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In the present study, particular aspects of the large-signal switching properties and electromechanical hysteresis of the lead zirconate titanate (PZT)-type porous piezoceramics were studied in comparison with the dense piezoceramics of the same composition. Large-signal ferroelectric polarization and strain hysteresis loops were recorded at the bipolar electric fields in the range of 0 ÷ 5 kV/mm and in the frequency range of 0.01 ÷ 5 Hz. Measurements and analysis were performed by means of the electromechanical measurement system (STEPHV) and electromechanical response characterization program (STEP), combining large-signal modeling of the mechanical and electrical behavior of ferroelectric materials. [ABSTRACT FROM AUTHOR]

In this work, the piezoelectric hysteresis and relaxation process induced by a weak DC electric field in ferroelectric ceramics were studied using the impedance spectroscopy method and piezoelectric resonance analysis program (PRAP). The DC field and time dependences of the complex dielectric constants were measured for the radial extensional mode of vibrations of thin piezoceramic disks. It was found that the hysteresis and relaxation nature of the field and time dependences of the complex dielectric constants were caused by the reversible displacements of 90° domain walls as well as the space charge transformation. [ABSTRACT FROM AUTHOR]

Impulse excitation is a suitable tool to determine the temperature dependence of Young's modulus and to monitor the ferroelectric phase transition of unpoled barium titanate ceramics (tetragonal-to-cubic and vice versa). By measurement from room temperature to 200–300 °C and back, it is found that there is an elastic anomaly with a sharp minimum (at 120 °C during heating and 110 °C during cooling, with a completely reproducible hysteresis), below and above which Young's modulus exhibits values of 40–50 GPa and up to 90 GPa, respectively, and damping changes abruptly from values of order 0.01 to less than 0.001. [ABSTRACT FROM AUTHOR]

In this work, we studied the piezoelectric hysteresis effect induced by a weak dc electric field in ferroelectric ceramics. Precision measurements of the impedance spectra for the thickness vibrational mode of thin piezoceramic disks at different polarities of applied dc electric field were performed using the method and program of piezoelectric resonance analysis (PRAP). The field dependences of the complex piezoelectric constants of piezoelectric ceramics obtained by processing successively measured impedance spectra were analyzed and a physical interpretation of the results was proposed. [ABSTRACT FROM AUTHOR]

The hysteresis nonlinearity and rate dependence of piezoelectric actuators seriously affect their positioning accuracy in precise positioning. Proper compensation needs to be given to improve the positioning accuracy of the actuator. In this paper, the static hysteresis characteristics are described by improving the BP neural network model based on the adaptive particle swarm optimization algorithm, and the PI model is used as the hysteresis factor by the extended space method to realize the multi-valued mapping of hysteresis nonlinearity. And input three types of voltage signals, compare and analyze the experimental data and model prediction output, and use the maximum relative error and root mean square error as the evaluation indicators to prove the accuracy of the built model. Based on the improved BP neural network model, a second-order low-pass analog filter is introduced to construct a rate-dependent hysteresis model. Comparing and analyzing the rate-dependent hysteresis model and the static hysteresis model, the experimental results show that when the signal frequency is 10 Hz, 40 Hz, and 100 Hz, the predicted output of the rate-dependent hysteresis model is compared with that of the static hysteresis model, and the root mean square error decreases by 46.3%. %, 59.6%, and 65.1%, the model can more accurately describe the hysteresis characteristics of piezoelectric actuators. Finally, a rate-dependent hysteresis inverse model is established, and the rate-dependent hysteresis inverse model is used as a feedforward combined with a single neuron network PID control to form a composite controller, and the experimental verification is carried out. The results show that the maximum error between the composite controller and the actual expectation is only 2.15%. Therefore, the established model can accurately express the rate-dependent hysteresis characteristics of piezoelectric actuators, and the use of a composite controller can effectively reduce the accuracy error caused by the hysteresis nonlinear characteristics of piezoelectric actuators. [ABSTRACT FROM AUTHOR]

