Simulations of gradual domain-switching in polycrystalline ferroelectrics using an optimization-based, multidomain-grain model

Ferroelectric materials, characterized by their high dielectric constants, piezoelectricity, and pyroelectricity, find numerous applications in electronic products such as computer memory, highly sensitive sensors, and sonar devices. Additionally, they hold potential applications in fields like solid-state refrigeration, with their performance often closely linked to their microstructural evolution, including phase transitions and domain switching. Phase-field methods serve as highly advantageous tools for exploring, revealing, and predicting mesoscale ferroelectric domain evolution. Within ferroelectric phase-field models, diverse types of domain structures of ferroelectric materials, such as bulk single crystals and thin films, can be simulated by setting different mechanical and electrical boundary conditions. Various types of ferroelectric phase transitions can also be studied by setting conditions in the models such as temperature variations and the application of external electric fields. Furthermore, by applying external electrical or mechanical stimuli in the phase-field models, behaviors such as ferroelectric domain switching can be observed. Here we first outline the fundamental framework of phase-field models, followed by a comprehensive overview of various phase transitions in ferroelectric materials, including ferroelectric-to-paraelectric and antiferroelectric-to-ferroelectric transitions. Additionally, the review summarizes how phase-field models facilitate the induction of ferroelectric domain switching through various experimental stimuli, including electric fields and mechanical fields. This review concludes by summarizing and prospecting potential new applications of the phase-field method in the study of ferroelectric phase transitions and domain switching.

In this study, a generalized inverse-pole-figure (IPF) method has been suggested to analyze domain switching in polycrystalline ferroelectrics including composition of morphotropic phase boundary (MPB). Using the generalized IPF method, saturated domain orientation textures of single-phase polycrystalline ferroelectrics with tetragonal and rhombohedral symmetry have been analytically calculated and the results have been confirmed by comparison with the results from preceding studies. In addition, saturated domain orientation textures near MPBs of different multiple-phase polycrystalline ferroelectrics have been also analytically calculated. The results show that the generalized IPF method is an efficient method to analyze not only domain switching of single-phase polycrystalline ferroelectrics but also MPB of multiple-phase polycrystalline ferroelectrics.

The temperature in the ferroelectric and ferromagnetic materials may rise due to energy dissipation under loading. Thermal effects on the mechanical behavior in ferroelectric/ferromagnetic materials are investigated theoretically in this paper. First, the influence of stresses induced by domain switching on the subsequent domain switching and domain reversal process in ferroelectrics is investigated. Based on the electrical saturation model, the influence of thermal effect on the domain switching is studied, and the changes of stress and electric intensity factors brought by thermal effect are obtained. The accumulative influence of temperature rise on the domain switching zone and fracture behavior of ferroelectrics under cycle electric field is studied. Second, the above approach of ferroelectric materials is extended to analyze the thermal effect in ferromagnetic materials. Using the magnetic saturation model, the temperature fields around the tip of a narrow elliptic hole are calculated under different conditions. It is found that the magnitude of temperature increment strongly depends upon the geometrical shape of the hole, the frequency and wave shape of the magnetic loading. This study is helpful to gain a deep understanding of the fracture and fatigue behavior of ferroelectric/ferromagnetic materials.

Ferroelectric domain switching within individual nanoscale grains of a 100 nm thick polycrystalline PbZr0.2Ti0.8O3 thin film has been shown to depend on the relative crystallographic orientation of the adjacent grains. Using Piezoresponse Force Microscopy, the significance of local microstructure on the domain switching was demonstrated. Different regions within grains show different coercive fields under the same external electric field. In addition, neighboring grains also show a collective switching pattern, facilitating/suppressing switching on both sides of the grain boundaries compared to the center of the grain. These experimental observations were supported by numerical simulation demonstrating that changing the crystallographic orientation of a grain affects the switching loop of the neighboring grains. Based on both experimental and numerical simulation, the conclusion can be made that microstructural modulation of the local electric and stress field can significantly affect individual grain switching in polycrystalline thin films.

The study of domain switching and dielectric breakdown behavior of ferroelectrics together with their relations is crucial for understanding the essence of ferroelectric physics and exploring their applications. In this work, a phase-field method is developed to reveal the coupled domain structure and dielectric breakdown evolution in a ferroelectric single crystal (FSC) by employing the Ginzburg-Landau kinetic equation and Griffith type energy criterion. Results show that the domain switching mobility, symbolizing the speed of polarization evolution, has a significant influence on ferroelectric properties, namely coercive field, dielectric breakdown strength (DBS), discharge energy density (DED), and energy storage efficiency (ESE). It is found that FSC with the higher domain switching mobility always displays a lower coercive field and smaller remanent electric displacement (or polarization) together with a higher DBS, accounting for a higher DED and ESE. Such findings can provide effective guidance in understanding and designing high-DBS and high-energy-density ferroelectrics. In addition, the defect concentration has a significant influence on the DBS and the pattern of breakdown paths.

