Domain Switching In Ferroelectric Ceramics Research Articles

Macroscopic understanding of domain switching in ferroelectric ceramics under large compressive stress

Macroscopic understanding of domain switching in ferroelectric ceramics under large compressive stress

Influence of domain switching process on the electrical fatigue behavior of ferroelectrics

We report an experimental approach, designed based on the recent findings that domain switching in ferroelectric ceramics can be separated into three regimes during antiparallel electric field loading, to investigate the influence of domain switching process on the electrical fatigue behavior of ferroelectrics. Uniaxial compressive stress (−2 MPã -100 MPa) and thermal loading (20 °C–150 °C) were used to tune the domain switching process. Under the same loading condition, the bipolar electrical fatigue behavior of soft lead zirconate titanate ceramics was systematically characterized. The amplitude and frequency of the applied electric field are 2 kV/mm and 10 Hz, respectively. By analyzing the evolution of the domain switching process, combined with the measured polarization and strain response, as well as the cracks observed on the surface of the specimen, it is found that the fatigue of ferroelectric ceramics was mainly related to the domain switching process near the coercive electric field: the regime 2 defined in this paper. The underlying mechanism was further discussed by considering the interplay between the domain switching process with the main factors affecting the electrical fatigue of ferroelectrics, namely defect redistribution, charge carrier injection, and crack initiation.

Linking Internal Dissipation Mechanisms to the Effective Complex Viscoelastic Moduli of Ferroelectrics

Microstructural mechanisms such as domain switching in ferroelectric ceramics dissipate energy, the nature, and extent of which are of significant interest for two reasons. First, dissipative internal processes lead to hysteretic behavior at the macroscale (e.g., the hysteresis of polarization versus electric field in ferroelectrics). Second, mechanisms of internal friction determine the viscoelastic behavior of the material under small-amplitude vibrations. Although experimental techniques and constitutive models exist for both phenomena, there is a strong disconnect and, in particular, no advantageous strategy to link both for improved physics-based kinetic models for multifunctional rheological materials. Here, we present a theoretical approach that relates inelastic constitutive models to frequency-dependent viscoelastic parameters by linearizing the kinetic relations for the internal variables. This enables us to gain qualitative and quantitative experimental validation of the kinetics of internal processes for both quasistatic microstructure evolution and high-frequency damping. We first present the simple example of the generalized Maxwell model and then proceed to the case of ferroelectric ceramics for which we predict the viscoelastic response during domain switching and compare to experimental data. This strategy identifies the relations between microstructural kinetics and viscoelastic properties. The approach is general in that it can be applied to other rheological materials with microstructure evolution.

Polarizability Across Morphotropic Phase Boundary in Ferroelectric Ceramics

A two-scale micromechanics scheme is used to analyze domain switching in ferroelectric ceramics during poling. The drastically different polarizability characteristics of Pb(ZrxTi1-x)O3 ceramics across morphotropic phase boundary has been captured, it is demonstrated that a complete poling that exhausts 180° and non-180° domain switching is realistic at MPB but highly unlikely in both tetragonal phase and rhombohedra phase, the effects of the transformation strains are also highlighted.

709 3D Phase-field法を用いた圧電セラミックスの分域および分域反転の微視組織解析(OS9-2 材料の疲労と破壊におけるミクロ計測と損傷評価2,OS9 材料の疲労と破壊におけるミクロ計測と損傷評価)

709 3D Phase-field法を用いた圧電セラミックスの分域および分域反転の微視組織解析(OS9-2 材料の疲労と破壊におけるミクロ計測と損傷評価2,OS9 材料の疲労と破壊におけるミクロ計測と損傷評価)

Two-scale micromechanics-based probabilistic modeling of domain switching in ferroelectric ceramics

A two-scale micromechanics model is developed in this paper to analyze domain switching in ferroelectric ceramics, using a probabilistic domain switching criterion based on energetic analysis. The microstructure of ferroelectric ceramics at two distinct length scales, domains and grains, has been carefully analyzed. The interaction at domain level is accounted for by energy minimization theory, while the fluctuation at grain level is analyzed using ellipsoidal two-point correlation function. The model has been implemented by Monte Carlo method, and applied to simulate the electric poling and mechanical depoling of Pb ( Zr x Ti 1 - x ) O 3 (PZT) ceramics across morphotropic phase boundary (MPB). The drastically different switching characteristics of PZT ceramics across MPB has been captured, and good agreement with experiments has been observed. The effects of the transformation strains and spontaneous polarizations are highlighted, confirming the proposition of Li et al. [2005. Domain switching in polycrystalline ferroelectric ceramics. Nature Materials 4, 776–781] that the strain compatibility plays a dominant role in domain switching in ferroelectric ceramics.

