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Reports on the 10th International Meeting on Ferroelectricity which was held in Madrid, Spain from September 3 to 7, 2001. Highlights of the event; Names of speakers.

Processing of lead-based ferroelectric thin films with a chemical solution deposition on Pt/Ti/SiO 2 /Si requires excess lead in the alkoxide-precursor solutions. Excess lead results in the low-temperature processing and improved electrical properties. However, the effect of excess lead on the properties of resultant thin films are not well understood because of the extrinsic effects. In this paper, we investigate the effect of excess lead in the precursor solutions on dielectric and ferroelectric properties of the lead titanate thin films. [ABSTRACT FROM AUTHOR]

High power microwave properties of the ferroelectric phase shifters have been studied to reduce the effect of the nonlinear response of ferroelectrics under high power microwave with an applied dc bias field of 0 - 40 kV/cm. The Ba 0.6 Sr 0.4 TiO 3 ferroelectric films were prepared on (001) MgO single crystals by pulsed laser deposition. Coplanar waveguide (CPW) phase shifters were fabricated from 2 μm thick Au layer to reduce metal loss. The fabricated CPW phase shifters exhibited more than 100° of differential phase at 10 GHz with a 40 kV/cm dc bias field between ground and center conductors. Furthermore, the CPW phase shifter showed a constant differential phase shift with microwave power range from -10 to +30 dBm. Microwave power and/or dc bias field dependant responses of phase shifters are presented in the paper. [ABSTRACT FROM AUTHOR]

Travelling wave ultrasonic motors, TWUM, are based on the friction transmission of mechanical travelling waves excited on the stator by using high Q piezoelectric ceramics. When reducing the analysis to the optimal design of the motor stator, the electromechanical coupling factor can be defined as one of the objective function in the optimisation process. The present paper describes the work carried out in the process of optimising TWUM operation. First, the paper describes a novel modelling suitable for parametric optimisation of the motor performance. secondly, parameters having the most relevant influence on motor performance are identified as optimisation parameters. Finally, the proposed objective functions and the optimisation results are discussed. [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]

This paper reports a newly proposal on the estimation method for piezoelectric transducer properties i.e. power generator and energy conversion ones in application for power MEMS devices. Electrical and mechanical properties of piezoelectrics could be estimated for the mobile electric devices with measuring apparatus built as a trial. The output peak power of PZT transducer is obtained to be 3 μW, which consists of 1.8 V in voltage and 1.7μA in current, in case of 40 N input applied load. Since output voltage and current have linear relationships with applied load, the output electrical power is equal to the square of the applied load. On the other hand, the electro-mechanical coupling constant is estimated to be 0.53 in case of PZT in use of the same apparatus in short and open circuit conditions. It is possible to extract mW power in the equipment of piezoelectric transducers attached to the sole of the shoe, where human total weight is applied most efficiently. This mW output power is enough for actuation of the mobile electric devices. [ABSTRACT FROM AUTHOR]

Multi-layer actuators are used for applications that require large displacements at comparatively low drive voltages compared to monolithic materials. The aim of this paper is to demonstrate methods by which the complete device is characterised by measuring (i) the displacement profile using a non-contact three-dimensional profilometer and (ii) an adapted piezometer to measure the charge per unit force of the device. Experimental measurements are compared with predicted values using a simple analytical analysis. [ABSTRACT FROM AUTHOR]

In order to optimize the broadband response of a piezoelectric transducer, different impedance matching procedures are used, looking for a compromise between efficiency and bandwidth. In this paper a general methodology for the evaluation of acoustic and electrical matching schemes is presented. Broadband acoustic impedance matching schemes are evaluated in the frequency domain using the transmission line analogy. Electrical matching networks at the reception stage are evaluated using the transmission matrix approach. In practical cases of ultrasonic imaging and NDE, electronic "spike" generators based on capacitive discharges are used. The special topology of such generators (including semiconductor devices) conditions the electrical driving pulse at the transducer terminals. This driving waveform (determined by the interactions among the spike generator, the electrical matching network and the transducer) is approximately evaluated in the frequency domain for the low Megahertz range. Several examples in emission and reception illustrate the methodology, including a comparative study of criteria proposed for the optimum design of quarter-wave transmission line matching layers. [ABSTRACT FROM AUTHOR]