Domain switching kinetics in ferroelectric PbTiO3 nanostructures

We report on electrically switchable polarization and ferroelectric domain scaling over a thickness range of 5–100 nm in BiFeO3 films deposited on [110] vicinal substrates. The BiFeO3 films of variable thickness were deposited with SrRuO3 bottom layer using the pulsed laser deposition technique. The domains are engineered into preferentially oriented patterns due to substrate vicinality along the [110] direction. The domain width scales closely with the square root of film thickness, in agreement with the Landau–Lifschitz–Kittel (LLK) law. Switching spectroscopy piezo-response force microscopy provides clear evidence for the ferroelectric switching behavior in all the films.

Diffraction provides an effective means to characterize ferroelectric materials under dynamic loading conditions. This paper describes a typical time-resolved diffraction setup and one example of a time-dependent strain response to an applied electric field in a piezoelectric lead zirconate titanate (PZT) ceramic.

Many physical experiments have shown that the domain switching in a ferroelectric material is a complicated evolution process of the domain wall with the variation of stress and electric field. According to this mechanism, the volume fraction of the domain switching is introduced in the constitutive law of ferroelectric ceramic and used to study the nonlinear constitutive behavior of ferroelectric body in this paper. The principle of stationary total energy is put forward in which the basic unknown quantities are the displacement u i , electric displacement D i and volume fraction ρ I of the domain switching for the variant I. Mechanical field equation and a new domain switching criterion are obtained from the principle of stationary total energy. The domain switching criterion proposed in this paper is an expansion and development of the energy criterion. On the basis of the domain switching criterion, a set of linear algebraic equations for the volume fraction ρ I of domain switching is obtained, in which the coefficients of the linear algebraic equations only contain the unknown strain and electric fields. Then a single domain mechanical model is proposed in this paper. The poled ferroelectric specimen is considered as a transversely isotropic single domain. By using the partial experimental results, the hardening relation between the driving force of domain switching and the volume fraction of domain switching can be calibrated. Then the electromechanical response can be calculated on the basis of the calibrated hardening relation. The results involve the electric butterfly shaped curves of axial strain versus axial electric field, the hysteresis loops of electric displacement versus electric filed and the evolution process of the domain switching in the ferroelectric specimens under uniaxial coupled stress and electric field loading. The present theoretic prediction agrees reasonably with the experimental results given by Lynch.

Ordered coalescence of nano-crystals in alkaline niobate ceramics with high remanent polarization

Ferroelectric domain switching on the surface of a lithium niobate thin film can be induced by the tip of a scanning probe microscope, and gives rise to both regular and chaotic spatiotemporal patterns. Moreover, the long-range interactions that govern these phenomena can be tuned by varying temperature, humidity, domain spacing and tip bias.

The use of ferroelectric polarization to promote electron–hole separation has emerged as a promising strategy to improve photocatalytic activity. Although ferroelectric thin films with planar geometry have been largely studied, nanostructured and porous ferroelectric thin films have not been commonly used in photo-electrocatalysis. The inclusion of porosity in ferroelectric thin films would enhance the surface area and reactivity, leading to a potential improvement of the photoelectrochemical (PEC) performance. Herein, the preparation of porous barium titanate (pBTO) thin films by a soft template-assisted sol–gel method is reported, and the control of porosity using different organic/inorganic ratios is verified by the combination of scanning electron microscopy and ellipsometry techniques. Using piezoresponse force microscopy, the switching of ferroelectric domains in pBTO thin films is observed, confirming that the ferroelectric polarization is still retained in the porous structures. In addition, the presence of porosity in pBTO thin films leads to a clear improvement of the PEC response. By electrochemical poling, we also demonstrated the tuning of the PEC performance of pBTO thin films via ferroelectric polarization. Our work offers a simple and low-cost approach to control the morphology optimization of ferroelectric thin films, which could open up the development of materials with great potential for PEC applications.

Raman analysis of ferroelectric switching in niobium-doped lead zirconate titanate thin films

Macroscopic comparison of ferroelectric domain switching processes in a PZT wafer at high temperatures

New insights into ferroelectric domain switching and the emergence of intermediate phase during FE-AFE phase transition