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BaBi4Zr2Sn2O15, a modified ceramic sample belonging to the oxide family of layered ferroelectrics, is synthesized using the mixed oxide process after firing for calcination at 810 °C for 6 hrs. XRD study of the compound exhibits the growth of an orthorhombic single-phase structure at atmospheric temperature. The electrical properties of the sample are investigated in a broad temperature range (30–500 °C) and frequency range (100 Hz - 106 Hz). The dielectric properties recommend the transition from ferro to paraelectric state at 410 °C which is much more than room temperature. The impact of frequency and temperature on complex immittance parameters (impedance and modulus) are analyzed by an impedance analyzer in broad frequencies and temperature ranges. The electrical properties show; (i) the existence of semiconductor-like negative temperature coefficients of resistance behavior, (ii) evidence of electrical relaxation phenomena as a function of temperature, and (iii) the existence of single electrical relaxation ascribed to the existence of grain contribution to the electric properties. [ABSTRACT FROM AUTHOR]

BaBi4Sn4O15, a Sn-modified ceramic sample of layered ferroelectric oxide family, is developed using a high-temperature mixed oxide route after firing for calcination at 810 °C for 6 h in steps of 50 °C starting from 600 °C. An introductory XRD study of the compound displays the development of the new orthorhombic structured single-phase compound at atmospheric conditions. The electrical behaviors of the compound are investigated in a wide temperature span (30–500 °C) and frequencies ranging from 0.1 kHz to 1 MHz using an impedance analyzer. Dielectric behavior informs that the compound has a phase transition from Ferro to Paraelectric at 370 °C, which is well above room temperature. The impact of temperature and frequency on complex immittance parameters (impedance and modulus) is analyzed using an LCR meter in a broad temperature & frequency span. The electrical properties confirm; (a) the existence of semiconductor-like NTCR (negative temperature coefficients of resistance) behavior, (b) the evidence of the electric relaxation process as a function of temperature, (c) the existence of electric relaxation ascribed to the simultaneous contribution of bulk & bulk interfaces to the electrical behavior, and (d) presence of the non-Debye type relaxation phenomena. The frequency-dependent conductivity follows Jonscher's universal power law. [ABSTRACT FROM AUTHOR]

In this paper, detailed studies of effect of small amount of manganese substitution (at the zirconium site) on the structural, micro-structural, and electrical characteristics of lead zirconate titanate of Pb(Zr0.35–xMnxTi0.65)O3;x = 0, 0.02, 0.06, 0.10 (PZMT)) have been reported. The materials were prepared by using standard ceramic technology. The formation of the compounds and their basic crystal data have been studied through X-ray diffraction (XRD) method. The crystallite size and lattice strain of the compounds, evaluated from Scherrer's and Hall Williamson (H-W) equations, is found to be in the range of 40–50 nm and 11 × 10−4 to 50 × 10−4, respectively. Microstructures of different magnifications, revealing the surface nature of the compounds, have been recorded by field emission scanning electron microscope (FESEM). Effect of Mn+4 ions on electrical behavior (electrical impedance (Z*), electrical modulus (M*), conduction and relaxation phenomenon) of PZMT systems, over wide range of temperature and frequency, has been studied. [ABSTRACT FROM AUTHOR]

Carbon quantum dots doped ZnFe2O4 Spinel Ferrite, that is, CQD-ZSF hybrid nanocomposite was thrivingly synthesised exploiting sol-gel based synthesis technique. Structural assessment supports Fd-3m space group with cubic spinel structure with mean size of 10.33 nm as obtained from Scherrer formula. Raman spectra confirmed the existence of CQD in ZSF. The samples contained a variety of vibration bands, according to the FT-IR analysis. The dielectric permittivity (ε) and tangent losses (tan δ) was conducted with frequency from 100 Hz to 1 MHz range at different temperatures ranging from 300 to 773 K. It was found that ε as well as tan δ receded monotonously with extending frequency. This information reveals a space or interfacial dipolar relaxation phenomenon. The electrical properties and the ion hopping dynamics were probed with the assistance of an AC-electrical conductivity (σac) analysis. Frequency-dependent σac heeded Jonscher's law of power. The advent of arcs semicircular by nature in cole-cole plot indicates cloud of electronic process occurring within sample. At 300 K, by applying an external magnetic field varying till 1.5 Tesla magnetic field, the magneto-dielectric effects of the sample were measured by obtaining ε and tan δ versus frequency values displaying negative ML% (magneto-loss) and MD% (magneto-dielectric) coupling of −32.57% and −58.13%, respectively. [ABSTRACT FROM AUTHOR]