Bent-core molecules have been studied widely recently due to their biaxiality and novel phase ordering. A previous computer simulation study by the authors of this paper examined the effect of the bent-core shape on the phase diagram of a rod-like and bent-core liquid crystal models. This computer simulation study has been extended to include polar forces, specifically a transverse dipole, and to determine the effect on the phases formed, initially for the rod-like model. A central transverse dipole of strength μ* = 1.5 was employed. The rod-like model, γ = 0°, underwent a transition from the isotropic to a smectic B and finally to a ferroelectric solid. A nematic phase was observed in the apolar but not the polar system. [ABSTRACT FROM AUTHOR]

Theoretical aspects and experimental observations of nonlinear magnetoelectric phenomena concerning the optical second harmonic generation are discussed. The coexistence of ferroelectric and antiferromagnetic orders in the hexagonal manganites R MnO 3 leads to a new contribution to the nonlinear polarisation. Polarisation selection rules of this contribution allow to determine the magnetic space groups of the hexagonal manganites. Spectroscopic study of second harmonic generation in magnetoelectric garnet films reveals the role of bismuth substitution in these compounds. A new magnetic-dipole mechanism based on magnetoelectric excitation of second harmonic generation in the centrosymmetric antiferromagnet NiO is experimentally studied. Multiphoton resonance gives rise to a high efficiency of this mechanism in NiO. [ABSTRACT FROM AUTHOR]

We studied systematically the crystal structure of simultaneously ferroelectric and antiferromagnetic RMn 2 O 5 (R = Pr-Lu and Y, except Tm) oxides, based on powder X-ray diffraction and Rietveld analysis. We propose a simple picture of the change of the structure with the size of a rare earth ion. [ABSTRACT FROM AUTHOR]

The aim of this work is to understand surface properties of ferroelectric crystals towards gas adsorption. Various ferroelectric crystals involved in these studies readily adsorb carbon dioxide, thus our studies were centered on adsorption studies of this molecule. It has been claimed by other authors that a dipole moment is induced on carbon dioxide molecules that are near an oxide surface. Thus, our experiments explored the possibility of a dipole-dipole interaction between the gas molecule and the ferroelectric oxide surface in order to explain its adsorption. We describe Raman studies of small particles of BaTiO 3 and KNbO 3 in order to determine the ferroelectric nature of the particles as well as to study the temperature dependent phase transitions. We were able to correlate desorption of CO 2 with the occurrence of the Curie transition in BaTiO 3 and with the orthorhombic to tetragonal transition in KNbO 3 in particles of 50 μm size. [ABSTRACT FROM AUTHOR]

Thermal properties of two liquid crystals exhibiting antiferroelectric SmC A * and ferroelectric SmC* phases were studied using differential scanning calorimetry method as well as polarizing microscopy observations. The DSC measurements were performed both on heating and cooling of the samples. Both substances studied in this work are characterised by a complex polymorphism. The temperatures of phase transitions and enthalpy changes associated with them were determined. The transition from the liquid crystalline to the crystalline state showed significant hysteresis for the substances studied. The nature of particular phase was determined by the polarizing microscopy and electrooptic measurements. [ABSTRACT FROM AUTHOR]

