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Complex dielectric permittivity ε* = ε' -iε'' of lead-free (Na, Sr, Li)NbO3 ceramic composition exhibiting a relaxor-like dielectric behavior was studied in wide temperature (-180-500°C) and frequency (102-106 Hz) range. Some features characteristic of relaxors were observed, namely fulfilment of quadratic and linear Curie-Weiss laws for ε ' just above and well above the temperature Tm of ε' (T) peak respectively, the Vogel-Fulcher scaling of both ε' (T) and ε” (T) peaks. However, in contrast to canonical lead-containing relaxors Curie-Weiss temperature is lower than Tm and the scaling parameters differ for ε' (T) and ε”(T) suggesting different origin of dielectric relaxation in these two groups of materials. [ABSTRACT FROM AUTHOR]

We report on the influence of platinum electrodes on polarization switching in thin (80 nm-100 nm) ferroelectric Langmuir films of poly(vinylidene fluoride—trifluoroethylene) (P(VDF-TrFE)). Capacitors with top platinum electrodes show neither polarization switching nor paraelectric-to-ferroelectric phase transition. “Negative capacitance” phenomenon was observed for the devices. Such a behavior can be explained by hydrogen attack and chemical reactions promoted by platinum. Samples with bottom platinum and top aluminum electrodes have considerably lower coercive voltages and faster polarization switching if the top electrode is deposited after the annealing of the copolymer film. It may be caused by the re-arrangement of film's molecular chains, and the influence of aluminum oxide layer. [ABSTRACT FROM AUTHOR]

Polarization reversal process with the 90° domain wall structure at a low-frequency field was observed in the c-plate sample of Bi4Ti3O12 using a polarizing microscope. We found that the polarization reversal process with the 90° domain wall structure consists of some basic modes: the translation, pair annihilation, and generation of the 90° domain wall. All of the modes were found to satisfy the conditions of the compatibility of the strains at the wall (the Sapriel theory) and the reduction in the depolarization field. It is pointed out that these two conditions are the most important principles that govern the polarization reversal of the system with the 90° domain structure. [ABSTRACT FROM AUTHOR]

Polycrystalline sample of pyridinium perchlorate was studied by NMR method in the temperature range from 133 to 313 K. Assuming a reorientation of pyridinium cations over inequivalent potential energy barriers in the low-temperature and intermediate phases a temperature dependence of an asymmetry parameter Δ was determined from analysis of 2H line shape. By using the known potential shape and population of its minima, a temperature dependence of the spontaneous polarisation was calculated. The polarisation determined in this way compared with that measured by the pyroelectric effect revealed the mixed type of ferroelectricity in the crystal studied: the order-disorder and displacive one. [ABSTRACT FROM AUTHOR]

Spontaneous polarization (Ps), rotational viscosity (η) and response time (τ) have been determined as a function of temperature at different electric fields for an antiferroelectric liquid crystal [4,4-(1-methyloctyloxycarbonyl)phenyl]-4'-[3-(butanoiloxy)prop-1-oxy]biphenyl carboxylate (MOPB(H)PBC). Spontaneous polarization, rotational viscosity and response time increase with decrease in temperature. Critical electric field (the field at which the spontaneous polarization saturates) was found to be increased with decrease in temperature. [ABSTRACT FROM AUTHOR]

The influence of different metallic and semiconducting electrodes on the properties of thin ferroelectric films is considered within the framework of the phenomenological Ginzburg-Landau theory. Allowing for the effect of charge screening in metals and semiconductors, the contribution of electric field produced by charges in the electrodes is included into the functional of free energy and, hence, to the Euler-Lagrange equation for film polarization. Application of variational method to this equation solution permitted the transformation of the free energy functional into a conventional type free energy with a renormalized coefficient before P2, the coefficient being dependent on the both characteristics of a film and an electrode. This opens a way to calculate the size effect by substituting the coefficient into the conventional formula of the phenomenological theory. A comparison with experimental data for Pt, Ir, IrO2, SrRuO3 has shown a good agreement between theory and experiment. [ABSTRACT FROM AUTHOR]

