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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]

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]

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]

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]

We present detailed analysis of thermodynamics and kinetics of switching effects in ferroelectrics with 180° domains. First, the switching effects are investigated by the field theory approaches and, then, within the weak metastability domain they are analysed by means of the classical nucleation theory. All basic characteristics for the switching process are estimated, namely, evolution of the size distribution function for domains is found and the time dependence of changes in the density of domains and flow of domains during the process is determined. The growing mechanism of domains are investigated. An approach to define certain constants for ferroelectric crystals with respect to analysis of evolution of the switching current is proposed. [ABSTRACT FROM AUTHOR]

Nonlinear magnetoelectric effect was investigated experimentally in single crystal single domain samples of metastable orthorhombic ferroelectric ferroelastic β′-phases of rare earth molybdates Tb 2 (MoO 4 ) 3 , TbGd(MoO 4 ) 3 , DyGd(MoO 4 ) 3 , Gd 2 (MoO 4 ) 3 and Sm 2 (MoO 4 ) 3 . The field dependence of the electric polarization was measured in the magnetic field up to 20 Tesla at temperatures down to 0,4 K using the direct current method. The mechanism of the interaction between the magnetic and ferroelectric subsystems based on the magnetostriction is proposed. [ABSTRACT FROM AUTHOR]

Results reported on the dielectric properties, spontaneous polarization (Ps) and switching time of a FLC material and a mixture of the FLC material after having doped with a small quantity of optical adhesive polymer. The mixture has been prepared by dissolving NOA65 prepolymer and the FLC compound in chloroform. A homogenous mixture of FLC and polymer formed after chloroform is being evaporated. Dielectric and Ps measurements of FLC-Polymer (PSFLC) mixture have been performed in a 10 μm ITO coated cell after the cell being irradiated with UV radiation for Photo-polymerization in situ. It has been observed that the spontaneous polarization of PSFLC mixture is unexpectedly reduced in polymer network formed as a result of photo polymerization. Similarly the Goldstone mode dielectric strength is also significantly reduced and switching time has been increased. The Soft mode dielectric strength however remains unchanged. The reduction of spontaneous polarization and Goldstone mode dielectric strength of the PSFLC mixture is not the accordance with the mixing ratio. The results have been discussed. [ABSTRACT FROM AUTHOR]

We discuss theoretically the intriguing isotope effect (opposite trends for oxygen and for cations such as Ti or Ba) on the ferroelectric phase-transition temperatures in BaTiO 3 , SrTiO 3 and PbTiO 3 . The transition temperature is defined as the balancing temperature of the two forces; the force reinforcing the ferroelectric (low-temperature) structure (the long-range electron-phonon interaction force), and the thermal fluctuations which will stabilize the paraelectric (higher temperature) structure. Oxygen (anion) isotope exchange induces mainly change in the thermal fluctuation; resulting in that with light isotope introduction the phase transition temperature lowers. The cation isotope exchange induces change in the long-range force; resulting in that with light isotope introduction the phase transition temperature rises. [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]

Oxygen isotope exchange for quantum paraelectric SrTiO 3 induces ferroelectricity whose T c is given by T c = 30.4( x - 0.33) 1/2 for SrTi( 16 O 1 - x 18 O x ) 3 . Small frequency dispersion of Ƹ′, large amplitude and bias dependences of ℇ′, polarization above T c for poled samples, and time relaxation of polarization below T c as well as the results of optical measurements by Raman, Brillouin and optical birefringence conclude that properties of oxygen-isotope exchanged strontium titanate resemble to those of Ca-doped samples, i.e., domain state. Difference between oxygen-isotope exchanged and Ca-doped strontium titanate was observed only in the pressure dependence of T c , which may be able to the difference in the random fields in the system. [ABSTRACT FROM AUTHOR]

