EFFECTS OF RARE EARTH OXIDES ON SOME PHYSICAL PROPERTIES OF Li-Zn NANOPARTICLE FERRITES (original) (raw)
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Effects of rare-earth oxides on physical properties of Li–Zn ferrite
Journal of Alloys and Compounds, 1998
The influence of R O substitution on the structure, magnetic and electrical properties of LiZn ferrite is examined. The results obtained 2 3 reveal that by introducing a relatively small amount of R O (R5Yb, Er, Dy, Tb, Gd and Sm) instead of Fe O , an important 2 3 2 3 modification of both structure and properties can be obtained. R O facilitates the formation of the secondary phases(orthoferrite, garnet) 2 3 on the grain boundary which suppress the abnormal grain growth. The R ions tend to flatten the m -T curves, shift the Curie point to i lower temperature and increase the electrical resistivity. The effects of rare-earth ions were correlated with their ionic radius whichc hanges from 0.86 A in Yb to 1.0 A in Sm.
Substitution of Zn content on the structural, dielectric and electrical properties of Li0.15NixZn0.85-2xFe2+xO4 (x = 0.00, 0.10, 0.20, 0.30 and 0.40) ferrites prepared by standard double sintering ceramic technique, sintered at 1150 ºC for 5 hours have been studied. It has been observed that Zn-substitution on Li-Ni ferrites plays a remarkable role in improving its structural, electrical and dielectric properties. The bulk density, x-ray density and lattice constant of the samples decreases with increasing the Ni content. The porosity of the prepared samples didn’t show any trend with Ni content. The X-ray diffraction (XRD) pattern confirmed the single-phase cubic spinel structure of the samples without having any other intermediate phases. The real part of permeability, Loss factor and AC resistivity have been found to be decreased while the Quality factor increased with the increase in Ni-content. Frequency dependent dielectric constant decreased with increasing the frequency as well as Ni-content.
Synthesis and ac properties of mixed li-zn ferrites
2017
The mixed polycrystalline ferrites 〖Li〗_0.5(1-x) 〖Zn〗_x 〖Fe〗_(2.5-0.5x) O_4 were prepared by the conventional solid state method using high purity metal oxides ZnO,〖Fe〗_2 O_3 and LiCO_3for different concentration of Zn2+ions. Double probe electrode method was used to study the AC properties: the AC electrical conductivity (σ), the dielectric constant: real(e'), imaginary (e'') and complex (e*), and the dielectric loss tangent (tan δ) over therange of the appliedfrequency (f=1 KHz-5 MHz)at room temperature. σincreased exponentially with the increasing f where the maximum value was for the sample 〖Li〗_0.3 〖Zn〗_0.4 〖Fe〗_2.3 O_4. The obtained results of the dielectric parameter (e', e'', e* andtan δ), also, decreased exponentially with increasing f, which confirmsthe normal spinel ferrite behavior. The behavior of AC propertiescan be elucidated on the basis of the exchanged electrons between . The obtained results reveal that the AC properties change by substitut...
Correlation of the physico chemical properties of Zn-substituted Li–La ferrite
Ceramics International, 2005
The electrical resistivity, magnetic susceptibility, and the thermoelectric power of Zn-substituted Li-La mixed ferrite with formula Li 0.5-0.5x Zn x La y Fe 2.5-0.5xÀy O 4 at 0.1 x 0.9; y = 0.04 were studied as a function of temperature and frequency. X-ray analysis and Seebeck coefficient measurement were carried out in order to assure the formation of the sample in single spinel phase and to know the type of charge carriers participating in the conduction mechanism. The dependence of the electrical resistivity of Li-Zn ferrite on Zn content and temperature is explained on the basis of the cation distribution. The transition from the ferromagnetic to paramagnetic state is accompanied by an increase in the thermo EMF. Li-Zn ferrite shows n-and p-types conductivity due to the presence of Fe 2+ ions. The creation of lattice vacancies is due to the presence of Li ions which give rise of p-type conductivity. #
Low dielectric loss in nano-Li-ferrite spinels prepared by sol–gel auto-combustion technique
Bulletin of Materials Science, 2016
Pure and doped nano-Li-ferrite spinels were prepared by the sol-gel auto-combustion technique. The prepared ferrites were pelleted and heat treated at different temperatures. Structural characterization was carried out on the as-prepared samples and also on the heat-treated samples using X-ray diffraction (XRD). The studies confirmed the formation of single phase with spinel structures in all the samples. The crystallite size of the samples evaluated from XRD data was found to be 17-24 nm. Scanning electron microscopic photomicrographs revealed the microstructures and the grain size of these nanoferrites. The room-temperature dielectric constant and dielectric loss tangent, tan δ were measured as a function of frequency in the range 100 Hz-1 MHz. These nanoferrites showed the normal dielectric dispersion behaviour. The observed dielectric constant and dielectric loss tangent were found to be much lower than those measured on substituted Li-ferrites prepared by the conventional ceramic method. The results obtained were discussed in the paper.