Peculiarities in the nonlinear dielectric response of the relaxor lead magnoniobate (PMN) are explained within the classic Landau-Ginzburg-Devonshire theory. It turns out that a correction term proportional to the square of the polarization, P02, of polar nanoregions (PNRs) becomes relevant in relaxor ferroelectrics. These PNRs are stabilized by fluctuations of quenched random electric fields. In contrast to regular ferroelectrics with continuous phase transitions, where the third harmonic susceptibility, χ3, is negative at T > Tc, the contribution due to PNRs drives χ3 positive in PMN. The lack of an anomaly in χ3 at the freezing temperature, Tf, does not favor a glassy scenario of relaxors. [ABSTRACT FROM AUTHOR]

Studies of dielectric properties were carried out for MCM-41 molecular sieves whose pores were filled with NaNO2 particles and whose pore sizes vary from 20 to 37 Å. The experimental data obtained were used to calculate the permittivity of confined particles on the base of a theoretical model for two-component composites with hexagonal structure and cylindrical inclusions. Additional NMR measurements confirmed that sodium nitrite in pores occurs in two coexistent modifications. A modification with high spin relaxation was suggested to respond for elevated conductivity of the samples under study. It was shown that the increase of the real part of permittivity is caused by the Maxwell-Wagner polarization. [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.

Synthesis of the bent-shaped (or Λ-shaped) achiral liquid crystal Bent 7, viz., 1,3-phenylene bis(4-heptyloxy benzoate) with resorcinol as central moiety is reported. Supra molecular formation is confirmed by KBr solid state IR spectra. Polarized Thermal Microscopy(TM), Differential Scanning Calorimetry (DSC) and Spontaneous Polarization(PS) experiments infer a bivariant monotropic (cooling), phase sequence viz., Isotropic → B2(FE) → B5(AF) → solid. Phase transition temperatures determined from temperature variation of Dielectric Constant (or relative permittivity εr(T)) agree with TM and DSC. Dielectric dispersion reveals different re-orientation processes viz., a slow (LF∼ 1 kHZ) and a fast (HF∼ 1 MHz) one in both the B2 and B5 phases. Both the relaxations in B5(AF) phase follow Arrhenius shift to infer 1.12 and 0.89 eV of activation energies, respectively. Off-centred dispersion studied through the Cole-Cole plots in B5(AF) phase infer the increasing trend of dielectric increment Δ ε and distribution parameterα with decreasing temperature. Trends of Δ ε and α-parameter suggest a greater fall of response width during slow reorientation and a relative freezing rate during fast reorientation. [ABSTRACT FROM AUTHOR]

The relaxation of the domain structure of KH2PO4, CsH2PO4, and RbH2PO4 ferroelectric crystals was studied by means of measurements of time dependences of the low frequency dielectric permittivity. Non-equilibrium state of the domain structure was induced by polarization reversal under the ac electric field. [ABSTRACT FROM AUTHOR]

PZT(70/30) thick films were fabricated by the sol-gel method. The average grain size increased and the porosity decreased with increasing the number of PZT(30/70) sol infiltration. The thickness of all thick films was approximately 80-82 μ m. The relative dielectric constant increased and dielectric loss decreased with increasing the number of sol infiltration, the values of the 6-coated PZT-6 film were 656, 2.3% at 1kHz, respectively. The remanent polarization, coercive field and breakdown strength of the 6-coated PZT-6 thick films were 27.7 μ C/cm2, 13.5 kV/cm and 190 kV/cm, respectively. [ABSTRACT FROM AUTHOR]

The temperature dependence of the electric properties of lead-free piezoelectric ceramics, [Bi0.5(Na1 - xAgx)0.5]1 - yBayTiO3, were investigated. The dependence of the dielectric properties on temperature shows that when y = 0.06 and 0.08, two anomalies of dielectric constant corresponding to the depolarization temperature (Td) and the temperature (Tmax) where ε r has the maximum value are observed. And only one dielectric loss peak corresponding to the temperature which is lower than Td for 35-50°C is observed. The dependence of ferroelectric properties on temperature shows that the remanent polarization becomes zero at Td. Moreover, the Td decreases with the increasing amount of Ag+ in this system. [ABSTRACT FROM AUTHOR]

