Synthesis, structural, and magnetic characterisation of magnesium-doped lithium ferrite of composition Li< sub> 0.5 Fe< sub> 2.5 O< sub> 4 (original) (raw)
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Solid state communications, 2001
A study of the crystallographic structure and magnetic properties of the double perovskites Ba 2 MnMoO 6 and Sr 2 MnMoO 6 in polycrystalline form has been carried out by means of neutron powder diffraction (NPD) and magnetization measurements. The Rietveld analysis of room temperature data shows that the Mn 2+ and Mo 6+ ions are B-site ordered, i.e. the structure is a NaCl-type ordered double perovskite. Ba 2 MnMoO 6 crystallizes in the cubic space group Fm3m (a = 8.1680(1)) and Sr 2 MnMoO 6 crystallizes in the space group P4 2 /n (a = 7.9575(5), c = 7.9583(9)). Bond valence sum (BVS) calculation revealed that these compounds have the valency pair of {Mn 2+ (3d 5 ;t 3 2g e 2 g ), Mo 6+ (4d 0 )}. The magnetic measurements suggest that these compounds transform to an antiferromagnetic state below 10 K.
Magnetic study of nanocrystalline Mg-doped lithium ferrite
Czechoslovak journal of physics, 2002
NanocrystaUine magnesium doped ferrites with grain sizes between 50 and 11 nm were prepared by the ball milling. Magnetization of the non-milled ferrite diminishes monotonically with temperature and vanishes above the relatively high Curie temperature Tc of 900 K. A milling process suppresses Tc down to 830 K, which reveals the exchange interaction diminishing with the reduced grain sizes. The room temperature magnetic moment per formula unit diminishes from 2.15 #B for non-milled ferrite to 1.27 #n for 11 nm sample. The hyperfine magnetic fields derived from MSssbauer spectra are remarkably suppressed when the grain sizes are reduced below 20 ran. : 75.30, 76.80 The litllium spilml ferrites synthesized by various classical methods were studied for a long time due to their specific plLvsical properties and practical applications [1-9]. These ferrites axe distinguished by the high Curie temperature and relatively high electrical resistivity, which reduces power losses. The ball milling processing offers a new way of the solid state synthesis and allows to modify physical properties of materials . This work is aimed at magnetic and structural characterization doped lithium ferrites with nanometer size grains and approximate composition M go.24 L io. 44 Fe2. 44 0 4
2002
Abstract Spinel-related aluminum-substituted Li0. 5Fe2. 5O4 has been synthesized by heating a mixture of aluminum-substituted corundum-related α-Fe2O3 with Li2CO3 at 700 C which is ca. 450-500 C lower than temperatures at which the material is normally prepared with conventional ceramic methods. Rietveld structural refinement of the X-ray diffraction data is in favour of a model in which Al3+ ions exclusively occupy octahedral sites replacing Fe3+ and Li+ with some replaced Li+ ions substituting for Fe3+ at tetrahedral sites.
Structural properties of magnesium and aluminium co-substituted lithium ferrite
Materials Letters, 2003
The structural properties of Mg 2 + and Al 3 + co-substituted Li 0.5 Fe 2.5 O 4 are studied by synthesizing the spinel solid solution series Mg x Al 2x Li 0.5(1 À x) Fe 2.5(1 À x) O 4 . Polycrystalline samples of this series with x = 0.0, 0.1, 0.2, 0.3, 0.4 and 0.5 have been prepared by double-sintering ceramic method. The structural details like: lattice constant and distribution of cations in the tetrahedral and octahedral interstitial voids have been deduced through X-ray diffraction (XRD) data analysis. The x dependence of bond length, oxygen positional parameter, site ionic radii, bulk density, porosity and shrinkages have also been determined. D
Nano-crystalline lithium substituted magnesium ferrite was synthesized by solid state reaction method. Iron oxide , magnesium carbonate and lithium carbonate are used as raw materials to prepare circular pellets of size 35 mm diameter are subjected to X- ray diffraction (XRD) to calculate average nano – crystalline size using Debye - Scherrer’s formula. X-ray diffraction patterns of the synthesized ferrite particles in the samples are cubic spinel ferrite. The morphological analysis is performed using scanning electron microscope (SEM). SEM images show that particle size range was between 170 to 250 nm.