Glasses of various compositions in the system (100 - x )Li 2 B 4 O 7 - x (SrO-Bi 2 O 3 -Nb 2 O 5 ) (10 ≤ x ≤ 60) (in molar ratio) were prepared via a conventional melt-quenching technique. The glassy nature of the as-quenched samples was established by Differential Thermal Analyses (DTA). X-ray powder diffraction (XRD) and Transmission Electron Microscopic (TEM) studies confirmed the amorphous nature of the as quenched and crystallinity in the heat-treated samples. The formation of nanocrystalline layered perovskite SrBi 2 Nb 2 O 9 (SBN) phase, in the samples heat-treated at temperatures higher than 550°C, through an intermediate fluorite phase in the LBO glass matrix was confirmed by both the XRD and High Resolution Transmission Electron Microscopy (HRTEM). The samples that were heat-treated at two different temperatures, 550 and 625°C, (containing 0.35 and 0.47 μm sized SBN crystallites) exhibited broad dielectric anomalies in the vicinity of ferroelectric to paraelectric transition temperature of the parent SBN ceramics. A downward shift in the phase transition temperature was observed with decreasing crystallite size of SBN. The observation of pyroelectric and ferroelectric properties for the present samples confirmed their polar nature. [ABSTRACT FROM AUTHOR]

A recently reported pressure-induced phase transformation in PbZrO 3 is investigated by simulated annealing, with ab initio molecular dynamics and pseudopotentials. Our results suggest that, as pressure increases, M 3 -like oxygen rotations are frozen into the orthorhombic antiferroelectric structure. The first order phase transformation occurs at a pressure in reasonable agreement with experiments. This high pressure orthorhombic phase ( I ′) exhibits small but reproducible Γ-like (i.e., ferroelectric) distortions. We also re-examine the PbZrO 3 antiferroelectric phase structure at ambient pressure. Strain and metal ion relaxations are found to significant lowering in energy. The low temperature rhombohedral ferroelectric phase and the orthorhombic antiferroelectric phase are shown to be very similar in energy. [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]

A theory of the dielectric properties of oxygen-isotope-exchanged incipient quantum paraelectrics (SrTiO 3 , KTaO 3 and CaTiO 3 ) is developed. Taking into account the electron-lattice p - d interaction and the coupling of TO and TA vibration B , an expression of the soft mode frequency Ω for the quantum paraelectric is obtained. Frequency Ω is mass dependent including the dependence on the mass of an oxygen atom. In SrTi( 16 O 1 - x 18 O x ) 3 , there is a critical x = x c value, at which zero-point motion of atoms (quantum fluctuations) is partially suppressed and the ferroelectric phase transition occurs at x > x c . The dependence of the ferroelectric transition temperature T c on x in the electric field is calculated. [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]

New mechanism of dipolar ordering is revealed in disordered mixed perovskites Pb( B 1/3 Nb 2/3 )O 3 [ B = Mg, Zn]. Local potentials for oxygen atoms situated in B --O--Nb, B --O-- B and Nb--O--Nb chains are examined in A ( B 1/3 Nb 2/3 )O 3 compounds where A = Pb, Ba. Total energy cluster calculations are performed using ab initio Hartree-Fock method and taking into account electron correlations within Möller-Plesset method. It is found that in B --O--Nb and B --O-- B chains the shapes of the local potentials depend crucially on the chemistry of A site and are also strongly influenced by electron correlation interactions in contrast to Nb--O--Nb chains. It is found for Pb( B 1/3 Nb 2/3 )O 3 that in B --O--Nb chain oxygen atom moves in multi-well potentials with four additional minima shifted along [010] or [100] axes and in B --O-- B chains a local potential surface for oxygen atom has either one minimum in the center of cubic face with very small positive harmonic force constant in the mirror plane (for B = Mg) or four minima shifted in [100] or [010] directions (for B = Zn). Whereas in Ba( B 1/3 Nb 2/3 )O 3 oxygen atoms with all types of chemical environments move in single-well local potentials. [ABSTRACT FROM AUTHOR]

