Preparation of coprecipitated NiZn ferrite

A homogeneous NiZn ferrite of approximately theoretical density was produced by the incorporation of coprecipitation and hot- isostatic-pressing steps into standard powder-processing procedures. The metal ions were precipitated as oxalates from an aqueous solution, followed by conversion to ferrite by a two-stage calcining operation at 200 and 800°C. After milling, isostatically pressing, and sintering, the ferrite was hot-isostatically pressed at 1180°C under 2000 kg/cm²argon-gas pressure. A post-heat treatment in an oxygen atmosphere was required to provide a uniform oxygen content throughout the ferrite. Magnetic properties have been measured on the ferrite, which show that the permeability at 1 MHz was greater than 1700 and the saturation induction was greater than 3400 gauss.