The (1-x)Mg0.7Zn0.3Fe2O4 – (x)Ba0.7Sr0.3TiO3 composites with x = 0.40, 0.50 and 0.60 were prepared by solid state reaction under two step sintering. Two step sintering conditions were determined by the first step (T1) at 1350 °C for holding time of 60 min and cooled down to the second sintering temperature (T2) with different temperatures between 900 and 1100 °C for holding time of 5 h. The sample with high percentage of shrinkage and dense ceramic was obtained from 0.4Mg0.7Zn0.3Fe2O4-0.6Ba0.7Sr0.3TiO3 with sintering of T2 at 1100 °C. XRD pattern showed combination of ferrite phase (Mg0.7Zn0.3Fe2O4) and ferroelectric phase (Ba0.7Sr0.3TiO3) and secondary phase of ZnO. Rietveld analysis confirmed main phases of Mg0.7Zn0.3Fe2O4 and Ba0.7Sr0.3TiO3, including MgFe2O4 and ZnO as secondary phase. It was found that the unit cell volume of Ba0.7Sr0.3TiO3 was smaller than Mg0.7Zn0.3Fe2O4 unit cell volume. Therefore, the short distance between ions of Ba0.7Sr0.3TiO3 phase produced the dense composites with increasing ferroelectric phase contents. The average grain size of ceramic was in the range of 0.74–1.07 µm with grain square shape in Mg0.7Zn0.3Fe2O4 phase and the average grain size of 0.59–0.70 µm with round oval shape in Ba0.7Sr0.3TiO3 phase. The dielectric constant was between 0.8 × 103 and 5.4 × 103 in the temperature range of 275 °C − 360 °C. The highest dielectric constant was obtained from 0.6Mg0.7Zn0.3Fe2O4−0.4Ba0.7Sr0.3TiO3 with T1 at 1350 °C with holding time for 60 min and T2 at 900 °C with holding time for 5 h. The hysteresis measurement was carried out to determine saturation magnetization, remanent magnetization and coercivity of the composites. The results revealed that higher concentration of ferrite led to optimal magnetic properties. [ABSTRACT FROM AUTHOR]

Lithium tantalate LiTaO3 (LT) plates with various composition gradient along the polar axis were produced by partial vapor transport equilibration (VTE) with annealing temperature above phase transition. The proper annealing parameters allow creating a charged domain wall (CDW) in the center of the plate. The CDW morphology depends on the spatial distribution of stoichiometry deviation. The bidomain actuators manufactured from the LT plates after partial VTE procedure possess a linear voltage dependence of the displacement of the free end without any hysteresis. It is shown that increase in CDW roughness leads to a noticeable decrease in the effective piezoelectric coefficient. [ABSTRACT FROM AUTHOR]

Barium-strontium niobate Sr0.5Ba0.5Nb2O6 epitaxial thin films with SrRuO3 epitaxial bottom electrode were sputtered on MgO(001) substrates by RF cathode deposition in an oxygen atmosphere. The produced Sr0.5Ba0.5Nb2O6/SrRuO3/MgO is a high quality heterostructure without any impurity phases. The formation of domains with two orientations is observed in the Sr0.5Ba0.5Nb2O6 layer. In both layers of the heterostructure, there are rather strong deformations of unit cells. Hysteresis in the ε'/ε0(T, f) temperature dependences was found at the room temperature. [ABSTRACT FROM AUTHOR]

Polycrystalline compounds of Sn substituted Pb0.9Mn0.1(Zr0.52Ti0.48)1-xSnx O3 (where x = 0.05,0.1) are synthesized by conventional ceramic method. Raman spectroscopy study reveals the tetragonal structure of Sn substituted samples. Impedance spectroscopic studies reveal the non-Debye kind of relaxation process in the material. Grain and grain contribution to the electrical conduction was observed. The observed P-E hysteresis confirmed the ferroelectric nature of all the samples. With the increase of Sn doping, Pr, Ps and Ec values also increased. [ABSTRACT FROM AUTHOR]

