An analysis of iron ion occupation in barium hexaferrites prepared employing different synthesis techniques from magnetic and Mossbauer studies

Abstract

In the present investigation, the distribution of iron ions at octahedral and tetrahedral sites in BaFe₁₂O₁₉ prepared by employing four different synthesis techniques, namely, solid-state reaction, oxalate precursor route, sol–gel and wet chemical methods, have been examined using Mossbauer studies and compared with magnetization data. It was observed that the iron ions distribute in different preferential order at various sites for hexaferrites prepared using different synthesis methods, which is confirmed by Mossbauer spectroscopy. Prepared samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and Field emission scanning electron microscopy. Rietveld refinement of all samples revealed an M-type hexagonal structure confirming P63/mmc space group along with a minor peak belonging to the α-Fe₂O₃ phase, except for the sample synthesized by sol–gel route. A uniform spherical shape with a small grain size was observed in sol–gel prepared samples and the Williamson–Hall method was adopted to estimate the average crystallite size, which varies between 72 and 129 nm. The room temperature magnetization studies reveal that the sample synthesized via sol–gel route shows high coercivity and saturation magnetization values due to their smaller grain sizes. Mossbauer spectra of all BaFe₁₂O₁₉ samples were fitted with five sexets assigned to the hexagonal crystal structure of 4f₂, 4f₁, 2a, 12k and 2b sites, where the variation in their relative areas confirms the redistribution of iron ions at these sites.

Graphical abstract