Ferroelectric materials hold great promise for next-generation electronic devices, yet their practical implementation is often impeded by issues such as fatigue and loss. Unraveling polarization dynamics is pivotal to overcoming these hurdles. In this work, we employ a first-principles-based effective Hamiltonian formalism combined with molecular dynamics simulations to investigate the influence of depolarization fields on 180 degrees domain switching dynamics in ferroelectric thin films. Two distinct switching pathways are identified: under near-ideal charge screening (screening factor 9 = 1.00), domain switching proceeds via continuous shrinking of the original domain through inward propagation of 180 degrees domain walls (referred to as "domain-shrinking switching"); under relatively poor surface charge screening (9 = 0.90), switching is initiated by nucleation and growth of newly reversed domains in the central region of the original domain, with the outward polarization of the original domain being pinned initially and eventually vanishing (termed "central nucleation switching with pinned boundaries"). A continuous transition between these pathways occurs as 9 increases from 0.90 to 1.00. A phase diagram mapping the dependence of the switching pathway on charge screening conditions is constructed. Furthermore, the origin of these two distinct pathways is elucidated from a microscopic perspective, focusing on polarization reversal energy barriers and effective electric field distributions. This study highlights the decisive role of interfacial electrostatic screening in modulating domain wall dynamics and provides theoretical guidance for designing tunable ferroelectric devices.

The convergence of optics and electronics, driven by intelligent systems and wearable technologies, demands materials that seamlessly integrate optical transparency with robust electrical and mechanical functionalities. Transparent ferroelectric ceramics (TFCs) have emerged as a pivotal platform in this endeavor, uniquely bridging high optical transmittance with strong ferroelectric, piezoelectric, and electro-optic (EO) responses. This review comprehensively charts the evolution of TFCs, from fundamental material design to cutting-edge device applications. We systematically analyze the core strategies for achieving transparency in two representative transparent ferroelectric ceramic systems, namely, lead-based (Pb(Mg1/3Nb2/3)O3u2013PbTiO3, abbreviated as PMN-PT) and lead-free ((K,Na)NbO3, abbreviated as KNN) systems, while also discussing other important systems, such as (Pb,La)(Zr,Ti)O3 (PLZT), BaTiO3 (BTO), and (Bi0.5Na0.5)TiO3 (BNT), where appropriate for comparison. Critical mechanisms include grain and domain engineering, refractive-index matching, phase-structure tuning, and defect control. Representative functionalitiesu2014including transparent piezoelectricity, EO modulation, energy storage, photoluminescence, and photochromismu2014are highlighted, with their potential applications evaluated across photoacoustic imaging (PAI), adaptive optics, transparent robotics, smart windows, and optical communication. Finally, we identify key challenges and future opportunities, such as high Curie temperature (Tc) design, texture engineering, and multifunctional co-integration. Overall, this review aims to provide theoretical insights and material-design foundations for next-generation multifunctional transparent ferroelectric devices, accelerating their adoption in intelligent sensing, integrated photonics, and transparent optoelectronic systems.

Transparent piezoelectric ceramics (TPCs) have great application potential in electro-optical-mechanical multi-functional devices. Preparing high-performance TPCs, especially improving the transparency through microstructure regulation, has recently caused extensive discussion. However, there is still controversy about the influence of grains and pores on the transmittance of ceramics, and there is arbitrariness in the estimation of the theoretical transmittance limit. In this paper, taking PMN-PT-based ceramics as an example, theoretical mechanisms for the transmittance are discussed. An inhomogeneous reflection model is derived to improve the theoretical limit of transmittance. The effects of pores and grains scattering on transmittance are investigated. Rayleigh and RGD approximation are discussed to reveal the underlying scattering mechanisms. It is found that Rayleigh approximation is suitable for describing pore scattering, while RGD approximation is suitable for grain scattering. Thus, a Rayleigh-RGD combined model is proposed to describe light scattering in TPCs and successfully employed to fit experimentally measured transmittance curves.