Polycrystalline compounds of Sn substituted Pb0.9Mn0.1(Zr0.52Ti0.48)1-xSnx O3 (where x = 0.05,0.1) are synthesized by conventional ceramic method. Raman spectroscopy study reveals the tetragonal structure of Sn substituted samples. Impedance spectroscopic studies reveal the non-Debye kind of relaxation process in the material. Grain and grain contribution to the electrical conduction was observed. The observed P-E hysteresis confirmed the ferroelectric nature of all the samples. With the increase of Sn doping, Pr, Ps and Ec values also increased. [ABSTRACT FROM AUTHOR]

Epitaxial (Pb0.9La0.1)(Zi0.4Ti0.6)O3 (PLZT) film was prepared with Pt as the upper electrode and La0.5Sr0.5CoO3(LSCO) as the bottom electrode on (001) STO substrate by radio frequency (RF) magnetron sputtering. The dynamic hysteresis scaling behavior of the film, including the variation of remanent polarization (Pr), coercive field (Ec), and loop area () with external field (E0) and frequency (f) , was systematically studied. The evolution of scaling behavior in the PLZT film can be divided into two stages: minor loops and major loops, which are in the low and high E0 regions, respectively. The scaling relations take form of < A > ∝ f − 0.11 E 0 2.72 and < A > ∝ f − 0.03 E 0 1.27 in minor loops and major loops, respectively. The results show that the domain structure and domain reversal play an important role in the dynamic hysteresis behavior of ferroelectric materials. [ABSTRACT FROM AUTHOR]

The discrete Preisach model is popular to describe the hysteresis of smart materials, such as the piezoelectric and ferroelectric material. Re-explaining the discrete Preisach model of antiferroelectric materials after introducing an extended Preisach function, the special multilayer perceptrons with only two input nodes was designed intrinsically to satisfy the anticommutative property of hysteresis without superfluous hidden nodes (called aMLP), where its output equals to the difference between two predictive results that two signals in the normal and reverse sequence are imported to the aMLP model. Several training algorithms, including the normal/hybrid generic algorithm (GA) and the normal/hybrid particle swarm optimization (PSO), were used to adjust the parameters of the aMLP model, respectively. The comparing results indicate that the aMLP models designed with the winner operation function pair of [tanh, ReLU] and trained by both normal and hybrid PSO algorithms suggest the better performance when applying the working voltages more than 50 V according to the experimental data. It provides another accurate way for an aMLP model to estimate the anticommutative property of hysteresis of smart materials. [ABSTRACT FROM AUTHOR]

The electrophysical characteristics of the PZT film formed on a silicon by the method of high-frequency reactive plasma sputtering were studied, and their relationship with the structure of the film was established. In particular, the hysteresis in the capacitance-voltage characteristics of the metal - ferroelectric - semiconductor indicates the polarization of the film, which, in turn, indicates the presence of the perovskite phase in the PZT film. However, the crystallite size of this phase is so small that it cannot be detected by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

The present article addresses the old problem of correct estimation of ferroelectric parameters from the hysteresis loop. Experimental study of thin polycrystalline PZT films shows that the presence of leakage currents and dielectric losses causes distortion of the hysteresis loop and results in overestimated values of remanent polarization. The technique based on the measurement of the hysteresis at two frequencies (100, 200 or 300 Hz) is studied to obtain hysteresis loop cleared from dielectric losses. The modified Lorentz function was used for simulation of obtained hysteresis curves. This approach permits to obtain correct data generated from the dielectric hysteresis measurement. [ABSTRACT FROM AUTHOR]

The applicability of Landau-Devonshire phenomenological model with an extended kinetic energy term on the response of the hysteresis, including remanent polarization, coercive field, and loop area, to the wide-span frequency of time-varying external field is investigated for ferroelectric film. A suitable and typical physics parameter set is found to permit all three variables as a function of frequency to be single-peaked, which is as understandable as the common forced damping oscillation. The present power-law scaling in the low or high frequency range can be compared with previous observation and calculation. [ABSTRACT FROM AUTHOR]

