Polycrystalline Lead Zirconate Titanate Research Articles

Domain pattern formation in tetragonal ferroelectric ceramics

We present the results of high-resolution simulations of the ferroelectric domain evolution in polycrystalline lead zirconate titanate (PZT), using a phase-field framework that accounts for thermal fluctuations. Leveraging the parallel efficiency of a Fourier spectral scheme, we model micron-sized ceramic samples with thousands of grains at atomic-unit-cell spatial resolution. We introduce a method to automatically identify and track different types of domain walls from phase-field data, which we exploit to study their role during polarization reversal under applied electric fields. Results indicate that the density of domain walls and the domain width obey the Kittel-Mitsui-Furuichi-Roitburd square-root law with implications on the macroscopically observable piezo- and dielectric material properties. Moreover, analyzing the statistics of the domain pattern formation in simulated samples reveals correlations between the average polarization and strain within a grain and its crystallographic orientation, which is in agreement with high-energy x-ray diffraction experiments. Furthermore, we study the occurrence of the two predominant types of domain patterns – monodomain and laminate/twin domain structures – whose emergence within gains of a polycrystal is traced back to the grain orientation. Phase-field statistics are supported by a simple analytical model, which is based on minimizing the electric enthalpy and accurately predicts some of the reported correlations and allows us to further study the behavior of monodomains vs. laminate patterns in ferroelectric ceramics.

Study of the electrical properties of a PZT thin film formed on a metal substrate

Thin polycrystalline lead zirconate titanate (PZT) films with a Zr:Ti ratio close to morphotropic phase boundary were obtained by radiofrequency sputtering at a temperature of 540 °C on a metal substrate, and their structural and electrophysical properties were studied. The piezoelectric coefficient, remnant polarization, coercive field, and dielectric constant of the PZT film are 3.84 μC/cm2, 1.20 ÷ 1.26 μC/cm2, 1.1 ÷ 1.3·105 V/cm, and 145, respectively. Domains of the perovskite phase are located on the surface of the film protrusions. The magnitude of the piezoelectric modulus of the domain is 17.9 ÷ 22.4 pC/V.

Dielectric relaxations of lead zirconate titanate films up to millimeter‐wave frequencies

AbstractModern high‐frequency applications critically depend on the availability of data on the dielectric properties of functional materials in the microwave and millimeter‐wave range. This paper investigates the dielectric response of polycrystalline lead zirconate titanate (PZT) thin films prepared by solution deposition at frequencies between 10 MHz and 70 GHz and temperatures of 305–395 K by measuring the S‐parameters of coplanar waveguides (CPW). The real and imaginary parts of the permittivity of the PZT film are de‐coupled from the electrical properties of both the fused silica substrate and the copper electrodes. Two dielectric relaxations are identified: one around 850 MHz, with room‐temperature permittivity dropping from 1080 to 560, and one around 36 GHz, with permittivity dropping below 100, respectively. The low‐frequency relaxation shows a shift to lower frequencies with increasing temperature; it is explained by the conventional Arlt model of mechanical shear mode resonance across the film thickness. The high‐frequency relaxation, which is practically independent of temperature, is attributed to the response of ferroelectric domain walls.

Projector design for imaging of buried unexploded ordnance

Recent modeling and field experimentation has shown very-shallow-water acoustic imaging of buried unexploded ordnance (UXO) can place stringent requirements on the sonar transmit system. Achieving high-resolution imagery requires large transmit bandwidth. Imaging deeply buried UXO requires low operating frequencies and high source levels to overcome sediment attenuation. Imaging UXO near the sediment–water interface requires short transmit waveforms that require projectors with a low mechanical quality factor for accurate reproduction. This work presents the results of a recent design study, device fabrication, and acoustic testing of a new projector intended for operation as part of a buried UXO imaging system. The analysis will focus on the design and material selection of the head mass and the ring stack used in the tonpilz device. The head mass design trade considered construction from aluminum or an aluminum beryllium metal matrix composite (AlBeMet). The ring stack design trade considered traditional polycrystalline lead zirconate titanate (PZT), ternary single crystal lead indium niobium–lead indium manganese niobium titanate (PIN-PMN-PT), and textured manganese doped lead magnesium niobate–lead zirconate titanate (Mn-PMN-PZT). Finite element simulations and measured results will be presented.

