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• High on/off ratio ferroelectric resistive memory. • Enhanced durability and retention characteristics. • Remarkably Low-energy synaptic emulation. Ferroelectric capacitors hold great promise for non-volatile memory applications. However, the challenge lies in fabricating resistive switching devices with a high on/off ratio, excellent non-volatility, and a simple manufacturing process. Here, a novel approach is introduced by demonstrating the efficacy of the coupling effect between ferroelectric polarization and oxygen vacancy-based conductive filaments in Hf 0.5 Zr 0.5 O 2 (HZO) films for the creation of non-volatile resistive switching memory devices, achieving an impressive on/off ratio of 6.8 × 103 at +1.8 V. An in-depth exploration of the resistive switching mechanism is provided and subsequently the outstanding durability and retention characteristics of these devices for resistive switching is validated. Furthermore, the device's capacity to emulate non-volatile synaptic functionalities is assessed. Our results reveal that under pulsed conditions of 1 V/–2 V with 1 µs pulses spaced 50 ms apart, the device can robustly achieve potentiation/depression synaptic plasticity, while exhibiting energy consumption (0.16 fJ for potentiation, 0.12 fJ for depression) reduced by 1–2 orders of magnitude compared to biological synapses. This work holds significant value as a reference for the fabrication of energy-efficient, non-volatile memory and synaptic devices. [Display omitted] [ABSTRACT FROM AUTHOR]

We investigate the role of polycrystalline disorder on the effective ferro-electro-elastic behavior of perovskite ferroelectric ceramics under electro-mechanical loading. Assuming random initial grain orientations, we use high-resolution phase-field simulations and periodic homogenization of two-dimensional model polycrystals to study the evolution of the domain microstructure within and across grains as well as the resulting effective, macroscopic polarization and strain fields under loading. The number of randomly-oriented grains in simulations, at fixed grain size and fixed numerical resolution per grain, is used to control the polycrystalline disorder. Results indicate that, when the polycrystalline samples are sufficiently disordered (i.e., when sufficiently many randomly-oriented grains are considered), their effective electromechanical response under uniaxial compression is stable, and the concomitant polarization and deformation are always aligned with the mechanical load. Thus, the present study supports the viewpoint that polycrystalline disorder in bulk perovskite ceramics stabilizes the overall ferro-electro-elastic response despite the underlying nonconvex polarization energy landscape. [ABSTRACT FROM AUTHOR]

We present an analytical framework to study the impact of electromechanical properties on the growth of a ferroelectric nucleus. Ferroelectric domain evolution is typically simulated by phase-field models, which have shown that nuclei evolve from needle-like structures into complex domain patterns. However, there has been limited in-depth analysis of the interplay between electrostatics, mechanics and piezoelectricity and their effect on nucleus growth because of the complexity involved in the phase-field description. In this study, we describe the ferroelectric domain wall as a sharp interface and solve for the fields inside an elliptic ferroelectric nucleus via Eshelby's inclusion problem. We analytically determine the driving traction profile around the nucleus to gain insight into the movement of the domain wall with and without applied electromechanical loading. We analyze how the growth is affected by the permittivity, elasticity, and piezoelectricity as well as the nucleus' eccentricity. We further demonstrate that applied loads do not significantly affect nucleus growth, which is primarily determined by the self-equilibrated mechanical and electric field, and that the anisotropy in material properties is essential in determining the growth of a ferroelectric nucleus. [ABSTRACT FROM AUTHOR]

Ferroelectric materials are widely used in energy applications due to their field-driven multiferroic properties. The stress-induced phase transformation plays an important role in the functionality over repeated and consecutive operation cycles, especially at the micro/nanoscales. Here we report a systematic in-situ uniaxial compression tests on cuboidal Barium titanate (BaTiO 3) nanopillars with size varying from 100 nm to 3000 nm, by which we explore the stress-induced transformation and its interplay with plastic deformation. We confirm the superelasticity achieved in pillars by martensitic phase transformation from tetragonal to orthorhombic. There exists a critical size, 330 nm, for the yield stress. Above 330 nm, martensitic phase transformation aids slip along the plane with a low Schmid factor, in turn, the pseudo-compatible twins form within the shear band. The scaling exponent of size-dependent yield strength is found to be exactly 1. For nanopillars smaller than 330 nm, no twins form, only slips with large Schmid factors are activated, and size effect vanishes. All pillars with sizes from 100 nm to 300 nm achieve the theoretical yield limit around 9 GPa. Our experimental results uncover the interplay between twins and slips in BaTiO 3 nanopillars, which pave the way for the optimization of microstructure design of ferroelectric materials for microelectronic applications at small scales. [ABSTRACT FROM AUTHOR]

