Mössbauer study and magnetic properties of MgFe2O4 crystallized from the glass system B2O3/K2O/P2O5/MgO/Fe2O3

An iron containing magnesium borate glass with the mol% composition 51.7 B2O3/9.3 K2O /1 P2O5/27.6MgO/10.4Fe2O3was prepared by the conventional melts quenching method followed by a thermal treatment process at temperatures in the range from 530 to 604°C.The thermally treated samples were characterized by X-ray diffraction, scanning and transmission electron microscopy. It was shown that superparamagnetic MgFe2O4 nanoparticles were formed during thermal treatment. The size of the spinel type crystals was in the range from 6 to 15nm. Mössbauer spectra of the powdered glass ceramic samples and the extracted nanoparticles after dissolving the glass matrix in diluted acid were recorded at room temperature. The deconvolution of the spectra revealed the crystallization of two spinel phases MgFe2O4 (as a dominant phase) and superparamagnetic maghemite, γ-Fe2O3 (as a secondary phase). Room temperature magnetic measurements showed that, increasing the crystallization temperature changed the superparamagnetic behavior of the samples to ferrimagnetic behavior. The Curie temperatures of the samples were measured and showed a higher value than that of the pure bulk MgFe2O4.