A problem of pure theoretical evaluation of Ising ( J ij ) and tunneling (Ω H/D ) parameters in pseudospin Hamiltonians is considered for H-bonded ferroelectrics. The TKHS family is examined as a example. Two methods of J ij evaluation are applied. Various quantum-chemical approaches are probed. The Ω H/D determination using proton potential energy profiles is also discussed. The obtained parameters allow to explain qualitatively the quantum paraelectric behavior of H-members and the antiferroelectric behavior of D-members of this family even by molecular field approximation. The latter overestimates T c values. The cluster approximation allows to substantially approach the estimated T c to experimental ones. [ABSTRACT FROM AUTHOR]

Editorial. Highlights Seventh Russia/CIS/Baltic/Japan Symposium on Ferroelectricity held in Saint Petersburg, Russia Federation from June 24-28, 2002. Information related to previous symposiums held in the same topic; Organizers of the symposium; Several topics covered in the symposium related to ferroelectricity.

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]

Femtosecond time-domain observations of SrTi( 18 O x 16 O 1 - x ) 3 [STO18] in ferroelectric phase transition have been conducted by impulsive stimulated Raman scattering (ISRS). The phonon-polariton of A 1 -symmetry can be detected at the first time by the use of the heterodyne detection method with an optical phase mask. The static dielectric constant, which is calculated from the dispersion relation of the observed phonon-polariton, agrees well with the value reported in dielectric measurement. This fact indicates that the observed mode is the phonon-polariton originated from the coupling system between the ferroelectric soft mode and photon. [ABSTRACT FROM AUTHOR]

In a Tutton's-salt like family with Fe atom, three compounds K 2 Fe(SO 4 ) 2 · n H 2 O ( n = 2,4, or 6) are known. The phase transition in K 2 Fe(SO 4 ) 2 ·2H 2 O was already examined by the authors' group. Anomalies of both specific heat and dielectric constant were recently found on K 2 Fe(SO 4 ) 2 ·4H 2 O at 283 K. Structure analyses were performed, therefore, at 300 K (monoclinic, space group C 2/ m ; a = 11.853(1), b = 9.544(1), c = 9.951(1)å, β = 94.81(1)°, V = 1121.7(5)å 3 ; Z = 4) and 123 K ( P 2 1 / a , Z = 4). [ABSTRACT FROM AUTHOR]

Selective effect of weak permanent magnetic field on nominally pure ferroelectric triglycine sulfate crystal has been observed for the first time. The prolonged changes of permittivity and Curie point were observed after short-term treatment of the crystal in a narrow interval of magnetic field ∼0.1 T . The effect is explained by magnetic field assisted depinning of domain walls from point defect clusters by spin-depended mechanism similar to depinning of dislocations from paramagnetic obstacles in magnetoplasticity. The point defect clusters are assumed to be H-bonded ones. [ABSTRACT FROM AUTHOR]

Data on the growth of single crystals of protein amino acids and their compounds are presented. The structure and symmetry of the crystals are discussed. The piezoelectric response was studied at temperatures between 120 K and 320 K. The results of studies of optical second harmonic generation and optical activity from the literature are presented. [ABSTRACT FROM AUTHOR]

The existing results on the relaxor-like dielectric behavior which is characterized by a broad maximum in a dielectric permittivity as a function of temperature and the low frequency dielectric dispersion are reviewed for different ferroelectric and non-ferroelectric materials. The general and distinctive features of the relaxor and relaxor-like dielectric anomalies are discussed. Brief discussion of the existing treatments of dielectric data, which take into account not only, the bulk properties of the materials but also the interfacial effects is given. New model explaining the relaxor-like response on the base of the association-dissociation theory of impurity dipole complexes is proposed. [ABSTRACT FROM AUTHOR]

The temperature evolution of the crystal structure of KD 2 PO 4 (DKDP) embedded in a porous glass with 7 nm pore diameter has been studied by neutron diffraction in temperature interval 90 K-308 K. It is shown that confined DKDP forms interconnected clusters with characteristic size of 18(0.5) nm. The structure of this nanocomposite material is found to be monoclinic and corresponds to the space group P 2 1 . The lattice parameters and characteristic cluster size are temperature independent and do not reveal any peculiarities in the vicinity of expected ferroelectric phase transition of 223 K. [ABSTRACT FROM AUTHOR]

