Rhombohedral Lead Zirconate Titanate Research Articles

Grain size effect on piezoelectric properties of rhombohedral lead zirconate titanate ceramics

Lead zirconate titanate (PZT)-based piezoelectric ceramics are important functional materials for various electromechanical applications due to their excellent performance and temperature stability. Herein, the rhombohedral PbZr0.55Ti0.45O3 ceramics with increasing average grain size from 3.57 μm to 10.85 μm were prepared by a conventional solid-state reaction method. The grain-size dependent dielectric, ferroelectric and piezoelectric properties were systematically investigated. With the increasing grain size, a significant softening effect with enhanced electromechanical properties was observed. Results of piezoresponse force microscopy show that the formation of non-180° domain walls was strongly repressed in the fine-grain samples, resulting in decreased domain wall mobility. Meanwhile, a noteworthy hardening effect was also observed in the coarse-grain samples with high domain wall mobility, which may be related to the enhanced bulk effect with increasing grain size. The results of this work confirmed that grain size engineering is an effective strategy for designing piezoelectric materials with excellent combination properties.

Control of Domain States in Rhombohedral Lead Zirconate Titanate Films via Misfit Strains and Surface Charges

AbstractUsing the Landau–Ginzburg–Devonshire approach and numerical modeling, an influence of the misfit strain and surface screening charges as well as the role of the flexoelectric effect have been studied in the case of a rhombohedral lead zirconate titanate ferroelectric/ferroelastic thin film with an anisotropic misfit caused by a substrate. The magnitude and sign of the misfit strain influence the domain structure, providing misfit‐dependent phases with different favorable polarization components. Whilst strong enough compressive misfit strains favor a phase with orthorhombic‐like polarization directions, strong tensile misfits only yield in‐plane polarization components. The strength of surface screening conditions the existence of closure domain structures and, by increasing, supports the single‐domain state. The flexoelectric effect exhibits a weak influence on the phase diagram of multi‐domain states when compared with the phase diagram of single‐domain states. Its effect, however, becomes significant in the case of skyrmion topological states spontaneously formed near the film surface when compressive misfit strains are applied. Cooperative influence of the misfit strain, surface screening charges, and temperature can set a thin rhombohedral ferroelectric film into a number of different polar and structural states, whereby the role of the flexoelectric effect is pronounced for topologically nontrivial structures.

Domain pinning near a single-grain boundary in tetragonal and rhombohedral lead zirconate titanate films

The interaction of grain boundaries with ferroelectric domain walls strongly influences the extrinsic contribution to piezoelectric activity in Pb(Zr,Ti)O3 (PZT), ubiquitous in modern transducers and actuators. However, the fundamental understanding of these phenomena has been limited by complex mechanisms originating from the interplay of atomic-level domain wall pinning, collective domain wall dynamics, and emergent mesoscopic behavior. This contribution utilizes engineered grain boundaries created by depositing epitaxial PZT films with various Zr:Ti ratio onto 24o SrTiO3 tilt bicrystals. The nonlinear piezoelectric response and surface domain structure across the boundary are investigated using piezoresponse force microscopy whilst cross section domain structure is studied using transmission electron microscopy. The grain boundary reduces domain wall motion over a width of 800±70 nm for PZT 45:55 and 450±30 nm for PZT 52:48. Phase field modeling provides an understanding of the elastic and electric fields associated with the grain boundary and local domain configurations. In conclusion, this study demonstrates that complex mesoscopic behaviors can be explored to complement atomic-level pictures of the material system.

Structural and electrical characteristics of rhombohedral lead zirconate titanate single crystals

Two PbZr x Ti1−x O3 (PZT) single crystals, from a batch prepared by the flux method, were analysed to assess their chemical composition. The two single crystals were found by electron microprobe analysis to have the chemical compositions PbZr0.60Ti0.40O3 and PbZr0.65Ti0.35O3. X-ray diffraction at −93 °C revealed that both crystals have the R3m space group, which means that the R3m ↔ R3c phase transition is not observed in this composition range for temperatures above −93 °C. The dielectric permittivity was measured along the [001] direction at several frequencies from 1 kHz to 1 MHz, at varying temperatures up to 460 °C, and the parameters of the Curie–Weiss law were determined. The parameters of a thermodynamic model for the rhombohedral phase were determined by fitting the experimental data with the theoretical model. The polarization was calculated as function of the temperature for both crystals and the results were used to observe the order of the phase transition. The polarization increases when the concentration of PZT approaches the morphotropic region from the rhombohedral side. This fact, already observed in ceramic samples, is for the first time reported in single crystals which contributes for the clarification of the maximum of electrical properties in the morphotropic region.