Temperature dependences of dielectric permittivity and polarization in the vicinity of the transition temperature T C were studied for ferroelectric compounds of K 1 - x (NH 4 ) x H 2 PO 4 mixed crystals. The experimental results revealed the appearance of intermediate mixed glassy-ferroelectric state above T C . Characterizing the irreversibility of electric polarization in the crystal with ammonium concentration close to ferro-glassy concentration boundary. The dielectric relaxation in these is caused by both domain mechanism and mechanism related to the motion of polar microregions. [ABSTRACT FROM AUTHOR]

We conducted X-ray diffraction study of YMn 2 O 5 single crystals with an orbital--radiation X-ray source to determine the lattice distortions related to the ferroelectric phase transition. At present, no anomaly of temperature dependence of lattice parameters has been detected around the ferroelectric transition point T CE = 39 K within the accuracy of lattice parameters, ±1 × 10 -4 Å. Moreover neither splitting of Bragg peaks nor appearance of a super lattice reflection were noticed below T CE . These facts indicate that ionic displacement at T CE is much smaller in YMn 2 O 5 than in typical ferroelectrics. On the basis of symmetry consideration, we discuss a possible ionic displacements at the ferroelectric transition. [ABSTRACT FROM AUTHOR]

We designed multifunctional measuring system for ferroelectric thin films which differs from analogous ones by open architecture. Special model taking into account interface layers close to metal electrodes has been suggested. These procedures have been used for investigation of ferroelectric structures based on Pt/PbZr 0.52 Ti 0.48 O 3 /Pt/Ti/SiO 2 /Si (PZT). Appreciable asymmetric capacitance-voltage curves and hysteresis loops behavior has been obtained for some specimens. These results provide an explanation for the models, which describes the Pt/PZT/Pt structure as a series circuit of three depletion layer capacitors. To explain the electrical asymmetries, we assumed that they came from the interfacial state difference between the top Pt/PZT and the bottom PZT/Pt. Following this method for the high field voltage, we could obtain values of associated parameters, such as the depletion layer capacitance, bulk permittivity, and space-charge density. [ABSTRACT FROM AUTHOR]

The polarization waves propagating in the paraelectric phase of ferroelectric thin films are studied beyond the electrostatic approximation that we previously proposed. Using realistic numerical parameters we demonstrate that the retardation electromagnetic terms mainly affect the fundamental even Transverse-Electric (TE) mode which shows a vanishing frequency at zero wave vector. Concerning the other excitations, the electrostatic approximation provides satisfactory results for surface wave vectors k exceding the cut-off value defined by ω = c k where c is the light velocity in the surrounding medium. [ABSTRACT FROM AUTHOR]

Growth, structure and properties of a -axis oriented ferroelectric Bi 3.25 La 0.75 Ti 3 O 12 thin films on SrRuO 3 -electroded, buffered Si(100) substrates are compared with those of (116)-oriented ferroelectric SrBi 2 Ta 2 O 9 thin films on the same substrate. It is shown how the ferroelectric properties of (116)-oriented SrBi 2 Ta 2 O 9 films suffer from certain inherent crystallographic properties of the films, whereas a -axis oriented Bi 3.25 La 0.75 Ti 3 O 12 thin films are free from such shortcomings. In result, the latter have a very large remanent polarization in amount of 32 μC/cm 2 --a new record for bismuth-layered perovskite thin films on substrates--pointing to the superiority of a -axis oriented Bi 3.25 La 0.75 Ti 3 O 12 thin films with respect to memory applications. [ABSTRACT FROM AUTHOR]

The PSN-PLuN solid solutions have been prepared in the whole composition range for the first time. The dielectric, pyroelectric and hysteresis loops measurements of the 0.25PSN-0.75PLuN ceramics stress-free or under the stress (0-1.5 kbar) have been carried out. It is found that compressive stress shifts the phase transformation and decrease the field-polarization hysteresis. These effects can be mainly connected with the change in domain walls dynamics and with polarization switching under the action of stress. [ABSTRACT FROM AUTHOR]