Modeling on domain switching in ferroelectric ceramics near the morphotropic phase boundary

In this paper, domain switching in ferroelectric ceramics near the morphotropic phase boundary (MPB), where tetragonal phase and rhombohedral phase coexist, is analyzed by a micromechanical model using an inverse-pole-figure (IPF) method. Charge screening effect in ferroelectric ceramics is taken into account, thus the depolarization field by polarization switching vanishes. The mechanical constraint caused by non-180° switching, however, cannot be neglected and is assumed to be proportional to the switching strain caused by non-180° domain switching with a factor β as the measure of the constrained level. Using the IPF method, the domain switching induced polarization and strain can be explicitly obtained via integrations over the unit spherical surface. Two limiting cases are studied in this paper, i.e., the energy barrier for the interphase non-180° domain switching is equal to or much larger than that for the in-phase non-180° switching. In the former case, it is found that domains always tend to switch to the rhombohedral phase especially when the constrained level is high, i.e., at a large value of β. If the mechanical constraint is neglected, i.e., β=0, the maximum achievable polarization and strain can be analytically obtained in this case. While in the latter case, interphase domain switching is suppressed, thus domain switching in MPB ceramics is only a superposition of independent in-phase domain switching in tetragonal ceramics and rhombohedral ceramics.

Observation of Crystal Orientation, Domain and Domain Switching in Ferroelectric Ceramics by EBSP Method

Piezoelectric ceramics are widely applied to the components of electric devices and actuators. Therefore, the reliabilities of PZT are very important. In this study, the domains in a crystal of PZT were observed by the EBSP method. However, it was very difficult to observe the crystal orientations and domains by EBSP method, because PZT ceramics were non-conducting materials and solid solutions. But, by using the acid chemical etching in combination with mechanical polishing for specimen surface finishing, the laminar domain structures on a nanoscale, were able to be observed by EBSP method. In addition, observation of domain switching behavior by Vicker's indentation test was conducted. The specimen was poled in the across-the-width direction (PS specimens) parallel to the crack front line. After the indentation tests, the mechanical loading-induced domains switching, 90° domain switching, were observed by EBSP method. Especially, the domain switching was most obvious in the intensity change of the (001) pole figure. The c-direction before loading was changed into two mutually-perpendicular directions by the mechanical loading.

Advances in the characterisation of domain switching in ferroelectric ceramics

In ferroelectric materials, extrinsic contributions such as domain wall vibrations, domain switching, and interphase boundary motion contribute to fatigue and aging, nonlinearity, and hysteresis in the piezoelectric response. It also affects the deformation behaviour, and influences the fracture mechanics. The most prevalent extrinsic contribution is ferroelectric/ferroelastic domain switching. Recent advances in diffraction techniques offer many opportunities for novel characterisation of domain switching and its influence on macroscopic properties. This paper presents the results of two such techniques which have been used to characterise extrinsic mechanisms in situ in a soft lead zirconate titanate (PZT) ceramic. In the first example, stroboscopic, time-resolved neutron diffraction is used to represent the ferroelectric/ferroelastic domain switching during a single cycle of a 1 kHz unipolar electric field with a magnitude of half of the coercive field. In the second example, highenergy X-ray microdiffraction is used to measure the spatial distribution of ferroelastic domain switching around a crack tip in transmission geometry under an applied stress intensity factor of KI=0.71 MPa•m. Introduction Ferroelectric ceramics are used in a wide variety of electromechanical devices including sonar, ultrasound, sensors and actuators, non-volatile memories, and micro-electromechanical systems (MEMS). In ferroelectric ceramics, changes in the ferroelectric/ferroelastic domain structures can affect the measurable bulk properties in an advantageous or disadvantageous manner. For example, domain wall motion during dynamic actuation increases the electric-field-induced strain but also contributes to nonlinearity, hysteresis, and fatigue [1]. Domain switching also contributes to fracture toughness enhancement in ferroelectric/ferroelastic ceramics, which is expressed both as an increase in the initiation toughness as well as a rising R-curve behaviour. It is therefore important to characterise such mechanisms in order to reveal their exact role in these and other cases. 442 European Powder Diffraction Conference, EPDIC 10 A schematic diagram of the process of domain switching is shown in figure 1. As shown, the application of an electric field or stress along particular directions of a bulk ceramic sample leads to a change in the volume fraction of domain types present within individual grains. Domain structures have been characterised using diffraction for decades [2]. The essence of such measurements is the relationship between the diffracted intensity of particular Bragg peaks and the volume fraction of ferroelectric/ferroelastic domains present within the sample. The simplest representation (i.e., for a sample with tetragonal symmetry) of the changes in the diffraction pattern is shown in figure 1(c).

