Structural and magnetic characterization of Ti-substituted Li0. 5Fe2. 5O4 prepared using hydrothermal and solid-state routes (original) (raw)
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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.
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.
Journal of Magnetism and Magnetic Materials, 2011
Sintering temperature and particle size dependent structural and magnetic properties of lithium ferrite (Li0.5Fe2.5O4) were synthesized and sintered at four different temperatures ranging from 875 to 1475 K in the step of 200 K. The sample sintered at 875 K was also treated for four different sintering times ranging from 4 to 16 h. Samples sintered at 1475 K have the cubic spinel structure with a small amount of α-Fe2O3 (hematite) and γ-Fe2O3 (maghemite). The samples sintered at≤1275 K do not show hematite and maghemite phases and the crystals form the single phase spinel structure with the cation ordering on octahedral sites. Particle size of lithium ferrite is in the range of 13–45 nm, and is depend on the sintering temperature and sintering time. The saturation magnetization increased from 45 to 76 emu/g and coercivity decreases from 151 to 139 Oe with an increase in particle size. Magnetization temperature curve recorded in ZFC and FC modes in an external magnetic field of 100 Oe. Typical blocking effects are observed below about 244 K. The dielectric constant increases with an increase in sintering temperature and particle size.► Lithium ferrite with heat treatment. ► Structure changes from disordered system to ordered system. ► Magnetization increases with sintering temperature. ► Blocking temperature increases with sintering temperature. ► Coercivity decreases with sintering temperature.
Synthesis and cation distribution of copper-substituted spinel-related lithium ferrite
Journal of Physics and Chemistry of Solids, 2006
Single-phased Cu 2+ -substituted spinel-related Li 0.5 Fe 2.5 O 4 was synthesized by sintering a mixture of Cu 2+ -substituted corundumrelated a-Fe 2 O 3 and Li 2 CO 3 at 700 1C which is $325-400 1C lower than the temperature at which the material is prepared by the conventional ceramic methods. X-ray powder diffraction, X-ray photoelectron spectroscopy, Mo¨ssbauer spectroscopy and magnetic measurements were used to characterize the material. In contrast to high-temperature synthetic routes, the present one leads to a Cu +and Fe 2+ -cation free material, thereby optimizing its technological value. Rietveld refinement of the XRD data favors a structural model in which Cu 2+ substitutes for both Fe 3+ and Li + at the octahedral sites. Mo¨ssbauer and magnetic data are consistent with this model if spin thermal reversal and/or spin canting are taken into account for the later. r
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
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.
Preparation of Nanoparticle Li-Ferrite Materials by Different Chemical Method
2015
Lithium ferrite is one of promising material that has many applications in a civil field. Primarily, there are two chemical methods for preparation Li0.5Fe2.5O4 spinal structure were dependent, represented by Low Temperature Solid State Reaction (LTSSR) and Modified Combustion Method (MCM) instead of freeze drying method that was used previously. The purpose of this research concentrated on how to produce nanoparticle of Li0.5Fe2.5O4 spinal structure. The analysis those were used to investigate the aim of this research were X-ray Diffraction (XRD), and Transmission Electron Microscope (TEM). The phase and homogeneity of ferrite was proved by X-ray diffraction. The finite and homogenous powder was investigated by Transmission Electron Microscope (TEM). The results showed the MCM method is better than other one, because the first was the presence of pure phase of Li-ferrite whereas the LTSSR-method showed a multiphase. Regarding to TEM analysis, both methods were perfect in producing ...