The microscopic mechanism of spontaneous polarization and refractive indices in 180° ferroelectric domain walls of tetragonal Potassium niobate (KNbO 3 ) is discussed by using a microscopic model. This model bases on the orbital approximation in correlation with the dipole-dipole interaction due to the local field acting on all constituent ions within the domain wall. It is found that the behavior of both the spontaneous polarization and refractive indices depends on the thickness of the domain wall which was varied between 5-20 Å. Moreover, the spontaneous polarization shows a hyperbolic tangent shape for domain walls of a larger thickness which then vanishes at the center of the domain wall. The refractive indices suggest the domain wall to act like a biaxial crystal resulting in refractive index profiles of a Gaussian shape for domain walls of ∼20 Å. This dramatically affects optical transmission through the domain wall specifically for light being polarized parallel to the domain wall. [ABSTRACT FROM AUTHOR]

We investigate the ferroelectric phase transition and the domain formation in a periodic multilayer structure consisting of alternate ferroelectric (FE) and paraelectric (PE) layers of nanometric thickness. The principle result of this study is that the polarization domains formed in the different FE layers interact with each other through the PE layers via an inhomogeneous depolarizing electric field emerging from the domains of the neighboring FE layers. We call this a proximity effect. Based on electrostatic equations coupled with those obtained by the minimization of the Ginzburg-Landau functional for a ferroelectric, we calculated the renormalization of T c as a function of the FE/PE superlattice modulation period. We can describe quantitatively the recent experiments on the thickness dependence of the ferroelectric transition in KNbO 3 -KTaO 3 strained-layer superlattices. [ABSTRACT FROM AUTHOR]

Editorial. Introduces a series of articles related to ferroelectrics, published in the 2003 issue of the journal "Ferroelectrics." Evolutions in the field of ferroic domains and mesoscopic structures; Issues related to the FeRAMs and integrated ferroelectric films.

Pyroelectric infrared sensor arrays are imaging devices for infrared radiation that utilize the temperature dependence of the remanent in polarization in pyroelectric materials. We use the finite element method for the calculation of the coupled thermo-electro-mechanical fields for an instance of a linear sensor array, derive the modulation transfer function from the simulation data, and compare the result to an analytical solution. [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]

Piezoelectric and pyroelectric properties in semicrystalline polymers originate from dipole disorientation, dimensional changes in the amorphous and crystalline phases, motion of charges necessary for compensation and stabilizing the polarization of the crystallites and reversible changes of crystallinity. Using thermally stimulated discharge currents, isothermal charging and discharging currents the relaxation of space charge and dipolar charge are analyzed. The measurements were carried out for polyamide 11 in a large temperature range below and above the glass-rubber transition temperature of the amorphous phase and for different fields and times to allow an effective selective polarization. By appropriate choice of the polarization parameters, the effects related with permanent dipoles in the crystalline phase, the polarization of the dipoles in the amorphous phase, the effect of the space charge and interfacial polarization are identified. The major part of the charge measured during charging is stored in the sample. The polarization induced by stretching of the sample at room temperature is very stable up to temperatures as high as 150°C. [ABSTRACT FROM AUTHOR]

This article presents information on proceedings of the 6th European Conference on Applications of Polar Dielectrics (ECAPD), held at Aveiro, Portugal, in September 2002. The main purpose of ECAPD is to bring together scientists, application engineers and managers in order to present and discuss recent advancements in the area of applications of polar dielectrics, fundamental research, application-oriented research and technology development. The conference was hosted by the Department of Ceramics and Glass Engineering of the University of Aveiro.

