PZT Crystals Research Articles

COMPARISON OF STRUCTURES OF PIEZOELECTRIC CRYSTALS USED IN DOPPLER ULTRASONIC DIAGNOSTICS

For the effective operation of a Doppler sensor, it is necessary to select the piezoelectric material that will form the basis of the ultrasonic sensor in a competent and accurate way, as its selection has a great impact on the efficiency of its operation. This review research paper examines a variety of piezoelectric crystal structures used in ultrasonic Doppler diagnostic system sensors, focusing on the consideration of their properties and characteristics. The paper performs a comparative analysis to identify the distinctive characteristics of three types of transducers: PZT, PMN-PT and Lithium Niobate (LiNbO3) mono crystals. The research includes breaking down all the data into tables and visualising them in the form of histograms for better understanding. Keywords: Ultrasound, Doppler ultrasonography, Ultrasonic transducers, Piezo crystal structures, Transducer performance, Polarisation, Data visualisation.

Strong piezoelectric properties and electric-field-driven changes in domain structures in a PbZr0.87Ti0.13O3 single crystal

PbZr1-xTixO3 perovskite materials, known as PZT, are highly applicable, mainly due to their extraordinary piezoelectric properties. Recently, a technology of PZT crystals growth has been elaborated and opened new investigation possibilities for these compounds. In this paper, we demonstrate a highly piezoelectric response in PbZr0.87Ti0.13O3 single crystal. Under the action of an electric field, the piezoelectric coefficient d33 turns out to be over 2500 pm V-1. The optical studies performed have proved a significant influence of the domain dynamics on such high-efficiency piezoelectric response. Monoclinic M and rhombohedral R phases have been observed in the lead zirconate-titanate crystals with a low Ti content. This coexistence of phases with different symmetries and dense domain walls are the primary sources of high piezoelectric response. We have observed that strong electric fields may act on randomly oriented polarization vectors so that the total piezoelectric activity disappears, and the unusual isotropization point near 250 °C appears.

A review of EBSD: from rudimentary on line orientation measurements to high resolution elastic strain measurements over the past 30 years.

Considering that the Electron Back Scatter Diffraction technique, EBSD, features in more than 60% of the papers published in the current conference proceedings, this review concentrates on the most recent development in the last ten years, that is, High Resolution EBSD. An outline of the theory is presented and four-point bend test results are shown proving the sensitivity of the technique for measuring elastic strain is 1 part in 10000. Other examples of its use included here are strains surrounding indents in silicon, mapping the stress concentration at grain boundaries ahead of dislocation pile ups and dislocation generation at grain boundaries due to strain ahead of nano indentations. An application is presented to distinguish the c axis direction in slightly tetragonal PZT crystals and developments in obtaining absolute strain measurement as opposed to the relative strain measurement currently the norm are discussed.

Nanogenerators consisting of direct-grown piezoelectrics on multi-walled carbon nanotubes using flexoelectric effects

We report the first attempt to prepare a flexoelectric nanogenerator consisting of direct-grown piezoelectrics on multi-walled carbon nanotubes (mwCNT). Direct-grown piezoelectrics on mwCNTs are formed by a stirring and heating method using a Pb(Zr0.52Ti0.48)O3 (PZT)-mwCNT precursor solution. We studied the unit cell mismatch and strain distribution of epitaxial PZT nanoparticles, and found that lattice strain is relaxed along the growth direction. A PZT-mwCNT nanogenerator was found to produce a peak output voltage of 8.6 V and an output current of 47 nA when a force of 20 N is applied. Direct-grown piezoelectric nanogenerators generate a higher voltage and current than simple mixtures of PZT and CNTs resulting from the stronger connection between PZT crystals and mwCNTs and an enhanced flexoelectric effect caused by the strain gradient. These experiments represent a significant step toward the application of nanogenerators using piezoelectric nanocomposite materials.

Solvothermal Synthesis of Size-Controlled Lead Zirconate Titanate Particles

Nanocrystalline lead zirconate titanate (PZT) powders have been synthesized by solvothermal method, in which a mixed solvent of ethanol and water was used as reactive medium and Pb (NO3)2, ZrOCl2·8H2O, C16H36O4Ti, KOH and NH3·H2O were used as raw materials. It was found that PZT particle sizes decreased from 2 μm to 100 nm with the ratio of Vethanol/Vwater increasing from 1/2 to 2/1 under a KOH concentration of 4 mol/L at 200 °C for 4 h. It indicated that the Vethanol/Vwater of mixed solvent played an important role in controlling the morphology and size of PZT crystals, as well as reaction temperature.