Polar skyrmions have demonstrated rich physics and exotic properties for developing novel functionalities. However, so far, skyrmion nanodomains exist only in a few material systems, such as ferroelectric/dielectric superlattices, free-standing PbTiO3/SrTiO3 epitaxial bilayers and ultrathin Pb(Zr,Ti)O3/SrTiO3/Pb(Zr,Ti)O3 sandwiches. These heterostructures are fabricated with elaborately designed boundary conditions to meet the delicate energy balance for stabilizing topological phases. This requirement limits the broad applications of skyrmions in electronic devices. Here we show widespread skyrmion nanodomains in ferroelectric-antiferroelectric solid solutions, composed of ferroelectric PbTiO3 and one antiferroelectric PbSnO3 (Pb(Ti1-xSnx)O3), PbHfO3 (Pb(Ti1-xHfx)O3) or PbZrO3 (Pb(Ti1-xZrx)O3). The skyrmionic textures are formed by engineering dipole-dipole and antiferrodistortive-dipole couplings in competition between ferroelectric and antiferroelectric polar orderings, allowing the stabilization of topological phases. A phase diagram is built for the three solid solution series, revealing the stabilization regions of skyrmion nanodomains. In addition, the non-trivial domains also exhibit improved switching character, reversible writing/erasure and long-term retention for the electrical manipulation of polar configurations. These findings open an avenue for the investigation and exploitation of polar skyrmions in ferroelectric-based materials, providing opportunities in topological electronics.

Topological textures like vortices, labyrinths, and skyrmions formed in ferroic materials have attracted extensive interest during the past decade for their fundamental physics, intriguing topology, and technological prospects. So far, polar skyrmions remain scarce in ferroelectrics as they require a delicate balance between various dipolar interactions. Here, it is reported that PbTiO 3 thin films in a metallic contact undergo a topological phase transition and hold a broad family of skyrmion‐like textures including Q = ±1 skyrmions, multiple π‐twist target skyrmions, and skyrmion bags, with independent controllability, analogous to those reported in magnetic systems. Weakly‐interacted skyrmion arrays with a density over 300 Gbit/inch 2 are successfully written, erased, and read out by local electrical and mechanical stimuli of a scanning probe. Interestingly, in contrast to the relatively short lifetime (<20 hours) of the normal skyrmions, the multiple π‐twist target skyrmions and skyrmion bags show topology‐enhanced stability with a lifetime of over two weeks. Experimental and theoretical analysis implies the heterostructures carry electric Dzyaloshinskii–Moriya interaction mediated by oxygen octahedral tiltings. The results demonstrate ferroelectric‐metallic heterostructures as fertile playgrounds for topological states and emergent phenomena.

Understanding the temperature-dependent electro-optic behaviors in (1 − x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] [(1 − x)PMN-xPT] is central to its device applications. In this work, 0.5 mol. % La-(1 − x)PMN-xPT transparent ceramics with different solid solution ratios (i.e., x = 0.10, 0.15, 0.20, 0.25) were fabricated to study the temperature-dependent electro-optic behaviors. Two distinct temperature dependencies are revealed: for 0.85PMN-0.15PT and 0.90PMN-0.10PT, the measured electro-optic coefficient decreases with increasing temperature, while for 0.75PMN-0.25PT and 0.80PMN-0.20PT, the electro-optic coefficient first increases and then decreases rapidly with the increase in temperature. Based on the temperature-dependent dielectric, ferroelectricity, x-ray diffraction, and piezoresponse domain image analysis, the ferroelectric–ferroelectric phase transition is suggested to play a dominant role, with the ferroelectric state to relaxor state transition providing an auxiliary enhancement. This study provides valuable insights into understanding temperature-dependent electro-optic behaviors and should be instructive for the design and optimization of advanced electro-optic devices.

Transparent ferroelectric materials have been attracting enormous attention due to their simultaneously ultrahigh transparency and piezoelectricity, which are highly desirable for electro-optical-mechanical devices. However, it is very challenging to achieve excellent optical transparency in ferroelectric materials because of the severe light scattering of the domain wall. Here, a domain wall scattering model is developed to reveal the mechanism of light scattering caused by domain walls and to quantitatively calculate the scattering of light by different domain walls. The reliability of such a model is verified by the good agreement between theoretical predictions and recent experimental measurements. Based on the model, both domain wall type and orientation are found to greatly determine the transmittance of transparent ferroelectric crystals. The influence of domain size is also investigated. This work provides a theoretical basis for regulating the transmittance of transparent ferroelectric crystals through domain wall engineering.

