Effect of Solid Reducing Agent of Si on Formative Condition of SrFe₂-W Type Ferrite and Magnetic Properties

The W-type hexagonal ferrite, with the chemical formula of Sr(Ba)Fe²⁺₂Fe³⁺₁₆O²⁷, is the future candidate ferrite because of its 10% higher saturation magnetization in comparing with that of M-type ferrites. A complicated atmosphere control during sintering process is, however, required in manufacturing of W-type ferrites, which will be unsuitable for industrial production. Recently, it is reported that a high performance SrFe₂-W type ferrite can be produced with using a carbon powder as a solid reducing agent and controlling the drying temperature of green compacts. The energy product (BH)_max of this SrFe₂-W type ferrite is reported to be 5.3MGOe. The purpose of this study is to clarify the effects of drying treatment of green compacts, and addition of Si as a new solid reducing agent on the formative condition of SrFe₂-W type ferrite. The drying treatment at 373K and following by firing at 1473K for 10 hours in P_O2=250 Pa are the suitable formative conditions for silicon addition to achieve high volume fraction of SrFe₂-W phase and this sample has the(BH)_max of 10.3kJ·m^-3.