engleski

Formation and Characterization of NiFe2O4

Synthesis of nickel ferrite, NiFe2O4, was performed applying the thermal treatment of the corresponding mixed metal hydroxides or the solid state reaction between NiO and alpha-Fe2O3. The samples were studied by X-ray diffraction, Fourier transform IR spectroscopy and Fe-57 Mossbauer spectroscopy. Ball-milling of NiFe2O4 caused a decrease of hyperfine magnetic fields corresponding to Fe3+ ions in tetrahedral and octahedral sites, an increase of the Mossbauer spectral line widths, as well as a slight increase of isomer shifts. It was supposed that the ball-milling of NiFe2O4 had more influence on the degree of inversion than on other structural properties of the spinel. It was found that the heating temperature, and not the heating time, had the ultimate effect on NiFe2O4 microstructure. Samples heated up to 500 degrees C showed a pronounced size-correlated diffraction line broadening, corresponding to the coherent domain size of about 13 nm, and rather small crystalline disorder. Samples heated at temperatures above approximate to 1000 degrees C had much larger crystallites, exhibiting very small disorder. [References: 34]

Oxide phases. Mossbauer. Nickel ferrite; Particles. Fine powders

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