Tetragonal Lead Zirconate Titanate Research Articles

Crack tip process zone domain switching in a soft lead zirconate titanate ceramic

Non-180° domain switching leads to fracture toughness enhancement in ferroelastic materials. Using a high-energy synchrotron X-ray source and a two-dimensional detector in transmission geometry, non-180° domain switching and crystallographic lattice strains were measured in situ around a crack tip in a soft tetragonal lead zirconate titanate ceramic. At K I = 0.71 MPa m 1/2 and below the initiation toughness, the process zone size, spatial distribution of preferred domain orientations, and lattice strains near the crack tip are a strong function of direction within the plane of the compact tension specimen. Deviatoric stresses and strains calculated using a finite element model and projected to the same directions measured in diffraction correlate with the measured spatial distributions and directional dependencies. Some preferred orientations remain in the crack wake after the crack has propagated; within the crack wake, the tetragonal 0 0 1 axis has a preferred orientation both perpendicular to the crack face and toward the crack front.

Direct observation of 90° domain switching in lead zirconate titanate thick films using x-ray diffraction

Using an x-ray diffraction with reciprocal space mapping, 90° domain switching in tetragonal lead zirconate titanate (PZT) thick films under an applied field was studied. An increase in the c-axis lattice constant and a decrease in the a-axis lattice constant due to the piezoelectric effect and switching from a domain to c domain (90° domain switching) were observed under an applied field. The contribution from 90° domain switching to the total strain was estimated to be 60%–100%, which is almost the same as that for bulk PZT. High value is consistent with the intrinsic nonlinearity in a tetragonal film.

Time-resolved diffraction measurements of electric-field-induced strain in tetragonal lead zirconate titanate

The dynamic electric-field-induced strain in piezoelectric ceramics enables their use in a broad range of sensor, actuator, and electronic devices. In piezoelectric ceramics which are also ferroelectric, this macroscopic strain is comprised of both intrinsic (piezoelectric) and extrinsic (non-180° domain switching) strain components. Extrinsic contributions are accompanied by hysteresis, nonlinearity, and fatigue. Though technologically significant, direct measurement of these mechanisms and their relative contributions to the macroscopic response has not yet been achieved at driving frequencies of interest. Here we report measurements of these mechanisms in ceramic lead zirconate titanate during application of subcoercive cyclic driving electric fields using an in-situ stroboscopic neutron diffraction technique. Calculations are made from the diffraction measurements to determine the relative contributions of these different strain mechanisms. During applied electric field square waves of +0.5Ec unipolar and ±0.5Ec bipolar, at 1 Hz, non-180° domain switching is found to contribute 34% and 40% of the macroscopically measured strain, respectively.

‘Time-resolved and orientation-dependent electric-field-induced strains in lead zirconate titanate ceramics

Electric-field-induced lattice strains in a tetragonal ferroelectric lead zirconate titanate bulk ceramic are characterized under application of subcoercive cyclic electric fields using neutron diffraction and a stroboscopic data collection technique. At a driving electric field equal to half of the coercive field, the field-induced lattice strains are found to be a function of orientation with the greatest electric-field-induced strain coefficient of 680pm∕V in crystal orientations such that the 211 pole is parallel to the electric field. A time dependence of the 111 strain was also observed. Suggestions as to the nature of these dependences are discussed.

Chemical modifications of Pb(Zr0.3,Ti0.7)O3 precursor solutions and their influence on the morphological and electrical properties of the resulting thin films

Tetragonal lead zirconate titanate thin films on platinized silicon wafers have been prepared from chemically different precursor solutions by chemical solution deposition. Literature known routes have been evaluated and an optimized standard process has been developed leading to Pb(Zr0.3,Ti0.7)O3 films with a high degree of (111) orientation which consequently shows square hysteris loops with Pr values of 34 μC/cm2. Other solvents, different alkoxides of the transition metals, and different carboxylates of lead have been systematically introduced in this standard process and their influence on the final morphological and electrical properties has been studied. It has been found that the use of lead (II) propionate and titanium tetra n-butoxide for solution synthesis leads to a decrease of the remanent polarization of ∼50%. Furthermore the reaction atmosphere after spinning and during the pyrolysis has been investigated. Increased ambient humidity after the spin coating process also caused a significant deterioration of the final film properties. The findings have been explained in terms of a hindered formation of the (111) texture promoting intermediate Pt x Pb phase.