Ferroelectric materials are considered candidates for functional device application since their discovery in 1920. The functionality is realized by polarization evolution itself or the resulting effects. Studies on ferroelectrics have been going on over a century with a rough journey, because they have the excellent physical properties and also the fatal disadvantages for the device applications, where polarization microstructure and the dynamics are always the core issues. The demand for miniaturization, low energy consumption, and intelligence of devices leads to the advancement of the studies on the polarization microstructure and dynamics towards microscopic and ultrafast scales, as well as precise manipulation. This review mainly focuses on the inherent logic of the development of the theoretical modeling on the polarization dynamics. We would like to discuss the historical background of the development of theoretical models and their limitations, following the historical trajectory how to understand the multiscale nature of polarization microstructure and dynamics and the developing demand of functional devices applications, based on which the prospect and future development direction of theoretical modeling are proposed.

Recently, the flexoelectric effect has triggered considerable interest in energy-related applications, such as flexo-actuation, flexo-photovoltaic, and flexo-catalysis, because of its ubiquitous feature allowing the creation of electric polarity, i.e., the flexoelectric polarization (P-flexo), in non-polar materials by strain gradient. Here, we show a flexoelectric strategy in electrocatalytic water splitting. Remarkably enhanced oxygen evolution reaction (OER) properties are achieved in strain-gradient LaFeO3 (LFO) thin-film heterostructures owing to the promotion of kinetic processes by P-flexo. The improved OER is demonstrated by increased current density of similar to 300% in linear sweep voltammetry and lowered charge transfer resistance by two orders of magnitude in electrochemical impedance spectroscopy. These are ascribed to the flexoelectric-induced downward bending of the LFO band, as revealed by density functional theory calculations and band structure measurements. With P-flexo in the thin-film heterostructure catalysts, the adsorption of hydroxyl ions is strengthened on the polar LFO surface, and the transfer of electrons is accelerated from the reactants/key intermediates to the catalyst across the band-tilted LFO layer. These findings indicate the significance of flexoelectric effect in OER kinetics and open a new perspective for exploiting catalytic mechanisms and performances in water splitting.

Transparent ferroelectric ceramics are popular due to their ability to couple optical and electrical properties. However, simultaneously achieving high electrical and optical performance in ceramics remains a formidable challenge. By using the two-step sintering process combined with a rare earth doping strategy, xLa-24PIN-42PMN-34PT transparent piezoelectric ceramics were prepared, achieving the coexistence of the highest known d33 (>1000 pC/N), excellent transmittance (T = 66.2% at 1600 nm), and the piezoelectric properties decrease by only 26.8% when approaching TC. PFM and in situ XRD results indicate that the parallel stripe-like and watermark-like coexisting ferroelectric domain structures, which are induced by La3+ doping, generate large piezoelectric responses. Light scattering loss is reduced by the small size of the ferroelectric domain structure. Excellent thermal stability is ensured by the tetragonal-dominated morphotropic phase structure. This work provides a valuable idea for the subsequent preparation of transparent ferroelectric ceramics with high performance.

Polarization switching in ferroelectrics by applying external fields is a typical thermodynamic process. Heat dissipation plays an inevitable role, especially in ultrafast and nonequilibrium switching processes. Its role has long been neglected in existing theoretical models focusing on conservative actions. In this paper, a dynamic phase diagram is derived to consider the heat dissipation on equal footing with the work done by external field. Their competition leads to four switching mechanisms. The dynamic and thermodynamic analyses are then performed to verify the inevitable mechanisms dominated by heat dissipation. Our finding refreshes the understanding of polarization dynamics.

Polarization dynamical response is a fundamental issue for both physics and functional device applications for ferroelectrics. The phase field model has been proved as an efficient and indispensable method to capture the polarization evolution behaviors. With the size of polar element reducing to be atomic scale, the underlying physics in the phase field model should be well clarified. Starting from the generalized many-body stochastic dynamics, we discuss the thermodynamics of the polarization dynamics simulated based on the phase field scheme. It is found that the presence of random force guarantees the thermodynamics of polarization system. The numerical simulations indicate that the thermal fluctuations induced by random force give rise to a different heat dissipation mechanism during the process of polarization dynamical responses, which is not taken into account in the conventional phase field simulations. In addition, the thermal fluctuations of random force are found to lead to the unexpected phase instability when considering the atomic-scale polarization dynamical behaviors, which is considered to be originated from the incompatibility between the free-energy functional and random force used in the current phase field model. If simply revising the free-energy functional to get rid of such contradiction, the possible phase instability can be eliminated, but it results in the underestimation of thermal fluctuations and the associated polarization dynamical behaviors. In our opinion, the viable solution is to reconstruct the potential field, making it be compatible with the thermal fluctuation induced by random force. Our discussion could help to provide hints for the development of multiscale modeling scheme in polarization dynamics based on a phase field model.

