Effect of Zn substitution on the structure and magnetic properties of Sr0.1La0.45Ca0.45Fe11.7−xZnxCo0.3O19 hexagonal ferrites

M-type strontium ferrites Sr0.1La0.45Ca0.45Fe11.7−xZnxCo0.3O19 (x = 0, 0.05, 0.1, 0.15 and 0.2) were synthesized by ceramic process. The effects of Zn substitution on phase composition, microstructure, sublattice occupation and magnetic properties of the ferrites were systematically investigated using X-ray diffraction, field emission scanning electron microscopy, 57Fe Mössbauer spectroscopy and magnetic properties test instrument, respectively. The results showed that all the samples were single hexagonal ferrite phase with no observation of other phases, while the lattice constant a did not vary basically and the lattice constant c increased continuously with increase of the Zn substitution amount. Simultaneously, the FESEM micrographs showed that more platelet shaped grains were observed. Mössbauer spectra have revealed that Zn2+ ions occupied both 4f1 and 4f2 sites, but Zn2+ ions would prefer to occupying 4f2 site with increasing Zn substitution. In addition, the remanence (Br) of the sintered ferrites increased firstly and then decreased, while the intrinsic coercivity (Hcj) decreased continuously. The sintered ferrites with the optimal Zn doping level of x = 0.05 exhibited high magnetic properties, including Br= 439.7 mT, Hcj= 371.8 kA/m and (BH)max= 36.88 kJ/m3.