Identification of crystalline elastic anisotropy in PZT ceramics from in-situ blocking stress measurements

High energy x-ray diffraction measurements of lattice strains were performed on a rhombohedral Lead Zirconate Titanate ceramic (PZT 55-45) under combinations of applied electric field and compressive stress. These measurements allow the construction of blocking stress curves for different sets of crystallographic orientations which reflect the single crystal elastic anisotropy. A micro-mechanical interpretation of the results is then proposed. Assuming cubic symmetry for the crystalline elastic stiffness tensor and isotropy for the macroscopic elastic properties, the elastic properties of the single crystal are extracted from the measured data. An anisotropy ratio close to 0.3 is found (compared to 1 for isotropic materials). The high level of anisotropy found in this work suggests that crystalline elastic anisotropy should not be neglected in the modelling of ferroelectric materials.

Identical scaling behavior of saturated dynamic hysteresis in rhombohedral lead zirconate titanate bulk ceramics

The scaling behaviors of dynamic hysteresis were investigated in serial rhombohedral Nb-doped Pb(Zr1-xTix)O3 (PZT) bulk ceramics as a function of frequency (f) and field amplitude (E0). Three distinct regions were plotted including linear loops, minor loops, and saturated loops with an increase of E0. When the external fields were over ∼1.5 times of coercive field (Ec), the scaling relations of saturated loops for these PZT ceramics could be expressed with an identical form as hysteresis area ⟨A⟩ ∝ f 0.01E00.10, which indicated that similar ferroelectric systems with different compositions could display a uniform scaling law under high-E0 and low-f regions.

Converse longitudinal piezoelectric response of a ferroelectric thick film elastically coupled with a supporting substrate or underlayer

Effects of elastic coupling between a ferroelectric thick film and a supporting substrate or underlayer with finite thickness on the apparent longitudinal piezoelectric coefficients are analysed in this work. General analytical solutions of the effective d33 converse piezoelectric coefficients of a film–substrate couple are given as a function of the electromechanical properties, crystalline structure and orientation, as well as the thickness ratio of the couple. Computations of effective d33 coefficients as a function of the thickness ratio are performed for typical tetragonal and rhombohedral lead zirconate titanate ferroelectric films with a composition near its morphotropic phase boundary. These results are compared with those for thin films with the same compositions, where the substrate clamping effect is dominant.

Domain switching in rhombohedral PZT ceramics under electrical and mechanical loading

Ferroelectric domain switching in rhombohedral lead zirconate titanate (PZT) ceramics has been studied using high energy synchrotron X-ray diffraction. The diffraction data for a range of different grain orientations were obtained rapidly, with a data acquisition time of 20 s, using a Frelon CCD camera. Changes in the lattice strain and ferroelectric domain fractions under an applied electric field or compressive stress were determined by measuring the positions and relative intensities of the diffraction peaks. It was observed that domain switching under an electric field occurred over a narrow range of field strength, whereas that due to a compressive stress occurred more gradually, over a wider range of applied stress. This effect is due to a combination of factors, including the influence of residual stress, the presence of the electrical depolarisation field, and the nature of the electric field and stress tensors. It was confirmed that the work required for domain switching is the same under electrical or mechanical loading, and approximately equal to 0˙34 MJ m−3.

Memory effect of a mechanical anomaly related to ferroelastic domain switching in rhombohedral lead zirconate titanate ceramics

An anomaly in the temperature dependent mechanical properties of a lead zirconate titanate ferroelectric ceramic has been observed by dynamic mechanical analysis. The anomaly, seen as a rise in modulus, accompanied by a decrease in internal friction, occurs in the low-temperature phase below TC. The temperature of the anomalies varies systematically with the applied forces and the anomaly does exhibit a memory effect. The corresponding static bending deformation, mainly from remnant strain by ferroelastic domain switching, is analyzed, and a critical remnant strain value for triggering the anomaly is obtained. The anomaly is thought to be induced by pinning and depinning of domain walls. The results confirm that the memory effect and the occurrence of the anomaly are controlled by ferroelastic domain switching.

Analysis of elastic strain and crystallographic texture in poled rhombohedral PZT ceramics

The elastic strain and crystallographic texture of a rhombohedral lead zirconate titanate ceramic have been characterised in the remanent state, after poling, using high-energy synchrotron X-ray diffraction as a function of the grain orientation ψ relative to the poling direction. It is observed that the (2 0 0) diffraction peak exhibits pronounced shifts as a function of ψ, indicating an elastic lattice strain, while others ({1 1 1}, {1 1 2} and {2 2 0}) show marked changes in intensity as a result of preferred ferroelectric domain orientation. It is shown that the (2 0 0) peak is not affected by the domain switching itself but rather acts like an elastic macrostrain sensor. A simple Eshelby analysis is used to demonstrate that both the elastic strain and texture vary systematically with ψ according to the factor (3cos 2 ψ − 1). This angular dependence is evaluated through micromechanics modelling. The physical meaning of the texture variations with ψ is also discussed.