Ferroelectric field effect transistor (FeFET) memory has shown the potential to meet the requirements of the growing need for fast, dense, low-power, and non-volatile memories. In this paper, we propose a memory architecture named crossed-AND (C-AND), in which each storage cell consists of a single ferroelectric transistor. The write operation is performed using different write schemes and different absolute voltages, to account for the asymmetric switching voltages of the FeFET. It enables writing an entire wordline in two consecutive cycles and prevents current and power through the channel of the transistor. During the read operation, the current and power are mostly sensed at a single selected device in each column. The read scheme additionally enables reading an entire word without read errors, even along long bitlines. Our Simulations demonstrate that, in comparison to the previously proposed AND architecture, the C-AND architecture diminishes read errors, reduces write disturbs, enables the usage of longer bitlines, and saves up to 2.92X in memory cell area. [ABSTRACT FROM AUTHOR]

1. Ferroelectric polarization value and o-/t- mixed phase fraction of HZO thin films can be largely enhanced by implementing W capping electrode. 2. Less wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 1010 cycles were obtained for W/HZO/W capacitor. 3. The influence of the top electrode on the ferroelectricity of metal/HZO/metal capacitor is more important than that of the bottom electrode. This paper reports the improvement of electrical, ferroelectric and endurance of Hf 0.5 Zr 0.5 O 2 (HZO) thin-film capacitors by implementing W electrode. The W/HZO/W capacitor shows excellent pristine 2 P r values of 45.1 μC/cm2 at ±6 V, which are much higher than those of TiN/HZO/W (34.4 μC/cm2) and W/HZO/TiN (26.9 μC/cm2) capacitors. Notably, the maximum initial 2 P r value of W/HZO/W capacitor can reach as high as 57.9 μC/cm2 at ±7.5 V. These strong ferroelectric polarization effects are ascribed to the W electrode with a fairly low thermal expansion coefficient which provides a larger in-plane tensile strain compared with TiN electrode, allowing for enhancement of o-phase formation. Moreover, the W/HZO/W capacitor also exhibits higher endurance, smaller wake-up effect (10.1%) and superior fatigue properties up to 1.5 × 1010cycles compared to the TiN/HZO/W and W/HZO/TiN capacitors. Such improvements of W/HZO/W capacitor are mainly due to the decreased leakage current by more than an order of magnitude compared to the W/HZO/TiN capacitor. These results demonstrate that capping electrode material plays an important role in the enhancement of o-phase formation, reduces oxygen vacancies, mitigates wake-up effect and improves reliability. [Display omitted] [ABSTRACT FROM AUTHOR]

• The excellent photovoltaic performance with ultrahigh open-circuit voltage of 23 V (575 V/cm) was achieved. • The open-circuit voltage of PIMN-34PT ceramics is larger than almost all of the reported ceramics. • The high domain wall density with a huge intrinsic potential drop is an important factor for the origin of ultrahigh open-circuit voltage. Recently, the anomalous photovoltaic effect of ferroelectric materials has attracted considerable attention in the construction of efficient solar cells owing to the above-bandgap photovoltage of these materials. In this study, we investigate the anomalous photovoltaic effect of relaxor-based ferroelectric Pb(In 1/2 Nb 1/2)O 3 -Pb(Mg 1/3 Nb 2/3)O 3 -PbTiO 3 (PIMN-PT) ceramics with large remnant polarization and a narrow optical bandgap. Excellent photovoltaic performance with an ultrahigh open-circuit voltage of 23 V (575 V/cm) is achieved, which is higher than the open-circuit voltages of all reported polycrystalline materials with similar thickness. The phase structure, microstructure morphology, domain structure, ferroelectric and optical characteristics are analyzed, which could provide clues to the origin of the ultrahigh open-circuit voltage of PIMN-PT ceramics. The results suggest that the relaxor-based ferroelectric PIMN-PT system is a potential candidate for photovoltaic solar energy conversion devices. [ABSTRACT FROM AUTHOR]

A patent has been issued to Taiwan Semiconductor Manufacturing Company Limited for an interfacial dual passivation layer for a ferroelectric device. The patent describes a semiconductor structure that includes a ferroelectric field effect transistor with a gate dielectric comprising a stack of a ferroelectric dielectric layer, a metal-rich hafnium oxide layer, and a stoichiometric HfN layer. The interfacial dual passivation layer improves the ferroelectric characteristics of the ferroelectric dielectric layer. The patent provides detailed information about the structure and composition of the semiconductor device. [Extracted from the article]

