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A model of the high-frequency impedance of metal-ferroelectric-semiconductor structures has been composed and analyzed. An algorithm is formulated for recovering the impedance of the potential drop across the ferroelectric layer, band bending in a semiconductor, the total concentration of charged boundary states and minority charge carriers on the semiconductor surface from the experimental field characteristics as a function of the voltage across the structure. The results of high-frequency measurements of the capacitance and conductivity of Ni–Ba 0.8 Sr 0.2 TiO 3 –Pt and Ni–Ba 0.8 Sr 0.2 TiO 3 –Si structures in the paraelectric phase are presented. It is shown that Si does not evolve into a state of strong depletion in the entire range of external voltages, and the capacitances of the semiconductor and the metal-ferroelectric-silicon structures practically coincide. This is due to the almost complete screening of the ferroelectric layer polarization by the charges of electron traps at the Ba 0.8 Sr 0.2 TiO 3 –Si contact. It is proposed to use dangling bond passivation methods realized in planar silicon technology to reduce the concentration of active trapping centers at the ferroelectric-semiconductor interface. [ABSTRACT FROM AUTHOR]

PbHf(1−x)Sn(x)O(3) (PSH) ceramics were synthesised by a conventional solid-state reaction method. Dielectric properties were investigated in the temperature range of 20–650°C. As the Sn^4+ content goes up, the phase transition temperatures of an antiferroelectric (AFE1) to another intermediate antiferroelectric (AFE2) phase and AFE2 to the paraelectric (PE) phase decrease gradually. When x≥0.1 for PSH ceramics, the ferroelectric (FE) phase appears around 225°C, and phase transition temperature from FE phase to PE phase goes up with the increasing concentration of Sn^4+. Moreover, high-temperature dielectric relaxation (HTDR) phenomenon can be seen from all samples. Mechanism of HTDR was discussed from impedance spectroscopy and conductivity for PSH ceramics. It was found that three dielectric responses were observed in complex impedance plots and HTDR was involved with the movement of oxygen vacancies. Activation energy calculated from dielectric data suggested that the HTDR was governed by the hopping conduction process.

The article focuses on enhanced ferroelectric property of film using room-temperature crystallization for high-performance ferroelectric device applications and ferroelectric field effect transistors (feFET) and mechanical energy harvesting devices. It mentions use of conventional process of thermal annealing (TA), a room temperature annealing method and the phase is depicted by a different molecular structure. It also mentions films were measured and compared using X-Ray Diffraction (XRD).

In this paper, we study the behavior of the particle in the paraelectric phase near the bulk critical temperature (a = 0) (in our units) and near the particle critical temperature (ad) using the fluctuation-dissipation theorem through the power spectrum density S(ω) at zero frequency ω = 0 in the particle. This power spectrum density is found here to have three regimes as concerning the temperature dependence for a given particle diameter. The first one is above the bulk critical temperature, the second one is at the bulk critical temperature and the third is below the bulk critical temperature and above the particle critical temperature. Decreasing temperature fluctuations of the order parameter (polarization) change from the bulk-like to the particle-like due to particle form. Divergency of the bulk spectrum density Sb(0) at the bulk critical temperature a = 0 is compensated in the particle by the contribution ≈a2 due to the particle form. The power spectrum density S(0) near the particle critical temperature diverges with the exponent 2, we obtain , where Tc, d is the particle critical temperature in the temperature variable T. Our results are new and are exact within the model used. [ABSTRACT FROM AUTHOR]

The dielectric dynamic susceptibility of a particle is studied numerically using the exact susceptibility expression in other to understand particle physical properties. There exist one peak in the imaginary part and two peaks in the real part of the susceptibility. Constant behavior of peaks width and height is found in the imaginary and real part of the susceptibility going from the center. A decrease of peaks to zero is an effect of boundary. Our results are in contrast with behavior of susceptibility behavior found variationally where there is no constant behavior of the susceptibility peaks changing r. These results are new in literature of dielectrics. [ABSTRACT FROM AUTHOR]

We study the Cole-Cole diagram for the case of a paraelectric particle for which the relaxation time is the same for every mode and the resonance frequency changes and there is an infinite number of such modes. We will calculate the Cole-Cole diagram for temperature a = 10 and damping g = 1 in a and g units (see below) from exact expression for the dynamic susceptibility. We have found that there is a smooth Cole-Cole diagram the curve of which starts from small frequencies 0.001 from the point near Y = 1.5 and X = 0 on the diagram down to the peak (in imaginary part) values of X near 1.6 and Y near 0.5 increasing frequency. Increasing further frequency to 20, the real and imaginary parts tend to zero value. Thus there exists a single maximum of the imaginary part of the susceptibility (for 1000 modes and for 5000 modes), and a single maximum and minimum for the real part of the susceptibility. [ABSTRACT FROM AUTHOR]

