Defect clusters in titanium-substituted spinel-related lithium ferrite

The cation distribution in spinel-related titanium-substituted lithium ferrite, Li0.5+0.5xFe2.5−1.5xTixO4 has been explored using interatomic potential and ab initio calculations. The results suggest that the cation distribution with Ti4+ substituting for Fe3+ on octahedral B sites and excess Li+ substituting for Fe3+ on tetrahedral A sites is stabilised by the formation of clusters of two octahedrally coordinated Ti4+ ions and one tetrahedrally coordinated Li+ ion linked through a common oxygen

Magnetic study of nanocrystalline Mg-doped lithium ferrite

Nanocrystalline magnesium doped ferrites with grain sizes between 60 and 11 run were prepared by the ball milling. Magnetization of the iron-milled ferrite diminishes monotonically with temperature and vanishes above the relatively high Curie temperature T-C of 900 K. A milling process suppresses TC down to 830 K, which reveals the exchange interaction diminishing with tire reduced grain sizes. Tire room temperature magnetic moment per formula unit diminishes from 2.15 mu(B) for non-milled ferrite to 1.27 mu(B) for 11 run sample. Tire hyperfine magnetic fields derived from Mossbauer spectra are remarkably suppressed where the grain sizes are reduced below 20 nm

The influence of ball milling and subsequent calcination on the formation of LiFeO2

The influence of ball milling and subsequent calcination of a 1: 1 molar mixture of alpha-Fe2O3 and Li2CO3 on the formation of LiFeO2 has been investigated. Pre-milling was found to lower the temperature of ferrite formation by ca. 200degreesC and a thermally stable gamma-LiFeO2 phase was found to form in the temperature range 500-600degreesC. Slow cooling of the pre-milled mixture calcined at higher temperatures resulted in the formation of some LiFe5O8

The influence of TiO2 polymorph, mechanical milling and subsequent sintering on the formation of Ti-substituted spinel-related Li0.5Fe2.5O4

Single-phased spinel-related titanium-substituted Li0.5Fe2.5O4 has been synthesized by sintering in air a mechanically pre-milled mixture of lithium carbonate, corundum-related iron (III) oxide and the rutile polymorph of titanium (IV) oxide at 700 °C (12 h). This temperature is ca. 450–500 °C less than the temperatures at which the material is normally prepared by conventional ceramic techniques. On replacing the rutile polymorph of titanium (IV) oxide in the pre-milled mixture by the anatase form the formation of single-phased titanium-substituted Li0.5Fe2.5O4 was not achieved even after sintering the mixture at 1,000 °C (12 h)

Lithium insertion in compounds of the type alpha-Fe2-xTixO3

Lithium has been chemically inserted into compounds of the type alpha -Fe2-xTixO3 (x -Fe2O3 structure. Similar results have been recorded from materials of formulation alpha -Fe2-xMxO3 (M = Sn, Mg)

On the synthesis and cation distribution of aluminum-substituted spinel-related lithium ferrite

Spinel-related Al-substituted Li0.5Fe2.5O4 has been synthesized by sintering a mixture of Al-substituted corundum-related alpha-Fe2O3 and Li2CO3 at 700 degreesC which is ca. 450-500 degreesC lower than the temperatures normally used to prepare the material by conventional ceramic methods. The cation distribution in the material was investigated with X-ray diffraction, Mossbauer spectroscopy and magnetic measurements. Rietveld refinement of the X-ray diffraction data shows the Al3+ ions to substitute for both Fe3+ and Li+ ions on octahedral B-sites while the displaced Li+ ions substitute for Fe3+ ones at tetrahedral A-sites. This structural model is consistent with Mossbauer and magnetic data

Synthesis and cation distribution of copper-substituted spinel-related lithium ferrite

Single-phased Cu2+-substituted spinel-related Li0.5Fe2.5O4 was synthesized by sintering a mixture of Cu2+-substituted corundumrelated alpha-Fe2O3 and Li2CO3 at 700 degrees C which is similar to 325-400 degrees C lower than the temperature at which the material is prepared by the conventional ceramic methods. X-ray powder diffraction, X-ray photoelectron spectroscopy, Mossbauer 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 Fe2+-cation free material, thereby optimizing its technological value. Rietveld refinement of the XRD data favors a structural model in which Cu2+ substitutes for both Fe3+ and Li+ at the octahedral sites. Mossbauer and magnetic data are consistent with this model if spin thermal reversal and/or spin canting are taken into account for the later

The formation of lithiated Ti-doped alpha-Fe2O3 nanocrystalline particles by mechanical milling of Ti-doped lithium spinel ferrite

The milling of spinel-related Ti-doped Li0.5Fe2.5O4 for different times is studied with XRD, Mossbauer spectroscopy and magnetic measurements. Milling converts the material to Li-Ti-doped alpha-Fe2O3 nanocrystalline particles via an intermediate gamma-LiFeO2-related phase. The role played by the dopant Ti-ion in the process is emphasized

Magnetic properties of nanocrystalline Fecu(x)Cu(1-x) alloys prepared by ball milling

X-ray diffraction, Mossbauer and magnetization measurements were used to study FexCu1-x alloys prepared by ball-milling. The X-ray data show the formation of a nanocrystalline Fe-Cu solid solution. The samples with xgreater than or equal to0.8 and xless than or equal to0.5 exhibit bcc or fcc phase, respectively. Both the bcc and fcc phases are principally ferromagnetic for xgreater than or equal to0.2, but the sample with x=0.1 remains paramagnetic down to 78 K. The influence of the local environment on the hyperfine parameters and the local magnetic moment are discussed using calculations based on the discrete-variational method in the local density approximation

The influence of TiO_2 polymorph, mechanical milling and subsequent sintering on the formation of Ti-substituted spinel-related Li_0_._5Fe_2.5O_4

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