Journal of Physics: …, 2010
Single-phased spinel-related Ti 4+ -substituted Li 0.5 Fe 2.5 O 4 has been synthesized by the heating mixture of hydrothermally prepared Ti 4+ -substituted α-Fe 2 O 3 and Li 2 CO 3 at 850°C (12 h). This temperature is ca. 250-350°C lower than those at which the material is conventionally prepared by the ceramic techniques. X-ray diffraction was used to analyze the evolution of the formation process and, in conjunction with Mössbauer and magnetization measurements, to determine the cation distribution of the resulting ferrite. The results imply that the Ti 4+ ions substitute for Fe 3+ ones at the octahedral (B) sites whilst the excess Li + ions, required for balancing the charge in the spinel-related structure, replace Fe 3+ ions at the tetrahedral (A) sites.
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.
Materials Research Bulletin, 2012
The position of magnesium ions in Mg 2+ -doped lithium ferrite of the composition Li 0.5À0.5x Mg x-Fe 2.5À0.5x O 4 , which has been a matter of uncertainty among some experimentalists, is investigated using interatomic potential and ab initio DFT calculations. Among possible 19 defect structure models, some of which have been reported experimentally to be the most favorable, the lowest energy is found for Mg 2+ ions evenly replacing Li + and Fe 3+ ion on octahedral sites. This gives a decrease in magnetisation for the Mg 2+ -doped ferrite relative to the un-doped lithium ferrite. The results suggest that some experimental observations of increased magnetisation of spinel lithium ferrite on Mg 2+ -doping could be due to substitution of Mg 2+ or Li + on tetrahedral sites at the high temperatures used in preparation of the solid and/or the presence of undetected defects in the initial precursors. ß
Physica B-condensed Matter, 2009
Lithium ferrite has been considered as one of the highly strategic magnetic material. Nano-crystalline Li 0.5 Fe 2.5 O 4 was prepared by four different techniques and characterized by X-ray diffraction, vibrating sample magnetometer (VSM), transmission electron microscope (TEM) and Fourier transform infrareds (FTIR). The effect of annealing temperature (700, 900 and 1050 1C) on microstructure has been correlated to the magnetic properties. From X-ray diffraction patterns, it is confirmed that the pure phase of lithium ferrite began to form at 900 1C annealing. The particle size of as-prepared lithium ferrite was observed around 40, 31, 22 and 93 nm prepared by flash combustion, sol-gel, citrate precursor and standard ceramic technique, respectively. Lithium ferrite prepared by citrate precursor method shows a maximum saturation magnetization 67.6 emu/g at 5 KOe.
Applied Nanoscience, 2020
In this study, we report the influence of Co 2+ on structure and magnetic properties of nano-sized Li 0.5−x/2 Fe 2.5−x/2 Co x O 4 (where x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) synthesized using sol-gel auto-combustion method. The X-ray diffractometric analysis of samples confirmed the formation of pure Li 0.5−x 2Fe 2.5−x 2Co x O 4 nanoparticles ranges crystallite size from 36 to 43 nm with co-doping. There is a structural transformation from ordered P4 3 32 to random Fd3m observed, which is caused by the localization of cobalt ions. RT-Mössbauer the showed presence of 57Fe in both sublattices. Position identification was performed based on the distribution of the over exchange fields and isomeric shift data. Magnetic measurements showed that the saturation magnetization increases to x ≤ 0.8 and then decreases with Co-content due to the change in cationic distribution. The cobalt substitution turns Li-Co ferrite from soft-magnet to hard-magnet.