Manganese-zinc ferrite produced from ultra-fine particles

摘要

A manganese-zinc ferrite is used as either a high frequency power ferrite or as a ferrite with high permeability at high frequency, depending on the dopant type, and has an as-fired grain size of 1-15 mu /!20% for the high frequency power ferrite and 30-50 mu /!20% for the high permeability ferrite, the as-fired density being more than 95% of the theoretical density of the ferrite phase. Preferably, (i) the high frequency power ferrite has the composition (in mol%) 53-54.5% Fe2O3, 32-38% MnO and 8-13.5% ZnO and contains a dopant combination of (by wt.) 0.03-0.15% each of SiO2 and CaO and 0.05-0.15% each of Bi2O3 and CoO; and (ii) the high permeability ferrite has the composition (in mol%) 50-52.5% Fe2O3, 24-26.5% MnO and balance ZnO. Also claimed is a process for producing the above manganese-zinc ferrite, in which the ferrite components are finely ground to a mean particle size of below 1 mu (with absence of greater than 5 mu size particles), pressed to above 3.1 g/cm<3> density and sintered under controlled conditions providing uniform grain growth.