In this work, a new method for study of the process of domain orientations and space charge relaxation in ferroelectrics using the surface acoustic waves (SAW) has been developed. The results of an experimental study of the dc electric field influence on the parameters of SAW propagation in piezoceramics with different ferroelectric "hardness" are presented. [ABSTRACT FROM AUTHOR]

In the present paper, Nd, Nb co-doped La2Mo2O9 system is investigated to understand phase transition, ionic conductivity and dielectric relaxation phenomenon. X-ray diffraction study confirms order-disorder phase transition by disappearance of peak splitting of (231) in co-doped LMX system, which is associated with monoclinic phase and is observed for LMX-Pure at around 2θ = 47–48°. In co-doped system, two dielectric relaxation peaks are observed, which are associated with diffusion process between O(1)-O(2) and O(1)-O(3) oxygen ion ←→ vacancies sites, while diffusion process O(1)-O(3) is supposed to be occurred in parent system having single relaxation peak. Thus dielectric relaxation phenomenon indicates phase transition is proceeding with static-to-dynamic disorder transition. Electric modulus data are revealed to ascertain correlation of relaxation dynamics and oxy-ion conductivity in co-doped LMX system. The extracted data of activation energy of oxy-ion conductivity at intermediate temperature range (500–700 °C) of co-doped samples is found relatively lower than that of the parent sample. The study reveals that incorporation of Nd, Nb co-doped in LMX system successfully suppress the phase transition and enhanced ionic conductivity at intermediate temperature range and found suitable as electrolytes for intermediate temperature solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

The structure in real planar samples of ferroelectric liquid crystals as well as the collective modes characterizing these structures, are strongly affected by surface anchoring of molecules. This is reflected in dielectric properties, which become significantly dependent on the sample thickness. The dielectric strength and the relaxation frequency of the characteristic modes (pinned Goldstone mode for the thick samples and twisted mode for the thin ones) are determined and found that for both types of structures the dielectric strength increases and the relaxation frequency decreases with increasing the sample thickness. We proved theoretically predicted thickness dependences of various physical parameters for new ferroelectric liquid crystalline compound. We concluded the experimental results are in accordance with the theory taking into account the real structure of the samples. [ABSTRACT FROM AUTHOR]

For the first time, the dielectric properties of the 9:1:7 TTB phases Ba9M2+Nb14O45(M = Co, Mg, Zn) which form in Ba-deficient high-Qperovskite niobates Ba(M2+1/3Nb2/3)O3have been measured in the radio-frequency and microwave range. The low-temperature dielectric relaxation found in Ba9M2+Nb14O45was shown to give a strong contribution into their microwave dielectric loss. The measured data were used for a simple simulation of theQ-factor of a perovskite-TTB composite. Calculated parameters have been shown to correspond well to the measured data. [ABSTRACT FROM PUBLISHER]

Dynamical equations for transverse and longitudinal mean projections of elastic-deformed kinetic chain units (Gaussian subchains) with anisotropic local intra- and interchain orientation interactions of dipolar type and spectra of relaxation times for large-scale motions of the chains in an isotropic and ordered state were obtained. The long-range orientation planar order in the 3D-layered systems leads to an anisotropy of large-scale relaxation properties of the chains (relative to the axis perpendicular to layers). The anisotropy increases with increase of the chain bending rigidity, the strength of interchain interactions and decrease of the scale of its motion. It disappears for most large-scale motions of chains. [ABSTRACT FROM AUTHOR]