The purpose of the paper is to establish a constitutive model for the hysteretic properties in ferroelectrics. Both the polarization and the electric field are simultaneously independent variables so that the constitutive functions depend on both of them. This viewpoint is naturally related to the fact that an hysteresis loop is a closed curve surrounding the region of interest. For the sake of generality, the deformation of the material and the dependence on the temperature are allowed to occur. The constitutive functions are required to be consistent with the second law of thermodynamics. Among other results, the second law implies a general property on the relation between the polarization and the electric field via a differential equation. This equation shows a dependence fully characterized by the free energy and a dependence which is related to the dissipative character of the hysteresis. As a consequence, different hysteresis models may have the same free energy. Models compatible with thermodynamics are then determined by appropriate selections of the free energy and of the dissipative part. Correspondingly, major and minor hysteretic loops are plotted. [ABSTRACT FROM AUTHOR]

The article offers information on the different forms of supermemories. Magnetoresistive random access memory (MRAM) chip uses magnetization to store information within two thin layers of magnetic material. Ferroelectric random access memory (FeRAM) utilizes electrical effects in order to control a transistor-like structure and store data. Meanwhile, phase-change random access memory (PCRAM) stores information in the atomic structure of materials in amorphous and crystalline phases.

A recent study conducted at Qingdao University in China has explored the potential of lead-free ferroelectric ceramics for solid-state refrigeration based on the electrocaloric effect (ECE). The researchers examined the effects of different levels of Sm doping on the properties of 0.5BZT-0.5BCT ceramics, including phase structures, dielectric properties, ferroelectricity, and electrocaloric properties. The results showed that an appropriate level of Sm doping improved the dielectric, ferroelectric, and electrothermal properties of the ceramics. This research provides valuable insights into the development of efficient and environmentally friendly refrigeration technologies. [Extracted from the article]

A recent study conducted by researchers at the National University of Singapore explores the potential of hybrid organic-inorganic perovskites (HOIPs) in the field of electronics. The study focuses on a new class of layered HOIPs called diammonium-halide-diammonium (DHD) perovskites, which exhibit diverse functionalities such as chirality, ferroelectricity, and photovoltaics. The researchers successfully synthesized lead-free double perovskite systems based on the DHD perovskite family and demonstrated the potential applications of this new class of perovskites. The study highlights the importance of exploring structural motifs beyond the well-studied classes of HOIPs and provides insights into their chemical and structural design considerations. [Extracted from the article]

The semiconductor memory device according to claim 1, further comprising: a first insulating layer provided between the first gate electrode layer and the second gate electrode layer, the first insulating layer being in contact with the third region. The semiconductor memory device according to claim 1, further comprising: a third gate electrode layer extending in the first direction, the third gate electrode layer spaced from the first gate electrode layer in the third direction; a fourth gate electrode layer extending in the first direction, the fourth gate electrode layer spaced from the third gate electrode layer in the second direction, the semiconductor layer provided between the fourth gate electrode layer and the third gate electrode layer; and a second insulating layer provided between the first gate electrode layer and the third gate electrode layer, wherein the dielectric layer is provided between the third gate electrode layer and the semiconductor layer, and the dielectric layer is provided between the fourth gate electrode layer and the semiconductor layer. The semiconductor memory device according to claim 2, further comprising: a third insulating layer extending in the third direction, the third insulating layer surrounded by the semiconductor layer, wherein a material of the first insulating layer is different from a material of the third insulating layer.". [Extracted from the article]

Exotic new materials with remarkable properties are poised to transform computing, cosmology and medicine. Stephen Ornes reports [ABSTRACT FROM AUTHOR]

We propose a supervised learning model that enables error backpropagation for spiking neural network hardware. The method is modeled by modifying an existing model to suit the hardware implementation. An example of a network circuit for the model is also presented. In this circuit, a three-terminal ferroelectric memristor (3T-FeMEM), which is a field-effect transistor with a gate insulator composed of ferroelectric materials, is used as an electric synapse device to store the analog synaptic weight. Our model can be implemented by reflecting the network error to the write voltage of the 3T-FeMEMs and introducing a spike-timing-dependent learning function to the device. An XOR problem was successfully demonstrated as a benchmark learning by numerical simulations using the circuit properties to estimate the learning performance. In principle, the learning time per step of this supervised learning model and the circuit is independent of the number of neurons in each layer, promising a high-speed and low-power calculation in large-scale neural networks. [ABSTRACT FROM PUBLISHER]