The phenomenological theory of the incommensurate phase transition in thin films is presented for the case of the single-component order parameter. The distribution of the order parameter over the film was obtained under the assumption of slowly-varying amplitude. The size effect on the temperature of the phase transition into the incommensurate phase was considered. [ABSTRACT FROM AUTHOR]

Ferroelectric blends of vinylidene fluoride (VDF)/trifluoroethylene (TrFE) copolymer with different molar ratio of 56/44, 60/40, 63/37, 67/33, 70/30, 73/27 and 77/23 were fabricated by casting from methyl ethyl ketone solution. Thermally stimulated depolarization current (TSDC) of the samples has been measured on the modified apparatus of thermal electric analyzer. Wide angle X-ray diffraction shows two peaks in the region of 2θ = 18-20° for all the blends, which indicates that the blends have the same crystal lattice structure as the copolymers. DSC results present that the blends display the phase transition characters of both copolymers of 77/23 and 56/44. TSDC spectra of the blends exhibit the characters of the both components at different polarization temperatures. [ABSTRACT FROM AUTHOR]

The calculation of random field distribution function in the relaxor ferroelectrics was performed in the statistical physics framework. The point charges and electric dipoles randomly distributed in Burns reference phase were considered as the main sources of random electric field. The influence of the surfaces was calculated in the model of image charges and dipoles distributed in all the space. The contribution of these real and image sources of random field was taken into account. The characteristic features of calculated random field distribution function namely its half-width and the most probable electric field value were shown to be dependent both on the field sources parameters and on the dielectric permittivity of the surrounding media and ferroelectric material. It was shown that in general case the degree of disorder in the film of a relaxor could be either larger or smaller than in the bulk. Because of this the change of phase diagram with transformation of dipole glass state into ferroglass and vice versa can be expected. The developed theory opens the way of calculation of the disordered ferroelectrics film properties by averaging of the properties, calculated in host phase (Burns reference phase for the relaxors) as functions of electric field. [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]

Results of studies of the effect of the buffer layer 1.3PbO 0.5ZrO2 0.5TiO2 (conditional composition is Pb1.3(Zr0.5Ti0.5)O3) on the properties of Pb(Zr0.5Ti0.5)O3 films on Ti and Pt substrates are considered. The films are obtained by metal organic deposition method (MOD). Films deposited on Pt substrate (with the buffer layer or without it) do not show fatigue up to N = 109 (where N is number of switching cycles) on Pr(N) and Ec(N) dependences. For films deposited on Ti substrates with the intermediate buffer layer Pr(N) dependences demonstrate a basically new feature: after ∼108 switching cycles the remanent polarization increases. The increase of Pr is 50% at N = 1010, the increase of coercive field is small. [ABSTRACT FROM AUTHOR]

The processes of the formation and evolution of grain structures in binary systems of solid solutions (1-x)NaNbO3-xCa2Nb2O7(Sr2Nb2O7), where 0 ≤ x ≤ 1, are discussed. The multifractal parameterization of the sections of grain boundaries was performed. A correlation between multifractal and electrophysical parameters of niobate ferroelectric ceramics was established. A possibility of the quantitative description of microstructures in the systems under study by means of multifractal ideas is shown. The results obtained were used for optimization of the processes of preparation of new ferroelectric materials. [ABSTRACT FROM AUTHOR]

The problem proton-glass and ferroelectric phases coexistence in Rb1-x(NH4)xH2AsO4 (RADA) and K1-x(NH4)xH2PO4 (KADP) crystals based on dielectric studies up to temperature 0.3 K is presented. The measurements were performed in the helium-3 cryostat in the temperature range from 300 K to 0.3 K. Glass behavior for the RADA is present even for a small concentration x = 0.01, whereas for the KADP the proton glass occurs for a concentration x > 0.05. The partial phase diagrams of RADP and KADP as a function of fractional ammonium concentration x and temperature T are presented. [ABSTRACT FROM AUTHOR]

