The Relations between Sintering Conditions and Magnetic Properties of SrMg2W – type Ferrites Prepared by Spark Plasma Sintering Method

The effects of sintering condition to magnetic properties of the SrMg2W–type ferrite (SrMg2Fe16O27) prepared by the Spark Plasma Sintering (SPS) method were investigated. SrMg2W–type ferrite powders with average particle sizes of 0.43 µm were prepared by iron ball-milling for 10 hours. Some kinds of SrMg2W–type ferrite samples were obtained by sintering SrMg2W–type powders by the SPS method at 1073−1173 K for 0−20 min as holding time. Compared to the SrMg2W–type ferrite prepared at 1523 K by the conventional solid reaction method, all the spark-plasma-sintered samples had larger coercivity. Mass magnetization of the SPS samples were almost the same (51.9～54.3 Am2/kg @1 T) regardless of the sintering condition. In the case of SPS without holding time, the coercivity of the SPS samples increased with increasing the sintering temperature, and reached 191 kA/m at 1173 K. When the samples sintered at 1073 K, the coecivity became the maximum (190 kA/m) at 10 min. From the results of X-ray diffraction, it was found that the coercivity of the samples enhanced as lattice strain of them was small. The influence of the lattice strain on the coercivity was discussed using the Kronmüller equation.