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Synthesis (via solid-state reaction) and characterization (structure, microstructure, dielectric, electrical, and ferroelectric behavior) of brownmillerite polycrystalline material NaBiFe2O5 (NBFO) are discussed in this paper. The formation of a triclinic structure has been analyzed by the X-ray diffraction method. The morphology of the ceramic sample was analyzed using a field emission scanning electron microscope (FESEM) and energy-dispersive X-ray analysis (EDX). It is found that the grains are uniformly distributed through well-defined grain boundaries of the sample containing all the constituent elements (Na, Bi, Fe, and O). The study of both frequency (1 kHz–1MHz) and temperature (25–450 °C) dependent dielectric and AC-conductivity predicts the presence of Maxwell-Wagner type of dielectric dispersion and thermally activated relaxation mechanism of NBFO. The impedance spectra support the semiconducting behavior of the brownmillerite NBFO at high temperature. The resistance of the material falls with a rise in temperature favors the negative temperature coefficient resistance behavior of the material. The study of electric polarization suggests the possibility of the ferroelectric properties of the studied sample. The high dielectric constant and low tangent loss suggest the possibility of the material for device applications. [ABSTRACT FROM AUTHOR]

Synthesis (via solid-state reaction) and characterization (structure, microstructure, dielectric, electrical, and ferroelectric behavior) of brownmillerite polycrystalline material NaBiFe2O5 (NBFO) are discussed in this paper. The formation of a triclinic structure has been analyzed by the X-ray diffraction method. The morphology of the ceramic sample was analyzed using a field emission scanning electron microscope (FESEM) and energy-dispersive X-ray analysis (EDX). It is found that the grains are uniformly distributed through well-defined grain boundaries of the sample containing all the constituent elements (Na, Bi, Fe, and O). The study of both frequency (1 kHz–1MHz) and temperature (25–450 °C) dependent dielectric and AC-conductivity predicts the presence of Maxwell-Wagner type of dielectric dispersion and thermally activated relaxation mechanism of NBFO. The impedance spectra support the semiconducting behavior of the brownmillerite NBFO at high temperature. The resistance of the material falls with a rise in temperature favors the negative temperature coefficient resistance behavior of the material. The study of electric polarization suggests the possibility of the ferroelectric properties of the studied sample. The high dielectric constant and low tangent loss suggest the possibility of the material for device applications. [ABSTRACT FROM AUTHOR]

We report the preparation and characterization of vanadium substituted four-layer Aurivillius compound Bi5Fe1.5V0.5Ti2O15 using spin coating method. Ferroelectricity in the prepared films are confirmed from the well saturated polarization vs electric field (P-E) loops having remnant polarization (2 Pr) around 12.94 µC/cm2 at room temperature. In addition, low temperature P-E measurements show a decrease in Pmax and 2 Pr, which is attributed to the stabilization of defect dipole complexes and domain pinning, as seen in bismuth-based ferroelectrics. Additionally, this decrease in polarization is accompanied by an increase in imprint, confirming the presence of defect dipoles manifested as internal fields. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of PZT30/70 seed layer as a nucleation aid on the microstructure and electrical properties of 0.93PMN-0.07PT thin films. Pyrochlore phase was totally eliminated at an annealing temperature as low as 650°C. Seeded 0.93PMN-0.07PT thin film possessed a denser structure, larger grain size, and thus higher permittivity, spontaneous polarization and pyrocoefficient than unseeded film. The slim P-E loops and the frequency dependent Tm observed in both films indicated a relaxor-like behavior. [ABSTRACT FROM AUTHOR]

This paper reviews the spontaneous polarization of ferroelectric ceramics and its variations with applied electric field, stress and temperature, especially at induced phase transitions. Normally, there are two kinds of field dependence of the induced polarization, the linear and nonlinear dependence. In this paper the nonlinear relationship will be emphasized. The application of these ceramics for underwater transducers, shock wave power generators, pyroelectric energy converters and pyroelectric voltage transformers are listed. [ABSTRACT FROM AUTHOR]