Ferroelectric barium strontium titanate (BST) glass–ceramics doped with different content of La2O3 were prepared via the melt-quenching technique followed by controlled crystallization. The microstructures of crystallized samples were examined by X-ray diffraction and scanning electron microscopy. Dielectric properties were also investigated. The aliovalent substitution of Ba by La induced dispersion of semiconducting Ba x Sr1−x TiO3 crystallites sealed in a glassy silicate matrix, which increased the ε r and loss tangent values of the BST glass–ceramic. The experimental results indicate that aliovalent substitution is an effective method to process glass–ceramics with better dielectric properties. [Copyright &y& Elsevier]

Abstract: In recent years increasing interest in functional materials such as ferroelectric polymers and ceramics has been shown. For those materials, electric polarizations and viscous effects cause dissipative phenomena, such as the characteristic dielectric and butterfly hystereses. The deformation of polymers is characterized by large strains and rotations. This work develops a general framework for the formulation and numerical implementation of ferroelectric materials at finite deformations. In particular, continuous and discrete variational principles for the dissipative response of quasi-static finite electro-mechanics are developed, which fully determine the continuous evolution and incremental update problems. These principles recast the framework into a canonically compact structure, that makes the model-inherent symmetries of the coupled problem transparent. In the algorithmic stetting, two-step update schemes are developed, first for the local internal variables and next for the global primary fields, both fully determined by the exploitation of incremental potentials. Specific constitutive assumptions are proposed for finite ferroelectricity. A critical point is the definition of kinematic assumptions in the large-strain context, such as the multiplicative decomposition of the deformation gradient into reversible and remanent parts. The proposed formulation allows to reproduce dielectric and butterfly hystereses together with their rate-dependency and accounts for macroscopically non-uniform distributions of the polarization at finite deformations. The performance of the proposed methods is demonstrated by means of benchmark problems undergoing large deformations. [Copyright &y& Elsevier]

The atomic dipoles in the Rabi lattice model exhibit quantum Ising dynamics in the limit of strong atom-photon interaction. It governs the paraelectric to ferroelectric phase transition in the ground state. On an open chain, it implies the existence of two Majorana-like, albeit topologically unprotected, edge modes in the ordered phase. The relation pILx = p8 between the end-to-end dipole correlation pILx and the spontaneous polarization p is proposed as an observable signature of these edge modes. The density-matrix renormalization-group calculations on the one-dimensional Rabi lattice support the strong-coupling quantum Ising behavior and correctly yield the proposed end-to-end dipole correlation. The conditions that protect the edge modes against the adverse perturbations are also identified. [ABSTRACT FROM AUTHOR]

Abstract: We present a family of phase-field models for fracture in piezoelectric and ferroelectric materials. These models couple a variational formulation of brittle fracture with, respectively, (1) the linear theory of piezoelectricity, and (2) a Ginzburg–Landau model of the ferroelectric microstructure to address the full complexity of the fracture phenomenon in these materials. In these models, both the cracks and the ferroelectric domain walls are represented in a diffuse way by phase-fields. The main challenge addressed here is encoding various electromechanical crack models (introduced as crack-face boundary conditions in sharp models) into the phase-field framework. The proposed models are verified through comparisons with the corresponding sharp-crack models. We also perform two dimensional finite element simulations to demonstrate the effect of the different crack-face conditions, the electromechanical loading and the media filling the crack gap on the crack propagation and the microstructure evolution. Salient features of the results are compared with experiments. [Copyright &y& Elsevier]

Abstract: In this paper, a novel atomic-level computational method of perovskite ferroelectrics is established by combining the shell model and atomic-scale finite element method (AFEM). Its applicability is carefully testified for both bulk and nanoscale ferroelectrics, by comparing the calculated structural parameters and polarizations with the molecular dynamics (MD) simulations, first-principles calculations and experiment results. A comparison of the CPU time demonstrates that the developed method has a computational speed about 10 times over that of shell model MD method and its advantage becomes more evident as the computational scale becomes larger. Moreover, two effective calculation skills of long-range Coulomb force are introduced which can further enhance the computational efficiency by about 10 times. Using the developed atomic-level method, we investigate the various patterns of nanoscale domain structures in BaTiO3 and their evolutions under electrical loadings. A domain structure with coexistence of vortex and streamline polarization patterns is revealed. Furthermore, the simulations of domain evolutions not only reproduce well the two-step 90° domain switching process observed in experiments on single domain under an anti-parallel electric field, but also provide a full evolution diagram among different domain patterns under various electric fields. A quantitative analysis indicates that the direction-dependent coercive field of multi-domain structure can be well described by that of single domain based on a simple analytical model. This study on domain patterns and evolutions may help us understand the behaviors of ferroelectrics from the atomic level. [Copyright &y& Elsevier]