In this paper we report the mechanism and nature of relaxor ferroelectric behavior in the environmental friendly lead free Barium Zirconate Titanate (BZT) system. A revised complete (Structure:Property) phase diagram of Ba(ZrxTi1-x)O3, with compositions 0.00≤ × ≤1.00 has been developed based on their electrical properties. Two different kinds of relaxor behaviors have been observed in the BZT system; one is dominated by polar Ti-rich regions and another by non-polar Zr-rich regions. All the BZT relaxor compositions are characterized by dielectric properties with and without bias, pyroelectric and thermal expansion measurements in the wide range of temperatures. The structure of the BZT compositions has been evaluated by XRD, Neutron diffraction study. Further the local structure of the BZT compositions has been probed by micro-Raman spectra. Although the global structure of BZT relaxors is cubic as observed in Neutron diffraction studies, the local symmetry is non-cubic as evident in the micro-Raman spectra of BZT relaxors as well as in their thermal strain measurement, dielectric and pyroelectric behavior. [ABSTRACT FROM PUBLISHER]

Single crystal barium phosphate and cadmium doped barium phosphate has been grown by a room temperature solution technique. Single crystal x-ray diffraction (XRD) establishes that the grown crystal belongs to the orthorhombic system. The dielectric and a.c conductivity properties were investigated thoroughly with regard to change in temperature and frequency. The variation of the dielectric constant (ϵ/), dielectric loss (tanδ) and a.c conductivity ln(σac) was measured in the frequency range of 5 kHz to 1 MHz and in the temperature range of 40 to 420°C. The increase in the value of ϵ/ is almost linear at low temperature whereas, at high temperature its value increases sharply. However, in barium phosphate crystals, there is a shift in the value of ϵ/ at higher temperature indicating relaxor type behaviour of the material. The dielectric measurements indicate the transition in the material to be a diffuse phase transition, whose nature can be explained by the relation 1/ϵ/ − 1/ϵ/ max = A (T – Tc)γ. The tanδ and ln (σac) shows the temperature as well as frequency dependence. The activation energy at various fixed frequencies is calculated from the slope of the graph between ln (σac) versus 1/T (x 103 K−1). [ABSTRACT FROM PUBLISHER]

The comparative experimental analysis of the polarization reversal kinetics in non-uniform Te(OH)62NH4H2PO4(NH4)2HPO4 (TAAP) and relaxor Sr0.61Ba0.39Nb2O6 (SBN:61) crystals have been performed. Micro-scale studies of domain switching in conjunction with electrical measurements allowed us to establish a relationship between local properties of domain dynamics and macroscopic response; polarization hysteresis loop and switching currents. We investigated the microscopic features of 180 degree domain walls dynamics and relate its dynamics to the defect structure in both type of the crystals. The domain structure was studied by means of the nematic liquid crystal decoration method. [ABSTRACT FROM PUBLISHER]

Behaviour of ferroelectric properties in Na1/2Bi1/2TiO3-CdTiO3 solid solutions correlates with dependence of lattice symmetry versus concentration of constituents. However, some overlapping is observed in concentration range close to the morphotropic phase boundary. The properties of dielectric permittivity, characteristic for relaxor ferroelectrics, diminish, if concentration of CdTiO3 increases, but it is not influenced by the change of crystallographic symmetry. The electromechanical properties are mostly pronounced in the range of cubic-tetragonal morphotropic phase boundary. [ABSTRACT FROM PUBLISHER]

Dielectric properties of Sr0.75Ba0.25Nb2O6 (SBN-75) ceramics in the range of low and infra-low frequencies are reported. The values of ϵ′ and, in particular of ϵ″, in ceramics are found to be much smaller compared with SBN-75 single crystals below the temperature (Тm) of the ϵ′(T) maximum a sharp increase of the values of dielectric parameters observed above Тm being also different from their thermal behaviour in single crystals. The broadening of phase transition and dependence of the response on sample history are similar to the features observed in other relaxor materials. [ABSTRACT FROM PUBLISHER]

Investigations presented in the present work are concerning the other member of the Aurivillius family, the BaBi2Nb2O9 (BBN). This compound, which seems to be very interesting from the potential applications point of view. The dielectric characterization of this materials and influence of sintering condition on grain structure and properties of those materials had been very widely described in our previous paper. Now we would like to present the hitherto unreported electric properties of BaBi2Nb2O9 ceramics, investigated by the impedance spectroscopy (IS). IS is nondestructive method, which allows to separate grain and grain – boundary effects due to the different frequencies of the relaxation process in grain and grain boundaries. This enables us to determine the temperature dependences of grain (Rg) and grain-boundary (Rgb) resistance and evaluate their respective activation energies (Ea). Additionally a comparison between macroscopic results obtained by Impedance Spectroscopy and miroscopic direct local LC-AFM conductivity measurements are presented. [ABSTRACT FROM PUBLISHER]

