Choice of grade of ferric oxide and hot-pressing conditions for the preparation of high-permeability manganese-zinc ferrites

Abstract

In the formulation of new ferrite materials for magnetic head cores starting raw materials and conditions of preparation of ferrite powders must be chosen with regard to the conditions prevailing in the hot-pressing process. The differences in the properties of the two hot-pressed ferrite batches investigated are attributable to the difference in the activities of the ferric oxide grades used (MM2 and SP) in the solid-phase synthesis and sintering reactions. Use of grade MM2 ferric oxide in the preparation of ferrite powders and hot pressing and annealing under optimum conditions (psp = 40 MPa, Thp = 1663°K, τih = 2.4 ksec, Tann = 1613°K and τann = 7.2 ksec) enable specimens to be obtained combining high values of initial magnetic permeability (μin = 10,000) and density.