Recently a theoretical model of the polarization modulated and layer undulated (B7) structure in the systems formed by bent-core (bow-shaped) molecules was presented. In contradiction to the general expectation the model suggests that polarization splay is possible only when the molecules are tilted with respect to the layer normal, i. e. when the chiral symmetry of the system is broken. In this paper we present a detailed stability analysis of the tilted and the nontilted structure with respect to polarization modulation and show, that polarization modulation in the nontilted phase is not possible because the system has no possibility to relieve the stress in the domain walls, neither by bending the layers nor by reducing the smectic order. [ABSTRACT FROM AUTHOR]

A SPICE-based model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. This model was used to generate the I-V characteristic of several logic gates. The use of ferroelectric field effect transistors in memory circuits is being developed by several organizations. The ability of FFETs to have different characteristics depending on the initial polarization can be used to create logic gates. These gates can have properties not available to standard CMOS logic gates, such as memory, reconfigurability and memory. This paper investigates basic properties of FFET logic gates. [ABSTRACT FROM AUTHOR]

There has been extensive research activity since the discovery of fatigue free La-doped Bi 4 Ti 3 O 12 films on Pt electrodes. These films show superior ferroelectric properties and require a lower deposition temperature than the previously discovered SrBi 2 Ta 2 O 9 . Substitution of Bi by lanthanide elements other than La is of interest due to change in the magnitude of the structural distortion in the perovskite block, thereby, changing the remanent polarization. In this paper we discuss the doping of bismuth titanates with other lanthanide elements (Nd, Sm). The films were prepared by spin coating on Pt coated Si substrates. Structural characterization was performed by X-ray diffraction followed by ferroelectric characterization. [ABSTRACT FROM AUTHOR]

Investigation of mesoscopic inhomogeneities caused by the coexistence of FE and AFE phases is carried out in PLLZT solid solutions Pb1-x(Li½La½)x (Zr1-y Ty)O3 with x = 0.1 and 0.15, in which the energy difference between FE and AFE states is small. A weak distinction in free energy leads to the coexistence of the said phases domains at temperatures lower than the point of paraelectric phase transition In the discussed PLLZT solid solutions equivalent crystallographic sites are occupied by ions differing in the size. In the vicinity of the interphase border a process of ions segregation takes place. In the present paper, development of the process of "stratification" of the solid solutions in the course of time is studied. The said process is shown to be entirely completed in the course of 100-120 h. [ABSTRACT FROM AUTHOR]

Today, great emphasis is placed on the creation of lead-free compounds that may be used in multi-functional equipment. This report describes the synthesis (through the solid-state technique) and physical characteristics (structural, electrical, and ferroelectric) of a polycrystalline Sr3Bi2WO9 compound (SBWO). A monoclinic crystal structure with cell parameters; a = 9.0285 Å, b = 16.6457 Å, c = 5.6787 Å with β = 93.13° is studied by analysis of X-ray diffraction method (crystallite size 100.77 nm). The purity, morphology, and elementary composition of elements were studied by SEM (grain size 0.582 μm) and EDX. The temperature-frequency variation of εr, tan δ, and σac were investigated. The drop in grain resistance value with increasing temperature demonstrates the NTCR property of the compound. It has been reported that the conduction process of the compound is based on a study of the modulus spectrum. SBWO is a possible choice for devices because it exhibits outstanding temperature-independent εr characteristics and reduced tanδ. Ferroelectric properties of the material (Ec=0.2655 kV/cm, Pr=0.00454 μC/cm2, Emax=2.478 kV/cm, and Pmax=0.0367 μC/cm2) shown by the electric field-dependent polarization at 25 °C. [ABSTRACT FROM AUTHOR]

The study of basic crystal structure, dielectrics, magnetic and electrical characteristics of a high temperature sintered dysprosium (Dy) substituted bismuth ferrite (BFO) ceramic material, Bi(Fe0.90Dy0.10)O3 (abbreviated as BFDO10) has been reported in this work. The solid-state reaction (SSR) technique is adopted for synthesizing the material. Study of the X-ray diffraction (XRD) data shows an orthorhombic symmetry. The approximate crystallite size is found to be 29 nm. The field emission scanning electron micrograph (FESEM) shows a high density grains of the sample and energy dispersive X-ray micro-analysis (EDXMA) reveals the presence of its basic components. The extensive analysis of the dielectric and electrical properties of the sample was carried out within a frequency from 1 kHz to 1000 kHz and temperature ranges from 25 to 500 °C. A study of the impedance spectroscopy reveals a negative temperature coefficient of resistance (NTCR) behavior and a non-Debye type of dielectric relaxation process of the compound. The ac-conductivity (σac) of the material follows Jonscher's universal power law. A study of the electric field polarization confirms the enhancement in remnant polarization and coercive field. The magnetic property shows an enhancement in ferromagnetic orders by virtue of this doping. Moreover, several other interesting features which could be utilized for modern device applications also specified in this article. [ABSTRACT FROM AUTHOR]