Ba1−x Sr x TiO3 ceramics, doped with B2O3-Li2O glasses have been fabricated via a traditional ceramic process at a low sintering temperature of 900 °C using liquid-phase sintering aids. The microstructures and dielectric properties of B2O3-Li2O glasses doped Ba1−x Sr x TiO3 ceramics have been investigated systematically. The temperature dependence dielectric constant and loss reveals that B2O3-Li2O glasses doped Ba1−x Sr x TiO3 ceramics have diffusion phase transformation characteristics. For 5 wt% B2O3-Li2O glasses doped Ba0.55Sr0.45TiO3 composites, the tunability is 15.4% under a dc-applied electric field of 30 kV/cm at 10 kHz; the dielectric loss can be controlled about 0.0025; and the Q value is 286. These composite ceramics sintered at low temperature with suitable dielectric constant, low dielectric loss, relatively high tunability and high Q value are promising candidates for multilayer low-temperature co-fired ceramics (LTCC) and potential microwave tunable devices applications. [Copyright &y& Elsevier]

Against expectations, robust switchable ferroelectricity has been recently observed in ultrathin (1 nm) ferroelectric films exposed to air [V. Garcia et al., Nature (London) 460, 81 (2009)]. Based on first-principles calculations, we show that the system does not polarize unless charged defects or adsorbates form at the surface. We propose electrochemical processes as the most likely origin of this charge. The ferroelectric polarization of the film adapts to the external ionic charge generated on its surface by redox processes when poling the film. This, in turn, alters the band alignment at the bottom electrode interface, explaining the observed tunneling electroresistance. Our conclusions are supported by energetics calculated for varied electrochemical scenarios. [ABSTRACT FROM AUTHOR]

Abstract: Electric, magnetic and magnetoelectric properties of the nano-structured multiferroic composites were studied by using an energy formulation with the consideration of the surface, interface, and size effect. Coupled thermodynamic evolution equations with respect to the spontaneous polarization and magnetization were established, in which the elastic fields in the matrix and inclusions were solved based on the Eshelby''s equivalent inclusion concept and the Mori–Tanaka method. Physical properties of the composite, such as the spontaneous order parameters, piezoelectric/piezomagnetic properties, and the magnetoelectric coupling effect are highly dependent on the stress state and the microstructures of the nano-composites. Magnetoelectric coupling voltage coefficient was unstable in the vicinity of the critical size and disappeared below the critical size. The model is versatile enough for various composite structures. [Copyright &y& Elsevier]

Abstract: The present paper investigates the capability of micromechanical material models to predict the ferroelectric behaviour of morphotropic PZT ceramics in a rate-independent approximation based on realistic microscopic material parameters. Starting point is a three-dimensional tetragonal model, which builds on the model of Pathak and McMeeking [2008. Three-dimensional finite element simulations of ferroelectric polycrystals under electrical and mechanical loading. Journal of the Mechanics and Physics of Solids 56, 663–683]. Volume fractions of the crystallographic variants represent the domain structure inside the grains. Interactions between the grains are taken into account by means of a representative volume element of the grain compound. A simplified set of realistic microscopic material parameters of the lattice in terms of Young''s modulus, Poisson''s ratio, dielectric constant, and spontaneous strain and polarisation is derived from experimental data and theoretical results given in the literature. The simulation of the macroscopic remanent polarisation and strain response due to two load cases shows explicitly that the tetragonal model is not capable to reproduce the behaviour of morphotropic PZT. Therefore, the model is extended by the rhombohedral phase, allowing a mixture of both phases with varying quantities inside the grains. A comparison of our results with experimental data shows a remarkably good agreement, revealing the capability of the extended model. [Copyright &y& Elsevier]

Abstract: This paper presents a variational-based modeling and computational implementation of the non-linear, rate-dependent response of piezoceramics under electro-mechanical loading. The point of departure is a general internal variable formulation that describes the hysteretic electro-mechanical response of the material as a standard dissipative solid. Consistent with this type of dissipative continua, we develop a variational formulation of the coupled electro-mechanical boundary-value-problem based on incremental potentials for the stresses and the electric displacement. We specify the variational formulation to a model that describes time-dependent, electric polarizations accompanied by remanent strains. It is governed by a dual dissipation function formulated in terms of the internal driving forces. The model reproduces experimentally observed dielectric and butterfly hystereses, which are characteristic for ferroelectric materials. It accounts for the rate-dependency of the hystereses and the macroscopically non-uniform distribution of the polarization in the solid. An important aspect of our treatment is the numerical implementation of the coupled problem. The monolithic discretization of the two-field problem appears, as a consequence of the proposed variational principle, in a symmetric format. The performance of the proposed methods is demonstrated by means of a spectrum of benchmark problems. [Copyright &y& Elsevier]