Comparison of Metal-Based PZT and PMN-PT Energy Harvesters Fabricated by Aerosol Deposition Method.

In this study, polycrystalline lead magnesium niobate–lead titanate (PMN–PT) was explored as an alternative piezoelectric material, with a higher power density for energy harvesting (EH), and comprehensively compared to the widely used polycrystalline lead zirconate titanate (PZT). First, the size distribution and piezoelectric properties of PZT and PMN–PT raw powders and ceramics were compared. Thereafter, both materials were deposited on stainless-steel substrates as 10 μm thick films using the aerosol deposition method. The films were processed as {3–1}-mode cantilever-type EH devices using microelectromechanical systems. The films with different annealing temperatures were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and dielectric behavior measurements. Furthermore, the mechanical and electrical properties of PMN–PT- and PZT-based devices were measured and compared. The PMN–PT-based devices showed a higher Young’s modulus and lower damping ratio. Owing to their higher figure of merit and lower piezoelectric voltage constant, they showed a higher power and lower voltage than the PZT-based devices. Finally, when poly-PMN–PT material was the active layer, the output power was enhanced by 26% at the 0.5 g acceleration level. Thus, these devices exhibited promising properties, meeting the high current and low voltage requirements in integrated circuit designs.

Direct Observations of Changes in Ferroelectric Domain Configurations Around the Indentation and Ahead of the Crack Front

The indentation response of polycrystalline lead zirconate titanate (PZT) with varying ferroelastic domain configurations is investigated using nano and micro indentation. In the fully depoled state (with completely random domain configurations), PZT exhibit higher hardness, H as compared to poled PZT. Severe cracking is observed at the imprint corners at high indentation loads and the ferro-elastic domain configurations are visualized in the vicinity and ahead of the crack using piezoresponse force microscopy. The domains remain fully plastic in the regions from where the crack has propagated and just ahead of the crack while farther from the crack their remain elastic. The results are rationalized using remanent strain, e r results highlight the toughening mechanisms in the as poled PZTs. and converse piezocharge coefficient, d *33 measured around microcrack. The results highlight the toughening mechanisms in the as poled PZTs.

Thermal Conductivities of PZT Piezoelectric Ceramics under Different Electrical Boundary Conditions

<p>Physical properties of polycrystalline lead-zirconate-titanate (PZT) changes according to electrical boundary conditions and poling. This paper reports the thermal properties of poled and unpoled PZT's in the poling direction for open circuit and short circuit conditions. The authors found that the short-circuit condition exhibited the largest thermal conductivity than the open-circuit condition. In the relationship between these two thermal properties, the authors propose the "electrothermal" coupling factor k<sup>κ</sup><sub>33</sub>, which is similar to the electromechanical coupling factor k<sub>33</sub> relating the elastic compliances under short- and open-circuit conditions. On the other hand, the thermal conductivity of the unpoled specimen exhibits the lowest thermal conductivity, in comparison with the poled specimens, which suggests the importance of phonon mode scattering on the thermal conductivity with respect to elastic compliance.</p>

In-situ observation of evolving microstructural damage and associated effective electro-mechanical properties of PZT during bipolar electrical fatigue

We investigate the fatigue behavior of bulk polycrystalline lead zirconate titanate (PZT) during bipolar electric field cycling. We characterize the frequency- and cycle-dependent degradation in both the effective electro-mechanical properties (specifically, the electrical hysteresis and the macroscopic viscoelastic stiffness and damping measured by Broadband Electromechanical Spectroscopy, BES) and the microstructural damage evolution (quantified via scanning electron microscopy). The BES setup enables the mechanical characterization while performing electrical cycling so as to measure the evolving viscoelasticity without remounting the sample; particularly measuring the viscoelastic damping allows us to gain insight into the ferroelectric domain wall activity across the full electric hysteresis and over the full range of cycles. A clear dependence on the electric cycling frequency is observed in the rates of degradation of all measured properties including an up to 10% increase in dynamic compliance and a 70% decrease in electric displacement magnitude. We quantify the evolving micro-crack density across wide ranges of numbers of cycles and compare with changes in the effective compliance. Interestingly, the observed strong degradation in the ferroelectric hysteresis is contrasted by relatively mild changes in the effective viscoelastic moduli, while samples clearly indicate increasing levels of micro-damage.

