization, and shifts from x = 0.48 at room temperature to x = 0.52 at 10 K.
TL;DR: In this article, a lead-free Li-(K,Na)NbO3 (KNN) piezoceramics with high normalized strain d33* up to 538 pm/V at electric fields as low as 1 kV/mm, comparable to a commercial soft lead zirconate titanate (PZT) sample, is presented.
Abstract: Lead-free Li-(K,Na)NbO3 (KNN) piezoceramics shows surprisingly high normalized strain d33* up to 538 pm/V at electric fields as low as 1 kV/mm, comparable to a commercial soft lead zirconate titanate (PZT) sample. The special treating process of aging and re-poling is essential for this achievement. The extrinsic piezoelectric contribution related to domain wall motion is proposed of primary responsibility for the strain, which endows the sample with a direct piezoelectric coefficient of 324 pC/N. Strain behavior with regard to both electric field level and frequency was investigated to prove the assumption. The present study proves the possibility of preparing PZT-comparable lead-free piezoceramics in simply Li-doped KNN by conventional sintering.
TL;DR: In this paper, high-textured Pb(Zr0.53Ti0.47)O3 films were grown on platinized Si substrates using sol-gel deposition.
Abstract: Highly (100)-textured Pb(Zr0.53Ti0.47)O3 films (Lotgering factors ≥90%) with thicknesses ranging from 20 to 260 nm were grown on platinized Si substrates using sol-gel deposition. Ferroelectric hysteresis, low field dielectric permittivity, and nonlinear dielectric response as well as converse longitudinal piezoelectric response (d33,f) of the ultrathin films were studied at 1 kHz. The measurements revealed the existence of a critical film thickness, ∼50 nm, below which the extrinsic contributions to the dielectric response are almost completely suppressed. Piezoelectric response of the films also showed a significant (∼50%) drop at the same critical thickness. Due to the columnar microstructure of these films the critical dimension of the ferroelectric is represented by the thickness rather than the lateral grain size, where the latter is invariant across the samples. The critical thickness led also to a deviation of the thickness dependence of the dielectric permittivity from the in-series capacitors mo...
TL;DR: Rietveld refinement of different structural models using neutron diffraction data for a series of powders of lead zirconate titanate, PbZr(1 - x)Ti(x)O(3) (PZT), finds that at all the compositions and temperatures studied the best results include contributions from more than one phase.
Abstract: Rietveld refinement of different structural models using neutron diffraction data for a series of powders of lead zirconate titanate, PbZr1 − xTixO3 (PZT), is described. It is found that at all the compositions and temperatures studied the best results include contributions from more than one phase in order to fit the data. Consequently a new phase diagram is proposed.
TL;DR: The obtained results show that this broadband array transducer is promising for acquiring high-resolution endoscopic ultrasonic images in many clinical applications.
Abstract: In this paper, 07Pb(Mg1/3Nb2/3)O3-03PbTiO3 (PMN-PT) single crystal/epoxy 1/3 composite was used as the active material of the endoscopic ultrasonic radial array transducer, because this composite exhibited ultrahigh electromechanical coupling coefficient (kt = 081%), very low mechanical quality factor (Qm = 11) and relatively low acoustic impedance (Zt = 12 MRayls) A 691 MHz PMN-PT/epoxy 1/3 composite radial array transducer with 64 elements was tested in a pulseecho response measurement The -6-dB bandwidth of the composite array transducer was 102%, which was ~30% larger than that of traditional lead zirconate titanate array transducer The two-way insertion loss was found to be -323 dB The obtained results show that this broadband array transducer is promising for acquiring high-resolution endoscopic ultrasonic images in many clinical applications
Abstract: Mechanisms and magnitudes of the large piezoelectric response observed in lead-free (1-x) BiFeO3-xBaTiO3 (BFBT) ceramics are investigated. Preceding studies reported significant strain hysteresis and hard ferroelectric behavior in BFBT leading to a small low-field piezoelectric coefficient, instability of the poled domain state, and rapid degradation of piezoelectric properties. The current investigation shows that under application of a suitable direct current (dc) bias to stabilize the ferroelectric phase low- and high-field piezoelectric coefficients (d33) of 150 pC/N and 250 pC/N are observed for the composition 0.67BiFeO3-0.33BaTiO3 + 0.1 wt% MnO with a Curie temperature of 605 °C. Such enhancement of electromechanical properties under dc bias is in contrast to the expected behavior in traditional piezoelectric materials such as soft lead zirconate titanate (PZT). The large piezoelectric coefficients confirm strong intrinsic and extrinsic contributions to the piezoelectric response in BFBT, which coupled with high ferroelectric Curie temperature TC > 500 °C, suggests BFBT-based materials as promising lead-free alternatives to PZT piezoceramics.
TL;DR: In this paper, a magnetic field sensor based on magnetoelectric coupling is presented, which demonstrates high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency.
