Fabrication of M-type ferrites with high La-Co concentration through Ca2+ doping

Ca2+ doped Sr0.45-xCaxLa0.55Fe11.6Co0.4O19 (x = 0, 0.15, 0.3, and 0.45) ferrites were fabricated through a conventional ceramic process. The influences of Ca2+ doping on the microstructure and magnetic properties of ferrites were investigated. Ca2+ doping could mitigate the presence of impurity phase (CoFe2O4) in ferrites. Single phase M-type ferrites could be fabricated when x ≥ 0.3. Additional Co2+ ions entered the crystal lattice and preferentially occupied the 4f2 site with Ca2+ doping. This effect greatly improved the remanence (Br) and intrinsic coercivity (Hcj) when x increased from 0 to 0.3. The average grain size of sintered ferrites slightly increased with the amount of doped Ca2+ ions. This behavior led to the deterioration of Hcj when x increased from 0.3 to 0.45. Consequently, ferrite prepared with x = 0.3 presented the highest maximum energy product ((BH)max) of 5.24MGOe. This performance is much higher than that of conventional La-Co substituted Sr-ferrites.