Bi4Ti3O12 (BIT) thin films with TiO2 anatase layer have been prepared on the Pt/Ti/SiO2/Si substrates by metalorganic chemical vapor deposition. The BIT thin films with TiO2 anatase layer exhibit highly a- and b-axes orientation, although the BIT thin film with no layer exhibits a c-axis orientation. The interdiffusion between BIT thin film and Pt substrate was prevented by inserting TiO2 anatase layer. The ferroelectricity depends on the thickness ratio of the BIT thin film to the TiO2 anatase layer, indicating that the TiO2 anatase layer acts not as barrier layer but as an initial nucleation layer. When the thickness ratio was fixed at [(BIT)/(TiO2)] = 15, the remanent polarization (Pr) and the coercive field (Ec) were 2Pr = 81.6 μC/cm2 and 2Ec = 250 kV/cm, respectively. The dielectric constant (εr) is 160. [ABSTRACT FROM AUTHOR]

A method for fabrication of highly (100)-oriented Pb(ZrxTi1-x)O3 thin films by RF magnetron sputtering with a special buffer of PbOx (RFMS-SBP) was developed. With this method, highly (100)-orientated Pb(Zr0.2Ti0.8)O3 films were prepared on PbOx/Pt(111)/Ti/SiO2/Si(100) substrates, and the preferential (100) orientation of the film is 92%. The effect of the thickness of PbOx buffer layer on Pb(Zr0.2Ti0.8)O3 films was investigated. The PZT thin films with proper thickness of PbOx buffer layer possesses excellent ferroelectric properties with higher remnant polarization (Pr = 69.7 μC/cm2), lower coercive field (Ec = 97.5 kV/cm), and the larger pyroelectric coefficient (p = 2.6 × 10-8 C/cm2.K) at room temperature. [ABSTRACT FROM AUTHOR]

Highly oriented 0.55Pb(Sc1/2Ta1/2)O3-0.45PbTiO3 (PSTT) thin films were prepared by RF magnetron sputtering. The x-ray diffraction patterns show that the films were highly (220) preferred orientation. The piezoresponse force microscopy observations show that both in-plane and out-of-plane polarization exist in the same areas of the film. This films possess dielectric constant εr = 570 with loss tg δ = 0.03 at 1 kHz. Ferroelectric hysteresis loop of this film showed the remanent polarization 2Pr and the coercive field 2Ec were 52 μC/cm2, 172 kV/cm, respectively. The leakage currents of the films at ± 200 kV/cm were in the order of 10-7A/cm2. [ABSTRACT FROM AUTHOR]

Epitaxial Pb(Zr0.3Ti0.7)O3 films with different thicknesses and a preferential c-axis orientation were successfully fabricated on PbTiO3/Pt(100)/MgO(100) substrates from an amorphous state by hot isostatic pressing (HIP). Based on the results of X-ray pole figures, all the PZT films with ferroelectric layer thicknesses of 100-300 nm after HIP were almost completely epitaxial. Since the 200-nm-thick PZT film has the largest initial pulse-derived switchable polarization and an intermediate reduction rate of the three samples, its polarization fatigue characteristics are relatively superior to these of the others. From the measurements of static imprint characteristics, the observed shifts of the PZT samples apparently decreasing with decreasing film thickness. [ABSTRACT FROM AUTHOR]

Highly (100)-oriented PbTiO3/(Pb0.90La0.10)Ti0.975O3/PbTiO3 multi-layer films were prepared on the PbOx/Pt(111)/Ti/SiO2/Si(100) substrates at the temperature of 600°C by RF magnetron sputtering. The thickness of PbOx buffer layer plays a significant role on the phase purity, and the PbTiO3 layer plays an important role in improving the properties of the multi-layer films. Highly (100)-orientated PbTiO3/(Pb0.90La0.10)Ti0.975O3/PbTiO3 multi-layer film possesses good ferroelectric properties with remnant polarization 2Pr = 44.1 μC/cm2. The pyroelectric coefficient of the film at room-temperature is 2.425 ×10-8 C/cm2.K. The results indicated that the highly (100)-oriented PbTiO3/(Pb0.90La0.10)Ti0.975O3/PbTiO3 film possesses larger remnant polarization together with larger pyroelectric coefficient at room temperature. [ABSTRACT FROM AUTHOR]