The possibility of ferroelectric switching in one monolayer of Langmuir-Blodgett film is demonstrated. The sample studied consisted of separate ferroelectric copolymer with nonferroelectric antrakhinon. [ABSTRACT FROM AUTHOR]

Editorial. Focuses on the Ferroelectric Thin Films 2002 Workshop (FTF 2002) and the Second Open Franco-Ukrainian Meeting on Ferroelectricity (FUMF-2), held at Dinard, France in October 2002. Features of both meetings; Number of scientists which attended FTF 2002 and FUMF-2; Issues related to ferroelectricity, ferroelectric thin films and its applications discussed at both meetings.

(100) and (001) oriented Pb(Zr x Ti 1 - x )O 3 films with x = 0.5 and 0.7 have been grown in situ at 500°C on Pt electrode by RF sputtering. The influence of oxygen content on their electrical properties has been investigated by varying the O 2 /(O 2 + Ar) ratio in the sputtering gas (2.5% and 25%). It was found that the ferroelectric properties of Pt/PZT/Pt capacitors deposited on both MgO and SiO 2 /Si substrates are strongly related to the oxygen partial pressure during the PZT deposition. In particular, the O 2 /(O 2 + Ar) ratio providing the best electrical properties depends on the Zr/Ti ratio of the PZT film. Furthermore, for oriented films with similar crystallographic properties, the remnant polarisation, the coercive field and the dielectric constant can be changed by a factor of more than two, depending on the oxygen partial pressure during the PZT deposition. [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]

In the present paper the phenomena predicted in [1] for substances with coexisting FE and AFE phases coexistence is experimentally shown. The examples of PZT-based solid solutions are investigated. The solid solutions for which FE and AFE states have equal or close energy stability possess the following experimental properties: - a high degree of (paraelectric) PE phase transition diffuseness; - an essential dispersion of permittivity in the region of diffuse maximum of the dependences ℇ′(T) and ℇ′′(T) and fulfilment of the Fogel-Fülcher law; - an increase of the measuring AC field amplitude E 0 leads to a linear decrease of T′ m and to an increase of ℇ′(T′ m ); the tangent of T′ m (E 0 ) dependence decreases with an increase of AC field frequency; - the presence of effects which point to the existence of polar phase domains at temperatures essentially higher than T′ m and T′′ m ; - dependence of their properties on the sample's history; - a long-duration relaxation. [ABSTRACT FROM AUTHOR]

In the present paper the phenomena predicted in [2] for substances with FE and AFE phases coexisting is experimentally shown for Pb(Mg 1/3 Nb 2/3 )O 3 and Pb(B′ 1/2 B′′ 1/2 )O 3 -type compounds. Special attention is paid to analysis of their phase diagrams. The influence of external factors on the properties of these substances is considered. It is shown that all peculiarities in the behaviour of the substances in question are described on the basis of phase transitions between FE and AFE states. [ABSTRACT FROM AUTHOR]

This is a review of properties of PbB′ 0.5 B′′ 0.5 O 3 perovskites, which hold a special position among ferroelectric and antiferroelectric perovskites because of the presence of two sorts of B ions in the sublattice of the oxygen octahedra. The B′ and B′′ ions may be ordered, disordered or partially ordered, and this has a tremendous influence on the properties of these compounds. So, when one speaks about this class of perovskites, one should also indicate the degree of ion ordering in them. In this review, an analysis is made of specific features of phase transitions in perovskites with different degrees of ion ordering: diffuse phase transitions and relaxor properties in materials with ion disorder, so-called spontaneous phase transitions, and ferroelectric-to-antiferroelectric transformations at the ion ordering. Some related problems are also discussed. [ABSTRACT FROM AUTHOR]