Potential relief along the direction perpendicular to the face of the cube for oxygen atom located in Mg--O--Nb chain in Pb(Mg 1/3 Nb 2/3 )O 3 (PMN) is considered. Accurate total energy cluster calculations are performed in the framework of ab initio restricted Hartree-Fock (RHF) method plus 2nd order Moller-Plesset perturbation theory (MP2) electron correlation corrections. It is found that the equilibrium oxygen position is shifted by 0.0664 Å from the middle point towards Nb atom. It is shown that electron correlation effects strongly influence on the equilibrium atomic positions in PMN. [ABSTRACT FROM AUTHOR]

The results of a study of polarization distribution in PLZT relaxor ceramics are presented. It is shown that for PLZT-8/65/35 ceramics the value of polarization in the surface layer is much smaller than in the volume, moreover the distribution of polarization in the surface layer is not sensitive to the external electric field. It is suggested that the observed type of polarization distribution is conditioned by the fractal surface nonuniformities existing in this material. [ABSTRACT FROM AUTHOR]

The covalency of the chemical bonding in perovskites is shown to lead to correlations of ionic displacements, which can result in the appearance of additional lines in X-ray absorption spectra. These possibilities are discussed in connection with the explanation of the nature of the ferroelectric phase transition in prototype ferroelectrics like BaTiO 3 and KNbO 3 . [ABSTRACT FROM AUTHOR]

The physical kinetics of single domain ferroelectric materials are studied employing Landau-Khalatnikov equation. The resulting hysteretic curves are obtained numerically. The effective coercive electric field is found to be theoretically dependent on the driving amplitude and frequency as observed in the experimental hysteretic measurements of ferroelectric materials. The effects of thermal noise on the polarization switching time are analyzed using the Fokker-Planck kinetic equation. It is found that the effect of thermal noise is rather significant in a single domain of small volume. It is also shown that for low temperatures quantum effects dominate classical thermal effects in inducing polarization switching in a single ferroelectric domain. [ABSTRACT FROM AUTHOR]

The full set of piezoelectric stress coefficients and the spontaneous polarization of ferroelectric Im2m sodium nitrite were calculated by first-principles quantum-mechanical methods. The Berry phase approach, implemented in the periodic LCAO computational scheme, was employed with an all-electron basis set and the Hartree-Fock Hamiltonian. Suitable deformations are applied to crystal structure, and derivatives of the Berry phases are computed numerically with respect to the strain parameters, so as to obtain the eik = (∂Pi/∂εk)E quantities. The piezoelectric constants obtained were e21 = -0.094, e22 = 0.168, e23 = -0.092, e34 = 0.123, and e16 = -0.127 Cm-2. A spontaneous polarization value Ps = 0.169 Cm-2 was calculated for the Hartree-Fock least-energy crystal structure. [ABSTRACT FROM AUTHOR]

Results of first-principles calculations are reported for KDP and DKDP as a function of pressure. The global energy barrier between the two stable (oppositely polarized) equilibrium configurations, and the separation between the corresponding positions of the H-atoms in the O-H-O bridges, are analyzed in terms of a previously proposed, self-consistent double-well model. We argue that the experimentally observed similarity of the H(D) off-centering distance in KDP and DKDP at the transition temperature can be explained only by means of important geometric isotope effects. [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]

Bismuth ferrite is a magneto-electric material, which simultaneously has polarization and spin orders. We have used electron spin resonance (ESR) as a local probe of the magnetic order in the magnetic field range of 0-25 Tesla, in the frequency domain of 115 to 360 GHz, and at a temperature of 4.2 K. [ABSTRACT FROM AUTHOR]

Recovery of the molecular dynamics of Rb3H(SO4)2 after the crystal has been cooled from the disordered superprotonic phase to the low-conducting phase is reported. The observed room temperature changes of the Raman bands of the (SO4)2- and (HSO4)-1 stretching modes are related to a complex process of reconstruction of O3SO-H···OSO3 dimers, characteristic of the low-conducting phase. [ABSTRACT FROM AUTHOR]