Using n-fold way dynamic algorithm we have studied the dynamical decay of the autocorrelation function of 3D clusters composed of Ising-type dipoles. Trying to reproduce the situation in real ferroelectric materials, we (i) instead of Glauber dynamics, assumed that the spin before the flip has no a priori knowledge of its final energy and (ii) used open boundary conditions assuming that in real experiment, due to existence of impurities, the system consists of finite domains of different sizes. In particular, we followed the behavior of the longest ('ergodic') relaxation time of a finite domain, the time which is related to flips of a cluster polarization below transition temperature Tc. We found that ergodic relaxation time scales with Lεν and is proportional to exp[const(Lεν)3.2]. This result is supported by calculation of surface tension obtained from probability distribution of polarization at T < Tc. Accounting for the contributions of the longest relaxation times, we obtained the relaxation times distribution function characterized by two (sharp and robust) maxima in its relaxation time dependence. Our results qualitatively confirm the assumption that the non-Debye relaxation in dipolar glasses and relaxors might be caused by distribution of sizes of clusters, consisting of ordinary Ising-type dipoles. [ABSTRACT FROM AUTHOR]

While macroscopic observation reveals non-switching of domain in Na0.5Bi0.5TiO3 (NBT)-BaTiO3 (Ba;0.33%) rhombohedral (001) plate, microscopic observation, using the piezoresponse force microscopy (PFM), reveals two kinds of piezoresponse images, one with domain switching and the other without one. Such microscopic remarkable difference of domain switching depends on the coercive field caused by localized nucleation of domains with reversed polarization. Such coercive fields was discussed from the viewpoint of the relaxor states resulting from random fields based on lattice defects due to Bi ions and oxygen vacancies. [ABSTRACT FROM AUTHOR]

It has for a long time been considered that polar nanoregions in relaxors form at Burns temperature Td≈600 K. Dielectric investigations of Pb(Mg1/3Nb2/3)O3 (PMN) and 0.7PMN-0.3PbTiO3 systems, performed in a broad temperature range, and the analysis of the intrinsic response in terms of the universal scaling imply, however, much higher Td or formation of polar nanoregions in a broad temperature range. High values of the dielectric constant manifest that polar order already exists at the highest measured temperatures of 800 K. The obtained values of critical exponents indicate critical behavior associated with universality classes typically found in spin glasses. [ABSTRACT FROM AUTHOR]

Temperature dependence of the dielectric constant under the DC biasing field was measured in Pb(Zn1/3Nb2/3)O3-8%PbTiO3. The temperature-field phase diagram was clarified in the field range below 2.5 kV. The existence of the critical end point at 172 ± 3°C and 1.75 ± 0.25 kV/cm was confirmed. [ABSTRACT FROM AUTHOR]

The low-frequency light-scattering spectrum in Pb(Mg1/3Nb2/3)O3 single crystal is investigated at 297 K. A quasielastic scattering is found, and its line shape is identified as a 'power-law' type, instead of a single Lorentzian or superposition of two Lorentzian curves. The power-law spectrum implies the existence of a wide distribution of relaxation times in relaxors. [ABSTRACT FROM AUTHOR]

Micro-Brillouin scattering and dielectric experiments were performed on PLZT-x/65/35 (x = 8.0, 9.0, 9.4, 10.0) relaxor ferroelectric ceramics in thermally depoled state. Local polarization with random orientation associated to polar nanoregions (PNRs) indeed appeared in these ceramics. A low temperature anomaly was observed in the dielectric constant showing clear aging character of PLZT relaxor ceramics. [ABSTRACT FROM AUTHOR]

Results of experimental investigation of relaxational aging processes in Pb(Zr,Ti)O3 based solid solutions after action of DC and AC by electric fields, heating, uniaxial pressure are presented. The said process is long-time and is described by logarithmic function of time. For used in our experiments amplitudes of external excitations process of returning into the initial state is reversible. The criterion of a reversibility is linearly increasing dependence of the speed of a relaxation on amplitude of exciting force. A mechanism of long-time relaxation considering the entrapment of charges, evolved in the annealing process, by vacancies in PZT lattes is suggested. [ABSTRACT FROM AUTHOR]