Abstract: A miniature, quasi one dimensional, magnetic field sensor based on magnetoelectric coupling is presented. The magnetoelectric sensor makes use of the d31 coupling mode between a piezoelectric lead zirconate titanate tube and FeNi magnetostrictive wire. The sensors demonstrate high sensitivity, high signal-to-noise ratio, and low noise floor at zero DC magnetic bias field and at low frequency resulting in smaller, lower power consumption, and volumetric efficiency. Experiments indicate a zero bias field sensitivity of 16.5 mV/Oe at 100 Hz stemming from a magnetoelectric coefficient of 1.65 V/cm-Oe. The results are quantitatively described by a theoretical model of laminate composites.
TL;DR: In this paper, the symmetry of single-crystal piezoelectric PbZr was investigated by high-resolution x-ray diffraction, both at room temperature and up to and above the Curie temperature.
Abstract: The symmetry of single-crystal piezoelectric PbZr${}_{1\ensuremath{-}x}$Ti${}_{x}$O${}_{3}$, with $x\ensuremath{\approx}0.31$ and $x\ensuremath{\approx}0.46$, has been investigated by high-resolution x-ray diffraction, both at room temperature and up to and above the Curie temperature. Reciprocal space maps around a selection of Bragg reflections were collected and self-consistent patterns showing Bragg splittings were observed. The analysis of the separation of peaks from different twin domains provides precise information on PbZr${}_{1\ensuremath{-}x}$Ti${}_{x}$O${}_{3}$ symmetry when approaching the morphotropic phase boundary at $x=0.48$ from the zirconium-rich side.
TL;DR: In this article, the fabrication process to obtain 1-3-type porous lead zirconate titanate (PZT) ceramics with one-dimensional pore channels by using tert-butyl alcohol-based directional freeze-casting method was described.
Abstract: Porous lead zirconate titanate (PZT) ceramics are of great interest for hydrophones and medical imaging applications. The 0–3 type and 3–3 type porous PZT ceramics have been extensively discussed these years but the 1–3 type PZT ceramics have seldom been reported. This paper describes the fabrication process to obtain such 1–3 type porous PZT ceramics with one-dimensional pore channels by using tert-butyl alcohol-based directional freeze-casting method, and presents analysis of both microstructure and functional properties. The 1–3 type porous PZT ceramics with porosity ranging from 28.1% to 68.7% were fabricated by adjusting initial solid loading. With the increase of porosity, relative permittivity (ɛr) decreased slightly and longitude piezoelectric coefficient (d33) exhibited only a small decline, which could be attributed to the special 1–3 type porous structure. The resultant samples with 61.3% porosity possessed a high value of hydrostatic figure of merit, >100 times higher than that of dense materials. The acoustic impedance (Z) showed a linear dependence on porosity with the lowest magnitude reaching 1.3 MRayls (106 kg·(m2·s)−1), matching very well with biological tissue or water.
TL;DR: In this paper, the polarization state in three-dimensional porous polycrystalline ferroelectric networks has been modelled to eliminate the oversimplification of these idealized unit cells.
Abstract: Micromechanical models of porous ferroelectric ceramics have often assumed that the material is fully polarized in a particular direction and/or consists of a single isolated pore. In this work the polarization state in three-dimensional porous polycrystalline ferroelectric networks has been modelled to eradicate the oversimplification of these idealized unit cells. This work reveals that microstructural network models more closely represent a porous ferroelectric microstructure since they are able to take into account the complex polarization distribution in the material due to the presence of high and low permittivity regions. The modelling approach enables the prediction of the distribution of poled and unpoled material within the structure. The hydrostatic figures of merit and permittivity were determined for a variety of porous lead zirconate titanate microstructures and found to be in good agreement with experimental data. The decrease in piezoelectric activity with porosity was observed to be associated with the complex polarization state within the material. Model results were shown to be much improved when compared to a model assuming a fully polarized model.
TL;DR: In this article, a strain sensor based on piezoelectric paint film has been designed to be used in structural vibration monitoring applications, and the sensor sensitivity, defined as the electric displacement relative to the biaxial strain of the substrate surface in which the sensor is attached, has been analyzed as a function of various parameters: the electric field applied to polarize the sensor, the time during which the electric fields applied; the film thickness; the electrode area; and the concentration of PZT by weight.
Abstract: A strain sensor based on piezoelectric paint film has been designed to be used in structural vibration monitoring applications. The piezoelectric paint film can be considered as a piezoelectric composite constituted by two phases: lead zirconate titanate (PZT) ceramic powder (active phase) homogeneously distributed in a water-based acrylic polymer (passive phase). Two electrodes placed to both sides of the film are required to measure the electric charge generated by the sensor. Because PZT is a ferroelectric material, the film must be polarized with a high electric field across the electrodes prior to use. The sensor sensitivity, defined in this work as the electric displacement relative to the biaxial strain of the substrate surface in which the sensor is attached, has been analyzed as a function of various parameters: the electric field applied to polarize the sensor; the time during which the electric field is applied; the film thickness; the electrode area; and the concentration of PZT by weight. From the analysis of the experimental results a mathematical model has been proposed which defines the sensor sensitivity as a function of the previously mentioned parameters.