Ferroelectric polymer-ceramic composite thick films for energy storage applications

We have successfully fabricated large area free standing polyvinylidene fluoride -Pb(Zr0.52Ti0.48)O3 (PVDF-PZT) ferroelectric polymer-ceramic composite (wt% 80–20, respectively) thick films with an average diameter (d) ∼0.1 meter and thickness (t) ∼50 μm. Inclusion of PZT in PVDF matrix significantly enhanced dielectric constant (from 10 to 25 at 5 kHz) and energy storage capacity (from 11 to 14 J/cm3, using polarization loops), respectively, and almost similar leakage current and mechanical strength. Microstructural analysis revealed the presence of α and β crystalline phases and homogeneous distribution of PZT crystals in PVDF matrix. It was also found that apart from the microcrystals, well defined naturally developed PZT nanocrystals were embedded in PVDF matrix. The observed energy density indicates immense potential in PVDF-PZT composites for possible applications as green energy and power density electronic elements.

Polymer-Assistant Hydrothermal Synthesis of 2.6 nm-Sized Lead Zirconate Titanate Nanoparticles

A facile synthesis route for monodispersed lead zirconate titanate (PZT) nanoparticles was developed by simple hydrothermal reactions under the assistance of polymer blend including polyvinylalcohol (PVA) and polyacrylate acid (PAA). It was found that PZT particles with an average size of 2.6 nm as well as a very narrow size distribution could be obtained with a 19.0 g/L polymers solution under a low KOH concentration of 2 mol/L at 200 °C for 14 h, indicating that the polymer additives played an important role in controlling the morphology and size of PZT crystals. The simple polymer-assistant hydrothermal synthesis is feasible for the mass production of PZT nanoparticles and is expected to be used in the miniaturization of electronic devices.

One-Axis-Oriented Crystal Growth of Lead Zirconate Titanate Thin Films on Metal Substrates Using Perovskite-Type Oxide Nanosheet Layer

One-axis-oriented Pb (Zr,Ti)O3(PZT) films were fabricated using a chemical solution deposition technique on (111)Pt/TiO2/(100)Si and Inconel625 substrates buffered by nanosheet Ca2Nb3O10(ns-CN). The (001)-oriented PZT crystals (Zr/Ti=0.40:0.60, tetragonal) were preferentially grown on (001)ns-CN/Inconel625, whereas the PZT crystals deposited on (001)ns-CN/(111)Pt/ TiO2/(100)Si exhibited preferential PZT(100) orientation. The resulting PZT film on (001)ns-CN/Inconel625 indicated remanent polarization of approximately 59 μC/cm2, which was significantly larger than that on (001)ns-CN/(111)Pt/TiO2/(100)Si.

Highly stable piezoelectrically tunable optical cavities

We have implemented highly stable and tunable frequency references using optical high finesse cavities which incorporate a piezo actuator. As piezo material we used ceramic PZT, crystalline quartz, or PZN-PT single crystals. Lasers locked to these cavities show a relative frequency stability better than 1 x 10^{-14}, which is most likely not limited by the piezo actuators. The piezo cavities can be electrically tuned over more than one free spectral range (> 1.5 GHz) with only a minor decrease in frequency stability. Furthermore, we present a novel cavity design, where the piezo actuator is prestressed between the cavity spacer components. This design features a hermetically sealable intra cavity volume suitable for, e.g., cavity enhanced spectroscopy.

Impact of surfactants on Pb (Zr0.53Ti0.47) O3 nanocrystal formation

In this article, we studied how surfactants can impact Pb (Zr0.53Ti0.47) O3 (PZT) nanocrystal formation to result in interesting nanohexagon and nanorod shapes of PZT crystal. The PZT nanohexagons/nanorods with typical diameters and bounding lengths within the nanometer range were synthesized by sintering the mixture of PZT crystals. After annealing at 800°C for 3h, PZT nanohexagons were formed with Tween 20. Using the same sol–gel method and growth condition but with Tween 20 replaced by Triton X-100, PZT nanocrystals were formed having nanorod shapes. Their single-crystalline nanostructures and compositions were confirmed by high resolution transmission electronic microscopy (HR-TEM), X-ray diffraction (XRD) and Raman Spectra. The results of this study demonstrated new insight on how surfactants impact the morphology of PZT formation.