Effective piezoelectric coefficients e33*, d33*, g33*, and h33*, squared figures of merit d33*g33* and dh*gh*, and other related parameters of novel 0-3 and 0-3-0 composites based on single crystals of relaxor-ferroelectric solid solutions of (1-x)Pb(Mg1/3Nb2/3)O3-xPbTiO3 are studied using the effective field method, effective medium method and finite element method. The volume-fraction dependences of a number of parameters and figures of merit are determined using the above methods and compared for composites with aligned prolate spheroidal inclusions. Four parameter ratios that determine interconnections between the effective electromechanical constants of the 0-3-type composites are first introduced. These parameter ratios are used to interpret the longitudinal dielectric and piezoelectric response of composite structures with prolate inclusions that exhibit high piezoelectric activity. The role of piezoelectric anisotropy and activity of the composite components in forming the longitudinal piezoelectric effect is analysed. Specific novel composite architectures with high piezoelectric sensitivity (longitudinal and hydrostatic) are identified and discussed. [ABSTRACT FROM AUTHOR]

We demonstrate that the substances with coexisting ferroelectric and antiferroelectric phases possess properties characteristic for the 'dipole glasses'. Possible phase diagrams of such substances are discussed. Main attention is paid to the long-time relaxation of physical characteristics of these compounds after their thermodynamic equilibrium was disturbed by external influences. The long-time relaxation and the pronounced frequency dependence of parameters (for example, dependence of characteristics on the frequency of measuring field) are the main features due to which these systems are classified as dipole glasses. Our main purpose is to call attention to the fact that one has to be cautious during the interpretation of experimental results in substances with inhomogeneous states of coexisting domains of ferroelectric and antiferroelectric phases. [ABSTRACT FROM AUTHOR]

Hypersonic elastic anomalies are investigated in ferroelectrics with perovskite structure by micro-Brillouin scattering to make clear the role of polar nanoregions (PNRs) and static random fields. In order to clarify the role of dynamic PNRs, the nearly second order normal ferroelectric phase transition is studied in 12 mol% KF substituted BaTiO3 (KF-BT/0.12). The precursor elastic behaviors and the critical slowing down are clearly observed above the Curie temperature TC. While in relaxor ferroelectric 0.93Pb(Zn1/3Nb2/3)O3-0.07PbTiO3 (PZN-0.07PT) with PNRs and static random fields, below the intermediate characteristic temperature T*, the suppression of slowing down of relaxation time is observed. The equation of stretched slowing down well reproduces the observed temperature dependence above TC. The growth of the characteristic localized length of dynamic PNRs is estimated as a function of temperature. [ABSTRACT FROM AUTHOR]

Relaxor ferroelectric terpolymer, Poly (vinylidene fluoride-trifluoroethylene-chlorofloroethylene) can be applied in many modern electronics systems. In this paper, the terpolymer films were deposited on aluminum-coated silicon substrates by horizontal Langmuir-Blodgett technology. The X-ray diffraction pattern indicates that the films have good crystallinity. The optical dispersion of the films were measured by variable-angle spectroscopic ellipsometry over a range from 300-1300 nm. The data Ψ and Δ at multiple incident angels (θ = 75° and 85°) were fitted using the Cauchy model. The refractive index n, the extinction coefficient k and the thickness of each film were obtained. [ABSTRACT FROM AUTHOR]

Ceramics of a new solid solution, (1 - x)Pb(Mg1/3Nb2/3)O3-xBi(Zn1/2Ti1/2)O3 [(1-x)PMN-xBZT], have been prepared (with x = 0.05-0.30) and investigated for their structure and relaxor ferroelectric properties. The structure remains pseudocubic (or rhombohedral) up to the solubility limit of x = 0.275. All the compositions studied show broad and diffuse peaks in the temperature and frequency dependences of dielectric permittivity, indicating typical relaxor behavior. The temperature dependences of dielectric permittivity for all the samples studied follow an empirical quadratic law that describes the high temperature slope of the permittivity. The diffuseness in the dielectric peaks was found to increase linearly with the increasing amount of BZT, which can be attributed to the increase in chemical disorder in the system. [ABSTRACT FROM AUTHOR]