Influence of low-frequency (2-Hz-10MHz) AC field on LC phases exhibited by chiral hydrogen bonded liquid crystal dimer, viz., M*SA:9OBA is investigated. Phase transition temperatures Tc determined by capacitance C(T) and loss factor TanΔ(T) agree with the earlier report. Induced surface polarization reflected through capacitance C(E) exhibited hysteresis in behavior SmC* phase. Growth of primary order parameter in SmC* phase investigated by tilt angle θ(T) inferred critical field exponent β1. Secondary order parameter investigated as spontaneous polarization Ps in SmC* inferred Mean field exponent β2. Dipole moment (μ) is resolved as longitudinal (μl) and transverse (μt) components. Reorientation of μ to the field analyzed. Relaxation studied at different temperatures in SmC*; SmBcryst and SmG phases inferred a low-frequency (LF fR∼100Hz) and another high frequency (HF fR∼100kHz) reorientation processes. LF relaxation in SmC* phase is influenced by dc bias field to suggest polarization helix formed by coupling of field μt. Threshold field (Vth) for polarization switching estimated from the data of field variation of loss εmax″(E). LF relaxation in SmC* is identified with Goldstone mode (GM) manifested as the suppressed ε″max(E) with field. HF relaxation in SmC* is identified with Soft Mode (SM) by its decreasing trend of fR towards TIC*. Activation energies (Ea) estimated from Arrhenius behavior of fR(T) agree with reports. Field influence on GM manifests through shift of loss ε″max(E) and fR(E). Activation energy Ea is estimated from the shift of fR(E) in terms of equivalent temperature plots. Dispersion, ε″ versus ε′ in LC phases infers a non-Debye distribution of relaxation times. Cole-Cole plots inferred large shift of static permittivity εo. Data of dielectric relaxation parameters, i.e., relaxation frequency fR, relaxation time τR, activation energy Ea, loss maxima ε″max, static permittivity (εo), high frequency permittivity ε∞, dielectric strength Δε and distribution (α) parameter are presented. Dielectric strength analyzed for SM in SmC* phase confirms Ferro-Electric Curie-Weiss behavior. [ABSTRACT FROM AUTHOR]

Present article presents ferroelectric hysteresis behavior of [(Ba0.825+x Ca0.175−x)(Ti1−xSnx)O3] ceramics for x = 0.0625, 0.0875 and 0.100 samples. Temperature-dependent ferroelectric hysteresis scaling affiliation for remnant polarization (Pr) and coercive field (Ec) have been recommended. In view of scaling, the power law temperature proponent was efficiently settled for the hysteresis parameters. The dynamic hysteresis scaling of Pr and Ec at sintering temperature of 1450 °C for 2 h harvest Pr α T−0.92and Ec α T−038. By Arrhenius law, the back switching polarization (Pbc) and domain dynamics also evaluated in the form of temperature (T). [ABSTRACT FROM AUTHOR]

A detailed analysis of the thermodynamic properties of uniaxial ferroelectrics is carried out within the framework of an exactly soluble model with an infinite radius of interactions. The free energy of a ferroelectric in a power series in the order parameter is expanded and it is shown that all the coefficients of even degree depend strongly on temperature, including the change of their signs at temperatures below the Curie point. The equation of state of a ferroelectric in an external field is derived. A relationship between the width of the zone of metastable states of the ferroelectric and the temperature interval is established. An expression is derived for the height of the energy barrier separating the metastable and stable states of a ferroelectric. The results obtained within the framework of the exact solution of the model are compared with the results within the framework of the Landau-Devonshire phenomenological theory. It is shown that for dimensionless temperatures any Landau-like polynomial approximations for free energy lead to significant errors both in calculating the free energy and in calculating the equilibrium values of the order parameter. [ABSTRACT FROM AUTHOR]