Static dielectric susceptibility for the paraelectric phase of a particle was calculated exactly. Temperature and diameter dependence are described analytically. There are two regimes of the susceptibility: for temperatures above the bulk critical ferroelectric temperature of the particle and below it. The critical transition temperature from the exact calculation is the same as that from the soft mode approach. [ABSTRACT FROM AUTHOR]

Temperature dependent dielectric permittivity is a crucial parameter in determining the physical property of ferroelectric materials. A method of using temperature to predict the dielectric permittivity of some ferroelectric materials is studied. The object of this work is to search for the applicable method of using temperature to predict the dielectric permittivity and control the transition of some ferroelectric materials from ferroelectric phase to paraelectric phase. A typical numerical method is highlighted and discussed in light of the potential applications to the various experimental results. The simulations agree very well with the observed spectroscopy of twelve curves for dielectric permittivity versus temperature. The minimum value of correlation coefficients between actual and calculated data is 0.98. The maximum data of mean relative errors is 6.98%. This study may make a contribution to the theoretical and the practical aspects of the ferroelectric materials. [ABSTRACT FROM AUTHOR]

The ferroelectric crystal structure of SbSBr is composed of [Sb(S, Br)]∞ chains parallel to the [001] axis. In paraelectric phase, the crystal structure is disordered. The theoretical investigation of dependence of potential energy VP(z) of Sb atoms on amplitudes of B1u vibration symmetry coordinates along c(z)-axis have showed that each atom is shifted from the xy mirror plane by [image omitted] up or down along [001]. The theoretical investigation of the average potential energy [image omitted] of all Sb atoms in unit cell revealed that in paraelectric phase in region of phase transition [image omitted] has double-well shape. This strong anharmonicity of [image omitted] is created by interaction between phonons. [ABSTRACT FROM AUTHOR]

The dielectric permittivity and loss in these composites are important parameters characterizing their performance. In this study, the relative permittivity and loss of PCLT/PVDF-TRFE nanocomposites with various volume fractions of ceramic have been measured as function of frequency and temperature. Polymer-based 0-3 nanocomposites, consisting of nanocrystalline calcium and lanthanum modified lead titanate (PCLT) powder embedded in a vinylidenc fluoride-trifluoroethylene (palyvinylidenefluoride (PVDF)-trifluoroethylene (TRFE)) copolymer matrix, also have shown good potential in pyroelectric and piezoelectric applications.. The copolymer and nanocomposites exhibit a dielectric relaxation at the ferroelectric-to-paraelectric phase transition and another relaxation near room temperature (at-1 MHz). [ABSTRACT FROM AUTHOR]

Single crystals of RbK(SO4)·Te(OH)6 are obtained by slow evaporation at room temperature. The frequency and temperature dependencies of the real part of the permittivity, εr′, show that this material presents three phase transitions at T1 = 490 K, T2 = 535 K and T3 = 580 K. DSC measurements on RbK(SO4)·Te(OH)6 have been carried out in the temperature ranges 350–650 K. It reveal three endothermic peaks at around T1, T2 and T3. Complex impedance measurements are performed on this material at various temperatures. A substantial jump of the conductivity, attributed to the motion of H+, is observed at high temperatures. This behavior indicates the presence of superprotonic phase transition in RbK(SO4)·Te(OH)6.Raman spectra of RbK(SO4)·Te(OH)6, recorded at various temperatures (300–550 K) in the frequency range 200–1200 cm-1, confirm the presence of the phase transitions and especially the ferroelectric and the superprotonic phase transition. [Copyright &y& Elsevier]

The title compound β-phenylethylammonium pentachlorothallate III crystallizes in the monoclinic system with space group P21. The unit cell dimensions are: a=9.5470(1) Å, b=7.5660(1) Å, c=15.9180(1) Å, β=101.3420°(9), with Z=4. Its crystal structure was determined and refined down to R=0.0402. The structure of this compound consists of β-phenylethylammonium cations and polynuclear anions in which slightly distorted [TlCl6]3- octahedral sharing two cis vertices are interconnected into chains. These chains are themselves interconnected by means of the N&z.sbnd;H…Cl hydrogen bonds. Two phase transitions at T1=353 K and T2=389 K were detected and studied by differential scanning calorimetry, dielectric and impedance spectroscopy measurements. The evolution of the dielectric constant and dissipation factor as a function of frequency and temperature revealed the first transition to be ferroelectric–paraelectric. Crystallographic studies show that this material presents a noncentrosymmetric space group at room temperature which is in agreement with our last deduction. The second phase transition at 389 K is characterized by a strong jump in the conductivity plot. It is assumed that the reorientation of NH3+ ions is responsible for this phase transition. [Copyright &y& Elsevier]