Ferroelastic Properties of PZT: Characterization Under Compressive and Tensile Stress, Finite-Element Simulation, and Lifetime Calculation.

Finite-element (FE) simulations, based on a phenomenological nonlinear constitutive model, were carried out to show the impact of ferroelastic switching on compressive and tensile loading of a soft and hard ferroelastic polycrystalline lead zirconate titanate ceramic (PbZr1-xTixO3, PZT). Hereby, a model assembly is used that simulates mechanical stresses generated by the contact of a ceramic element with a concave counterpart. In order to parameterize the constitutive model, the elastic and piezoelectric tensors are determined by the small signal resonance method and by the direct measurement under compressive/tensile loads. In addition, the large field ferroelectric and ferroelastic behavior of polarization and strain were characterized. The simulations show that the tensile stress level within the piezoceramic is much lower compared to a linear elastic model, which is related to ferroelastic switching. This is demonstrated to have a significant influence on mechanical lifetime predictions. To validate the parametrized FE model, a four-point bending experiment was used. The comparison of the calculated and measured strain on the compressive and tensile sides of the sample showed very good correlation.

Formation Mechanisms for Hetero-Phase Ferroelectric Films of Lead Zirconate Titanate

An experimental and theoretical study of the formation processes of "impurity" phase inclusions in ferroelectric oxides is carried out via example of polycrystalline lead zirconate-titanate (PZT) films. A feature of these compositions is relatively high volatility of lead oxides, which can lead to deficiency of these components in the composition of the ferroelectric film formed during high-temperature crystallization. To avoid lead losses, some excess is added to the solution in the process of synthesis. Experimental samples of PZT films are obtained using sol-gel method with different contents of lead oxide, the crystallization of the ferroelectric phase of the films is carried out in air at 600 °C. In the films, the inclusions of lead oxide impurity phase are found, and the size distribution of these inclusions are obtained. Model concepts are presented and a system of equations is proposed describing the dispersed inclusions formation kinetics of new phases of different stoichiometric composition at the interfaces in polycrystalline films of multicomponent ferroelectric oxides due to bulk diffusion and grain-boundary segregation. Comparison of the experimental data with the theoretical model gives qualitative agreement. The approach generality makes it possible to extend the model to other systems of multicomponent ferroelectric polycrystalline materials.

Unexpectedly high piezoelectricity of Sm-doped lead zirconate titanate in the Curie point region

Large piezoelectric coefficients in polycrystalline lead zirconate titanate (PZT) are traditionally achieved through compositional design using a combination of chemical substitution with a donor dopant and adjustment of the zirconium to titanium compositional ratio to meet the morphotropic phase boundary (MPB). In this work, a different route to large piezoelectricity is demonstrated. Results reveal unexpectedly high piezoelectric coefficients at elevated temperatures and compositions far from the MPB. At temperatures near the Curie point, doping with 2 at% Sm results in exceptionally large piezoelectric coefficients of up to 915 pm/V. This value is approximately twice those of other donor dopants (e.g., 477 pm/V for Nb and 435 pm/V for La). Structural changes during the phase transitions of Sm-doped PZT show a pseudo-cubic phase forming ≈50 °C below the Curie temperature. Possible origins of these effects are discussed and the high piezoelectricity is posited to be due to extrinsic effects. The enhancement of the mechanism at elevated temperatures is attributed to the coexistence of tetragonal and pseudo-cubic phases, which enables strain accommodation during electromechanical deformation and interphase boundary motion. This work provides insight into possible routes for designing high performance piezoelectrics which are alternatives to traditional methods relying on MPB compositions.