We present a HREM study performed on PbK 2 LiNb 5 O 15 at room temperature where the compound presents a ferroelectric and ferroelastic phase. The results display ferroelastic domains and the quality of images allows the use of CRISP software which permits to rule out one of both space groups proposed after X-ray diffraction refinements. The ambiguity on the structure is thus removed: the correct structure is with Pba 2 symmetry. [ABSTRACT FROM AUTHOR]

The weak-field dielectric dispersion studies (100 Hz-13 MHz, 100 K < T < 300 K) of pyrochlore relaxor ferroelectric Cd 2 Nb 2 O 7 modified with Ni 2+ or Cu 2+ on the Cd 2+ site (at x = 0.02, 0.1, and 0.2) are presented and discussed. With increasing x , a relaxor behaviour of the system is manifested at higher temperature (around T C = 196 K and above). Around T C , the dielectric absorption spectra and relaxation-time distribution exhibit developing of two LF dielectric relaxation processes, in addition to ferroelectric domain wall motions: non-Debye relaxation typical of relaxors and Debye-like relaxation of quasi-isolated dipoles. The order parameter characterizing a deviation from Curie-Weiss dielectric behaviour in relaxors is nonzero up to ∼280 K, much higher than T C . The role of disorder on the Cd 2+ -site caused by randomly distributed off-center Ni or Cu ions (at x ≥ 0.1) is discussed. [ABSTRACT FROM AUTHOR]

Substitution of Pb with Gd in the Pb 2 KNb 5 O 15 phases leads to a new composition of solid solution with chemical composition Pb 2(1 - x ) Gd x K 1 + x Nb 5 O 15 (0 ≤ x ≤ 1) which crystallizes with TTB type structure. Powders are pressed and heated into ceramics and their compaction is about 90%. Thermal evolution of the real part of the dielectric permittivity presents different behavior according to the composition. The dielectric permittivity of compounds with Gd composition above x = 0.30 shows two anomalies. The first one appears at T C and is associated to the ferroelectric-paraelectric phase transition. The origin of the last one at which occurs at T 1 is up to now unknown. Domain structure should exhibit strong changes both with temperature and composition. [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]

A computer model of light scattering from the domain structure of Pb 3 MgNb 3 O 9 (PMN) was obtained by the T-matrix method. First we discuss numerical aspects of T-matrix computations specific for ellipsoids and present results of benchmark computations for a simple ellipsoid model. Then we report results of extensive computations for poly-disperse, randomly oriented ellipsoids with the refractive index of PMN [2.15 + ki, ( k = 0.01, 0.008, 0.015)] semi-axis ratios of 1/2, 1/1.5, 1/3, 1/4 and effective size parameters ranging from 0 to 15. These computations parallel to our previous study of light scattering by poly-disperse, randomly oriented spheroids are used to compare scattering properties of two classes of particles. [ABSTRACT FROM AUTHOR]

Disorientation angle of a ferroelastic domain twin resulting from phase transitions cubic → tetragonal, tetragonal → orthorhombic and orthorhombic → monoclinic phases is expressed in crystallographic unit-cell parameters of the low-symmetry phase. These results are compared with those based on spontaneous strain tensor components. [ABSTRACT FROM AUTHOR]

X-band electron paramagnetic resonance (EPR) investigations of single crystals of Cr 3+ -doped dimethylammonium aluminium sulphate hexahydrate (DMAAS) are presented from 100 K to room temperature. The crystal undergoes a phase transition at 152 K from ferroelastic to ferroelectric phase. The spin Hamiltonian parameters have been determined for both phases. The spin Hamiltonian parameters in the ferroelectric phase are: g = 1.980 ± 0.003, b 2 0 = (1140 ± 15) · 10 -4 cm -1 , b 2 2 = (214 ± 10) · 10 -4 cm -1 . Remarkable EPR linewidth changes confirm the order-disorder character of the ferroelectric phase transition on a microscopic level and demonstrate that the dimethylammonium reorientation freezing-out is the prime reason for this transition. [ABSTRACT FROM AUTHOR]