Orientation-dependent lattice strains in lead zirconate titanate under mechanical compression by in situ neutron diffraction

The electromechanical response of piezoelectric ceramics is a product of the micromechanics of individual grains; a variety of grain orientations with unique responses contribute to the macroscopic bulk ceramic response. In this paper, the lattice strains of tetragonal lead zirconate titanate are measured for many different grain orientations under compressive stress by in situ time-of-flight neutron diffraction. The diffractometer HIPPO at LANSCE is ideal for such orientation-dependent measurements because multiple detector panels measure diffraction vectors oriented throughout the sample orientation space. Parallel to the compression axis at high applied stresses, the 002 lattice strains are larger than the macroscopic strains. Ceramic intergranular stresses prevent each grain from becoming single-domain and less preferred orientations remain.

Thermal effects on domain orientation of tetragonal piezoelectrics studied byin situx-ray diffraction

Thermal effects on domain orientation in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) have been investigated by using in situ x-ray diffraction with an area detector. In the case of a soft PZT, it is found that the texture parameter called multiples of a random distribution (MRD) initially increases with temperature up to approximately 100°C and then falls to unity at temperatures approaching the Curie temperature, whereas the MRD of hard PZT and PT initially undergoes a smaller increase or no change. The relationship between the mechanical strain energy and domain wall mobility with temperature is discussed.

Determination of domain orientation in lead zirconate titanate ceramics by Raman spectroscopy

Raman spectroscopy was employed to investigate the domain orientations of poled and unpoled tetragonal lead zirconate titanate ceramics. Using backscattering geometry, the ceramics were rotated 360° relative to the polarization direction of the incident beam. The ratio of the crossed to parallel polarization intensities in the poled sample demonstrates periodicity with respect to the rotation angle, while that of the unpoled sample does not. The angular periodicity of the intensity ratio is related to the domain orientations through the Raman tensor. Raman spectroscopy is thereby demonstrated as a quantitative technique that can measure domain switching distributions in ferroelastic ceramics.

Identification and quantification of stress concentrations in ferroelectrics using Kikuchi pattern indexing

Transmission electron microscopy has been used to investigate the junction between two lamellar bands in a tetragonal lead zirconate titanate (PZT) ceramic. It is found that significant bending occurs in the area due to the matching of different domains on <101> planes. Analysis of CBED patterns shows that the orientation relationships between the long boundaries between lamellae is much as expected and allows quantification of local c/a ratios. The short boundaries at the band junction, however, are highly stressed and deviate significantly from ideal misorientation values. This reveals that the areas between the 4- domain junctions in the band junction are highly stressed with peak stresses in the GPa range, which are highly likely to function as the source of microcracks under the additional strains found in device application.

Domain texture distributions in tetragonal lead zirconate titanate by x-ray and neutron diffraction

The domain structure of ferroelectric ceramics can be altered by the process of electrical poling. This paper develops quantitative approaches for reflection geometry and spherical harmonic texture analysis, both of which describe these changes at angles parallel to and tilted from the poling axis. The x-ray-diffraction approach uses the relative intensity ratio of ferroelectric poles in poled and unpoled lead zirconate titanate to calculate a domain switching fraction (η) or a multiple of a random distribution, which are shown to be linearly related. An x-ray area detector diffractometer was used for these measurements, although the technique applies to any x-ray reflection geometry. The neutron-diffraction approach employs a Rietveld refinement with a spherical harmonic texture model. Both approaches calculate similar domain textures for two poling fields and the small differences between the approaches can be attributed to surface domain texture. This paper shows that the March–Dollase pole distribution function can inadequately describe domain textures.