Dielectric constants in Pb(Zn1/3Nb2/3)O3-PbTiO3 were measured under the zero-field heating after a preceding field cooling. It was confirmed that a sharp phase transition between ferroelectric phases in Pb(Zn1/3Nb2/3)O3 appears at 114°C, and the phase boundary connects to the morphotropic phase boundary in the Pb(Zn1/3Nb2/3)O3-PbTiO3 (PZN-PT) solid solution system. A new phase diagram in the poled sample of PZN-PT was proposed in a wider temperature range. It is concluded that the phase transition between ferroelectric phases of PZN is the one between the tetragonal and rhombohedral phases. [ABSTRACT FROM AUTHOR]

In the present publication we report the results of dielectric spectroscopy investigations of two classes of materials-relaxors and dipolar glasses. As model relaxor was chosen PLZT 8/65/35 concentration. The real distribution function of the relaxation times f(τ) of the relaxor ferro-electric ceramics PLZT 8/65/35 and 9.5/65/35 was calculated from the dielectric measurements results in the wide frequency range (101-1012 Hz). Below the Burns temperature TB = 620 K, when the clusters begin to appear on cooling, the distribution function of the relaxation times is symmetrically shaped. On cooling the dispersion and loss spectra strongly broaden and slow down, the f(τ) function becomes asymmetrically shaped and the second maximum appears. The width of the f(τ) function was calculated at different temperatures. The longest relaxation times diverge according to the Vogel-Fulcher law with the freezing temperature 299 and 252 K for the 8/65/35 and 9.5/65/35 samples, respectively. The shortest relaxation time is about 10-12 s and it remains almost temperature independent. Similar behaviour was observed in dipolar glasses BP/BPI. Much more information was obtained from two dimensional distribution of the relaxation times. This result confirmed Meyer-Neldel law in relaxors and dipolar glasses. [ABSTRACT FROM AUTHOR]

The giant electrocaloric (EC) effect is of great importance for application in cooling or heating devices of new generation, which would be friendlier for environment. Recent predictions of the existence of the giant EC effect in polymeric and inorganic ferroelectric relaxors are based solely on the indirect measurements of the electric polarization and not on a direct measurement of the EC effect itself. Here a method and analysis of direct measurements of the giant EC effect in various soft and solid ferroelectric materials in the form of thick and thin films is presented. The field dependence of the EC effect is shown for PbMg1/3Nb2/3O3 (PMN) ceramics and P(VDF-TrFE) (68/32 mol%) copolymers. [ABSTRACT FROM AUTHOR]

All sequential steps of transfer from relaxor to normal ferroelectric phase transition are found in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 if concentration of PbTiO3 increases. The relaxor properties in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3 solid solutions are described by the power law and Vogel-Fulcher relationship. Concentration dependence of the relevant parameters is discussed. Stability of relaxor and ferroelectric phases is discussed by analyzing behaviour of critical electric fields. [ABSTRACT FROM AUTHOR]

Novel lead-free piezoelectric single-crystal with a morphotropic boundary composition (0.94Na1/2Bi1/2TiO3-0.06BaTiO3) was characterized by dielectric spectroscopy, far-IR reflectivity and Raman spectroscopy. Analysis of polarized Raman spectra suggests that the three principal Raman bands are associated with polar optic modes. [ABSTRACT FROM AUTHOR]

The relaxor-based ferroelectric single crystals Pb(In1/2Nb1/2)O3- Pb(Mg1/3Nb2/3)O3-PbTiO3 were grown successfully using the vertical Bridgman technique. The crystals were spontaneously nucleated and induced to grow by the seed respectively, with diameter of Ø25-40 mm and length of 80-170 mm. The [001]-oriented wafers of as-grown crystals showed the excellent electrical characterizations (ε∼5500, tanδ∼1.35%, d33 ∼1900pC/N, k33∼0.9). Both the higher rhombohedral-tetragonal phase transition temperature (Tr/t ∼100-120°C) and Curie temperature (Tc ∼170-200°C) enlarged the operating temperature range of the devices. The crystals had the stable time dependence of piezoelectric properties. Therefore, the successful growth and high performance made the crystal be a promising candidate for the ultrasonic applications. [ABSTRACT FROM AUTHOR]