Recent light scattering studies on the oxygen-isotope exchanged strontium titanate SrTi18O3 (STO18) have reported a new feature of the ferroelectric phase transition; a perfect softening of the polarEu mode at TC has been found in 95% exchanged STO18 by a high-resolution interferometric spectroscopy. The frequency of the polar Eu mode becomes zero atTC without any anomalous increase of the attenuation. The phase transition mechanism is an ideal displacive type induced by the instability of the Slater-type polar mode. The Raman scattering at ultra-low temperature using the 3He cryostat elucidates importance of inhomogeneity enhanced by the distribution of18O atoms in STO18-x, where x is the concentration of 18O. [ABSTRACT FROM AUTHOR]

Synopsis: The in-situ observations of the polarization reversals with the 90° domain wall structures under the low frequency field of 25 mHz were carried out in the c-plate of the ferroelectric Bi4Ti3O12 crystal using a polarizing microscope. We found that there exist three kinds of modes in the polarization reversal with respect to the a-domain, that is, changes of the width in a-domains, annihilations of needle like a-domains, and polarization reversals within the a-domain. Computer simulations of the polarization reversal with the 90° domain wall structure were performed on the basis of the Landau theory. Essential parts of the polarization reversal with the a-domain were confirmed to be well reproduced. It was pointed out that the a-domain in the 90° domain wall structure plays an important role in the polarization reversal process. [ABSTRACT FROM AUTHOR]

We investigated crystal structure and ferroelectric properties of bismuth layered-structure compounds prepared by alloying Ce substituted Sr1- xCexBi2Ta2O9 (SCBT) with Bi3Si4O12 (BSO) using a solid state reaction method. From the P-E hysteriesis measurement, the SCBT has larger Pr and Ec compared with SBT. Pr increased and Ec decreased by adding BSO to SCBT. The crystal structure was determined by the Rietveld analysis using neutron powder diffraction data. The results of analysis indicated that the SCBT and that added with BSO had a larger spontaneous polarization, and a smaller tilting angle (αa) in comparison with those of SBT. Moreover, the distortion of TaO6 octahedron was changed in the SCBT and that added with BSO. [ABSTRACT FROM AUTHOR]

Dielectric and impedance spectroscopies were employed to study intergrowth Bi5TiNbWO15 ferroelectrics. It was observed one ferroelectric phase transition at 1096 K and two dielectric relaxation processes involving bulk and grain boundary effects. It was also found that the bulk response within the material is of localized relaxation process, the temperature dependence of the relaxation strength is analogous to the Curie-Weiss law and the interactions between the oxygen vacancies in the bulk material follow the traditional point defects relaxation theory. Based on the analysis of the crystal structure, a short range diffusion mechanism of oxygen ions coordinating A sites was proposed. [ABSTRACT FROM AUTHOR]

A review is given on the studies of microscopic magnetic properties and macroscopic dielectric properties as functions of temperature, magnetic field, and the variety of R3 + (R = rare-earth, Bi, and Y) ions in the multiferroic RMn2O5 compounds by neutron diffraction and dielectric measurements. We have observed successive dielectric and magnetic phase transitions, which concomitantly takes place and a so-called "multiferroics" is realized. In this system, the ferroelectricity is magnetically induced and the commensurate magnetism is indispensable to produce a spontaneous electric polarization. The microscopic origin of the magnetically induced ferroelectricity and the role of rare-earth magnetic moment for a colossal magnetoelectric effect in RMn2O5 will be discussed in the viewpoint of the magnetic structure. [ABSTRACT FROM AUTHOR]

The third-order dielectric susceptibility χ3 of a ferroelectric is described within classic Ginzburg-Landau-Devonshire theory. It turns out that a correction term proportional to the square of the polarization, P2, becomes relevant in relaxor ferroelectrics close to, but above the Curie temperature. It is due to the quasi-static polarization of polar nanoregions (PNRs), which are stabilized by fluctuations of quenched random electric fields. In contrast to normal ferroelectrics with continuous phase transitions, where χ3 is negative at T > Tc, the contribution due to PNRs drives χ3 positive in relaxors like strontium barium niobate (SBN). It becomes negative at enhanced driving field amplitudes when activating the flipping dynamics of the polar nanoregions. [ABSTRACT FROM AUTHOR]

