A Feature-Engineering Approach to Support Vector Machine-Based Damage Detection in Lead Zirconate Titanate Ceramics Via Point-Contact Wavefield Measurement

Ferroelastic domain switching in electrically-poled lead titanate zirconate (PZT) ceramics were investigated during uni-axial compression up to 400MPa, at a series of temperatures from 25°C to 180°C. It is found that both the stress-induced switchable polarization and switchable strain in the electrically-poled PZT samples decrease steadily with the increasing temperature. By measuring the polarization variations and strain variations of unpoled, prepoled and depoled PZT samples during a full cycle of heating-cooling, it is found that the reduced switchable polarization by stress is caused by the pyroelectric effect and the reduced switchable strain is due to the lattice distortion and thermal shrinkage effect. The fracture toughness of electrically poled and mechanically depoled PZT ceramics were both measured by Vickers indentation and it is found that the fracture toughness anisotropy can even reach 3.63 in the later, significantly larger than that of 2.62 in the former.

Configuration of domain walls in undoped and Fe+3-doped lead zirconate titanate (PZT) ceramics at the morphotropic phase boundary has been investigated by the transmission electron microscopy. The distance between domain walls in undoped PZT is on the order of hundreds of nanometers and is drastically reduced to tens of nanometers by acceptor doping. The properties of doped and undoped samples are compared and discussed in terms of domain size, phase mixture, and presence of dopants. It is suggested that the small domain size cannot be a dominant effect in the enhancement of the properties in morphotropic PZT.

The processing, electromechanical properties, and microstructure of lead zirconate titanate (PZT) ceramics over the grain‐size range of 0.1‐10 μm were studied. Using measurements over a large temperature range (15‐600 K), the relative role of extrinsic contribution (i.e., domain‐wall motion) was deduced to be influenced strongly by the grain size, particularly for donor‐doped PZT. Analytical transmission electron microscopy studies were conducted to investigate the trend in domain configurations with the reduction of grain size. The correlations between domain density, domain variants, domain configurations (before and after poling), spontaneous deformation, and the elastodielectric properties were qualitatively discussed, leading to new insights into the intrinsic and extrinsic effects and relevant size effects in ferroelectric polycrystalline materials.

The mechanical and electrical properties (electromechanical coupling coefficient, piezoelectric constant and dielectric constant) of lead zirconate titanate (PZT) ceramics are investigated during mechanical static and cyclic loading. There are several failure characteristics which can alter the material properties of PZT ceramics. The elastic constant increases and electrical properties decrease with increasing the applied load. This is due to the internal strain arising from the domain switching. In this case, 90° domain switching occurs anywhere in the samples as the sample is loaded. It is also apparent that electrogenesis occurs several times during cyclic loading to the final fracture. This occurrence is related to the domain switching. The elastic constant and electrical properties can decrease because of crack generation in the PZT ceramics. Moreover, the elastic constant increases with increase of the mechanical load and decreases with decrease of the load. On the contrary, the opposite sense of change of the electrical properties is observed.

Bipolar pulse poling and space charge field in lead zirconate titanate ceramics

Lead Zirconate Titanate (PZT) ceramics can be formed over a wide range of PbTiO3/PbZrO3 ratios and exist in a number of crystal structures. This study involved the use of various fracture mechanics techniques to determine critical fracture toughness, KIC, as a function of composition, microstructure, temperature, and electrical and thermal history. The results of these experiments indicate that variations in KIC are related to phase transformations in the material as well as to other toughening mechanisms such as twinning and microcracking.

We studied the effect of repeated bipolar pulses applied to soft and hard lead zirconate titanate (PZT) ceramics on ferroelectric properties. Almost symmetric P-E hysteresis loops were observed in the case of soft PZT ceramics. On the other hand, the loops in the case of hard PZT ceramics were asymmetry and shifted to the positive electric field. It was found that a space charge field was generated while applying pulse and the direction of the field was fixed independent of the pulse cycles. The possibility of bipolar pulse poling was investigated. Furthermore, we discuss the effect of pulses on planar coupling factor when the pulses were applied to poled soft and hard PZT ceramics.

The properties of lead zirconate titanate (PZT) ceramics are determined by the microstructure and chemical homogeneity of Zr, Ti, and dopants within the grains as well as the presence of secondary grain boundary phases. Stoichiometric 53/47 PZT and compositions with 3 mol% PbO excess were prepared by the mixed‐oxide process, and were densified by pressureless sintering in oxygen. The influence of PbO content and different La concentrations on the densification behavior was analyzed by dilatometric measurements. Quantitative image analysis showed a different relative density and grain size dependence for samples containing >0.5 mol% additives compared to samples with <0.5 mol% La. On the basis of a model experiment and by using different analytical methods (microprobe analysis, HRTEM, STEM, and Auger spectroscopy) three types of inhomogeneities could be detected in conventionally prepared PZT ceramics: the existence of Ti and La enrichment in the core of PZT grains, and PbO‐rich secondary phases in triple junctions as well as in grain boundary films. The results of the microstructural characterization and the analysis of the densification behavior were finally combined to deduce a sintering model based on a Pb‐vacancy concentration gradient within the PZT grains.