Ferroelectric crystals show spontaneous electric polarization even in the absence of an electric field. Lead hydrogen arsenate (LHA) is a member of the group of Lead hydrogen phosphate (LHP) type ferroelectric crystals. We have modified earlier two sub-lattice pseudospin model (PLCM) Hamiltonian for LHA crystal. phonon anharmonic terms, four body interaction terms, and extra spin-lattice terms have been added to the model. For the LHA crystal, formulas for Cochran's frequency, dielectric constant, and loss tangent have been determined using Green's function approach, and a strong agreement is displayed when comparing our theoretical results to other researchers' experimental findings. [ABSTRACT FROM AUTHOR]

Depolarization field Edemerging from spontaneous polarizationPSis considered to play an essential role in the characteristics of ferroelectrics. For the estimation of Ed, correct dc-permittivityϵdis necessary but is still a controversial issue such as background permittivityϵb. This paper examines the permittivityϵdin the case of 1-dimensional insulating single-domained ferroelectric, by noting thatϵddepends on howPSis defined. This examination shows thatϵdshould be unity when experimentalPSor self-consistentPSis used. Without relying on special theories, a generic consideration based on this results shows that 1-dimensional insulating single-domained ferroelectric having 1st order ferroelectric transition cannot exist thermodynamically. [ABSTRACT FROM PUBLISHER]

The present paper investigates the dielectric and repolarization properties of ferroelectric SiO2– NaNO2and Al2O3– NaNO2composites. It is found that the behavior of the main electrical characteristics is affected by the size of ferroelectric particles and their relative positions in the dielectric matrix. [ABSTRACT FROM PUBLISHER]

In this paper scanning probe microscopy investigations of surface morphology and local ferroelectric properties of sol-gel deposited PZT thin films are presented. It is shown that the films have sufficiently low surface roughness about 2 nm and small grain size about 20 nm. Possibility of the film polarization by applying both positive and negative DC voltage between the SPM probe and the sample is demonstrated. Additionally, times of residual piezoresponse signal relaxation are measured and domain wall velocity for the PZT films is calculated. [ABSTRACT FROM AUTHOR]

The paper describes the results of dynamic simulation of electron beam-induced polarization reversal process in ferroelectrics with a focus on a fractal approach. The methods of fractal analysis were used to estimate the scaling characteristics of TGS-domain structure images and polarization switching current obtained with the SEM. The computer simulation results of domain configuration geometry and corresponding form of switching current are presented. Using modified Kolmogorov-Avrami model, the polarization current was determined taking into account differential equation with fractional derivative. The main features of simulation curve of polarization switching current correspond to experimental data observed. [ABSTRACT FROM AUTHOR]

The coupling between the spatial modulation of the order parameter and the electric polarization, known as the flexoelectric effect in liquid crystals, appears in spin structures in the case of magnetic media. In this paper the various implications of spin flexoelectricity are reviewed including: magnetically induced electric polarization in magnets, electric field driven magnetic domain wall motion, tilting of the domain wall plane, and switching of domain wall chirality as well as the pinning of a magnetic domain wall at the ferroelectric one in multiferroics. [ABSTRACT FROM AUTHOR]

Piezoresponse force microscopy provides an efficient mean for the visualization of the domains with a nanoscale resolution. In this paper, PFM studies have been carried out on ferroelectric materials of special interest. Occurrence of both ferroelectric and ferroelastic properties in the same material is a unique phenomenon which can be used for numerous device fabrication. Bismuth Titanate and Lead Potassium Niobate are the ferroics studied here. Bismuth titanate has one of its crystallographic axes slightly tilted out of the plane resulting in a strong polarization component along the lateral direction. The surface and the phase plots, both along the vertical z-direction and on the x-y plane, have been captured and discussed. In the case of PKN ferroelectric b-axis and ferroelastic c-axis orthogonality relationship in bulk breaks down on the nanoscale observation. [ABSTRACT FROM PUBLISHER]