Corresponding Author: Structural and Electrical Properties of Lanthanum Substituted Spinel Ferrites
A series of La-substituted Manganese-Zinc based ferrites of nominal composition Mg Zn La Fe 0.5 0.5 2x 2-O for x = 0.00-0.05 in steps of 0.01 was produced by conventional ceramic technique. From X-Ray diffraction 2x 4 patterns, all samples showed single cubic spinel structure as a main phase along with small traces of second phase (LaFeO). The Lattice constant shows a decreasing trend with the substitution of lanthanum. This may 3 be due to large difference in the ionic radii of Fe and La ions. La ions may not enter into the spinel lattice 3+ 3+ 3+ due to large ionic radius. During the sintering process, some of the La ions diffused in to the grain boundaries 3+ and can form an insulating ultra thin layer around the grains. This causes the shrinkage of the spinel lattice and hence lattice constant decreases. Dc resistivity and activation energies showed increasing trend with increasing La contents. The temperature dependent resistivity and activation energy decreases with increasing...
In this work we report a study of the structural and electrical behaviors of Zn substituted Li-Ni ferrite prepared by double sintering ceramic technique having the general formula Li0.15NixZn0.85-2xFe2+xO4 (LNZFO), where x = 0.00, 0.10, 0.20, 0.30 and 0.40. The samples were sintered at 1050oC for 4 hours in the normal atmosphere. The prepared samples were confirmed in the single-phase cubic spinal structure by the X-ray diffraction method. The bulk density of LNZFO increased whereas lattice parameter decreased with increasing the Ni content. The complex permeability, loss factor and Q-factor were measured as a function of the frequency in the range from 102 Hz to 108 Hz, respectively. Real part of permeability and Q-factor were decreased whereas imaginary part of permeability and loss factor were increased with increasing Ni-content for the frequency dependent cases. Dielectric constant and AC resistivity of LNZFO decreased with increasing frequency.
Structural Analysis and Normalised Susceptibility Study of Zn Substituted Li-Cu Ferrite
OALib, 2014
Lithium ferrites have attracted considerable attention because they have been used as replacements for garnets due to their low cost. A series of polycrystalline ferrite samples with the composition of Li x Zn 0.6−2x Cu 0.4 Fe 2 O 4 (x = 0.05, 0.1, 0.15, 0.2, 0.25, 0.3) at different chemical reaction temperature (100˚C, 125˚C and 150˚C) were prepared using non-conventional microwave sintering method. The characterization was carried out using X-rays technique. The X-ray analysis confirms the formation of single phase cubic structure. The lattice parameter ranges from 8.3690 Å to 8.4653 Å. The X-ray density shows the variation as a function of temperature of synthesis. The variation of AC susceptibility with temperature shows the existence of single domain structure for x ≥ 0.2 when the chemical reaction carried at 125˚C and 150˚C and exhibits super paramagnetic structure for all the composition prepared at 100˚C. The samples x ≤ 0.2 shows multidomain structure for all the samples prepared at 125˚C and 150˚C. The Curie temperature obtained using the susceptibility data are found to be in the range 350˚C to 700˚C. An attempt has been made to synthesis the nanoparticles at lower reaction temperature by using non-conventional microwave sintering method.
2014
Ni substituted Li-Zn ferrites with compositional formula Li0.4-0.5xZn0.2NixFe2.4-0.5xO4 where 0.02 ≤ x ≤ 0.1 in steps of 0.02 was fabricated by using citrate precursor method. X-ray diffraction was used to confirm the spinel phase. The dielectric constant was investigated as a function of composition, frequency and temperature. Room temperature dielectric constant showed a decrease with addition of Ni2+ ions. It was explained in terms of space charge polarization and koops two layer model. The variation in dielectric constant with frequency showed dispersion. Variation of dielectric constant with temperature was studied at different frequencies and an increase was observed as temperature rises. The possible mechanisms responsible for the above behavior are explained.
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.