Mechanical control of ferroelectric domain evolution has attracted much interest over the past decade. Nevertheless, bidirectional 180° mechanical switching, i.e., a complete cycle of mechanical writing and then erasing of a ferroelectric nanodomain, has not yet been realized in tip-film architectures. Here, via first-principles-based molecular dynamics simulations, we demonstrate that bidirectional 180° mechanical switching is possible in tip-film architectures when screening condition of ferroelectric films and tip loading force are within an appropriate window. The switching utilizes a delicate competition between the flexoelectric field and an overlooked effective dipolar field. The effective dipolar field dominates at small tip force and trigger switching from a downward single-domain state to an upward poly-domain state, whereas the flexoelectric field dominates at relatively large tip force and enables a back-switching. Bidirectional mechanical switching is achieved by applying tip force pulses with alternatively varying strength. The dipole-dipole interaction dynamics play important roles in mechanical switching.

Polarization relaxation fundamentally determines the speed, energy consumption, and functionality of ferroelectric materials and devices, which is considered as the core aspect of ferroelectric-based applications and attracts considerable attention. The relaxation time, describing the temporal characteristics of polarization relaxation, has been reported to vary from subpicoseconds to hundreds of nanoseconds in ferroelectrics, and the microscopic picture is still an open question. In this paper, starting from atomistic models for ferroelectrics, a generalized Langevin equation is proposed to describe the dynamical behaviors of polarization at the mesoscale or macroscale. On one hand, through the artificial construction of adiabatic processes, it is derived that the relaxation time is connected with the lifetimes of the phonon modes involved in a many-body ferroelectric system, bridging the thermodynamics of polarization with the dissipation behavior of the phonon modes at the microscale. On the other hand, the relaxation time is then linked to the kinetic coefficient used in the time-dependent Ginzburg-Landau equation, for the polarization evolution on the meso- or macroscale. Furthermore, based on driven Brownian motion, we propose a theoretical model of the dependence of the polarization switching time with an applied external electric field on a ferroelectric monodomain system. The prediction of the switching time is found to agree well with the dynamical simulation data, which verifies the applicability and reliability of the physical picture of the relaxation time clarified in the current work. Our discussion of the physical picture of the polarization relaxation time provides useful ideas for the development of multiscale modeling method for ferroelectrics.

Artificial neural networks have gained intensive attention in recent years because of their potential in effectively reducing energy consumption and improving computation performance. Ferroelectric materials are considered to be promising candidates for artificial synapses because of their multiple and nonvolatile polarization states under external stimuli. Despite artificial ferroelectric synapses with multilevel states, long retention and fast switching speed have been reported, and some key fundamental issues, e.g., the influence of domain wall configuration and evolution on the performance of synapse behaviors, also remain unclear. In this work, we study the performance of artificial synapses based on the motion of 180° ferroelectric domain walls of stripe domain and cylinder domain in ferroelectric thin films via a dynamical phase field model. The results demonstrate that artificial synapses based on the stripe domain exhibit high linearity and symmetry in weight update under a weak electric field, compared with the cylinder domain. Based on such artificial synapses, the accuracy of an artificial neural network for the Modified National Institute of Standards and Technology handwritten digit recognition is over 92%. This work provides a domain-wall-based strategy to improve the weight updating linearity and symmetry of artificial synapse devices and the recognition accuracy of artificial neural networks.

Dynamical phase field simulation is performed to reveal the dynamic characteristics of the tip-force-induced polarization switching in ferroelectric thin films. We demonstrate nontrivial influences of kinetic coefficient μ related to the second-order time derivative term in the dynamic equation of polarization on the mechanical switching behavior. It is found that such a term causes an oscillation feature of the switching process. Two characteristic switching times, i.e., the time when the inversed polarization begins to appear (denoted as τS1) and the time when the fraction of switched (c−) domain is largest during the loading process (denoted as τS2), can be defined to describe the tip-force-induced switching behavior. Both τS1 and τS2 are found to be affected by factors like misfit strain, temperature, and film thickness. Remarkably, the mechanical switching of polarization can be rather fast, with the switching time comparable to that of electrical switching. Due to the nontrivial dynamical effects, other important phenomena are observed: (a) the size and the pattern of switched domain (i.e., cylinder vs ring) in a single-point switching event strongly depend on the loading time, (b) the critical force of mechanical switching may be largely decreased by choosing a proper loading time, and (c) a large and stable domain pattern can still be written by a sweeping tip despite that the switched domain is not stable in the single-point switching event. Our study should provide new insights into the ultrafast phenomena in ferroelectric polarization switching under mechanical stimuli.