Reconstruction of the domain orientation distribution function of polycrystalline PZT ceramics using vector piezoresponse force microscopy

Lead zirconate titanate (PZT) is one of the prominent materials used in polycrystalline piezoelectric devices. Since the ferroelectric domain orientation is the most important parameter affecting the electromechanical performance, analyzing the domain orientation distribution is of great importance for the development and understanding of improved piezoceramic devices. Here, vector piezoresponse force microscopy (vector-PFM) has been applied in order to reconstruct the ferroelectric domain orientation distribution function of polished sections of device-ready polycrystalline lead zirconate titanate (PZT) material. A measurement procedure and a computer program based on the software Mathematica have been developed to automatically evaluate the vector-PFM data for reconstructing the domain orientation function. The method is tested on differently in-plane and out-of-plane poled PZT samples, and the results reveal the expected domain patterns and allow determination of the polarization orientation distribution function at high accuracy.

Characterization methodology for lead zirconate titanate thin films with interdigitated electrode structures

The accurate evaluation of ferroelectric thin films operated with interdigitated electrodes is quite a complex task. In this article, we show how to correct the electric field and the capacitance in order to obtain identical polarization and CV loops for all geometrical variants. The simplest model is compared with corrections derived from Schwartz-Christoffel transformations, and with finite element simulations. The correction procedure is experimentally verified, giving almost identical curves for a variety of gaps and electrode widths. It is shown that the measured polarization change corresponds to the average polarization change in the center plane between the electrode fingers, thus at the position where the electric field is most homogeneous with respect to the direction and size. The question of maximal achievable polarization in the various possible textures, and compositional types of polycrystalline lead zirconate titanate thin films is revisited. In the best case, a soft (110) textured thin film with the morphotropic phase boundary composition should yield a value of 0.95Ps, and in the worst case, a rhombohedral (100) textured thin film should deliver a polarization of 0.74Ps.

Effect on High-Intensity Fields of a Tough Hydrophone With Hydrothermal PZT Thick-Film Vibrator and Titanium Front Layer.

A novel tough hydrophone was fabricated by depositing hydrothermally synthesized lead zirconate titanate polycrystalline film on the back-side surface of a titanium plate. Our developed tough hydrophone resisted damage in a high-pressure field (15 MPa) at a focal point of a sinusoidal continuous wave driven by a concave high-intensity focused ultrasound (HIFU) transducer with up to 50 W of power input to the sound source. The hydrophone was suitable for the HIFU field, even though the hydrophone has a flat-shape tip of 3.5 mm diameter, which is slightly larger than the wavelength of a few megahertz. In this paper, experiments are performed to assess the effect on the HIFU field of changing the shape of the tough hydrophone, with the aim of developing a tough hydrophone. The spatial distribution of the acoustic bubbles around the focal point was visualized by using ultrasonic diagnostic equipment with the tough hydrophone located at the focal point of the HIFU transducer. From the visualization, the trapped acoustic bubbles were seen to arise from the standing wave, which implies that the acoustic pressure is reduced by this cloud of acoustic bubbles that appeared during hydrophone measurement. Although cavitation and acoustic bubbles may be unavoidable when using high-intensity ultrasound, the estimated result of evaluating acoustic fields without misunderstanding by acoustic bubbles can be obtained by the aid of visualizing bubbles around the tough hydrophone.

Development of anti-cavitation hydrophone using a titanium front plate: Durability test in the high intensity focused ultrasound field

Our research group has developed new anti-cavitation hydrophones by depositing a hydrothermally synthesized lead zirconate titanate polycrystalline film with 15 μm thickness on the back surface of a titanium front plate with 50 μm thickness and 3.5 mm diameter. A durability test of the anti-cavitation hydrophone was performed when the anti-cavitation hydrophone under test was placed at the focal point of a concave focused ultrasound transducer with 100 mm diameter and at a resonant frequency of 1.75 MHz. The amplified 80 Vp-p (calculated electric input power: about 40 W) signal was applied to the concave ultrasound transducer at the focal point of the focused ultrasound system and high-intensity ultrasound waves were irradiated in water. The irradiated sound pressure at the focal point was about 4 MPa. Through this research, we will report that the fabricated new anti-cavitation hydrophone was robust and was not damaged easily, even in a high intensity focused ultrasound field with sound pressure of where acoustic cavitation occurred. We will make a durability test by increasing the acoustic power at the focal point of the focused acoustic field with sound pressure higher than 15 MPa.