This paper describes an automated-measurement system of ferroelectric hysteresis loops, which was developed in LabView environment based on Virtual Instrument. The system provides a function obtaining nonlinear polarization current from measured current data, which is important for properly estimating ferroelectricity of a dielectric, especially for one with high electric loss. In addition, the relationship between nonlinear polarization current density and external electric field of a ferroelectric reveals more information which is helpful for researches of polar order and/or ferroelectric characteristics. [ABSTRACT FROM AUTHOR]

YBaCu3O7-x film is considered as an ideal electrode material of PZT film due to: (i) its good conductivity at room temperature; (ii) the similar perovskite structures and good lattice matching between the prepared film and YBCO substrate. Up to now, much has been reported on such preparation methods of hetero-structure PZT/YBCO as physical method PLD and magnetron sputtering, etc. The film physical properties have been studied. However, little has been done on its ferroelectric property because of the very limited thickness of PZT film prepared by these methods. In this paper, Pb1.1Zr0.52Ti0.48O3 thin film with (001)-texture and thickness of 1 um is prepared on YBCO/LaAlO3 (LAO) substrate by sol-gel method. The microstructure and the ferroelectric properties of the film are studied. The results show that both PZT and YBCO thin films have not only the same (001) orientation but good lattice matching as well. In comparison with the randomly-orientated PZT film, the remnant polarization (Pr) of the (001)-textured PZT thin film is 28.7umC/cm2 increased by over 60%. Bipolar switching cycle experiment indicates that the remnant polarization of Pt/PZT/YBCO capacitor has no observable decay after 109 cycles. This result indicates that the anti-fatigue property of the film is improved. [ABSTRACT FROM AUTHOR]

This paper uses structured diffuse scattering to compare and contrast the local crystal structure behaviour of the normal ferroelectric BaTiO3 with a range of relaxor ferroelectric substituted BaTiO3 materials. The results strongly suggest that both normal ferroelectric BaTiO3 and the relaxor ferroelectric substituted BaTiO3's have the same underlying polarisation mechanism i.e. inherent 1-D correlated Ti cation and neighbouring O anion displacements forming 1-D dipole clusters (or polar nano regions). The role of the substituting ions is not to induce the PNR's but rather to suppress homogeneous strain distortion, transverse correlation of the 1-D PNR's and a transition into a long range ordered ferroelctric state. [ABSTRACT FROM AUTHOR]

In a recent paper, the modified model by P. Weiss was applied to ferroelectrics. Typical ferroelectric properties could be simulated. A further generalization of the Weiss model is the assumption of a power law feedback with an exponent κ between the polarization of the permanent dipoles and the local field. The Weiss model is included for the exponent κ = 1 and we obtain a second-order type phase transition. For values κ > 1 the simulations yield first-order type phase transitions whereas we obtain diffusive-type phase transitions for values κ < 1. [ABSTRACT FROM AUTHOR]

In the paper we present analytical calculations of the profiles and average values of the correlation radius of polarization fluctuations and generalized susceptibility in thin ferroelectric films with in-plane and out-of-plane polarization orientation. The contribution of polarization gradient, surface energy and depolarization field were taken into account. For the second order ferroelectrics the correlation radius and generalized susceptibility diverge at the film critical thickness as anticipated. The surface energy, inhomogeneous distribution of polarization and depolarization field related with incomplete screening govern the size effects such as thickness-induced phase transition, corresponding correlation radius and a generalized susceptibility divergence in the phase transition point. [ABSTRACT FROM AUTHOR]