Creep Responses of Smart Sandwich Composites at Multiple Length Scales: Experiments and Modeling

In service, composite structures present the unique challenge of damage detection and repair. Piezoelectric ceramic, such as lead zirconate titanate (PZT), is often used for detecting damage in composites. This paper investigates the effect of embedded PZT crystals on the overall creep behavior of sandwich beams comprising of glass fiber reinforced polymer laminated skins and polymer foam core, which could potentially be used as a damage-detecting smart structure. Uniaxial quasi-static and creep tests were performed on the glass/epoxy laminated composites having several fiber orientations, 0 deg, 45 deg, and 90 deg, to calibrate the elastic and viscoelastic properties of the fibers and matrix. Three-point bending creep tests at elevated temperature (80°C) were then carried out for a number of control sandwich beams (no PZT crystal) and conditioned sandwich beams (with PZT crystals embedded in the center of one facesheet). Lateral deflection of the sandwich beams was monitored for more than 60 h. The model presented in this paper is composed by two parts: (a) a simplified micromechanical model of unidirectional fiber reinforced composites used to obtain effective properties and overall creep response of the laminated skins and (b) a finite element method to simulate the overall creep behavior of the sandwich beams with embedded PZT crystals. The simplified micromechanical model is implemented in the material integration points within the laminated skin elements. Fibers are modeled as linear elastic, while a linearized viscoelastic material model is used for the epoxy matrix and foam core. Numerical results on the creep deflection of the smart sandwich beams show good correlations with the experimental creep deflection at 80°C, thus proving that this model, although currently based on material properties reported at room temperature, is promising to obtain a reasonable prediction for the creep of a smart sandwich structure at high temperatures.

Ab initiostudy of Pb antisite defects inPbZrO3andPb(Zr,Ti)O3

We report an ab initio study of Pb antisite defects in ${\text{PbZrO}}_{3}$ (PZ) and $\text{Pb}(\text{Zr},\text{Ti}){\text{O}}_{3}$ (PZT) perovskites. Also, we calculated the enthalpy of formation of PZ. Our results show that, under strong oxidizing conditions, Pb on the Zr-site antisite defects are unavoidable in PZ. Moreover, a positive enthalpy of formation (0.15 eV) of PZ is found. This indicates that PZ is metastable for low temperature and may help explain the difficulty in synthesizing high-quality Zr-rich PZT crystals. The Pb antisite defects in PZT alloys have low formation energies. This result is in agreement with experiments, which report the predominance of this defect in PZT films. We find that the Pb antisite defect produces electron traps 0.2--0.8 eV below the conduction-band edge.

Electromechanical Properties of PMN–PZT Piezoelectric Single Crystals Near Morphotropic Phase Boundary Compositions

Pb(Mg1/3Nb2/3)O3–PbZrO3–PbTiO3 (PMN–PZT) ferroelectric single crystals near morphotropic phase boundary compositions were fabricated by solid‐state crystal growth. The Curie temperatures (TC) of the grown PMN–PZT crystals were found to be on the order of 210°C, with ferroelectric phase transition temperatures (TR–T) in the range of 96°–165°C. The electromechanical coupling factors k33 and k32 were found to be >90% and >−87%, respectively. The coercive field EC for all the compositions was on the order of 5 kV/cm, double the value of pure Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMNT) crystals. The temperature dependence of the piezoelectric and electromechanical properties and dc bias effect on the dielectric behavior were investigated. The temperature usage range under dc bias was found to be improved when compared with pure PMNT crystals with similar piezoelectric properties.

Structural and electronic effects of an Nb impurity in PZT crystals

Structural and electronic properties of technologically important lead–zirconate–titanate (PZT) crystals produced by Nb-doping are reported. The results are obtained using semi-empirical quantum–chemical simulations applied to a tetragonal PbZr0.53Ti0.47O3 monocrystal, i.e. the morphotropic phase boundary of the PZT. The proposed concentration of Nb impurity is 1.5%, which, according to some experimental data, gives better piezoelectric properties of the material at this concentration. Analysis of the displacements of atoms surrounding the defect, changes in atomic charges and electronic properties explaining the augmentation of electric conductivity are given in light of the available experimental data. The results suggest the occurrence of free electrons in the conduction band of the material. The former observation might explain the formation of conducting Jahn–Teller (JT) electron polarons previously found in the other titanates.

