Lithium ferrite: The study on magnetic and complex permittivity characteristics (original) (raw)
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Lithium Ferrite: Synthesis, Structural Characterization and Electromagnetic Properties
Magnetic Spinels - Synthesis, Properties and Applications, 2017
Lithium ferrite (LiFe 5 O 8) is a cubic ferrite, belongs to the group of soft ferrite materials with a square hysteresis loop, with high Curie temperature and magnetization. The spinel structure of LiFe 5 O 8 has two crystalline forms: ordered, β-LiFe 5 O 8 (Fd3m space group) and disordered, α-LiFe 5 O 8 (P4 1 32/P4 3 32 space group). It has numerous technological applications in microwave devices, computer memory chip, magnetic recording, radio frequency coil fabrication, transformer cores, rod antennas, magnetic liquids among others. It is also a promising candidate for cathode in rechargeable lithium batteries. In this work, the dc electrical conductivity, the impedance spectroscopy and the magnetization of Li 2 O-Fe 2 O 3 powders, with [Li]/[Fe]=1/5 (mol), heat-treated at several temperatures, are studied and related to their structure and morphology. The structural data were obtained by X-ray diffraction and Raman spectroscopy, and the morphology by scanning electron microscopy. The impedance spectroscopy was analysed in function of temperature and frequency, and it was observed that the dielectric properties are highly dependent on the microstructure of the samples. The dc magnetic susceptibility was recorded with a vibrating sample magnetometer, under zero field cooled and field cooled sequences, between 5-300 K. Typical hysteresis curves were obtained and the saturation magnetization increases with increase in heat-treatment temperature.
Journal of Non-Crystalline Solids, 2012
Lithium ferrite (LiFe 5 O 8 ) is one of the most known cubic ferrites which belong to the group of soft ferrite materials with high Curie temperature, presenting a square hysteresis loop, and high magnetization. It has attracted special attention due to its numerous technological applications in microwave devices, magnetic recording, transformer cores, rod antennas and possible applications in biomedics. It is also a promising candidate for cathode materials in rechargeable lithium batteries as well as low cost substitutes to garnet materials in microwave frequency applications. In the present work, amorphous Li 2 O-Fe 2 O 3 powders were prepared via wet ball milling method. The asprepared powders were heat-treated at temperatures between 400 and 1400°C and their structure analyzed by X-ray diffraction and Raman spectroscopy. The morphology was observed by scanning electron microscopy. Electrical and dielectric properties, in the frequency range between 100 and 2 MHz and temperatures between 200 and 360 K, were performed, and the results related with the structure and morphological characteristics.
Journal of Science: Advanced Materials and Devices, 2018
The electric and magnetic properties of Lithium ferrite (LF) synthesized using the solid state reaction technique have been reported. The structural, morphological, dielectric, Impedance spectroscopic, magnetic properties and magneto-electric voltage coefficient studies using XRD, FESEM with EDAX, LCR meter, VSM and SR 830 DSP lock-in amplifier respectively. The XRD studies reveal the cubic nature and the value of the crystallite size and lattice parameters calculated from the XRD. The crystallite size and the lattice constant are 16.84 nm and 2.847 Å respectively. The FESEM confirms the coarseness in the sample with a low porosity. The variations of dielectric constant and dielectric loss with the temperature at different frequencies have been studied and the dielectric constant increases more steeply in the negative direction with increasing temperature beyond 500 o C at 100 kHz. The impedance plot exhibits good semicircles. All the semicircles are complete at all temperatures and all the semicircles with their centers situated on the real axis, which suggests that the sample obeys Debye behavior. The VSM studies reveal the soft magnetic nature of LF. The value of ME voltage coefficient decreases with increasing magnetic field and attains a constant value in the high magnetic field.
Magnetic, Dielectric and Electrical Properties of Lithium-Magnesium Ferrites
A series of polycrystalline spinel type ferrites with composition Li x Mg 0.5 Ni 0.5-2x Fe 2+x O 4 , where x = 0.00 to 0.25 in steps of 0.05, have been prepared by standard double sintering method sintered at temperature 1200º C in air for 6 hours. In this work, investigations have been carried out by the measurements of X-ray diffraction (XRD), Curie temperature, permeability, loss tangent, Qfactor, dielectric constant and ac electrical resistivity of the samples. Some measurements have been done at room temperature while other measurements have been done as a function of temperature and as a function of frequency in the range from 1 kHz to 500 kHz. Curie temperature, the real part of initial permeability (µ i ʹ), the loss tangent (tanδ), and the Q-factor have been found to be decreased with the increase of Ni-content of Li x Mg 0.5 Ni 0.5-2x Fe 2+x O 4 ferrites. The frequency characteristic of dielectric constant and AC resistivity decreases with the increase in frequency and increases with the increase in Ni-content.