Use of Stress To Produce Highly Oriented Tetragonal Lead Zirconate Titanate (PZT 40/60) Thin Films and Resulting Electrical Properties

Thin films of Pb(Zr0.4TiO.6)O3 produced by chemical solution deposition were used to study the effects of stress from different platinized single‐crystal substrates on film orientation and resulting electrical properties. Films deposited on MgO preferred a (001) orientation due to compressive stress on the film during cooling through the Curie temperature (TC). Films on Al2O3 were under minimal stress at TC, resulting in a mixture of orientations. Those on Si preferred a (111) orientation due to templating from the bottom electrode. Films oriented in the 〈001〉 direction demonstrated lower dielectric constants and higher Pr and −d31 values than (111) films.

Improvement of Ferroelectric Properties of Lead Zirconate Titanate Thin Films by Ion-substitution using Rare-earth Cations

ABSTRACTRare-earth-substituted tetragonal lead zirconate titanate thin films were synthesized for improving the ferroelectric property of conventional lead zirconate titanate. Thin films of Pb1.00REx (Zr0.40Ti0.60)1-(3x /4)O3 (x = 0.02, RE = Y, Dy, Er and Yb) were deposited on (111)Pt/Ti/SiO2/(100)Si substrates by a chemical solution deposition (CSD). B-site substitution using rare-earth cations described above enhanced the crystal anisotropy, i.e., ratio of PZT lattice parameters c/a. Remanent polarization (Pr) of PZT film was enhanced by Y3+-, Dy3+- and Er3+-substitution from 20 μC/cm2 up to 26, 25 and 26 μC/cm2 respectively, while ion substitution using Yb3+ degraded the Pr value down to 16 μC/cm2. These films had similar coercive fields (Ec) of around 100 kV/cm. Improving the ferroelectric property of PZT film by rare-earth-substitution would be ascribed to the enhancement of the crystal anisotropy. We concluded that ion substitution using some rare-earth cations, such as Y3+, Dy3+ or Er3+, is one of promising technique for improving the ferroelectric property of PZT film.

Ferroelectric domain structures in lead free piezoelectric ceramics composed of Bi-layer structured SrBi 4Ti 4O 15

The domain switching and rotation in Bi-layer structured ceramics were evaluated by investigating the poling field and pulse response dependences of the ferroelectric properties. The effect of domain clamping on electromechanical coupling factor and dielectric constant at the coercive field was confirmed in Bi-layer structured ceramics as well as in the cases of soft and hard tetragonal lead zirconate titanate, lead titanate and barium titanate ceramics. The minimum frequency constant due to domain rotations was also observed in Bi-layer structured ceramics. The remanent polarization and coercive field increased linearly with increasing the pulse field. Although relatively high DC fields up to 10.0 kV mm −1 could be applied to the ceramics, the P–E hysteresis loop showed a round figure. Furthermore, the oriented polarization by DC poling was highly stable in the ceramics, even though a high bipolar pulse was applied.

Dynamics of nanoscale polarization backswitching in tetragonal lead zirconate titanate thin film

The dynamics of polarization backswitching in highly oriented Pb(Zr0.3Ti0.7)O3 (PZT) thin films has been studied in nanoscale using piezoresponse scanning force microscopy (SFM). Our measurements reveal that a SFM-written domain with diameter about 200 nm in PZT films loses its polarization through both the sidewise and forward backswitching. Both of these sidewise and forward domain wall motions follow a stretched exponential law. However, the characteristic time τ of forward backswitching are about ten times of that sidewise motion. The time dependence of sidewise domain wall velocity indicates that there is a time dependence of activation energy of the barrier that domain motions encounter.

