Investigating the preferential sites of Co2+ substitution in SrCoxFe12−xO19 using Mössbauer spectroscopy

Abstract

In this paper, a series of M-type hexagonal SrCoxFe[Formula: see text]O[Formula: see text] ([Formula: see text], 0.25, 0.5) samples have been prepared by sol–gel method. X-ray diffraction (XRD) showed that the samples produced were all p63/mmc space groups of single hexagonal crystals, and the lattice parameters a, b and c did not show the expected trend with increasing x. This was related to the valence changes and lattice distortion caused by the substitution of Co[Formula: see text] at the 2a and 4f2 sites. Room temperature Mössbauer spectra studies showed that when [Formula: see text], Fe[Formula: see text] ions were not uniformly distributed, preferring the 4f1, 4f2 and 2a sites; when [Formula: see text], Co[Formula: see text] ions preferentially displaced the 2a and 4f2 sites and the presence of Fe[Formula: see text] was detected; when [Formula: see text], Co[Formula: see text] ions preferentially displaced the 4f1 and 2b sites and the percentage of Fe[Formula: see text] occupancy was reduced, with a greater occupancy ([Formula: see text] occurring at the 12k site, indicating a preference of Fe[Formula: see text] of the doped sample for this site. This work will provide an important reference for the variation of properties induced by different ion doping substitutions of the Fe sites in the hexagonal ferrite family.