This paper studies the effect of porosity on the electrical properties and polarisation behaviour of hydroxyapatite based ceramics prepared in both dense and porous form. Porosity was introduced into the hydroxyapatite using either burnt-out polymer spheres to produce isolated pores or using polymer foams to create interconnected porosity. The samples were sintered in water vapour at 1300°C and polarised at 400°C with a dc voltage of 3kV/cm applied for 1 hour. Thermally stimulated depolarisation current measurements were used to investigate the degree of polarisation of the hydroxyapatite ceramics and dielectric spectroscopy used to measure the ac conductivity of the materials at the polarisation temperature. The porous materials were successfully polarised and the presence of a high surface area to volume ratio in the porous samples was thought to increase the level of polarisation. [ABSTRACT FROM AUTHOR]

The possibility of inducing a polarization state in PLZT-10 relaxor ceramics under exposure to external electric fields and intensive light illumination at room temperature was shown in this paper. Such polarization state was studied by a dynamic method of investigating pyroelectric properties. It was established that a fairly stable polarization state can also be created in PLZT-10 ceramics when studying it by means of the piezoelectric force microscopy. In the latter case, hysteresis loops of a local piezoelectric response have been obtained. [ABSTRACT FROM AUTHOR]

Isotope exchanged SrTi18O3(STO18) undergoes a ferroelectric transition at about Tc = 24 K. Its origin and mechanism have been investigated by many authors but even the direction of spontaneous polarization has not been clarified yet. In this paper from optical and Raman scattering studies, we report that the spontaneous polarizations are parallel to [1, ± 1,0]c, which is the crystal axes of the tetragonal phase. In Raman spectra, softening of TO modes are observed but the softening is not perfect. The displacement of soft mode is not parallel to the cubic axis [1, 0, 0]ccontrary to the expectation from Slater mode. Near Tc, a quasi-elastic mode appears which suggests the order-disorder nature of this transition. Although at temperatures far from Tc this transition is triggered by the soft TO mode, ferroelectricity in STO18 is a result of the percolation of polar clusters which exist already above Tc. The structure of STO18 below Tc is inhomogeneous mixture of the orthorhombic (C2v) ferroelectric domains with [image omitted] / / [110]c and [image omitted] / / [1[image omitted]0]c in the matrix of the tetragonal (D4h) structure. [ABSTRACT FROM AUTHOR]

We have examined whether or not it would be possible to obtain a giant spontaneous polarization in BiFeO3 (BFO) thin films, in agreement to our experimental data showing values of nearly 150 μ C/cm2. As our previous calculations have shown such values can only be obtained in a giant tetragonality structure of a perfect crystal, in this paper we are studying the defects' influence on the spontaneous polarization in a structure with a low tetragonality. We have found that, alike in conventional perovskite ferroelectrics such as BaTiO3 and PbTiO3, hole doping can enhance the ionic off-centering in BFO. [ABSTRACT FROM AUTHOR]

Relaxors have a wide variety of industrial applications because of their high permittivity and piezoelectricity around room temperature. Although the microscopic mechanism of the relaxor behavior has not been fully elucidated yet, there are some fundamental developments in the experimental studies in the last decade, which are briefly reviewed in this paper with particular reference to pioneering works of Professor Ginzburg on phase transitions in ferroelectricity. [ABSTRACT FROM AUTHOR]

The existence of Curie critical point (tricritical point in more recent terminology) was predicted by Landau in 1935. In 1945 Ginzburg created the phenomenological theory, of ferroelectricity based on Landau theory of the second order phase transitions. Ginzburg supposed, that ferroelectric phase transition of the first order in BaTiO3 takes place in vicinity of the critical Curie point. This correct supposition could not be confirmed experimentally at this time and accordingly the Curie critical point coordinates could not be obtained because corresponding critical pressure for BaTiO3 is more than 20 kbar. The first experimental observation of the critical (tricritical) point and estimation of its coordinates was performed in the ferroelectric SbSI crystals in 1967 and published next year. Later on, the tricritical point was found almost in the all ferroelectrics. This paper summarizes the results of experimental investigation of tricritical point in SbSI. [ABSTRACT FROM AUTHOR]

In this paper, three compositions, namely: 8/70/30, 10/70/30 and 12/70/30 of Lanthanum modified PZT (PLZT) thin films have been prepared on ITO coated glass substrates by sol-gel spin coating technique. The X-Ray Diffraction studies of these films show the strong peaks corresponding to the perovskite structure of ferroelectric materials. The dielectric constant (ε r ) and dielectric loss (tanδ) are measured as a function of frequency and temperature. The saturation polarization (P S ), remanent polarization (P R ) and coercive field (E C ) of polarization-electric field hysteresis loop are presented for these films. The I-V characteristics have also been obtained. [ABSTRACT FROM AUTHOR]