Helium diffusion in metals is the basic requirement of nucleation and growth of bubble, which gives rise to adverse degradation effects on mechanical properties of structural materials in reactors under irradiation. Lattice based Kinetic Monte Carlo approach is widely adopted to study the evolution of helium-vacancy clustering. However, the imple-mentation of Arrhenius law to prediction the event rate of single interstitial helium solute diffusion in metal is not always appropriate due to low-energy barrier. Based on a stochastic model, a modified formula is derived from the Brownian motion upon a cosine-type potential. Using the parameters obtained from molecular dynamics simulation for the diffusivity of single helium solute in BCC W, the prediction of our model is consistent with the results from dynamical simulation and previous model. This work would help to develop a more accurate KMC scheme for the growth of helium-vacancy clusters, as well as other low-energy reactions in materials science.

The substitution of helium atom inside BCC Fe results in (1) lattice distortion, (2) the resonance phonon modes, and (3) the scattering center, enhancing the anharmonicity of phonon and magnon. The ferromagnetic effects are analyzed by comparing results in the ferromagnetic and non-magnetic systems using spin-lattice dynamics simulations based on quantum fluctuation dissipation relation. The ferromagnetic effects are subtracted into static and dynamic contributions, where the former is found to be dominant. Neglecting ferromagnetic effects would bring with unexpected large error in the description of kinetics of helium in metals.

Skyrmion-based spintronic devices are considered one of the prime candidates for the next generation of functional devices. The mechanistic understanding of magnetomechanics arising from the intrinsic spin-lattice coupling in skyrmion materials becomes an attractive issue. In this paper, by taking MnSi as an example, we proposed an atomistic simulation model based on the developed spin-lattice dynamics scheme for skyrmion materials. The calculated magnetomechanical properties are examined to be qualitatively consistent with the experimental measurement, which suggests that our model is appropriate for the study of thermodynamics, magnetics, and mechanics of skyrmion materials. In addition, the microscopic understanding of the thermodynamic and kinetic aspects of magnetomechanics in skyrmion materials are presented. Through the intrinsic spin-lattice coupling, the transformation of magnetic ordering by external magnetic field results in the change of mechanical properties, for instance, the global mechanical anisotropy and local distortion of lattice structure. The calculation results indicate the magnetomechanics are the result of spin nonalignment induced by the synergistic effects of Dzyaloshinsky-Moriya interaction, Heisenberg exchange interaction, and Zeeman interaction of interspins and elastic interactions of interlattices. Further, the relaxation time of the lattice structure is calculated to characterize the speed of mechanical response against the magnetic ordering changes, which might provide hints of low-energy consumption and low applied electric current in driving skyrmions. The microscopic understanding provided by current study could help the research and design of skyrmion-based spintronic devices.

Sodium benzoate (SB) is widely used as a preservative in food industry, and bovine serum albumin (BSA) is a major carrier protein similar to human serum albumin (HSA), the study of the binding between the two has great significance on human health. In this paper, we systematically investigated the binding of SB and BSA under the simulated physiological conditions combining with various common analytical methods, e.g., fluorescence, UV–vis absorption, synchronous fluorescence and circular dichroism (CD) spectra, as well as molecular docking method. The fluorescence quenching measurements were respectively carried out at 298 K, 303 K and 308 K using the Stern–Volmer method. The results reveal that ground state SB–BSA complex was formed within the binding constants from 2.02 × 104 to 7.9 × 103 M−1. Meanwhile, the negative values of ΔH0 (− 43.92 kJ mol−1) and ΔS0 (− 111.6 J mol−1 K−1) demonstrated that both the hydrogen binding interaction and van der Waals forces contributed to stabilizing the SB–BSA complex. The site marker competitive experiments show that the SB and BSA bound at site I. Furthermore, the experimental results of UV–vis absorption, synchronous fluorescence and CD spectra indicate that the binding of SB and BSA may change the conformation of BSA. In addition, the molecular docking experiment suggests that hydrogen bond was formed in the interaction between SB and BSA.