The first-principles calculation had been adopted to investigate the intrinsic vacancies in bulk PbTiO3. The atomic relaxation and the formation energy of isolated neutral vacancy were studied respectively. And the defect reaction energies of Pb partial Schottky (VPb2-+VO2+), Ti partial Schottky (VTi4-+2VO2+), and full Schottky (VPb2-+ VTi4-+3VO2+), were obtained. It was found that both the formation energy of vacancy and the defect reaction energy were connected closely with the thermodynamic condition. By comparing the calculated formation energy values, Pb partial Schottky (VPb2-+VO2+) was considered to be the dominant defect species in the seven thermodynamic conditions, consistent with the experimental reports. [ABSTRACT FROM AUTHOR]

The longitudinal acoustic mode behaviors of three cubic perovskite relaxors and one tungsten-bronze uniaxial relaxor were compared in a widest temperature range by Brillouin scattering. All investigated relaxors exhibited substantial softening of the Brillouin shift upon cooling and a sudden increase in the hypersonic damping at a temperature lower than the Burns temperature, from which four characteristic temperatures were defined in relation to the temperature evolution of polar nanoregions. The Brillouin shift of the uniaxial Sr0.61Ba0.39Nb2O6 relaxor showed a positive slope at temperatures above the Burns temperature, which indicates the existence of coupling between some persisting relaxation process and the acoustic waves propagating along the polar axis. [ABSTRACT FROM AUTHOR]

The nonlinear magnetoelectric effect in a relaxor ferroelectric, which is randomly diluted by a (ferro)magnetic compound, is investigated on the basis of a phenomenological Landau-type free energy model. It is assumed that macroscopic electrostrictive and magnetostrictive deformations give rise to fourth-order magnetoelectric terms in the free energy functional. On a mesoscopic scale this implies that the local electric field inside a polar nanoregion (PNR), which is temperature [image omitted] dependent, is modified both by the applied electric field [image omitted] and magnetic field [image omitted]. The dielectric relaxation time is shown to obey a modified Vogel-Fulcher relation and diverges on a critical surface in the [image omitted] space. [ABSTRACT FROM AUTHOR]

The possibility to explain basic physical properties of relaxors within the concept of the dipole-glass transition is discussed. We argue that this concept provides the only consistent picture accounting of all known anomalous features of relaxors. The origin of their history-dependent properties can be naturally traced to the main paradigm of glass-state theory-the existence of numerous metastable states. Based on this paradigm phenomenological description of known history-dependent phenomena in relaxors agrees qualitatively with experiments. [ABSTRACT FROM AUTHOR]

In this work lead-free Sr0.8Bi0.2TiO3 ceramic have been investigated in the frequency range from 20 Hz to 36 GHz. The obtained results show pronounced dispersion below room temperature. It looks more similar to the one observed in dipolar glasses as in relaxors. Calculated relaxation time distribution function broadens towards longest relaxation times with decreasing temperature. The obtained most probable relaxation time fulfills Vogel-Fulcher relationship with the following parameters: dipole activation energy EA/kB = 1718 K, freezing temperature T0 = 65 K, attempt relaxation time, referring to dipole relaxation at very high temperatures, τ0 = 5.5·10-14 s. [ABSTRACT FROM AUTHOR]

By studying the dielectric properties of BaBi2Nb2O9 ceramics, a representative of layered ferroelectrics, significant dispersion of ε* has been revealed at low- and infra-low frequences in the region of phase transition. Dispersion of ε* observed in “low-temperature” region (T < Tm) is caused by relaxation of polar formations and their borders. The “high-temperature” dispersion is observed in the region T > Tm where the basic contribution to ε* is provided by processes of the Maxwell-Wagner relaxation. [ABSTRACT FROM AUTHOR]

The broadband dielectric permittivity of ordered 0.1PMN-0.9PSN and disordered 0.2PMN-0.8PSN ceramics was investigated. The anomaly of dielectric permittivity is clearly seen in the region of 370 K for 0.1 PMN-0.9 PSN at all frequencies. 0.2 PMN-0.8 PSN shows relaxor behaviour with huge frequency dispersion below 350 K. Calculated distribution of relaxation times shows noticeable influence of polar nano regions to the total dielectric spectrum below 320 K with the longest relaxation times edge diverging according to the Vogel-Fulcher law. In 0.1 PMN-0.9 PSN two a little overlapped peaks present in the distribution of relaxation times, influenced by displacive lead motions at high frequencies and possible conductivity phenomena at low frequencies. [ABSTRACT FROM AUTHOR]