Dielectric constants of complex perovskite oxide (Ba1 - xLax) (Ti1 - xCrx) O3 (BLTC) ceramics with 0.4 ≤ x ≤ 0.7 are measured, and a remarkable colossal dielectric relaxation which is quite similar to that of CaCu3Ti4O12 (CCTO) is found in higher temperature region above the ferroelectric phase transition. This kind of dielectric relaxation is successfully explained by an equivalent circuit model of a series of two R-C parallel circuits with temperature-dependent electrical conductivity and temperature-independent intrinsic dielectric constant. It is also found that the dc bias effect on the sample can distinguish this hetero-structure model and the proper Debye relaxation model of a homogeneous phase. [ABSTRACT FROM AUTHOR]

Piezoresponse Force Spectroscopy (PFS) has emerged as a powerful tool for probing polarization dynamics on the nanoscale. Application of a dc bias to a nanoscale probe in contact with a ferroelectric surface results in the nucleation and growth of a ferroelectric domain below the probe apex. The latter affects local electromechanical response detected by the probe. Resulting hysteresis loop contains information on local ferroelectric switching. The self-consistent analysis of the PFS data requires (a) deriving the thermodynamic parameters of domain nucleation and (b) establishing the relationships between domain parameters and PFM signal. Here, we analyze the early stages of switching processes and the effect of screening on the surface and at the domain wall on local polarization reversal mechanism. It is shown that the screening control both the domain nucleation activation energy and hysteresis loop saturation rate. [ABSTRACT FROM AUTHOR]

The change of pyroelectric reaction sign observed in ferroelectric materials in consequence of polarization reversal has been considered for ferroelectric memory (FEM) elements with pyroelectric readout (FEMPyER). For PZT-film/Si-substrate structures, fabricated by RF sputtering, the mutually complementary pyroelectric and electrophysical characterization for examining FEM elements operation in FEMPyER mode was performed. Pyroelectric response (Uπ) - applied voltage (V) hysteresis Uπ-V-loops in the current Uπ 1 and voltage Uπ 2 modes, dielectric permittivity - V loops from Uπ 1/Uπ 2 ratio, charge Q-V-, current I-V- and capacity C-V- hysteresis loops are presented. The prospects of development of FEMPyER elements based on PZT-film/Si-substrate structures are considered. [ABSTRACT FROM AUTHOR]

Expressions for calculating the potential distribution on the surface of a polarized electret depending on the polarization direction, the shape of nonuniformity and sign of the charge on this surface were obtained. These expressions allow one to calculate the potential distribution above the inhomogeneities that are of various sizes and forms, the latter can be represented by an "infinite" strip, a circle, a square or a ring. Within the limits of simple approximations, spectra of electron emission from a surface of poled dielectrics were calculated for the minimum and the maximum in the potential distribution and a comparison was drawn with the experimental spectra. A qualitative conformity was shown to exist between the theoretical and the experimental spectra. [ABSTRACT FROM AUTHOR]

An unconventional optical diffraction technique is exploited to characterize periodically poled lithium niobate crystals grown by the off-center Czochralski technique. The method, based on maps of the diffracted intensity in the reciprocal space, pointed out that a modulation in the refractive index occurs with a periodicity close to that measured by the chemical etching procedure. In this case, therefore, the linear optical properties of domains with opposite polarization are different. [ABSTRACT FROM AUTHOR]

Electrooptical effect, kinetics of recording and erasing of the hologram of the flat wave front in the films of polycomplex 4-methacryloyloxy-(4'-carboxy-3'-oxy)azobenzene with cobalt and 4-carboxy-3-oxy-3'-carboxy-4'-oxyazobenzene with cobalt are investigated for the first time. The electrooptical properties of the films are caused by spatial reorientation of dipole moments of the azobenzene groups induced by polarized light. These properties can be explained by occurrence of the forces effecting on the dipole moments and metallic ions in the external electric field. The characteristic time of the electrooptical effect as well as the time of formation of the holographic diffraction gratings are larger in the polymer with intra-chain coordination of the metallic ion. [ABSTRACT FROM AUTHOR]

