Magnetic and microstructural properties of M-type strontium hexaferrites with Pr-ZnAl substitution

We have investigated the influence of Pr-ZnAl substitution on the magnetic and microstructural properties of M-type strontium hexaferrites Sr1.0-xPrxFe12.0-x(Zn0.5Al0.5)xO19 (0.0 ≤ x ≤ 0.5) synthesized by the standard ceramic method. X-ray diffraction (XRD) was carried out to determine the crystal structure and the phase identification of the hexaferrites showed that a single magnetoplumbite phase was exhibited in the hexaferrites with Pr-ZnAl content (x) from 0.0 to 0.4 and impurity phase α-Fe2O3 was observed in the structure when Pr-ZnAl content (x) = 0.5. The morphology of the hexaferrites was analyzed by a field emission scanning electron microscopy (FE-SEM). The representative FE-SEM micrographs showed that the particles were regular hexagonal platelets and the average grain size basically kept unchanged with increasing Pr-ZnAl content (x). A magnetic property measurement system was used to measure the magnetic properties of the hexaferrites. The remanence (Br), maximum energy product [(BH)max] and Hk/Hcj ratio decreased with increasing Pr-ZnAl content (x) from 0.0 to 0.5. The intrinsic coercivity (Hcj) and magnetic induction coercivity (Hcb) first increased with increasing Pr-ZnAl content (x) from 0.0 to 0.1, and decreased with increasing Pr-ZnAl content (x) from 0.1 to 0.2, and then increased when Pr-ZnAl content (x) ≥ 0.2.