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Synthesis (via solid-state reaction) and characterization (structure, microstructure, dielectric, electrical, and ferroelectric behavior) of brownmillerite polycrystalline material NaBiFe2O5 (NBFO) are discussed in this paper. The formation of a triclinic structure has been analyzed by the X-ray diffraction method. The morphology of the ceramic sample was analyzed using a field emission scanning electron microscope (FESEM) and energy-dispersive X-ray analysis (EDX). It is found that the grains are uniformly distributed through well-defined grain boundaries of the sample containing all the constituent elements (Na, Bi, Fe, and O). The study of both frequency (1 kHz–1MHz) and temperature (25–450 °C) dependent dielectric and AC-conductivity predicts the presence of Maxwell-Wagner type of dielectric dispersion and thermally activated relaxation mechanism of NBFO. The impedance spectra support the semiconducting behavior of the brownmillerite NBFO at high temperature. The resistance of the material falls with a rise in temperature favors the negative temperature coefficient resistance behavior of the material. The study of electric polarization suggests the possibility of the ferroelectric properties of the studied sample. The high dielectric constant and low tangent loss suggest the possibility of the material for device applications. [ABSTRACT FROM AUTHOR]

Synthesis (via solid-state reaction) and characterization (structure, microstructure, dielectric, electrical, and ferroelectric behavior) of brownmillerite polycrystalline material NaBiFe2O5 (NBFO) are discussed in this paper. The formation of a triclinic structure has been analyzed by the X-ray diffraction method. The morphology of the ceramic sample was analyzed using a field emission scanning electron microscope (FESEM) and energy-dispersive X-ray analysis (EDX). It is found that the grains are uniformly distributed through well-defined grain boundaries of the sample containing all the constituent elements (Na, Bi, Fe, and O). The study of both frequency (1 kHz–1MHz) and temperature (25–450 °C) dependent dielectric and AC-conductivity predicts the presence of Maxwell-Wagner type of dielectric dispersion and thermally activated relaxation mechanism of NBFO. The impedance spectra support the semiconducting behavior of the brownmillerite NBFO at high temperature. The resistance of the material falls with a rise in temperature favors the negative temperature coefficient resistance behavior of the material. The study of electric polarization suggests the possibility of the ferroelectric properties of the studied sample. The high dielectric constant and low tangent loss suggest the possibility of the material for device applications. [ABSTRACT FROM AUTHOR]

This paper investigated the effect of PZT30/70 seed layer as a nucleation aid on the microstructure and electrical properties of 0.93PMN-0.07PT thin films. Pyrochlore phase was totally eliminated at an annealing temperature as low as 650°C. Seeded 0.93PMN-0.07PT thin film possessed a denser structure, larger grain size, and thus higher permittivity, spontaneous polarization and pyrocoefficient than unseeded film. The slim P-E loops and the frequency dependent Tm observed in both films indicated a relaxor-like behavior. [ABSTRACT FROM AUTHOR]

This paper reviews the spontaneous polarization of ferroelectric ceramics and its variations with applied electric field, stress and temperature, especially at induced phase transitions. Normally, there are two kinds of field dependence of the induced polarization, the linear and nonlinear dependence. In this paper the nonlinear relationship will be emphasized. The application of these ceramics for underwater transducers, shock wave power generators, pyroelectric energy converters and pyroelectric voltage transformers are listed. [ABSTRACT FROM AUTHOR]

Recently a theoretical model of the polarization modulated and layer undulated (B7) structure in the systems formed by bent-core (bow-shaped) molecules was presented. In contradiction to the general expectation the model suggests that polarization splay is possible only when the molecules are tilted with respect to the layer normal, i. e. when the chiral symmetry of the system is broken. In this paper we present a detailed stability analysis of the tilted and the nontilted structure with respect to polarization modulation and show, that polarization modulation in the nontilted phase is not possible because the system has no possibility to relieve the stress in the domain walls, neither by bending the layers nor by reducing the smectic order. [ABSTRACT FROM AUTHOR]

A SPICE-based model of an n-channel ferroelectric field effect transistor has been developed based on both theoretical and empirical data. This model was used to generate the I-V characteristic of several logic gates. The use of ferroelectric field effect transistors in memory circuits is being developed by several organizations. The ability of FFETs to have different characteristics depending on the initial polarization can be used to create logic gates. These gates can have properties not available to standard CMOS logic gates, such as memory, reconfigurability and memory. This paper investigates basic properties of FFET logic gates. [ABSTRACT FROM AUTHOR]

There has been extensive research activity since the discovery of fatigue free La-doped Bi 4 Ti 3 O 12 films on Pt electrodes. These films show superior ferroelectric properties and require a lower deposition temperature than the previously discovered SrBi 2 Ta 2 O 9 . Substitution of Bi by lanthanide elements other than La is of interest due to change in the magnitude of the structural distortion in the perovskite block, thereby, changing the remanent polarization. In this paper we discuss the doping of bismuth titanates with other lanthanide elements (Nd, Sm). The films were prepared by spin coating on Pt coated Si substrates. Structural characterization was performed by X-ray diffraction followed by ferroelectric characterization. [ABSTRACT FROM AUTHOR]

Investigation of mesoscopic inhomogeneities caused by the coexistence of FE and AFE phases is carried out in PLLZT solid solutions Pb1-x(Li½La½)x (Zr1-y Ty)O3 with x = 0.1 and 0.15, in which the energy difference between FE and AFE states is small. A weak distinction in free energy leads to the coexistence of the said phases domains at temperatures lower than the point of paraelectric phase transition In the discussed PLLZT solid solutions equivalent crystallographic sites are occupied by ions differing in the size. In the vicinity of the interphase border a process of ions segregation takes place. In the present paper, development of the process of "stratification" of the solid solutions in the course of time is studied. The said process is shown to be entirely completed in the course of 100-120 h. [ABSTRACT FROM AUTHOR]

We report the preparation and characterization of vanadium substituted four-layer Aurivillius compound Bi5Fe1.5V0.5Ti2O15 using spin coating method. Ferroelectricity in the prepared films are confirmed from the well saturated polarization vs electric field (P-E) loops having remnant polarization (2 Pr) around 12.94 µC/cm2 at room temperature. In addition, low temperature P-E measurements show a decrease in Pmax and 2 Pr, which is attributed to the stabilization of defect dipole complexes and domain pinning, as seen in bismuth-based ferroelectrics. Additionally, this decrease in polarization is accompanied by an increase in imprint, confirming the presence of defect dipoles manifested as internal fields. [ABSTRACT FROM AUTHOR]

Depolarization field Edemerging from spontaneous polarizationPSis considered to play an essential role in the characteristics of ferroelectrics. For the estimation of Ed, correct dc-permittivityϵdis necessary but is still a controversial issue such as background permittivityϵb. This paper examines the permittivityϵdin the case of 1-dimensional insulating single-domained ferroelectric, by noting thatϵddepends on howPSis defined. This examination shows thatϵdshould be unity when experimentalPSor self-consistentPSis used. Without relying on special theories, a generic consideration based on this results shows that 1-dimensional insulating single-domained ferroelectric having 1st order ferroelectric transition cannot exist thermodynamically. [ABSTRACT FROM PUBLISHER]