An aqueous solution technique has been used for the growth of TGSx· TGSe1 - x mixed crystals. The birefringence and rotation of the optical indicatrix of x selected samples has been measured using the high-accuracy universal polarimeter method. Simple relationships between the spontaneous optical quantities in the ferroelectric phase and the spontaneous polarization are observed. [ABSTRACT FROM AUTHOR]

In SSFLC and AFLC devices, the voltage over the liquid crystal is not only determined by the applied voltage, but also by the separation of ions and the spontaneous polarization. The motion of ions and the switching of the spontaneous polarization are therefore interfering phenomena. A simplified model for ion transport and switching of polarization is introduced which is able to explain the shift in apparent threshold voltage and the variation of the hysteresis width. [ABSTRACT FROM AUTHOR]

On the basis of the extended Landau mean field model for the SmA—SmC* phase transition the temperature dependence of the dielectric strength and of the characteristic relaxation frequency of the soft mode are analyzed and some parameters involved in the free energy expansion are determined. The analogies and differences between the influence of the aerosil density and a dc electric field are shown. [ABSTRACT FROM AUTHOR]

In this work, the nanoscale electromechanical properties of Pb-based perovskites that are currently the main candidates for piezoelectric applications are investigated by Piezoresponse Force Microscopy (PFM). Local response is compared with that studied via conventional technique. The effect of local polarization switching by mechanical force is demonstrated. This effect may limit the functionality of the films in piezoelectric applications. Local piezoelectric nonlinearity, as well as the nanoscale degradation are also studied by PFM. These measurements demonstrate that the defects may act as pinning centers for domain walls and thus influence nanoscale properties. Finally, local properties of ferroelectric relaxors are presented. [ABSTRACT FROM AUTHOR]

Scanning electrooptic microscopy provides optical imaging of surface ferroelectric polarization patterns by measuring modulation of the output optical signal induced by a sinusoidal electric field. Ferroelectric single crystals and inhomogeneous phase transitions in ferroelectric thin films were investigated by this technique. Here we report investigation of the domain structure in relaxor materials. We have observed formation and evolution of microscopic domains under the action of a dc bias electric field. Furthermore, the local electrooptic switching loops have been measured with sub-micron resolution. Features of electrooptic imaging in ceramic samples are also discussed. [ABSTRACT FROM AUTHOR]

The investigation of the local polarization switching including direct domain writing, local hysteresis measurements, and domain stability testing was carried out in single-crystalline stoichiometric lithium tantalate using the Scanning Probe Microscope. Piezoresponse Force Microscopy was utilized for domain visualization and recording of local switching characteristics. Two variants of domain patterning were shown: ‘direct writing’ and ‘self-assembled formation.’ The polarization reversal in direction opposite to applied field (‘anti-parallel switching’) was studied in details and attributed to screening of external field. [ABSTRACT FROM AUTHOR]

Composition-structure-properties relationships were studied in iron doped compositions of lead zirconate-titanate thin films using dielectric spectroscopy and atomic force microscopy. Samples under investigation were sol-gel deposited lead zirconate titanate PbZr0.50Ti0.50O3 ( PZT) family thin films on Pt/TiO2/SiO2/Si substrates. Spatially resolved piezoresponse imaging of poled regions and polarization switching response in various granular regions polar ferroelectric thin films was studied using scanning probe microscope operating in modified multi-pass regimes combining voltage lithography mode with immediate testing of local surface piezoresponse. [ABSTRACT FROM AUTHOR]

Real information data bits were written onto a ferroelectric medium in the form of the polarization direction of nano-domains. Local domain switching was carried out by applying a voltage pulse. Pulse voltage value was varied based on the polarization directions in the immediate environment to keep the bit size constant. As a result, writing and storing of real information data was demonstrated at a density of 1 Tbit/inch² and a bit error rate as low as 1.8 × 10-2. [ABSTRACT FROM AUTHOR]

Polarization-reversed optical (PRO) devices in ferroelectric LiNb03 (LN) and LiTaO3 (LT), and non-ferroelectric crystal quartz are reviewed. Efficient wavelength converters to mid-infrared and visible light and a low-frequency-chirp intensity modulator for high-speed fiber communication a re demonstrated with polarization-reversed structures. Spatial modulation of second-order susceptibility opens a new window to functionalize conventional materials, and will pave a road to integrated optical devices. [ABSTRACT FROM AUTHOR]

