Electrical Properties of Lithium Ferrite Nanoparticles Dispersed in a Styrene-Isoprene-Styrene Copolymer Matrix (original) (raw)
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Journal of Alloys and Compounds, 2010
Fine particles of Al-doped lithium ferrite of general formula Li0.5AlxFe2.5−xO4 (0.0 ≤ x ≤ 0.4, in step of 0.1) were synthesized by the citrate gel auto combustion method and characterized using XRD, dielectric and impedance spectroscopy. X-ray diffraction studies confirmed that all the samples exhibit single-phase cubic spinel structure. The average particle size of as obtained samples has been found in the range of 38–41 nm. Dielectric permittivity, ac conductivity and complex impedance of all the samples were evaluated as a function of frequency and composition at room temperature. The variation of dielectric properties ɛ′, ɛ″, tan δ and ac conductivity (σac), with frequency reveals that the dispersion is due to Maxwell–Wagner type of interfacial polarization in general and the hopping of charge between Fe+2 and Fe+3. Interestingly, Al-doped nano-crystalline lithium ferrite samples exhibit a very large value for dielectric constant of the order of 105. The impedance spectroscopy technique has been used to study the effect of grain and grain boundary on the electrical properties of Li0.5AlxFe2.5−xO4 ferrites. The analysis of data shows two semicircles corresponding to the grain and grain boundary volume suggesting that grain boundary is mainly involved in conduction mechanism. Magnetic properties have been measured by vibrating sample magnetometer (VSM) for all samples at room temperature.
Applied Nanoscience, 2021
In this study, we report the synthesis of nanosized Al-substituted lithium–iron ferrites Li 0.5 Al x Fe 2.5- x O 4 (0 ≤ x ≤ 1) by sol–gel auto-combustion method and by ceramic method with double sintering. Synthesized materials were studied using X-ray diffraction and impedance spectroscopy. The samples obtained by chemical methods have a higher homogeneity of the distribution of elements by volume, good repeatability of the result, high crystallinity, small crystallite size and perfect stoichiometry. Based on Koop's theory, the basic regularities of the behavior of the dielectric constant and the loss tangent are explained. The jump mechanism of conductivity has been realized by the transition of an electron between iron ions in different valence states. Samples synthesized by the sol–gel auto-combustion show technological characteristics, compared with systems obtained by solid-phase method.
The Li 0.5 Fe 2.5−x Cr x O 4 (x = 0.0-1.0) nanoparticles were prepared by the citrate gel autocombustion method. The diffraction spectra were carried out in order to confirm the formation of the single phase cubic spinel structure. The lattice parameter was noted to be decreasing from 8.433 to 8.381 Å with increase in Cr-content from 0.0 to 1.0. The morphology was analyzed using scanning electron microscopy and transmission electron microscopy. The achieved results revealed that the particles were almost spherical in shape. Further, the dc-electrical conductivity (σ dc) of nanoferrites was described as a function of composition and temperature. In addition, the dielectric properties such as dielectric constant (ε′) and dielectric loss (tan δ) were also discussed as a function of frequency at various temperatures.