Structural, dielectric, and multiferroic properties of (Bi_0.5K_0.5)(Fe_0.5Nb_0.5)O₃

Abstract

A polycrystalline sample of (Bi 0.5 K 0.5 )(Fe 0.5 Nb 0.5 )O 3 was prepared using a mixed oxide at 1000°C. The preliminary structural analysis using X-ray diffraction data of the compound indicates the formation of a single-phase rhombohedral structure similar to that of parent BiFeO 3 . Microstructural and elemental analysis using a scanning electron micrograph and energy-dispersive X-ray spectroscopy, respectively, were carried out at room temperature with higher magnification exhibiting a uniform distribution of grains and stoichiometry. The appearance of hysteresis loops (P-E) confirms the existence of ferroelectricity of the sample with a high remnant polarization of (2P r ) 17.76 Ccm −2 . Using impedance spectroscopy, the electrical properties of the material were investigated at a wide range of temperature (25-500°C) and frequencies (1 kHz -1 MHz) suggesting dielectric non-Debye-type relaxation in the material. The nature of the Nyquist plot (Z ϳ Z ) shows the dominance of the grain contribution in the impedance. The bulk resistance of the compound decreases with increasing temperature, like that of a semiconductor, which shows a negative temperature coefficient of resistance (NTCR) behavior. The frequency dependence of AC conductivity suggests that that the material obeys Jonscher's power law. Magnetic hysteresis (M-H) loop shows very weak ferromagnetic behavior at room temperature. Résumé : Nous préparons un échantillon poly-cristallin de (Bi 0.5 K 0.5 )(Fe 0.5 Nb 0.5 )O 3 par mélange d'oxydes à 1000°C. L'analyse préliminaire de structure à l'aide de la diffraction X indique la formation d'une structure rhomboèdre à phase unique, similaire à celle du parent BiFeO 3 . L'analyse micro-structurelle et fondamentale utilisant les techniques SEM et EDAX de micrographie électronique à balayage, à la température de la pièce et plus haute magnification, montre une distribution uniforme des grains et de la stoechiométrie. L'apparition de boucles d'hystérèse (P-E) confirme la ferroélectricité de l'échantillon avec une haute polarisation rémanente de (2P r ) 17.76 Ccm −2 . L'utilisation d'une technique de spectroscopie d'impédance permet une étude des propriétés électriques de l'échantillon, sur de larges domaines de température (25-500°C) et de fréquence (1 kHz -1 MHz), qui suggère une relaxation diélectrique dans le matériel qui n'est pas du type Debye. Le graphique (Z ϳ Z ) de Nyquist montre la dominance de la domination du grain dans l'impédance. La résistance en volume de l'échantillon décroit lorsqu'augmente la température, de façon similaire à un semi-conducteur avec un coefficient thermique de résistance négatif. La dépendance en fréquence de la conductivité ac suggère que le matériel obéit à une loi de puissance de Joncher. La boucle d'hystérèse (M-H) est caractéristique d'un très faible ferromagnétisme à la température de la pièce. [Traduit par le Rédaction]

Effect of the Zr-Substitution on the Structural and Electrical Properties of LaFeO3: XRD, Raman Scattering, SEM, and Impedance Spectroscopy Study

“…The lattice constant increased with increasing Zr content because the ionic radii of Fe 3+ (64 pm) are smaller than that of Zr 4+ (86 pm) and might be due to the changes in cation degree of Zr as compensation of electric charge. The average crystallite size was calculated based on Scherrer's method [9]:…”

Analysis of the electrical conduction in percolative nanocomposites based on castor‐oil polyurethane with carbon black and activated carbon nanopowder

“…The n value represents the degree of interaction between the charge carriers and the surrounding environment; typically, this universal behavior of the n value ranges between 0 and 1, suggesting that conduction occurs through hopping . On the other hand, several previous studies have reported n values greater than 1 . According to Papathanassiou et al, there is no physical argument to restrict the n value to less than 1 at the empirical universal law of Jonscher.…”

Impedance analysis of TiO2 nanoparticles prepared by green chemical mechanism

“…Z´ values for all temperatures converging at higher frequency zone indicating a temperature and frequency independent behavior of the material in that frequency range. This may be due to the release of space charges, as a result of reduction in barrier properties of the material with rise in temperature [17], [19]. Further, the decreases of Z´ values with the temperature increase at low frequency shows a negative temperature coefficient of resistance (NTCR), which is a very distinctive property that semiconductors possess in some range of temperature [19], [17], [20].…”

“…This may be due to the release of space charges, as a result of reduction in barrier properties of the material with rise in temperature [17], [19]. Further, the decreases of Z´ values with the temperature increase at low frequency shows a negative temperature coefficient of resistance (NTCR), which is a very distinctive property that semiconductors possess in some range of temperature [19], [17], [20]. The variation of the imaginary part of impedance Z with frequency at different temperatures for TiO2 sample is showed in Figure 4, it is observed that the Z´´ value increases with increasing the frequency reaching a maximum peak Z´´max called relaxation frequency, and then decreases with increasing in frequency.…”

“…The variation of the imaginary part of impedance Z with frequency at different temperatures for TiO2 sample is showed in Figure 4, it is observed that the Z´´ value increases with increasing the frequency reaching a maximum peak Z´´max called relaxation frequency, and then decreases with increasing in frequency. With the increase in temperature the graph shows that Z´´max decreases which indicates a decrease in the bulk resistance [19], it is also displayed a shifting toward higher frequency region and a broadening in each peak as an effect of the temperature variation, this behavior suggests the presence of a spread of relaxation time, that is, the existence of a temperature-dependent electrical relaxation phenomenon in the material, the relaxation process may be due to the presence of immobile species at low temperature and defects at higher temperature [6], [17], [20]. Finally, the merge of Z´´ at higher frequency region of all temperatures may be an indication of the accumulation of space charge in the material at lower frequencies and disappearance of space of charge at higher frequencies [1], [19], [20].…”