The ferroelectric characteristics in Fe-Ti-O system
TL;DR: In this paper, the dielectric constant and electrical conductivity of the synthetic ilmenite stabilised by non-magnetic bivalent metal ion were determined over a wide range of temperature (300-650 K).
About: This article is published in Solid State Communications.The article was published on 1994-12-01. It has received 7 citations till now. The article focuses on the topics: Curie temperature & Conductivity.
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TL;DR: In this article, the electron density distribution of ilmenite has been executed by maximum entropy method (MEM) using single-crystal diffraction intensity data, and the anisotropy in the electric conductivity has been clarified.
Abstract: Many of ilmenites ABO3 compounds bearing transition elements have semiconductive, ferroelectric and antiferromagnetic properties. The high-pressure diffraction studies of FeTiO3 have been conducted up to 8.2 GPa using synchrotron radiation in KEK at Tsukuba with diamond anvil cell. The compression mechanism of FeTiO3 ilmenite has been investigated by the structure refinements converged to the reliable factors R = 0.05. The deformations of the FeO6 and TiO6 octahedra were reduced with increasing pressure. In order to elucidate the electric conductivity change with pressure, electron density distribution of ilmenite have been executed by maximum entropy method (MEM) using single-crystal diffraction intensity data. MEM based on F
obs(hkl) of FeTiO3 clearly shows electron density in comparison with the difference Fourier synthesis based on F
obs(hkl) − F
calc(hkl). The radial distribution of the electron density indicates electron localization around the cation positions. The bonding electron density found in bond Fe–O and Ti–O is lowered with pressure. The isotropic temperature factors B
iso become smaller with increasing pressure. Nevertheless the thermal vibration is considerably restrained by the compression, the electric conductivity is enhanced with pressure. Neither charge transfer nor electron hopping between Fe and Ti along the c axis in FeTiO3 is plausible under high pressure. But the electric conductivity due to electron super-exchange in Fe–Fe and Ti–Ti has been clarified by the MEM electron density distribution. The anisotropy in the electric conductivity has been clarified.
42 citations
TL;DR: In this article, the currentvoltage characteristics of solid solutions of ilmenite-hematite (IH) (1− x )FeTiO 3 · x Fe 2 O 3, with x varying from 0 to 0.45, were studied.
41 citations
TL;DR: In this paper, the authors measured the permittivity of low grade Panzhuhua ilmenite ore at 2.45 GHz in the temperatures from 20 °C up to 100 °C using the technology of openended coaxial sensor combined with theoretical computation.
31 citations
Cites background from "The ferroelectric characteristics i..."
...VISWANATH and SESHADRI [13] studied the dielectric constant of ilmenite ore in the temperature range of 25−377 °C....
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01 Jan 2011
TL;DR: In this paper, the electron density in solids under external stress is studied and the modifications of electronic configurations and chemical bonding are studied through analysis of direct space indicators, including many experimental evidences.
Abstract: This chapter focuses on the electron density in solids under external stress. The modifications of electronic configurations and chemical bonding are studied through analysis of direct space indicators. Examples are given of elemental solids, ionic compounds and molecular crystals, including many experimental evidences.
14 citations
TL;DR: In this paper, the authors show that the electrical properties of natural ilmenite are modified by microwave irradiation, with a surface temperature in proportion to the irradiation time, and that the surface temperature measured on the samples were between 280 and 520 K.
Abstract: It has been observed that microwaves of 2.45 GHz heat dielectric materials. On subjecting natural ilmenite to microwave irradiation, the mineral is observed to heat, with a surface temperature in proportion to the irradiation time. With irradiation times from 40 to 240 seconds (increased in steps of 40 sec), the surface temperature measured on the samples were between 280 and 520 K. Electrical measurements made on the samples before and after irradiation show that the electrical properties are modified by the microwave irradiation. The real conductivity (σ′), dielectric constant (ɛ′) and the dielectric loss (ɛ″) plotted against frequency generally showed universal dielectric behaviour [1 and references therein] similar to that observed in other systems studied in the literature but using conventional heating techniques. Plots of σ′, ɛ′ and ɛ″ against the surface temperature of the sample showed frequency independent peaks around 460 K. The experimental dielectric loss (ɛ″) results fit a peak function of the form:
$$\varepsilon^{\prime\prime} = \varepsilon_0 + \frac{A}{\omega_0 T {\sqrt{2\pi}}} \exp \left(-\frac{\big(\ln\big(\frac{T}{T_p}\big)\big)^2}{2\omega_0^2}\right)
$$
where ɛ0, A, and ω0 are constants. The fitting of the dielectric loss results gives a frequency independent peak temperature (Tp) as 464 ± 5 K. Plotting the dielectric (γ′) and dielectric loss (γ″) exponents against temperature also gives an estimate of Tp close this value. The possibility of a ferroelectric transition in the samples is investigated by comparison with previous results obtained from synthetic ilmenite samples as it is the case with well known ferroelectric systems such as BaTiO3 [2].
12 citations
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TL;DR: In this paper, the authors make a study of the thermodynamics of a two-and a three-dimensional model of KDP considering only nearest neighbor interactions between protons which are described here as fictive spins.
Abstract: Nous etudions la thermodynamique de KDP en ne considerant que les interactions entre les spins fictifs associes aux protons premiers voisins dans des models plans et spatiaux. On montre d'abord qu'on decouple completement le mouvement des spins fictifs du mouvement des ions en definissant une nouvelle energie d'interaction entre les premiers et en renormalisant les seconds. On etudie ensuite l'effet tunnel entre protons formant un cycle ferme, en regardant successivement son influence sur les etats a une et deux excitations elementaires. Ceci permet de penser qu'une transition du 2eme ordre n'est pas exclue. Nous notons enfin que ce modele conduit a un mode mou correspondant a une diffusion de spins fictifs et non a un phonon optique.
A study is made of the thermodynamics of a two- and a three-dimensional model of KDP considering only nearest neighbour interactions between protons which are described here as fictive spins. It is shown that one may completely separate out the movement of the fictive spins from that of the ions by simultaneously redefining the interaction energy between the formers and renormalizing the latters. The tunneling effect between protons forming a closed ring is then studied by looking at its influence on one and two elementary excitation states. This allows to show that a second order phase transition is not a priori excluded. Finally a study is made of the soft mode associated with that model and it is shown that it corresponds to a fictive spin diffusion rather than to an optical phonon.
12 citations