Advances in the characterisation of domain switching in ferroelectric ceramics

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Domain switching in ferroelectric ceramics beyond Taylor bound

Domain switching in ferroelectric ceramics is a collective process among all the grains, and it was postulated that Taylor bound, which requires the transformation strain and spontaneous polarization in all the grains to remain uniform during switching, gives a good estimate on the extent of domain switching in ferroelectric ceramics. In this paper, we develop a two-scale micromechanics scheme to analyze domain switching in ferroelectric ceramics during poling. The disturbance field and the resulted energy variation are determined first using an inclusion method, and domain switching is then analyzed using energy minimization approach. It is demonstrated that a complete poling that exhausts both 90° and 180° domain switching is highly unlikely, so is a complete 180° domain switching that exhausts 180° domain switching but does not allow any 90° domain switching. It is also observed that any 90° domain switching beyond Taylor bound is rather difficult, while limited 180° domain switching beyond Taylor bound is possible. The analysis offers new insight into the domain switching process in ferroelectric ceramics and their nonlinear electromechanical behaviors.

Domain switch toughening in polycrystalline ferroelectrics

Mode I steady crack growth was analyzed to determine the toughening due to domain switching in ferroelectric ceramics. A multi-axial, electromechanically coupled, incremental constitutive theory is applied to model the material behavior of the ferroelectric ceramic. The constitutive law is then implemented within the finite element method to study steady crack growth. The effects of mechanical and electrical poling on the fracture toughness are investigated. Results for the predicted fracture toughness, remanent strain distributions, and domain switching zone shapes and sizes are presented. Finally, the model predictions are discussed in comparison discrete switching models and to experimental observations.

2742 機械的負荷による圧電セラミックスのドメインスイッチングの微視観察(S28-3 セラミックスおよびセラミックス系複合材料(3),S28 セラミックスおよびセラミックス系複合材料)

2742 機械的負荷による圧電セラミックスのドメインスイッチングの微視観察(S28-3 セラミックスおよびセラミックス系複合材料(3),S28 セラミックスおよびセラミックス系複合材料)

On the fracture toughness of ferroelectric ceramics with electric field applied parallel to the crack front

Mode I steady crack growth is analyzed to determine the toughening due to domain switching in ferroelectric ceramics with electric field applied parallel to the crack front. A multi-axial, electromechanically coupled, incremental constitutive theory is applied to model the material behavior of the ferroelectric ceramic. The constitutive law is then implemented within the finite element method to study steady crack growth. The effects of electric field on the fracture toughness of both initially unpoled and poled materials are investigated. Results for the predicted fracture toughness, remanent strain and remanent polarization distributions, and domain switching zone shapes and sizes are presented. The effects of the plane-strain constraint and transverse stress are also established. Finally, the model predictions are discussed in comparison to recent experimental observations.

Modeling of domain switching in ferroelectric ceramics: An example

The authors have recently proposed a continuum model for domain switching in polycrystalline ferroelectric ceramics in which each crystallite is modeled as a mixture of various domains characterized by their mass fractions, and domain switching corresponds to changes of the mass fractions of the corresponding domains. In order to explore the implications of this model, the authors present the explicit solution to an idealized one-dimensional ferroelectric system. The solution indicates that the orientation misalignment of crystallites results in a local electric field of strong inhomogeneity. The local electric field does not necessarily vanish in the absence of an externally applied electric field and its magnitude at certain locations can be substantially larger than that of the externally applied electric field. With a postulated domain switching criterion, the model produces the hysteretic response of the macroscopic polarization to the applied electric field due to local domain switching.

Numerical analysis of ferroelectric/ferroelastic domain switching in ferroelectric ceramics

A numerical approach predicting the behavior of ferroelectric ceramics under electric field and mechanical loading is proposed in this paper. In the model, macroscopic properties of ferroelectric ceramics are determined by microscopic structures. Ferroelectric ceramics are seen to be composed of many domains with different orientations, and domain switching is the source of the nonlinear constitutive behavior of the ferroelectric ceramics. Numerical calculations based on the model were carried out, and the computational results are compared with the experimental results, which shows the two sets of results consist with each other. The calculation approach can provide a guidance for the ceramics component design.