Development of anticavitation hydrophone using a titanium front plate: Effect of the titanium front plate in high-intensity acoustic field with generation of acoustic cavitation

Novel anticavitation hydrophones were fabricated by depositing a hydrothermally synthesized lead zirconate titanate polycrystalline film at the back of a titanium front plate. These anticavitation hydrophones were not damaged by the measurement of the acoustic field formed by a high-intensity focused ultrasound (HIFU) device. Their sensitivity was improved by approximately 20 dB over that of the conventional anticavitation hydrophone by modifying their basic structure and materials. The durability of the anticavitation hydrophone that we fabricated was compared by exposing it to a high-intensity acoustic field at the focal point of the HIFU field and in the water tank of an ultrasound cleaner. Therefore, the effect of the surface of the titanium front plate on acoustic cavitation was investigated by exposing such a surface to the high-intensity acoustic field. We found that the fabricated anticavitation hydrophone was robust and was not damaged easily, even in the focused acoustic field where acoustic cavitation occurs.

Effect of the synthesis conditions on the properties of polycrystalline films of lead zirconate titanate of nonstoichiometric composition

The model representations of the formation of the internal fields at the grain boundaries in polycrystalline lead zirconate titanate (PZT) films are discussed. According to the model proposed, the local distortion of the stoichiometric composition of the PZT films caused by the segregation of the oxygen and lead ions from the bulk PZT grains towards their boundaries during high-temperature annealing gives rise to electrical double layers near the grain boundaries and fixes the polarization in these areas. As a result, the ferroelectric polarization that can be switched by the electric field in polycrystalline PZT films decreases.

A low-cost UWB sensor node powered by a piezoelectric harvester or solar cells

We propose an autonomous battery-less wireless sensor node that combines on a single printed circuit board an ultra-wideband (UWB) transmitter and its printed antenna, together with a piezoelectric cantilever and a solar cell array to harvest vibrations and light energy, respectively. The co-design of the solar cell array with the printed UWB antenna allows a prototype size of only 85×35mm2, i.e., less than 65% of a credit card size. Low-cost is achieved by using inexpensive FR4 dual-layer substrate, standard-ceramic capacitors, and low-cost harvesters. The vibrational energy scavenger is fabricated at the wafer scale based on commercially available bulk polycrystalline Lead Zirconate Titanate (PZT), and the solar cells are fabricated by depositing amorphous-Si on 0.5mm thick glass substrate. The cold-startup time of the demonstrator is about 42min under indoor-ambient light conditions, and about 34min under 700mg vibrations at a frequency of 100Hz. Once started, the sensor requires only 12.6μW to allow a transmission rate of one temperature sensor readout every 34s, thanks to the UWB transmitter that consumes only 206 pJ per pulse and a custom protocol with a reduced overhead.

Investigation of the formation kinetics of grain boundary inclusions of lead oxide in lead zirconate–titanate films

The formation kinetics of disperse inclusions of lead oxide at the grain boundaries in polycrystalline lead zirconate–titanate (LZT) films is analyzed based on the combined solutio of the continuity and material balance equations. Functions of the inclusion distribution over sizes are constructed for various process times. It is shown that lead oxide inclusions in LZT films with a lead excess are aggregated at the grain boundaries with an increase of the temperature and duration of annealing when thermal processing has still not resulted in a substantial lead loss.

チタン前面板裏面に水熱合成チタン酸ジルコン酸鉛を成膜した耐音響キャビテーションハイドロホン

チタン前面板裏面に水熱合成チタン酸ジルコン酸鉛を成膜した耐音響キャビテーションハイドロホン