Thin films of Pb(Mg 1/3 ,Nb 2/3 )O 3 -PbTiO 3 (PMN-PT) were fabricated on Pt/Ti/SiO 2 /Si substrates by ultrasonic spraying MOCVD and their characteristics were investigated. The content of pyrochlore phase in PMN-PT films decreased with the increase of PT content and nearly single perovskite films were obtained at the composition of 80PMN-20PT. The 70PMN-30PT films with perovskite phase showed a typical butterfly type C-V curve which verifies the ferroelectricity and had the relative dielectric constant of about 500 and the resistivity of about 5 × 10 12 Ω · cm. [ABSTRACT FROM AUTHOR]

The lowest singlet-singlet and singlet-triplet electronic transitions of the nitrite molecular ion, responsible for the ferroelectricity of the nitrite crystal salts, have been investigated in a temperature range of 1.6–300 K. Polarized well-resolved spectra enabled dealing with separate spin substates of the excited triplet level, and for the nitrite-ion impurity incorporated in the nitrate crystals, to elucidate the effect of the symmetry correlations on the imbedding features of the impurity center. Parameters of the spin-orbit and electron-phonon interactions have been derived, and the microscopic characteristics of the crystal, mostly affecting the electron-phonon coupling, are deduced. [ABSTRACT FROM AUTHOR]

We report the investigation of frequency dependence of dielectric responses of lead magnesium niobate (PMN) in the range from 1 mHz to 10 MHz at various temperatures (200 K–350 K). Three relaxations were obsereved in PMN single crystal, one at high frequency, one at intermediate frequency, and one at low frequency. The high frequency relaxation falls into the frequency range over 1 MHz. The spectral width of the intermediate frequency (range from ∼⃒ 1 Hz to ∼⃒ 1 MHz) relaxation, which dominates the dielectric behaviors in the so-called “diffuse phase transition” region (260 K–280 K), broadens rapidly at about 270 K, and is almost independent on temperature for T [ABSTRACT FROM AUTHOR]

K 1- x Na x NbO 3 is considered as an alternative system for lead-based functional ceramics widely used in transducers, sensors and actuators. In some applications however, the composites of electroactive ceramic and polymer, with low acoustic impedance and dielectric permittivity that can be tailored to various requirement, are more useful. We studied dielectric relaxation processes in polyvinylidene fluoride (PVDF) loaded with K 0.5 Na 0.5 NbO 3 powder in wide temperature and frequency range. The powder was prepared by solid state synthesis and characterized by HRTEM and NIR Raman spectroscopy. The dielectric response of (K 0.5 Na 0.5 NbO 3 ) 0.32 (PVDF) 0.68 composite, of (0–3) connectivity, was found to be determined by the relaxation processes of the polymer matrix with an additional broad low-frequency anomaly at ∼⃒ 305 K that we relate to a response of water absorbed by the shell of KNN grains. [ABSTRACT FROM AUTHOR]

The inverse flexoelectric phenomenon describes the generation of a mechanical deformation in an insulating solid by an applied gradient of the electric field. Lead magnesium niobate-lead titanate (PMNT) ceramic permits study of the inverse flexoelectric behavior because of its large flexoelectric coefficient. Special conical samples were prepared for the generation of a high electric field gradient and cylindrical samples with uniform field. A strong deformation is caused by the electrostrictive behavior of PMNT ceramic. An asymmetric butterfly-shaped strain dependence on electric field is observed at wide temperature range on the conical samples. For evaluation of converse flexoelectric coefficient μ 33 (in matrix notation) it is necessary to know elastic properties of ceramic. The ultrasonic measurements on ceramic samples were performed for this purpose. In this letter we also report measurements of temperature dependence of flexoelectric coefficient μ 33 . The measurements confirmed a great enhancement of μ 33 coefficient in PMN ceramics, which cannot be explained exclusively by the high permittivity of the ceramic. [ABSTRACT FROM AUTHOR]