We have fabricated (Sr,Ba) 0.8 Bi 2.2 (Ta,Nb) 2 O 9 (SBBTN) thin films by the sol-gel technique to obtain a small remanent polarization and a large coercive field for ferroelectric-gate FET applications. Ba and Ta compositions are varied from 0 to 0.2 and from 0 to 0.5, respectively. It is demonstrated that the coercive field becomes large by the partial replacement of Ta with Nb atoms and that the Ba doping results in slight decrease of the remanent polarization. A remanent polarization as small as 5 μC/cm 2 and a coercive field as large as 100 kV/cm can be obtained for Sr 0.6 Ba 0.2 Bi 2.2 Ta 1.5 Nb 0.5 O 9 thin films, which were crystallized at 850°C. [ABSTRACT FROM AUTHOR]

The measurements of electric properties of Na 0.98 Li 0.02 NbO 3 ceramics for stress-free or samples under stress have been carried out. It was found that incorporation of Li-cations (2% mol) in antiferroelectric NaNbO 3 causes the induction of ferroelectric properties. It was also found that axial pressure shifts the phase transition and decreases the polarisation. These effects can be mainly connected with change in domain walls dynamics and with the switching of the polarisation under the action of axial pressure. [ABSTRACT FROM AUTHOR]

The article presents issues related to ferroelectrics materials. Volumes 293-296 of the journal "Ferroelectrics," are devoted to the Proceedings of the 6th European Conference on Applications of Polar Dielectrics (ECAPD) that took place 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 like fundamental research, application-oriented research and technology development.

The applicability of characterization techniques of ferroelectric dense materials to porous ferroelectric materials has been investigated. In fact nonlinearity effects are highly increased in porous materials, due to the discontinuities at the internal boundaries. Resonant and quasi-static techniques, based on direct or converse piezoelectric effect, were employed to obtain the physical properties of various types of ferroelectric porous materials. Soft PZT materials, obtained through the "starch consolidation method," with porosities ranging from ≈30% to ≈45% and high hydrostatic figure of merit, acoustical matching and mechanical resistance, as requested in many applications, were characterized. The properties of the dense and porous materials were measured and compared and it was evidenced that the same characterization techniques used for dense ferroelectric materials can be safely and reliably employed, with just slight modifications, for porous ferroelectric materials with porosities as high as 45%. [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]

PLZT x/80/20 (x = 6, 8, 10 at%) ferroelectric ceramics were prepared by conventional oxide mixture method. X-ray difraction analysis show pure perovskite phases. The dielectric properties were analyzed in a wide frequency and temperature ranges, specially around the transition temperature, taking into account the incorporation of the lanthanum into the lattice. A relaxor behavior with diffuse phase transition was observed for all compositions. [ABSTRACT FROM AUTHOR]

Local ferroelectric properties of single crystals (CH 3 NH 3 ) 5 Bi 2 Br 11 (MAPBB) are investigated by Scanning Probe Microscopy (SPM) in a piezoelectric contact mode. The SPM signal proportional to the effective piezoelectric coefficient, d eff , is measured along with the standard topography. Both ferroelectric domain imaging and local hysteresis measurements are performed at room temperature in the close vicinity of the phase transition temperature (T c ≈ 39°C). Lamellar domain structure with the phase contrast due to 180° domains is observed for the surfaces perpendicular to the polar direction. Local hysteresis loops acquired by SPM are well saturated with the average coercive voltage of ∼15 V. The shape of the loops is found to depend on the stiffness of the SPM cantilever. Local studies are complemented with the macroscopic measurements (polarization, piezoelectric coefficient, dielectric permittivity) performed in the temperature range including T c (20-39°C). The mechanisms of the domain contrast and prospects of using MAPBB for high-density data storage are discussed. [ABSTRACT FROM AUTHOR]