Microscopic Observation in Vicinity of Crack Tip for Tetragonal Lead Zirconate Titanate

Microscopic Observation in Vicinity of Crack Tip for Tetragonal Lead Zirconate Titanate

Investigation of Domain Switching and Retention in Oriented PbZr0.3Ti0.7O3 Thin Film by Scanning Force Microscopy

The polarization switching and retention in oriented tetragonal lead zirconate titanate films have been investigated by piezoresponse scanning force microscopy (SFM) on the nanoscale level. We observed the processes of polarization switching by choosing suitable poling conditions. It was found that the domain nucleated from the surface under the applied field and grew via both forward and sideways growth. This switching process was different from the conventional model in which sideways growth occurs after the forward growth reaches the opposite surface. Successive sideways and forward growth was observed with the stimulation of the applied field. We also studied the retention behavior of a single domain with a diameter of about 270 nm. Simultaneous forward and sideways backswitching of polarization led to the lowering of the piezoresponse of the retained domain together with the decrease of the domain area. The temporal dependence of the retained domain area was found to fit the stretched exponential law. This study demonstrates that the SFM technique is a powerful tool providing insight into the complicated behaviors of ferroelectric domains.

Effect of a Transverse Tensile Stress on the Electric‐Field‐Induced Domain Reorientation in Soft PZT: In Situ XRD Study

The effect of a transverse tensile stress on the electric‐field‐induced 90°‐domain reorientation in tetragonal lead zirconate titanate (PZT) near the morphotropic phase boundary was investigated in situ using X‐ray diffraction (XRD). The XRD intensity ratio, I(002)/I(200), which represents the ratio of the volume of the c‐domains to that of the a‐domains on the PZT surface, was examined as a function of the electric field at various stress levels. It was found that a transverse tensile stress changes the electric‐field dependence of I(002)/I(200), especially at higher electric fields. Without a transverse tensile stress, I(002)/I(200) began to saturate at E≈ 800 kV/m. With a transverse tensile stress of 75 MPa, I(002)/I(200) increased with an upward curvature with the electric field, indicating that the transverse tensile stress enhanced the field‐induced 90°‐domain reorientation, and increased the effective piezoelectric coefficients at larger electric fields. At E= 900 kV/m, the estimated d31,domain changed from −200 × 10−12 V/m at zero stress, to −350 × 10−12 V/m at 75 MPa.

Poling Field Dependence of Ferroelectric Properties in Barium Titanate Ceramics

The domain switching and rotation in barium titanate ceramics were evaluated by investigating the poling field dependence of the ferroelectric properties. The effect of domain clamping on the planar coupling factor and dielectric constant at the coercive field was confirmed in barium titanate ceramics as well as in the cases of soft and hard tetragonal lead zirconate titanate ceramics and lead titanate ceramics. The frequency constant peaks due to domain clamping were also observed in barium titanate ceramics. Furthermore, it is considered that domain rotations occurred at the fields required to obtain the maximum dielectric constant and the minimum frequency constant.

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

Domain switching and rotation in lead titanate ceramics were evaluated by investigating the poling field dependence of the relative intensity of the X-ray diffraction (002) peak and the electrical properties. Although the lead titanate ceramic surface was highly oriented in the direction of the c-axis by the poling field, it was difficult to align the crystal orientation of the ceramic bulk because of the large anisotropy of the crystal structure. The effect of domain clamping on the planar coupling factor and dielectric constant at coercive fields was confirmed in lead titanate ceramics as well as in the case of soft and hard tetragonal lead zirconate titanate ceramics. The peaks of frequency constant due to domain clamping were not observed in lead titanate ceramics. Further, it was thought that domain rotations occurred at the fields required to obtain the minimum frequency constant.

Lattice Strain and Domain Switching Induced in Tetragonal PZT by Poling and Mechanical Loading.

The X-ray diffraction method was applied to measure the change of the lattice strain and domain switching in tetragonal lead zirconate titanate (PZT) due to poling and external mechanical loading. The lattice strain was determined from the linear relation between the diffraction angle and sin2ψ(ψ is the angle between the normals of the diffraction plane and the specimen surface). The lattice strain measured by X-rays is less than 50% of the macrostrain determined from the dimensional change due to poling. The applied strain induced the increase of the lattice strain, and the amount of increase was about 50% of the applied strain. The amount of domain switching was evaluated by the change of the intensity ratio of 002 to 200 diffraction. The intensity ratio was decreased with the applied strain. 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.