Comparisons of Piezoelectricities of Lead Zirconate Titanate for Various Phases by a First-Principles Method

We calculated and compared the piezoelectric coefficients and Born effective charges of various PZT crystals, which have different B-site orderings and crystal symmetries by a first-principles method. The piezoelectric coefficient of rhombohedral structures is smaller than that of tetragonal structures because of the weakness of the hybridization change between the oxygen and B-site orbitals. We discuss this reason using a simple analytic model. We also performed the first-principles calculation of the piezoelectric coefficient with emphasis on its dependencies on the k-point number and calculation scheme (GGA or LDA), and found that calculated piezoelectric coefficients are very sensitive to these factors. This is due to the fact that the piezoelectric coefficient strongly depends on the small changes of the internal displacement gradient.

Quantum chemical modelling of Al-doped PZT crystals

Complete analysis of the electronic and structural changes of the lead zirconate titanate (PZT) crystal due to aluminium impurity doping is done based on the computationally obtained results. The PZT is modelled at a concentration of the morphotropic phase boundary with the stoichiometry equal to PbZr0.53Ti0.47O3 and the chosen concentration of Al impurity is about 1.5%. A spontaneous occurrence of conducting hole polarons in the upper valence band is observed. The obtained results are discussed in terms of the available experimental data.

High Orientation of PZT Single Crystal Grains and Piezoelectric Properties in 1-3 Type Composite Sheet

Since it is very difficult to grow PZT single crystal in a satisfying size in the composition near the morphotropic phase boundary (MPB, PZ/PT=52/48), there is few crystallography data on the ferroelectric and piezoelectric properties. According to our experience, the MPB PZT crystals obtained by a PbO flux method, though no more than several 10 μ m in size, exhibited a habit well-developing the six planes 100. From this cube-habit, it is suggested that the PZT grains can be arranged to the 100 plane. Such the situation is possible in a composite sheet of 1-3 type [1]. Though 1-3 composites made of PZT ceramics are widely studied for ultrasonic transducer application [2, 3], the one consisting of PZT single crystal grains is of quite new style and allow us to meet interesting physical properties, possibly like of single crystal.

Low Temperature Fabrication of Sol–Gel PZT Thin Films and Structural Characterisation of C60 Precipitates Formed in PZT–C60 Sol

Lead zirconate titanate (PZT) thin films were prepared at 400°C, in air by using PZT solutions containing C60, toluene, and acetic acid. All these additives provided well-developed perovskite PZT crystals, and the formation of pyrochlore crystals was suppressed. The 〈100〉 preferred orientation of perovskite PZT crystals was found to develop in the PZT thin films fabricated by using the solutions mixed with acetic acid. Needlelike and wirelike crystals of C60 were observed to precipitate in a PZT solution containing C60. The dielectric constant εr and the dielectric loss tan δ of a C60 doped PZT multilayer film prepared at 400°C were measured to be ∼ 200 and ∼ 3%, respectively, for a frequency range of 500–20 000 Hz. The present low temperature sol–gel processing is expected to be utilised as a method of intermediate heat treatment for the fabrication of thick multilayer PZT films for microactuators and sensors.

Hrtem Investigation of Pzt–c60 Thin Films

Lead zirconate titanate (PZT, Zr/Ti = 52 : 48) thin films with added C60 were prepared by firing at 400°C in air. The films were then examined by high resolution transmission electron microscopy (HRTEM). Analysis of the lattice constants and HRTEM images suggested that C60 prepcipiates retained in the films were polymerised. Perovskite PZT crystals were observed in contact with the C60 precipitates, indicating that the C60 precipitates acted as nucleation sites for the pervoskite phase of PZT.

Excess lead in the perovskite lattice of pzt thin films made by in-situ reactive sputtering

The incorporation of up to 40 % lead excess into the perovskite lattice of Pb(Zr,Ti)O3 (PZT) has been investigated. Three independent chemical composition analysis methods confirmed the correct determination of the lead excess, present as Pb2O3. High resolution TEM excludes any second phases and restricts the occurrence of lead excess to the perovskite lattice, suggesting a lead oxide perovskite of the form Pb2+Pb4+O3 with a 4-valent ion on the B-site. PZT containing such lead excess is thus a solid solution of PbZrO3, PbTiO3 and PbPbO3. The measured volume increase of the lattice due to a larger average B-ion matches very well with the calculated behavior based on standard ion radii and the B-ion radius dependence of the unit cell dimensions of PZT crystals. Structure factors as determined from Synchrotron X-ray diffraction are much better compatible with the B-site lead model than with the standard PZT ion lattice.