Thin films of organic ferroelectric 2-methylbenzimidazole (MBI) were grown by evaporation method on different substrates. The films consist of self-assembled spherulite blocks formed by elongated crystallites of MBI. Temperature, frequency, and electric field amplitude variations of in-plane hysteresis dielectric loops were measured using interdigital system of electrоdes and compared with analogous dependences in MBI single crystals. Simulation of remnant polarization Prem dependence on amplitude of electric field Emax in films is carried out in frames of a model considering the dipole moment of block as a sum of dipole moments of crystallites, which form spherulite with account of different orientation of crystallites relative to applied electric field. Deviations from the model are assosiated with complicated domain structure and presence of depolarizing fields. [ABSTRACT FROM AUTHOR]

Employing many-valued logic (MVL) data processing allows to dramatically increase the performance of computing circuits. Here we propose to employ ferroelectrics for the material implementation of MVL units basing on their ability to pin the polarization as a sequence of multi-stable states. Two conceptual ideas are considered. As the first system, we suggest using the strained ferroelectric films that can host the polarization states, allowing the effective field-induced multilevel switching between them. As the second one, we propose to employ the ferroelectric nano-samples that confine the topologically protected polarization textures, which may be used as MVL structural elements. We demonstrate that these systems are suitable for engineering of the 3-, 4- and even 5-level logic units and consider the circuit design for such elements. [ABSTRACT FROM AUTHOR]

Ferroelectric hysteresis loops were measured and the temperature evolution of the coercive field traced in [110]-oriented 0.8Pb(Mb1/3Nb2/3)O3–0.2PbTiO3 single crystal in the temperature range from 120 to 300 K at frequencies from 2 to 50 Hz. It was found that the coercive field rised with decreasing temperature in power-law manner at all frequencies. Temperature-dependent hysteresis model was used for approximation of acquired coercive field-temperature dependences. It was shown that nanoscale ferroelectric domains could be created at PMN-20PT surface by voltage pulses applied between the tip of atomic force microscope and bottom electrode at temperatures as low as 100 K. [ABSTRACT FROM AUTHOR]

Hysteresis phenomena were observed under electric fields two orders of magnitude lower than the coercive ones in ferroelectric copolymer vinylidene fluoride–tetrafluoroethylene. From the field dependences of the electrical displacement hysteresis, the volumetric energy density of electric loss was calculated. Its value increases with increasing amplitude of the sawtooth external field and is higher in case of lower external field frequency. Complex dielectric permittivity measurements indicate that the noted high-voltage hysteresis phenomena at polarization should be related to the process of space charge formation, which is due to the presence of heterogeneity in the copolymer under study. [ABSTRACT FROM AUTHOR]

By using a second-order time-dependent Ginzburg--Landau model, we simulate the polarization hysteresis behavior of a ferroelectric system subjected to a sinusoidal electric field. We examine polarization hysteresis loop structure as a function of both field amplitude and field frequency. Departing from previous work, the relationship between these field parameters and loop structure is quantified by considering the Fourier transform spectra of the time series of polarization. These spectra are used to determine deforming factors that measure the amplitude- and frequency-dependent distortions of hysteresis loop structures from ellipticity. Our results agree with experimental observations, thus validating the model. [ABSTRACT FROM AUTHOR]

The results obtained in the study of [(K0.44 Na0.52 Li0.04)0.97La0.01]Nb0.9Ta0.103 ceramics obtained by solid state sintering from the precursor NaNbO3 synthetized by the reactive templated grain growth (RTGG) technique are presented. X-ray diffraction studies show the coexistence of two crystals phases, orthorhombic and tetragonal, being the last one, the more abundant. Dielectric measurements make evident the effect of La doping through a decrease in the transition temperatures with respect to those reported for undoped KNN (tetragonal-cubic TT-C = 264 °C and orthorhombic -tetragonal TO-T = 90 °C. The maximum value for the dielectric permittivity is surprisingly high at 6800 at room temperature and 1 kHz. Piezoforce microscopy (PFM) shows domain switching areas in response to the applied electric field but also non-switching zones where the polarization is perpendicular to the applied field. Hysteresis obtained by PFM shows the effective piezoelectric coefficient deff = 164 pC N−1 comparable to the best values of PZT and KNN ceramics. [ABSTRACT FROM AUTHOR]