Processing and properties of cobalt-substituted lithium ferrite in the GHz frequency range
Ceramics International, 2005
Polycrystalline cobalt-substituted lithium ferrites with general formula Li 0 .5_ x /2Co x Fe2.5_ x /2O 4 (x = 0.0,0.2, 0.4 and 0.5) were prepared by a non-conventional citrate precursor method, which is advantageous over conventional (solid state sintering) method because of low temperature (600 8C) processing. Small amounts of Bi 2 O 3 (0.5 wt.%) were added to reduce the porosity and dielectric loss tangent at sintering temperatures (1000-1200 8C). The complex magnetic permeability (m 0-jm0 0) and complex dielectric permittivity (e 0-je 0 0) of cobaltsubstituted lithium ferrites were measured in the 8-13 GHz microwave frequency range. The systematic variations of the real and imaginary parts of both permeability and permittivity with frequency and composition have been analyzed. The minimum value of e 0 ~ 11.3 measured for x = 0.4 substituted lithium ferrite is observed for a sample sintered at 1000 8C. The highest values of e 0 and e0 0 were observed for samples sintered at 1200 8C. m0 varies between 1.84 and 3.90 for pure and cobalt-substituted lithium ferrite bulk ceramics. The spinel structure of the samples was confirmed by X-ray diffraction (XRD).
Improved dielectric and magnetic properties in modified lithium-ferrites
Ceramics International, 2015
Single phase polycrystalline lithium ferrites modified with Zn and Mn were synthesized by solid state reaction method. The prepared samples exhibit a markedly increased value in real part of dielectric constant (ε) and a lowest loss tangent (tanδ) for x =0.04 measured in the frequency range 70Hz to 1MHz. The saturation magnetic moment (M s) varies non-monotonically for different values of x. A maximum value of M s = 76 emu/g has been found for x = 0.02. Such results in lithium ferrite based ferrites being found rarely.
Journal of Magnetism and Magnetic Materials, 2000
Ferrite with the general formula ZnFe 2 O 4 was prepared by microwave hydrothermal (M-H) method. The as-synthesized powder was pelletized and samples were sintered at different temperatures (600, 700, 800 and 900 o C). The grain size was varied by sintering the ferrite at different temperatures up to 900 o C. The characterization studies were conducted by X-ray diffraction (XRD) and scanning electron microscopy (SEM).Dielectric constant (ɛ') and dielectric loss tangent (tan δ) were measured as a function of frequency and temperature DC conductivity (σ ac) was measured by temperature variation. A significant influence of sintering temperature on the microstructure and electrical properties was detected.
Crystal structure and electrical characterization of mixed lithium ferrite ceramics.
A Cobalt and Aluminium substituted Lithium ferrite ( M-type ) samples with the general chemical formula Li 0.5 Fe 0.5+x Al 12-2X Co xO 19 were synthesized using reacting oxide by high temperature solid state reaction technique. The structural characterization of compound has been carried out from X-Ray diffraction powder pattern. The compounds are in single hexagonal phase without traces of uncertainly ambiguous reflection. From XRD pattern lattice parameters has recorded with increasing doped aluminum element in the range from a = 5.807 Å to 5.906 Å and c = 22.507 Å to 22.585 Å pertaining the space group P6 3 /mmc (No.194). The mass density of the ferrites were found linearly varies and depends upon the mass and volume of sample. The X-Ray density has depends upon the lattice constant and molecular weight of the compounds. The average particle size was also estimated. The compounds were studies magnetically by using Guoy's method in the temperature range 300 to 550 K, the result shows that the compounds are paramagnetic in nature.The Curie molar constant was work out.
An Experimental Study Of Structural, Optical And Magnetic Properties Of Lithium Ferrite
2016
Nanomaterials ferrites have applications in making permanent magnets, high density information devices, color imaging etc. In the present examination, lithium ferrite is synthesized by sol-gel process. The x-ray diffraction (XRD) result shows that the structure of lithium ferrite is monoclinic structure. The average particle size 22 nm is calculated by Scherer formula. The lattice parameters and dislocation density (δ) are calculated from XRD data. Strain (ε) values are evaluated from Williamson – hall plot. The FT-IR study reveals the formation of ferrites showing the significant absorption bands. The VU-VIS spectroscopic data is used to calculate direct and indirect optical band gap (Eg) of 1.57eV and 1.01eV respectively for lithium ferrite by using Tauc plot at the edge of the absorption band. The energy dispersive x-ray analysis spectra showed that the expected elements exist in the material. The magnetic behaviour of the materials studied using vibrating sample magnetometer (VSM).
Microwave properties of chromium-substituted lithium ferrite
Ceramics International, 2009
A structure characterization of chromium-substituted lithium ferrite specimens was carried out by the X-ray diffraction technique and found that the lattice parameter decreases with increasing of Cr-substitution content and the microstructure was determined by scanning electron microscopy (SEM), which revealed that the average grain size of chromium-substituted lithium ferrite decreases gradually with increasing Crsubstitution content.