We account for the vectorial character of electromagnetic waves in the study of nonlinear self-action and transverse localization in dielectric anisotropic media. With reference to uniaxials, we address spatial solitons propagating in the nonparaxial regime in the presence of an arbitrary degree of nonlocality, going from the standard Kerr response to the highly nonlocal case, unveiling various effects, including transverse profile asymmetry and bending of the trajectory, as well as a weak effective nonlocality even in local media. [ABSTRACT FROM AUTHOR]

Sol-gel based soft lithography technique has been developed to pattern a variety of ferroelectric Pb(Zr0.52Ti0.48)O3 (PZT) microstructures, with feature size approaching 180 nm and good pattern transfer between the master mold and patterned films. X-ray diffraction and high-resolution transmission electron microscopy confirm the perovskite structure of the patterned PZT. Piezoresponse force microscopy (PFM) and switching spectroscopy piezoresponse force microscopy (SSPFM) confirm their piezoelectricity and ferroelectricity. Piezoresponse as high as 2.75 nm has been observed, comparable to typical PZT films. The patterned PZT microstructures are promising for a wide range of device applications. [Copyright &y& Elsevier]

Abstract: A model-based approach is proposed for the compensation of the piezoelectric hysteresis and creep effects in a feedforward control design for piezoelectric structures. The designed control commands can be favorably used in motion control for applications, e.g. for fast positioning with piezo flexures. They successfully realize fast rest-to-rest motion in the whole voltage operation range of the piezoelectric actuator material, i.e. specifically outside of the linear small-signal regime. The proposed control design combines a flatness-based inversion procedure for the structural dynamics under the assumption of linear piezoelectricity and an inverse piezoelectric operator for compensation of the piezoelectric hysteresis and creep large-signal effects. For that, the overall nonlinear system model is recast in a series connection of an input nonlinearity and the linear dynamics of the mechanical structure, which allows to design the feedforward control in two steps: First, a feedforward control for the linear model part is derived based on an approach exploiting the notion of flatness in combination with modal analysis of the linear dynamics. Thereby, the finite-element method is used to analyze the linear structural dynamics assuming small-signal operation of the piezoelectric material. Secondly, an inverse filter is designed based on the inversion of an operator-based hysteresis and creep model that is capable to compensate these nonlinear effects. By insertion of this filter, very good tracking control performance is achieved in both small and large-signal operation of the piezoelectric actuator. Simulations and experiments for a piezoelectrically actuated plate strip prove that the designed feedforward controls yields excellent tracking performance in large voltage ranges. The achieved time for the rest-to-rest transition is less than half the period of the first structural mode which is a typically limit of comparable methods. [Copyright &y& Elsevier]

Abstract: 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 (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. [Copyright &y& Elsevier]

Abstract: A thermodynamically consistent phenomenological model for the simulation of the macroscopic behavior of ferroelectric polycrystalline ceramics is presented. It is based on the choice of microscopically motivated internal state variables, which describe the texture and the polarization state of the polycrystal. Saturation states are defined for the internal state variables. The linear material behavior is modelled by a transversely isotropic piezoelectric constitutive law, where the anisotropy is history dependent. For non-linear irreversible processes, a switching function and associated evolution rules are applied, satisfying the principle of maximum ferroelectric dissipation. Saturation is modelled by the use of energy-barrier functions in the electric enthalpy density function. Numerical examples demonstrate the capability of the proposed model, to predict the typical experimental results. [Copyright &y& Elsevier]

Abstract: Ferroelectrics are polycrystalline materials consisting of intragranular regions with different polarization directions, called domains. The domains can be switched into different states by the application of an electric field or mechanical stress. We study the influence of grain-to-grain interactions on the overall and local switching behavior. The behavior inside each grain is represented by the micromechanics model of Huber et al. [1999. A constitutive model for ferroelectric polycrystals. J. Mech. Phys. Solids 47 (8), 1663–1697]. The predictions of a self-consistent model of the polycrystal response are compared with those of a multi-grain model in which grains are represented individually. In one flavor of the multi-grain model, each grain is represented by a single finite element, while in the other the fields inside each grain are captured in more detail through a fine discretization. Different electrical and mechanical loading situations are investigated. It is found that the overall response is only mildly dependent on the accuracy with which grain-to-grain interactions are captured, while the distribution of grain-average stresses is quite sensitive to the resolution of the intragranular fields. [Copyright &y& Elsevier]