Crystallization kinetics of homogeneously precipitated lead zirconate titanate using urea: Comparison with the conventional ammonia precipitated sample

Ultrafine, PbZr0.53Ti0.47O3 powder was synthesized by homogeneous precipitation of metal ions in aqueous solution using urea. The results obtained from different characterization methods were compared with those obtained from the conventional precipitation method using ammonia in terms of crystallization, homogeneity, and microstructure. The as-dried precipitate converted to the single-phase crystalline lead zirconate titanate powder when calcined at 550 °C and above. The calcined powder showed smaller particle size, minimum agglomeration, and uniform shape. The growth of the particles was very little at higher temperatures. Powdered samples that precipitated using urea crystallized directly to rhombohedral lead zirconate titanate, without any intermediate pyrochlore phase formation. The NH3-precipitated powder converted to rhombohedral lead zirconate titanate via metastable pyrochlore and it showed phase segregation upon annealing at higher temperatures. The reaction kinetics has been studied by x-ray diffraction, differential thermal analysis, and differential scanning calorimetry.

Polarized Raman scattering of highly [111]-oriented Pb(Zr,Ti)O3 thin films in the rhombohedral-phase field

Highly [111]-oriented rhombohedral lead zirconate titanate [Pb(Zr1−xTix)O3;PZT] thin films were prepared on Pt(111)∕Ti∕SiO2∕Si substrates by suitably combining pulsed laser deposition with sol-gel coating. Two distinctive types of the backscattering geometry were employed for the polarized Raman scattering study: (i) normal backscattering in which the propagation direction of relevant phonons is parallel to the principal [111] polar axis of the rhombohedral 3m(C3v) point group for observing E(TO) phonons, and (ii) side-view backscattering in which the phonon-propagation direction is normal to the [111] direction for isolating A1(TO) phonons. Room-temperature Raman spectra of the [111]-oriented PZT60∕40 film (with Zr∕Ti=60∕40) having the high-temperature rhombohedral form were examined and compared with those of the [111]-oriented low-temperature rhombohedral PZT90∕10 film which is characterized by the tilting of oxygen octahedra about the principal [111] direction. Similarities and differences in the observed Raman spectra between these two distinctive films were examined in the light of the Raman selection rules for R3m and R3c space groups.

X-Ray Study on Lattice Strain and Domain Switching Induced in Rhombohedral PZT by Poling and External Loading

The X-ray diffraction method was applied to measure the change of the lattice strain and domain switching in rhombohedral lead zirconate titanate (PZT) due to poling and external straining. The lattice strain was determined from the linear relation between the diffraction angle 2θ and sin2ψ (ψ is the angle between the normals of the specimen surface and of the diffraction plane). The lattice strain measured by X-rays is at most 15% of the macrostrain determined from the dimensional change due to poling. Domain switching caused a major part of the macrostrain. External loading induced domain switching and the lattice strain. The lattice strain induced by external loading was at most 25% of the applied strain. The amount of domain switching was evaluated by the change of the intensity ratio, I222/I222, of the 222 to 222 diffraction. The intensity ratio for the normal diffraction (ψ=0°) was decreased with increasing the applied strain, because the spontaneous polarization direction, the 222 direction, turned to the loading direction. The broadening of X-ray diffraction profiles obtained from the diffraction plane perpendicular to the poling direction was the maximum, indicating the largest microstrain in the poling direction.

307 菱面体晶PZTにおける格子ひずみとドメインスイッチングのX線的評価(材料力学-機能材料)

307 菱面体晶PZTにおける格子ひずみとドメインスイッチングのX線的評価(材料力学-機能材料)

菱面体晶ＰＺＴにおける格子ひずみとドメインスイッチングのＸ線的研究

The X-ray diffraction method was applied to measure the change of the lattice strain and domain switching in rhombohedral lead zirconate titanate (PZT) due to poling and applied strains. The lattice strain was determined from the linear relation between the diffraction angle and sin2ψ. The lattice strain measured by X-rays is at most 15% of the macrostrain determined from the dimensional change due to poling. A major part of the macrostrain was caused by domain switching. External loading induced domain switching and lattice strain. The lattice strain induced by external loading was at most 25% of the applied strain. The amount of domain switching was evaluated by the change of the intensity ratio of 222 diffraction to 222 diffraction. The intensity ratio for normal diffraction (ψ=0°) was decreased with the applied strain, because the spontaneous poling direction, 222 direction, turned to the loading direction. The broadening of X-ray diffraction profiles obtained from the diffraction plane perpendicular to the poling direction was the maximum, indicating the largest microstrain in the poling direction.