In the current work, polycrystalline BaTiO3 thin films have been synthesized on Pt/Ti/SiO2/Si substrates using the low temperature Sol gel hydrothermal method and different metal nanoclusters (Au, Ag, Cu and Al) have been fabricated over the surface of BTO thin film using thermal evaporation technique. The hysteretic behavior of the BaTiO3 (BTO) thin films integrated with various top metal electrodes is studied, and emphasis has been given on the effect of leakage current and trap generated current on the shape and measured polarization of the hysteresis loop. Cu, Au, Ag and Al metals were used as top contacts over BTO/Pt/Ti/SiO2/Si and difference in ferroelectric PE hysteresis loops were studied. Variation in hysteresis loops due to different metal contacts is related to the leakage current and trap generated current variations. It is concluded that the properties of the top electrode interface with the ferroelectric film significantly impact the ferroelectric properties. [ABSTRACT FROM AUTHOR]

In order to improve the high-frequency performance of magnetostrictive composites, the work fabricated a polymer-bonded Tb-Dy-Ho-Fe fiber composite. Its magnetic properties were investigated and compared with that of polymer-bonded Tb-Dy-Fe fiber composite. An experimental system was setup to measure the major and minor hysteresis loops of the given magnetostrictive composites at different frequencies. The results showed that Tb-Dy-Ho-Fe fiber composites demonstrates superior magnetic properties, such as lower saturation magnetic field (220 kA/m), smaller coercivity force (5 kA/m) and less dynamic magnetic loss (115 W/m3 at 20 kHz, only 60% of Tb-Dy-Fe fiber composites), compared with Tb-Dy-Fe fiber composites. The proposed composite is suitable for the application of sensing and ultrasonic. [ABSTRACT FROM AUTHOR]

Piezoelectric (lead zirconate titanate, PZT) fibers show hysteretic behavior when subjected to cyclic mechanical loading, under tension, and cyclic electric field. The hysteretic response under the above loading conditions is manifested due to microstructural changes such as reorientation of dipolar domains in the crystalline regions and other possible permanent microstructural changes such as cracking. In describing the above macroscopic behavior of PZT fibers a constitutive model based on a multiple natural configuration approach is formulated. It is assumed that the body has multiple natural configurations associated with the original and newly formed configurations. The new microstructure is formed when the body is subjected to external stimuli, i.e., stress and electric field, leading to reorientation of the dipoles in the crystalline regions. A constitutive model for the electro-mechanical coupling behavior is formulated by defining Gibbs potential in terms of the stress, electric field, and the volume fraction of the domain transformation. Internal state variables and their corresponding driving force for microstructural changes are identified. The model predictions of the hysteretic response are compared to experimental results. Finally, the effect of heat generation from the energy dissipation on the overall electro-mechanical response of PZT fibers is investigated. [ABSTRACT FROM AUTHOR]

We investigate current-voltage (I-V) characteristics of colemanite (Ca2B6O11.5H2O) at room temperature, at a high temperature of 400°F and under the influence of near ultraviolet light. We demonstrate that all three I-V plots exhibit hysteresis effects, and these new results shed new light on the resistance of colemanite, which have not been investigated before. These novel properties are explained on the basis of its microstructure indicating potential applications in devices with negative resistance, as well as in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Computer simulation of repolarization and inverse piezoeffect is realized by Monte-Carlo method in polymer ferroelectric materials, observed in AC electric field with different frequencies and amplitudes. For describing the interactions between the segments of polymer chains, Lennard-Jones potential was used with additional term describing exchange short-range orientational interactions. We investigate the influence of temperature and parameters of external electric field on the hysteresis curve area, which determines the absorption coefficient. It is shown that for ferroelectric systems there is a frequency of the external field, which accounts for the maximum absorptivity. [ABSTRACT FROM AUTHOR]

In this work, we consider the impact of theP-Ehysteresis on the performance of electrocaloric cooling using the phenomenological theory of ferroelectrics. For reasons of simplicity, we use approximations of sufficiently small electric fields and polarization. A large electrocaloric effect was obtained for a slimP-Ehysteresis (small remnant polarization and coercive field) and a weak dependence of the dielectric permittivity on the electric field. [ABSTRACT FROM AUTHOR]