Domain switching and rotation in soft lead zirconate titanate (PZT) ceramics were investigated in comparison with those in hard PZT ceramics by measuring the poling field dependence of the dielectric and piezoelectric properties. The minimum dielectric constant (εr) and maximum frequency constant (fcp) were observed at the coercive fields, which correspond to the poling fields required to obtain the minimum planar coupling factor. These phenomena were due to the 180° domain clamping at these fields. The fields of 90° (71° or 109°) domain rotation were estimated using the relationships between the maximum εr and minimum fcp. While minimum εr and maximum fcp due to domain clamping were observed in the compositions of tetragonal and rhombohedral soft PZT ceramics, domain rotations which caused maximum εr and minimum fcp were mainly observed in rhombohedral hard PZT ceramics. It was thought that the reason why domain rotations which caused maximum εr and minimum fcp were not obtained in soft PZT was the mechanical softness of the ceramics.

We report the first observation of positively charged Pb+3 defect centers in lead zirconate titanate (PZT) ceramics using electron paramagnetic resonance. The charged traps were optically generated using ultraviolet light energies roughly corresponding to the band gap of PZT (3.4 eV). The interpretation of the 207Pb+3 hyperfine parameters indicates that the defect’s unpaired electron is approximately 48% localized on the Pb nucleus. These observations may be of considerable importance since they prove that charged carriers created by optical excitation become trapped and form charged paramagnetic defects.

The possibility of preferential recovery of lead from lead zirconate titanate (PZT) ceramics by wet ball milling with aqueous H2SO4 solution was investigated. The wet ball milling was performed using a pot mill apparatus in air for 0-96h at room temperature with the rotational speed fixed at 300rpm. Untreated PZT was dipped in aqueous H2SO4 solution for comparison with the wet-ball-milled specimen. The diffraction lines of the PZT crystallites disappeared completely from the XRD results, and only the diffraction lines of PbSO4 were confirmed by the wet ball milling for more than 48h. For all the dipped specimens, the diffraction lines of PZT were identified even when the specimens were treated in 4.5mol/dm3 H2SO4 solution for 96h. According to ICP analysis of the dissolved components into the H2SO4 filtrate, the amounts of zirconium and titanium dissolved in the solution were found to increase with increasing treatment time, and the leaching behavior of both ions conformed closely to the collapsing behavior of the PZT crystal structure. As for lead ion in the solution, the dissolution amount was below 0.1% compared with the initial lead content in PZT ceramics under all the ball milling conditions. These results indicated that more than 99.9mass% of lead in PZT can be recovered as PbSO4 by wet ball milling for more than 48h. The purity of the recovered PbSO4 calculated from the ICP results was approximately 98mass%.

Ferroelastic domain switching fatigue in lead zirconate titanate ceramics

Many ferroelectric devices are based on doped lead zirconate titanate (PZT) ceramics with compositions near the morphotropic phase boundary (MPB), at which the relevant material's properties approach their maximum. Based on a synchrotron x-ray diffraction study of MPB PZT, bulk fatigue is unambiguously found to arise from a less effective field induced tetragonal-to-monoclinic transformation, at which the degradation of the polarization flipping is detected by a less intense and more diffuse anomaly in the atomic displacement parameter of lead. The time dependence of the ferroelectric response on a structural level down to 250 $\mu$s confirms this interpretation in the time scale of the piezolectric strain response.

Domain switching and rotation in soft lead zirconate titanate (PZT) ceramics were investigated in comparison with those in hard PZT ceramics by measuring the poling field dependence of the dielectric and piezoelectric properties. The minimum dielectric constant (fcp) and maximum frequency constant (fcp) were observed at the coercive fields, which correspond to the poling fields required to obtain the minimum planar coupling factor. These phenomena were due to the 180° domain clamping at these fields. The fields of 90° (71° or 109°) domain rotation were estimated using the relationships between the maximum fcp and minimum fcp. While minimum ϵt and maximum fcp due to domain clamping were observed in the compositions of tetragonal and rhombohedral soft PZT ceramics, domain rotations which caused maximum ϵt and minimum fcp were mainly observed in rhombohedral hard PZT ceramics. It was thought that the reason why domain rotations which caused maximum ϵt and minimum fcp were not obtained in soft PZT was the mechanical softness of the ceramics.

Piezoelectric Lead Zirconate Titanate (PZT) ceramics with different grain sizes were fabricated by changing the firing conditions. Using these samples, the grain size dependence of the third nonlinear piezoelectric coefficient in the transverse direction, ξD31, was experimentally investigated. The ξD31 decreased with the increase of grain size. This decrease of ξD31 was assumed to be caused by the promotion of poling in the samples with large grains. In order to demonstrate this fact, poling field dependence and MnO additive dependence of ξD31 were investigated. From the results of these three items of dependence, we concluded that the nonlinear motion of residual domain walls in poled samples exerts a large influence on the ξD31 value.