Dependence of structure-property relations on substituent distributions in lead zirconate titanate

Abstract The dependence of substituent distributions on A and B sites in rhombohedral lead zirconate titanate (PZT) was investigated in terms of dielectric spectroscopy, polarization switching characteristics and transmission electron microscopy techniques. Decreasing the higher-valence A-site substituent radii resulted in higher coercive fields, a smaller decrease in transition temperatures and the disappearance of relaxor characteristics with respect to the largest A-site substituents La3+. These smaller substituents have enhanced the tendency to exchange on to B sites, resulting in an effective lower-valence substituent, “wavy” domain morphology and “hard” PZT properties.

Preparation and Electrical Properties of Rhombohedral Pb(ZrxTi1-x)O3 Thin Films by RF Magnetron Sputtering Method

Rhombohedral lead zirconate titanate (PZT) thin films with a thickness of 0.3–1.2 µm were successfully grown on (111)Pb(La,Ti)O3/Pt/Ti/SiO2/Si and (111)Ir/SiO2/Si substrates by an RF magnetron sputtering method using a multi-target consisting of calcinated PbO and metal titanium pellets on a zirconium metal plate. The composition of the films could be controlled by adjusting the area ratio of PbO/Zr/Ti. The crystal structures of the films were sensitive to the area of PbO and the substrate temperature. The pyroelectric current, relative dielectric constant, Curie temperature, remanent polarization (Pr) and coercive field dependence on the Zr content of the films are described. The pyroelectric coefficient of the as-prepared PZT films showed a peak from 94°C [for Pb(Zr0.91Ti0.09)O3] to 36°C [for Pb(Zr0.97Ti0.03)O3], which corresponded to the phase transition from the low-temperature to high-temperature rhombohedral ferroelectric phase. The fatigue characteristic was also measured using a double bipolar pulse. The PZT films preserved an initial switching charge value over a switching cycle of 1012.

Poling Field Dependence of Ferroelectric Properties and Crystal Orientation in Rhombohedral Lead Zirconate Titanate Ceramics

Rhombohedral lead zirconate titanate (PZT) ceramics were evaluated statically and dynamically to examine the relationship between domain structures and electrical properties. The poling field dependence of the electrical properties and crystal orientation was investigated as a statical evaluation. When the poling field was varied, maximum dielectric constant, minimum planar coupling factor, minimum frequency constant and minimum relative intensity of the X-ray diffraction (222) peak were obtained at the poling fields of ±0.5, ±1.0, ±0.5 and ±0.75 kV/mm, respectively. Since 180° domain switching was the dominant factor affecting the coupling factor, it was thought that the electrical domain clamping occurred at ±1.0 kV/mm. Furthermore, responses to repeated voltage pulses applied to the ceramics were measured by a high voltage test system as a dynamical evaluation. From these evaluations, we could clarify the domain behavior for the switching and clamping of 180° domain, 71° and 109° domain rotations and transient phenomena on the domain orientation.

Disordered oxygen octahedral rotations and glasslike polarization characteristics in rhombohedral lead zirconate titanate

Disordered oxygen octahedral rotations have been observed in the low-temperature rhombohedral ferroelectric state in the Pb(Zr1−xTix)O3 crystalline solution. The development of disordered oxygen octahedral rotations within the ferroelectric state was found to result in the interruption of long-range polar order and the development of fluctuation effects. Dielectric relaxation was observed below ∼160 °C for Pb(Zr0.65Ti0.35)O3. In addition, double-looplike characteristics were observed in the polarization electric-field (P–E) response in the same temperature range. The results clearly reveal the nature of the coupling between the polarization and oxygen octahedral rotations in a perovskite ferroelectric structure. It was also shown that a small amount of La doping can enhance the degree of ordering of the octahedral tilted state. The enhancement of the ordering was verified by an intensity increase of the 1/2〈111〉 superlattice reflections in the selected area electron-diffraction pattern.

Phase transitions in lead zirconate-titanate and their applications in thermal detectors

The results of a collaborative study of the ferroelectric-ferroelectric transition in rhombohedral lead zirconate-titanate are described. Firstly, experimental evidence for the first-order nature of the transition is given together with an explanation of this in pure single crystals. Secondly, the use of bismuth-doped ceramic material in pyro-electric detection is discussed. By applying an electric field on the cooling cycle, thermal hysteresis can be reduced to a minimum.