In this work, effect of sintering temperature (1400–1500°C) and dwell time (3–6hr) on the ferroelectric properties are investigated for Ba0.85Ca0.075Sr0.075Ti0.90Zr0.10O3(BCSTZO) ceramics. The ferroelectric hysteresis scaling relations for coercive field (Ec) and remnant polarization (Pr) as a function of temperature have been estimated and power law exponents were calculated. Finally, to understand the domain dynamics, back switching polarization (Pbc) as a function of temperature (T) was also estimated using Arrhenius law and the average activation energy was evaluated. [ABSTRACT FROM PUBLISHER]

As theoretical solution cannot be acquired, fixed point iteration and the 4th order Runge-Kutta method are introduced to solving the Jile-Atherton hysteresis equations. As the iteration spends quite long time, some fitting functions are presented instead of the iterating process. The fitting effects of these functions, in calculating the anhysteretic magnetization and total magnetization, are contrasted. And then one precise and fast solving method is summarized. After analyzing the format of the fitting function, a series of calculating methods are presented. These methods can acquire higher computing precision if necessary. [ABSTRACT FROM AUTHOR]

The dynamic Monte-Carlo method for three-dimensional lattice model of rotators with anisotropic intra- and interchain interactions of dipole type is used to investigate dielectric properties of poly(vinylidene fluoride) in β-phase. Hysteresis curves are calculated. It is shown that the area of hysteresis curve in strong electric fields increases with the increase of interchain interactions. [ABSTRACT FROM PUBLISHER]

The temperature and frequency dependences of dielectric properties of the ferroelectric composite (NaNO2)0,95/(PbTiO3)0,05near the phase transition of sodium nitrite have been studied. A significant increase in the real part of the dielectric constant at low frequencies and its strong decrease with increasing frequency were discovered. The temperature hysteresis of phase transition is about 1.5 K. The dielectric constant upon cooling from the paraelectric phase to 273 K is less than during heating, while a similar dependence is observed for conductivity. The results are analyzed in the Landau – Ginzburg theory framework. [ABSTRACT FROM PUBLISHER]

Ferroelectrics are usually defined as polar materials that display polarisation hysteresis. This is a functional definition. A structural definition exists too, based solely on symmetry arguments. The structural definition, useful e.g. for design of new materials, says that a ferroelectric is a material that underwent a phase transition from a parent higher-symmetry phase into a ferroelectric phase, such that the polar directions in the ferroelectric phase are linked to each other by lost symmetry operations of the parent phase. Ferroelectrics are discussed in this paper from a structural point of view. The structural definition helps also in clarifying the relationship between ferroelectrics and antiferroelectrics, conducive for the design of new antiferroelectrics or tuning of existing ones. Relaxor ferroelectrics are discussed too, in the structural context. The contemporary material (Na1/2Bi1/2)TiO3is then used to illustrate the subjects discussed, the existing knowledge, and the missing understanding. This paper, on the occasion of the 500thvolume of the journal Ferroelectrics has the limited scope of (a) reemphasizing the structural aspects of ferroelectricity and (b) serving as a primer on ferroelectric materials for the novice. [ABSTRACT FROM AUTHOR]

The La doped ceramics PLZT-0.03/1-x/x (0.43 ≤ x ≤ 0.49) around morphotropic phase boundary (MPB) region were prepared by solid-state reaction. The ceramics exhibited diffused phase transition behavior, while MPB region showed the least degree of diffusion. It has been shown that distinct difference exists between poled and unpoled samples. All the samples exhibited thermal hysteresis behavior characteristic of the first order phase transition. The ferroelectric properties of the samples were also discussed. [ABSTRACT FROM AUTHOR]