The dynamic mechanism of the ferroelectric phase transition in SrTi(16O1-x18Ox)3induced by the isotope exchange of18O for16O is proposed. This mechanism is based on the electron-lattice p-d coupling, TO and TA phonon-phonon interactions and the quantum fluctuations (zero-point motion). The lowest zone center modeF1u(Γ) in the cubic phase splits intoA2u+Eumodes in the tetragonal phase and theEumode is the ferroelectric soft mode in SrTi18O3. It is shown that the application of hydrostatic pressure on the ferroelectric SrTi18O3depresses the transition temperature down to 0 K abovepc≈0.7 kbar through the electron-lattice strain coupling.∗Paper Originally Presented at 10th European Meeting on Ferroelectricity, Cambridge, U.K., August 3–8, 2003. E-mail:konsin@fi.tartu.ee [ABSTRACT FROM AUTHOR]

Femtosecond Impulsive stimulated Raman scattering of KD2PO4with an optical heterodyne detection has been applied to elucidate the ultra short-time dependence of the response function G(t) associated with a ferroelectric B2soft mode above Tc. In a time region 0&nvsim;200 fs, where the B2mode was excited at t=0 fs, G(t) shows clearly the existence of an initial excitation process followed by a relaxation process well explained in terms of the Debye model. The relaxation process indicates a critical-slowing down with lowering temperature toward Tcin contrast to the initial process independent of temperature due to its mechanical property.∗Paper originally presented at 10th European meeting on Ferroelectricity, Cambridge, U.K., August 3–8, 2003. [ABSTRACT FROM AUTHOR]

The paper investigates dielectric response of ferroelectric films obtained by a method of high-frequency cathode spraying of targets of stoichiometric composition of lead zirconate-titanate (PZT) in oxygen, with aluminum and platinum top-electrodes, and precipitated on stainless steel substrates. The authors make a conclusion that domain boundaries in ferroelectric films with different electrodes interact with defects in different ways. [ABSTRACT FROM AUTHOR]

The aim of the present paper is to review and briefly discuss recent experimental results on the effect of high pressure (p > 1.5 GPa) on relaxor ferroelectrics, exemplified by Na½Bi½TiO3 and PbMg⅓Nb2/3O3. The main result is that relaxor ferroelectrics present important polar and structural pressure-instabilities, which lead to both phase transitions of the average structure and considerable changes of the local structure. It is in particular the observation of a pressure-induced suppression of the relaxorcharacteristic X-ray diffuse scattering that points to important changes in the local order. The complementary use of Raman spectroscopy, X-ray diffraction and X-ray diffuse scattering allows the proposition of a mechanism for the observed changes. [ABSTRACT FROM AUTHOR]

The paper deals with phenomenological treatment of Lead Zinc Niobate--Lead Titanate (PZN:PT) crystals. Polarization and weak field permittivity as functions of temperature and bias electric field throughout the whole phase transitions range are of particular importance for the PZN-PT composition's behaviour close to the morphotropic phase boundary (MPB). The effect of DC bias field on phase transitions in PZN:PT solid solutions near the MPB was studied. A phase transition induced by electric field and associated changes in dielectric properties of PZN:PT were observed for different compositions of 4.5% and 8% PT. Relaxation behaviour was observed, too. [ABSTRACT FROM AUTHOR]

Investigating polarization loops of ferroelectric capacitors using a Sawyer-Tower test circuit may lead to some difficulties. It is indeed well-known that the plot of D-E loops may be subject to strong deformations hindering the ferroelectric polarization due to switching domains and preventing the accurate evaluation of remanent and spontaneous polarization ( P r and P s ) and of the coercive field ( E c ). These distortions originate from the unavoidable presence of circuit elements and/or from the leaky character of the ferroelectric capacitor under test. In this paper, a suitable expression for the release of the deformations and the computation of the polarization due to switching domains is proposed including both the measurement data and the parasitic effects of all parameters of a Sawyer-Tower circuit. A numerical procedure is then presented allowing not only to restore the true shape of the ferroelectric polarization but also to determine both the resistivity and the linear dielectric constant of a ferroelectric sample. Lastly the merits of this method is demonstrated through a successful application to a ferroelectric PZT thin film. [ABSTRACT FROM AUTHOR]