Investigations on barium neodymium titanate (BNT) prepared by solid state reaction techniques are presented in this paper. The samples were sintered at temperatures, Ts, in a range 1200–1300 °C. High density values and adequate microwave parameters were obtained by adding 0.5 mol PbO substitutional for BaO. A decrease of the Curie temperature with the increase of the Nd2O3 concentration was confirmed. For the sample with 28 wt.% Nd2O3, 0.5 mol PbO pyroelectric data indicate Curie temperature around 75 K, therefore, at room temperatures, the materials are in paraelectric phase. BNT ceramics with high Nd2O3 concentration (28 wt.%), sintered at 1250 °C for 2 h appear to be suitable for dielectric resonators for frequencies up to 3 GHz (#x03B5;r=80–90 and Q=2000). [Copyright &y& Elsevier]

Barium–strontium titanate (BST), ternary ceramic compounds with the molar formula (Ba1-xSrx)TiO3, were prepared by solid-state reaction from raw materials. Three compositions with x=0.25, 0.50 and 0.75, have been checked. Samples with two type of thermal treatment at 1230 and 1260 °C have been manufactured and analyzed. Perovskite type, polycrystalline structure of the BST ceramics was revealed by the X-ray diffraction data at room temperature. Strontium ion (Sr2+) enters substitutionally on the Ba2+ site. A small decrease in the unit cell volume with the Sr content increase was observed. Dielectric measurements have been performed at low and high frequencies. The temperature dependence of low frequency permittivity shows large interval of ferroelectric transition, which appears to be merely due to dispersion of crystallites dimensions. The increasing concentration of Sr ion leads to a shift of the Curie point below room temperature. Experimental data show a linear decrease of the Curie point TC (°C)≈120–360x, versus x strontium fraction. Room temperature permittivity and dielectric loss have been measured in microwaves by using the Hakki–Coleman method. BST samples prepared using water as a milling medium exhibit lower porosity and lower dielectric loss in microwaves than samples prepared using acetone as a milling medium. Dielectric loss of 10-3 at 1 GHz shows that this ceramic material is quite suitable for high frequency device applications. [Copyright &y& Elsevier]

A brief review is presented of recent results derived from the random field theory approach to describing relaxor ferroelectric properties. The key point in this approach is that the random field originating f rom chemical disorder of relaxor ferroelectrics destroys long range polar order, which could otherwise exist at temperatures below the Burns temperature Td. As a result, polar clusters appear of size Rc (the correlation radius of Burns reference phase), corresponding to the Cross superparaelectric phase. The relaxor properties can be calculated by averaging the electric field dependence of the paraelectric Burns reference phase with the random field distribution function of a suitable property. The distribution functions for the cases of linear and non-linear random field contributions are calculated using the statistical physics framework for electric dipoles, point charges and dilatational centres as random field sources. These calculations allow explanation of the observed Vogel–Fulcher law and non-Debye character of the dynamic dielectric response; of stiff and soft response to dc field of non-linear susceptibility; of unusual Rc temperature dependence; as well as of dielectric response anomalies in 1:1 family relaxors. The correlation radius and relaxation time distribution functions are calculated using the random field distribution function. Calculated phase diagrams for mixed relaxors, allowing for non-linear and spatial correlation effects, give a good fit to the experimental results. Comparison of calculated and observed properties leads to the conclusion that a mixed ferroglass phase with coexisting short and long polar order is the most probable state for all relaxors, the degree of mixing being the essential factor for a relaxor. [ABSTRACT FROM AUTHOR]

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

The crystal structures of the glycinium hydrogenphosphite (GPI) and its deuterated analogue (DGPI) were determined by the X-ray diffraction method in the paraelectric (T=295(2) and 360(2) K) and ferroelectric (T=180(2) and 295(2) K) phases. The crystal structures of the paraelectric phase are consistent with the data published by Averbuch-Pouchot [Acta Cryst. C49 (1993) 815]. In the deuterated crystal, the interphosphite hydrogen bonds are longer (by ca. 0.03 A˚) than those in the normal crystal. In the ferroelectric phase crystals remain monoclinic with space group P21. Due to symmetry lowering, two kinds of glycinium cations (GA and GB) and two kinds of hydrogenphosphite anions (PA and PB) appear in the ferroelectric phase. The protons in the interphosphite hydrogen bonds are ordered. The P–H distances in PA (1.314(10) A˚) and PB (1.222(9) A˚) hydrogenphosphite anions differ significantly for GPI. Their P–D analogues (1.310(10) and 1.279(9) A˚) in the DGPI crystal are slightly less different. Molecular mechanism of the ferroelectric phase transition is proposed. [Copyright &y& Elsevier]