Piezoelectric lead zirconate titanate (PZT) ceramic-cement composites using a high volume of ceramic content (80%) in 0–3 connectivity were fabricated. Piezoelectric Force Microscope (PFM) characterization was carried out and ferroelectric hysteresis behavior of the composites were investigated. Domain configurations of PZT ceramic can be seen at the interfacial zone of PZT-cement composites. Ceramic particles were seen to bind well with the cement matrix. The ferroelectric hysteresis loop at 50 Hz and 10–25 kV/cm showed a slim loop with low loss behavior for this type of composite due to increase in the PZT ceramic in 0-3 PZT-cement composites. [ABSTRACT FROM AUTHOR]

In this work, primary and secondary contributions to electrocaloric effect were investigated in a relaxor PMN-PT ceramic, by combining polarization and strain hysteretic measurements. Our results indicate that, although the ceramic shows a large electromechanical response, field-induced dimensional change (secondary effect) accounts for less than 19 % of the ceramic electrocaloric response over the 30-200°C temperature range. We believe that the method for the characterization of electrocaloric materials presented herein can provide valuable insights into the development of novel and optimized materials and heterostructures by tailoring primary and secondary contributions. [ABSTRACT FROM AUTHOR]

Pure BiFeO3(BFO) ceramics and Bi1-xBaxFeO3(x=0.1, 0.15, 0.2, and 0.25) ceramics were prepared by sol-gel method. A structural transition from rhombohedral R3c to triangle R3m occurs in the Ba doped BFO ceramics. The Ba doped BFO ceramics exhibit larger dielectric constant, smaller dielectric loss, and better ferroelectric hysteresis loop, which could be attributed to the lower concentration of charge defects and the structural transition. [ABSTRACT FROM AUTHOR]

The hysteresis loops and the transition properties of a ferroelectric (FE) thin film with seeding layers are studied using the effective field theory with a probability distribution technique that accounts for the self-spin correlation functions. The effect of the interaction parameters for the seeding layer on the hysteresis loops and phase diagram are also examined. We calculated the critical temperature and the polarization of the FE thin film for different seeding layer structures. We find that the seeding layer can greatly increase the Curie temperature and the polarization of the whole FE thin film. The hysteresis loops are obtained for some typical value of the exchange interaction and the transverse field for a film with one or two seeding layers. [ABSTRACT FROM AUTHOR]

Polarization-vs.-applied-voltage hysteresis curves are recorded on tubular-channel fluoroethylene-propylene (FEP) copolymer ferroelectrets by means of a modified Sawyer–Tower circuit. Dielectric barrier discharges (DBDs) inside the cavities are triggered when the applied voltage is sufficiently high. During the DBDs, the cavities become man-made macroscopic dipoles which build up an effective polarization in the ferroelectret. Therefore, a phenomenological hysteresis curve is observed. From the hysteresis loop, the remanent polarization and the coercive field can be determined. Furthermore, the polarization can be related to the respective piezoelectric coefficient of the ferroelectret. The proposed method is easy to implement and is useful for characterization, further development and optimization of ferro- or piezoelectrets. [ABSTRACT FROM PUBLISHER]

The methodology to obtain the loss factors in piezoelectric ceramics is proposed in this paper. There are three hysteresis loss components for piezoelectric vibrators, i.e., dielectric, elastic and piezoelectric losses. The equations were derived about the relations between mechanical quality factors and all contributing loss factors by the complex analysis of the admittance/impedance expressions for specific piezoelectric vibrators. By characterizing mechanical quality factors and coupling coefficients in k31, kt, k33, kp, and k15modes, 20 loss factors can be obtained for the piezoelectric ceramic with ∞mm or 6 mm crystal symmetry. [ABSTRACT FROM AUTHOR]

The dependence of dielectric properties on the uniaxial pressure (0–1500 bar) of 0.2Na0.5Bi0.5TiO3-0.8BaTiO3ceramic was investigated, revealing a significant influence of the external stress on their properties. This includes a shift of the phase transition, a diffuseness of the permittivity characteristics, a change of the dielectric dispersion and the thermal hysteresis. We discuss our results based on domain/nanoregions switching processes under applying of pressure. [ABSTRACT FROM AUTHOR]