In this paper dielectric spectra of 0.6PMN-0.4PZN ceramic obtained from broadband dielectric spectroscopy is presented. Measurements revealed an unusual relaxor like nature. Two different processes in the dielectric spectra have been observed. High frequency, or short relaxation times, behaviour is typical for ferroelectric crystals. Longest relaxation times do not follow Vogel - Fulcher dependence, which is unusual for relaxors. [ABSTRACT FROM AUTHOR]

From the dielectric measurements of the relaxor ceramics BaBi2Ta2O9 (BBT) in a wide frequency range (101-1011 Hz) the real distribution function of the relaxation times f(τ) was calculated. The shape of the distribution function is asymmetrical in all measured temperature interval with the expressed peak of relaxation times about 10- 12 s in higher temperatures. [ABSTRACT FROM AUTHOR]

In this paper the method of calculation of two dimensional distribution function from dielectric spectra is presented. Simulation showed, that it is possible to obtain distribution function from experimental dielectric spectra. [ABSTRACT FROM AUTHOR]

The relaxor ferroelectric polymers, i.e., the poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] based terpolymers and high energy electron irradiated copolymers, provide unique opportunity to investigate the ferroelectric relaxor behavior in polymeric materials. Experimental evidence shows that there is fundamental difference in the microstructures between the relaxor terpolymer and relaxor irradiated copolymer even though both exhibit similar macroscopic ferroelectric relaxor response. [ABSTRACT FROM AUTHOR]

In this work we have investigated the nature of the crossover from the ordinary ferroelectric to the relaxor state in (Pb 1 - x Ba x )(Zr 0.65 Ti 0.35 )O 3 ceramics through dielectric and structural characterizations. Based on the martensitic transformation concepts, it is proposed that the continuous addition of isovalent-ions in the normal ferroelectrics decreases the long-range elastic interaction, thus transforming the domain patterns from a micrometer polydomain structure, through single domains, to nanometer polar “tweed” structures with glasslike behavior, which are in turn strongly driven by defects. The electrical interaction between these weakly-coupled polar-tweed structures leads to a wide spectrum of relaxation times, thus resulting in a dielectric relaxation process. [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]

A new heterodyne experiment on the ferroelectric KH 2 PO 4 elucidates the extremely early stage of the excitation process of the ferroelectric relaxation mode. The time dependence of the response function G ( t ) shows a continuous rising from the time origin where the mode is excited by the ultra-short femtosecond pulses. The limit of the Debye model is overcome by a new phenomenological response function proposed here based on the experimental result. [ABSTRACT FROM AUTHOR]

Dielectric ceramics with compositions belonging to the Ba(Nd x Ti 1-2 x Nb x )O 3 with varying concentration of x were prepared through Solid State Sintering route using both conventional and microwave sintering. The phase transformations were studied by dielectric measurements in a wide range of temperature and frequency. The relaxor behaviour is almost favoured as the composition deviates more from BaTiO 3 and as the substitution is heterovalent in the 6-coordination number crystallographic site. [ABSTRACT FROM AUTHOR]

Single phase perovskite ceramic Pb(Mg 1/4 Cd 1/12 Nb 2/3 )O 3 (PMCN) was prepared by the high temperature solid-state reaction method. Dielectric constant and loss tangent were measured over a frequency range 1 kHz to 1 MHz in the temperature region -40 to 115°C. Dielectric studies revealed the relaxor behaviour with diffuse phase transition. The frequency dependence of the temperature of the permittivity maximum (T m ) has been modeled using Vogel-Fulcher relation. The dielectric relaxation in PMCN is found to be analogous to the magnetic relaxation in spin-glass system. [ABSTRACT FROM AUTHOR]

Coexistence of monoclinic and tetragonal domains is evidenced in a (001)-cut Pb(Mg⅓Nb2/3)0.61Ti0.9O3 (PMNT39%) single crystal from temperature dependent observation of domain structures and dielectric permittivity. The coexistence persists until the crystal transforms into the cubic phase near 455 K. As temperature increases, the monoclinic domains progressively transform to the tetragonal phase via polarization rotations of monoclinic distortions. This causes increasing volume of the tetragonal domain matrix as temperature increases before the cubic phase takes over. [ABSTRACT FROM AUTHOR]