Abstract: In a theoretical examination of the structures of liquid crystal phases, Robert B. Meyer in 1975 creatively utilized symmetry arguments to predict that tilted, layered liquid crystal phases of chiral molecules are ferroelectric. He then engaged the help of organic chemists to synthesize a compound that might possess such a phase, and once the material was in his hands, Meyer not only verified its ferroelectricity, but also suggested how such a phase could be used for extremely fast displays. This discovery of ferroelectricity in a fluid system with the possibility for unique applications surprised the entire condensed matter research community and quickly paved the way for both increased scientific understanding and significant technological advancement. For this creative synthesis of theory and experiment, Meyer was awarded the 2004 Benjamin Franklin Medal in Physics. [Copyright &y& Elsevier]

We study the electromechanical behavior of lead zirconate titanate ferroelectric ceramics (PZT), by means of a three-dimensional continuum model for deformable ferroelectric bodies in their polar phase characterized by spontaneous polarization and strain. Spontaneous polarization and strain organize into a domain structure which minimizes electrostatic and elastic energies and which can be modified by the application of electromechanical loads. Such process, which is called “domain switching”, is associated with electrical and mechanical hysteresis and can be studied as a minimization problem for a functional which reminds the micromagnetic energy of deformable ferromagnetics. In this paper, which is the first of two, we deal with the electromechanical model and related constitutive assumptions, as well as with the analysis of domain structure in PZT. In particular, following the discover of a new monoclinic phase in PZT carried by Noheda and co-workers, we analyze twinning between spontaneous strain at the various phase boundaries and show that both non-generic, non-conventional twins and finely-twinned laminates are possible, and also that the presence of a monoclinic phase may explain PZT exceptional properties. [Copyright &y& Elsevier]

The article looks at research into the ferroelectric properties of mammalian soft tissues. Topics include ferroelectricity of swine aortic walls, energy-dissipating ferroelectric proteins in seashells, and ferroelectric glycine in a crystalline lattice. Also discussed are potential medical uses for ferroelectricity in the body, such as a drug that could reverse the electrical charge within the aorta to repel cholesterol or as an internal memory source for implanted medical devices.

A phenomenological model for ferroelectric switching is presented in this paper. The model is based on ideas of plasticity. A switching surface is used as the criterion for non-linear response of the material. Hardening models are used to control the size and position of the switching surface in electric field space. The distinctions between kinematic, isotropic and combined hardening models are discussed. The predicted response to electric loading is computed using combinations of isotropic and kinematic hardening. The calculated hysteresis loop and poling curve are in good agreement with experimental data. [Copyright &y& Elsevier]

The (Bi0.9Ho0.1)3.999Ti2.997V0.003O12 (BHTV) films have been prepared on Pt/Ti/SiO2/Si substrates by solgel method. The microstructure and ferroelectric properties of the BHTV films were investigated. The BHTV films show a single phase of Bi-layered Aurivillius structure and dense microstructure. The Ho3+/V5+ co-substitution can effectively improve the ferroelectric properties. The BHTV film exhibits good ferroelectric properties with 2P r of 47.6°C/cm2, 2E c of 265 kV/cm (at applied field of 420 kV/cm), dielectric constant of 305, dielectric loss of 0.031 (at 1 MHz), good insulting behavior, as well as the fatigue-free behavior. [Copyright &y& Elsevier]

Ferroelectric ceramics are of interest for engineering applications because of their electro-mechanical coupling and the unique ability to permanently alter their atomic-level dipole structure (i.e., their polarization) and to induce large-strain actuation through applied electric fields. Although the underlying multiscale coupling mechanisms have been investigated by modeling strategies reaching from the atomic level across the polycrystalline mesoscale to the macroscopic device level, most prior work has neglected the important influence of temperature on the ferroelectric behavior. Here, we present a phase-field (diffuse-interface) constitutive model for ferroelectric ceramics, which is extended to account for the effects of finite temperature by considering thermal lattice vibrations based on statistical mechanics and by modifying the underlying Landau-Devonshire potential to depend on temperature. Results indicate that the chosen interpolation of the Landau energy coefficients is a suitable approach for predicting the temperature-dependent spontaneous polarization accurately over a broad temperature range. Lowering the energy barrier at finite temperature by the aforementioned methods also leads to better agreement with measurements of the bipolar hysteresis. Based on a numerical implementation via FFT spectral homogenization, we present simulation results of single- and polycrystals, which highlight the effect of temperature on the ferroelectric switching kinetics. We observe that thermal fluctuations (at the phase-field level realized by a thermalized stochastic noise term in the Allen-Cahn evolution equation) promote the nucleation of needle-like domains in regions of high heterogeneity or stress concentration such as grain boundaries. This, in turn, leads to a faster polarization reversal at low electric fields and a simulated domain pattern evolution comparable to experimental observations, stemming from the competition between nucleation and growth of domains. We discuss the development, implementation, validation, and application of the temperature-dependent phase-field framework for ferroelectric ceramics with a focus on tetragonal lead zirconate titanate (PZT), which we demonstrate to admit reasonable model predictions and comparison with experiments. [ABSTRACT FROM AUTHOR]