We propose a general framework for the description and understanding of the polarization dynamics in relaxors. This framework is based on the two time-scale motion of off-center ions within polar nanoregions and the increasing restrictions placed on this motion with decreasing temperature. Four general stages are identified. [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 concentration-temperature phase diagram of Rb2xTl2(1- x) Cd2(SO4)3 solid solutions is obtained. It is found that the sequence of phase transitions is P213 ↔ P21 ↔ P1 ↔ P212121 at x = 0-0.5, while the temperature of phase transition from the cubic phase rapidly increases at x = 0.5-1 and a new phase with the symmetry R3 is inclined between the phases with symmetries P213 and P21. [ABSTRACT FROM AUTHOR]

Natural-superlattice-structured Bi3TiNbO9-Bi4Ti3O12 (m = 2-3) (BTN-B1T) thin films have been grown on Pt/TiO2/SiO2/Si substrates at 400°C to 550°C by pulsed laser deposition (PLD) using a BTN-BIT (1 mol:1 mol) target. BTN-BIT film prepared at 550° C and 0.07 Torr has single phase whose c lattice parameter is estimated to 8.300 nm in consideration of periodicity of lattice structure. This lattice constant is very close to the value (8.316 nm) of that of two unit cells of BTN and one unit cell of BIT, which is 2-1 superlattice structure of BTN-BIT. The lattice constant (2.905 nm) of post-annealed BTN-BIT film prepared at 400°C is very close to the value (2.900 nm) of that of half unit cell of BTN and half unit cell of BIT, which is 1-1 superlattice structure of BTNBIT. The BTN-BIT film with 2-1 superlattice structure has large remanent polarization (2 Pr= 50 µC/cm²) due to the structural deformation through Bi2O2 layer. [ABSTRACT FROM AUTHOR]

Relaxor properties of 0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) thin films have been analyzed in terms of large frequency dispersion of dielectric response at temperatures below that of the peak permittivity. A wide spectrum of dielectric relaxation was observed in the frequency dependent response of imaginary part of dielectric permittivity. A cumulative response of Debye relaxators was experimentally observed at lower temperatures. The Cole-Cole plots (ε′ vs. ε″) showed a broad distribution in dielectric relaxation at lower temperatures. The temperature dependence of dielectric dispersion has been analyzed using Vogel-Fulcher relation. A little modification in the Vogel-Fulcher (V-F) relation was incorporated to avoid the singularity at the V-F temperature (Tf). The activation energy (E) and the freezing temperature in PMN-PT thin films were 40 mV and 400 K, respectively. Investigation of ferroelectric properties in terms of polarization hysteresis behavior confirmed presence of interaction among nanopolar clusters. [ABSTRACT FROM AUTHOR]

The measured dielectric constant as a function of electric field, at a frequency of 1MHz is reported for sol-gel deposited Barium-Strontium Titanate (BaxSr1–x TiO3) thin films with x = 0.0 to 0.6 at different temperatures and film thicknesses. The experimental data can be explained by Devonshire thermodynamic theory of free energy expansion in terms of power series of polarization. It is shown that the expansion upto the quadratic term is sufficient to explain the field dependence of dielectric constant. The coefficient C3 of the quadratic term is almost independent of electric field, thickness and temperature but appears to depend on composition and mechanical strains. The effect of strains on C3 shows that the electrostrictive coefficients Q11, Q12 and the elastic constants c11 and c12 are different in thin films with respect to the bulk. [ABSTRACT FROM AUTHOR]

The temperature dependence of dielectric properties and photoluminescence (PL) of glass semiconductor SbSI is studied. According to measurements of the dielectric constant and polarization the first-order structural phase transition into the polar state (dipolar glass) is realized at T = 198 K. A complex spectrum of the found PL in the glass SbSI is related to two types of structural units. A wide radiation band, PL maximum location and large Stocks shift prove the existence of a strong electron-phonon interaction. [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]

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∼⃒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 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]

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]