The polarization switching process was investigated in soft and hard PZT ceramics. The frequency dependence of the polarization revealed a relaxation process, which was related to 90°domain walls. The results revealed that the domain reorientation is strongly dependent of the kind of defects and their distribution into the lattice. An evidence of an upper frequency limit for the coercive field was observed.∗Paper originally presented at 10th European Meeting on Ferroelectricity, Cambridge, U.K., August 3–8, 2003. [ABSTRACT FROM AUTHOR]

The 180° light scattering experiment has been performed in SrTiO3single crystal under uniaxial stress in order to clarify the physical origin of the Broad Doublet (BD). Especially, the polarization analyses of the BD are made in the stress-induced quantum ferroelectric state (the stress ofσ= 19.4 kgf/mm2is applied along the [001]cdirection atT= 16.5 K). The analyses clearly show that the physical origin of the BD is “not” the second sound. The real physical origin of the BD is predicted to be a transverse acoustic mode propagating inside the ferroelectric regions. [ABSTRACT FROM AUTHOR]

The Landau theory of phase transitions has been widely used to study the static and dynamic properties of ferroelectric materials but mainly through numerical procedures. However the exact solution of the Landau-Khalatnikov equation produces several important consequences. Derivation of explicit expressions for the polarization switching time and the equilibrium polarization as functions of applied electric field and temperatures has enabled the unification of empirical phenomenological theories of dynamic ferroelectric behavior with the Landau theory of phase transitions for ferroelectrics under conditions of high electric fields and temperature. The role of the applied electric field in determining whether a ferroelectric material undergoes partial or complete polarization switching is established explicitly. Concurrently analytical tools for modeling dynamic properties of ferroelectrics have been developed as alternatives to empirical rules currently used in experimental work. [ABSTRACT FROM PUBLISHER]

Elastic properties of the ceramic 0.7SrTiO3-0.3BiScO3sample with relaxor ferroelectric properties were studied in the vicinity of the Burns temperature Td= 550 К. It was found that for the sample under study an anomalous decreasing of the Young's modulus takes place just below the temperature Td. This elastic softening is assumed to be due to electrostriction relationship between spontaneous polarization of polar nanoclusters and strain of the sample. [ABSTRACT FROM PUBLISHER]

It is shown that arising of regular triangular isolated domains in lithium niobate and lithium tantalate can be attributed to nonlinear bulk screening currents. Their role in restoration of C3 symmetry and time reversion violation is revealed. Various physical consequences of the presence of nonlinear currents during polarization reversal are discussed. [ABSTRACT FROM AUTHOR]

A brief review is given on the studies of ferroelectricity in perovskites. Early phenomenological theories of displacement-type ferroelectrics are considered. Two markedly different approaches based on density-functional theory are described. In one approach, the electron density of crystal is determined as a sum of Bloch functions. In the other, it is constructed as a superposition of the electron densities of individual ions. The latter approach gives a microscopic justification for the old phenomenological theories. We show that some phenomena in perovskites, which seemingly are of the order-disorder origin, can be explained by quasi-one-dimensional peculiarities of lattice dynamics. [ABSTRACT FROM AUTHOR]

The stoichiometric quasi-insulating BaTiO3 single crystals, in which the conductance due to the impurities are minimized, is found to exhibit an intrinsic conductance that is manifested as the sharp peaks at the phase transitions. To examine whether this conductance represents the conduction through the inside of the crystals or is apparent one due to the current flowing only in the external circuit such as the switching current by the domain motion, we measure the long-time changes of the conduction. The present results demonstrate that the observed peak corresponds to the real current conduction in the quasi-equilibrium state. Additionally, a new measurement scheme is proposed. [ABSTRACT FROM AUTHOR]

Ginzburg-Landau theory for ferroelectric phase instability is combined with Langevin, Fokker-Planck and imaginary time Schrödinger equation techniques to model impact of thermal noise in the kinetics of ferroelectric polarization. The proposed real space/real time numerical method allows to efficiently simulating relaxation, dynamic hysteresis and general dielectric response. [ABSTRACT FROM AUTHOR]