The article focuses on a research describing the ferroelectric behavior in crystalline croconic acid by Sachio Horiuchi at the National Institute of Advanced Industrial Science and Technology in Ibaraki, Japan, and colleagues published in an issue of "Nature."

Prospects for extending the battery life of hand-held devices such as cellphones and MP3 players have been boosted by the discovery that low-power memory chips made from "ferroelectric" materials could be made much denser than anyone thought. Until now, the bulkiness of ferroelectric memories has limited their use to applications in smart cards, which store only small amounts of data. Ferroelectricity is a phenomenon found in a class of materials knows as perovskites, in which ions in the material's crystal lattice are positioned in a way that separates positive and negative charges.

In this article, we demonstrate that the angles at which second-harmonic (SH) waves are generated at ferroelectric domain walls satisfy the Snell law for nonlinear media. Nonlinear reflection and refraction are observed experimentally and the relation is found to be in good agreement with theoretical predictions. The ratio of the intensities of refracted and reflected waves has been measured. Under an anomalous-dispersion-like condition, the forbidden nonlinear reflection and refraction is analyzed and found to have a behavior similar to that of the total internal reflection in linear optics. In the periodic domain structure, the coherent superposition of SH waves has been observed, on the basis of which we have proposed a comprehensive theory to explain nonlinear effects in multilayered structures. [ABSTRACT FROM AUTHOR]

The article reports on a multi-institutional team of researchers led by the Lawrence Berkeley National Laboratory of the U.S. Department of Energy (DOE) which provides the first atomic-scale of ferroelectric properties of nanocrystals. It states that the researchers map the ferroelectric structural distortions of germanium telluride and barium titanate in nanocrystals. It mentions that the maps produce at TEAM I of ferroelectric distortion patterns within the germanium telluride nanocrystals.

The article introduces the ferroelectric random access memory (FRAM) technology, one of the most mature in a class of next-generation nonvolatile memories in the U.S. FRAM aids automotive designers through its fast write speed and high-endurance characteristics. The most recent development, Grade 1 FRAM product, successfully past the AEC-Q100 qualification of a -40 to +125°C. Its qualifying components demonstrate operation at 125°C even after a variety of qualification stresses.

The article reports that researchers at Lawrence Berkeley National Laboratory have solved the mystery on ferroelectric materials that could boost solar cell voltages through the principle of electronic bucket brigade passing electrons to other materials.

The article discusses on the report of Korean researchers on their study with performance of solid-state drive (SSD). It mentions that SSD, like MacBook, suffer from the performance operations, specifically with speed during certain key operations. Researchers proposed the mixture of two types of memory, which will boost SSD's performance in a cheap cost. On the other hand, engineers at Seoul National University has created a prototype for SSD that employs a low amount of ferroelectric RAM for SSD's performance.

The article reports that researchers from Samsung Electronics Co. Ltd. claimed several important advances in phase-change and ferroelectrics random access memories in presentations at the 2005 Symposium on VLSI Technology. Enthusiasm for phase-change memories has waxed and waned over the past few years, with Intel Corp. admitting to difficulties in scaling its phase-change RAM (PRAM) past the 4-Mbit test stage due to various process and materials challenges. STMicroelectronics, an enthusiastic PRAM proponent, is continuing to work on the technology in cooperation with Philips Semiconductors.

The article presents information on a real-time study of the microscopic domain structure of a heteroepitaxial thin film of copper on a ruthenium substrate. By combining bright- and dark-field low-energy electron microscopy images, researchers could map both the stacking and rotational domains of the film and follow their temporal evolution on the time scale of seconds. The boundaries between stacking domains within a given rotational domain move quickly and smoothly but get stuck at the rotational boundaries.