Ferroelectric nanotubes were fabricated by the wetting on the pore wall of porous body such as Anodized Aluminium Oxide (AAO) thin films on silicon substrate. Sol-gel syntheses within the pores create the PbZrTiO 3 (PZT) nanotube arrays. The diameter and the aspect ratio of vertically aligned nanopores are about 40 nm and 8, respectively. Ferroelectric properties of PZT nanotubes were observed by the Electrostatic Force Microscope (EFM). These nanotubes should provide promising materials for fundamental investigations on nanoscale ferroelectricity, and be useful in ferroelectric nanostorages media. [ABSTRACT FROM AUTHOR]

Titanium-rich lead zirconate titanate compositions are very attractive for pyroelectric applications. Crystalline texture can result in significant thin film properties optimization. In contrast, preparation of textured films requires specific processing parameters. In this work, PbZr 0.20 Ti 0.80 O 3 -PZT20/80 thin films with a mixed (001)(100)/(111) texture on Pt(111)/Ti/SiO 2 /Si substrates were obtained through a chemical method by optimizing thermal treatment conditions. Pole figure exhibited a 6.5% texture for the (100) crystalline plane. Dielectric constant and dissipation values for textured PZT films at 100 kHz were 159 and 0.04, respectively. Remanent polarization and coercive field were 13 μC/cm 2 and 119 kV/cm, respectively. [ABSTRACT FROM AUTHOR]

Microscopic retention properties have been studied in detail. Domain growth and stability of ferroelectric Pb(Zr,Ti)O 3 thin films were investigated with electrostatic force microscope to understand microscopic polarization retention loss mechanism in polycrystalline and epitaxial Pb(Zr,Ti)O 3 thin films. Growth of domains and their relaxation behaviors were investigated and compared. The larger domains were the more stable than the smaller ones. The decay behavior of domain size could be fitted to a simple exponential function. The stretched exponential decay of the averaged polarization was attributed to the superposition of relaxation processes of all domains relaxing independently with their characteristic relaxation times. [ABSTRACT FROM AUTHOR]

The parallel capacitors of YBa 2 Cu 3 O 7 -δ /SrTiO 3 /YBa 2 Cu 3 O 7 -δ for SrTiO 3 with film thickness of 300 nm and 600 nm were fabricated by means of Pulsed Laser Deposition (PLD) and Chemical Mechanical Planarization (CMP) method. In order to investigate the polarization mechanism in the SrTiO 3 films, the frequency dispersions of dielectric constant and tan δ were studied. For 600 nm SrTiO 3 film, the dielectric frequency dispersion occurred at frequency above 10 5 Hz and tan δ at 1 kHz and 10 kHz are 0.001 and 0.015, respectively. These results revealed that the oxygen deficiency in the SrTiO 3 crystals is very small and polarization mechanism is dominated by dipoles polarization. [ABSTRACT FROM AUTHOR]

Attempting to validate our report of a spontaneous polarization in range of 150 μ C/cm 2 in BiFeO 3 (BFO) films, which is the largest measured to date in any ferroelectric material, we have performed first-principles calculations on BFO structures with rhombohedral and tetragonal symmetry. We have shown that the optimal tetragonal structure of BFO has a giant tetragonality ratio of 1.26 and can be obtained experimentally in BFO films deposited on La-doped SrTiO 3 substrates. The spontaneous polarization calculated ab initio for this structure is 143.5 μ C/cm 2 , matching well the experimental result and suggesting that such giant values should no longer be considered surprising for BFO. [ABSTRACT FROM AUTHOR]

The effects of the antiferrodistortive surface reconstruction and the interface with a SrTiO 3 substrate on the ferroelectric properties of PbTiO 3 ultrathin films are investigated using an interatomic potential approach with parameters determined from first-principles results. First we show that a shell model developed for the bulk describes properly the surface properties of PbTiO 3 , in particular the antiferrodistortive surface reconstruction recently observed from x-ray scattering. We investigate also the effects of the surface reconstruction on the polarization behavior of ultrathin films under open-circuit electrical boundary conditions, showing that the surface layer participates in the ferroelectricity. Finally, film-substrate interface effects on the ferroelectric properties are investigated simulating PbTiO 3 ultrathin films on a SrTiO 3 substrate. [ABSTRACT FROM AUTHOR]