Structural and magnetic properties of Ca-Mn-Zn-substituted M-type Sr-hexaferrites

The crystalline phases, microstructure, and magnetic properties of Ca-Mn-Zn-substituted M-type Sr-hexaferrites have been investigated with respect to the doping level of Ca, and various additives. Ca-Mn-Zn-substituted M-type Sr-hexaferrites, Sr1-xCaxFe11.8Mn0.1Zn0.1O19 (0 ≤ x ≤ 1.0) were synthesized by solid-state reaction. The solubility limit of Ca into the M phase, x, was found to be ∼0.5. The maximum saturation magnetization of 74.9 emu/g could be obtained at x = 0.3 (Sr0.7Ca0.3Fe11.8Mn0.1Zn0.1O19), which is higher than that of non-substituted SrFe12O19 by 3.2%. For the optimal composition of the calcined powder, Sr0.7Ca0.3Fe11.8Mn0.1Zn0.1O19, sintering processes were performed with various kinds of additives including SiO2, Mn3O4, ZnO, Co3O4, Al2O3, La2O3, and SrCO3. The better hard magnetic performances in the sintered samples of Sr0.7Ca0.3Fe11.8Mn0.1Zn0.1O19 could be achieved than in the non-substituted SrFe12O19 when the kind and amount of sintering additives were effectively controlled.