The ferroelectricity of the ABO 3 type perovskite-crystals CaTiO 3 , SrTiO 3 , BaTiO 3 and PbTiO 3 the local fields acting on the Ti ions are discussed. It is shown that the ferroelectricity in the last two crystals is related to the large electronic polarizability of Ba and Pb. [ABSTRACT FROM AUTHOR]

Ferroelectric liquid crystal (FLC) liquid crystal over silicon (LCOS) devices can address large arrays of pixels at very high frame rates. They can also allow the phase of the light to be modulated in a manner that is independent of the state of polarisation of the incoming light. The optical versatility of the liquid crystal can now be matched by the electronic versatility of CMOS (complimentary metal oxide semiconductor) silicon backplanes as developments in very small feature sizes (sub micron) allows more and more complex electronic structures to be integrated into the device. In this paper, we briefly review some possible future applications of this technology in the area of displays, image processing and optical switching. In order to create these new device structures, we need suitable FLC materials. [ABSTRACT FROM AUTHOR]

In bookshelf structures the so called uniform ϕ-theory allows simple analytical treatment. It means that the azimuthal angle ϕ, which specifies the position of the director on the cone, does not vary with depth into the liquid crystal. In this paper it is shown that also for chevron structures a uniform ϕ-theory exists that allows analytical treatment provided we define uniform as a non-variant component of the polarization along the electric field. The theory is applied to the Sony mode, which is an FLC in a chevron structure with the chevron angle δ very close to the cone angle θ, and allows grey levels with active addressing. It is shown that the Sony mode is ideal if the chevron angle equals the cone angle, but even small deviations cause light leakage and hysteresis. [ABSTRACT FROM AUTHOR]

This paper reports about investigations of the poling behavior of Functionally Gradient Materials (FGM). A model was developed to calculate the virgin loop P(E) of a layered system from measured virgin loops of its components. For the modeling, electrical conductivity is neglected and consequently the polarization is assumed to be constant in the FGM. The modeling allows to calculate the electric field strength and to estimate the poling degree of each layer. The results were compared with experimental data of monolithic BaTi 1-x Sn x O 3 - bending actuators consisting of layers with different amount of tin. Virgin loops of monolithic and conventional devices with 2, 3 and 4 layers were measured. A good agreement between modeling and experiment was obtained for the maximum value of polarization. Differences between the values of the remanent polarization were found and discussed. [ABSTRACT FROM AUTHOR]

Nanoscale structural and polar behavior in abalone and clamshell have been studied using the scanning probe techniques. Untreated pristine sample surfaces were probed to realize their intrinsic electrical properties. While prominent polarization switching under opposite bias field is observed in the clusters of nanograins of the abalone shell, the piezoelectric phase contrasts remained confined mostly at the grain-grain boundary regions in the clamshell. These shells mostly comprised of centrosymmetric CaCO3, the observed polar responses is attributed to the structural distortion initiated by the intra-granular organic phase of the biopolymers. The biopolymer-nanocrystalline layered (as found in abalone shell) or 3:1 composite structure (as found in clamshell) bear an analogy with the piezoelectric composites, where due to the stretching/twisting of the biopolymers under external mechanical stress, the piezoelectric responses get originated owing to the intrinsic electromechanical coupling. [ABSTRACT FROM AUTHOR]

Downscaling of magnetoelectric random access memory device (MELRAM) is considered by studying an example of the hybrid structure based on ferroelectric-magnetostrictive metal. Elastic mechanism of magnetoelectric interaction is analyzed by numerical modeling taking into account inhomogeneous distribution of anisotropic strain, ferroelectric polarization and electric field. The proposed shape of the cell allows to decrease the inhomogeneity of the strain in the magnetic subsystem and to achieve remarkable dynamic characteristics for a nanometric device sized nm3: we adopted an input voltage of V0 = 90 mV and obtained a switching time tS = 1.1 ns, an output readout voltage VME = 4.7 mV, and an ultra-low energy consumption 13 aJ/bit. [ABSTRACT FROM AUTHOR]