Coprecipitation methods and manufacture of soft ferrite materials and

Abstract

Manufacturing process for ferrimagnetic materials and pressure compacted soft ferrite components utilizing a 'wet' process for compositional preparation of materials in which metal carbonates and metal hydroxides are coprecipitated in controllably selected ratios. An aqueous solution of metal ions is formed by dissolving pure metals in acid. This aqueous metal ion solution is added to a predetermined solution of carbonate ions and hydroxide ions. Concentrations, temperature, and rates of addition are controlled to select the ratio of carbonate groups to hydroxide groups in the coprecipitated particles and the size of such particles. The controllably selected ratio of carbonate groups to hydroxide groups facilitates separation of the coprecipitation particles and maintains residual hydroxide groups in the material so as to extend solid-state reactivity of the coprecipitated particles for grain growth and densification purposes until the final heat treatment in which the pressure compacted articles are sintered. The intermediate materials can be processed in conventional dry processing equipment and the ferrimagnetic powders can be compacted in dies used for dry process ferrites because of matched shrinking ratios. High toroidal permeability and low loss factors are combined in components for telecommunications and higher frequency uses; e.g. manganese-zinc ferrites suitable for filter core and like uses have toroidal permeabilities above 2000 and loss factors in the range of 0.8 .times. 10.sup.-6 to 1.5 .times. 10.sup.-6 at 100 kHz. Other cores include NiZn ferrites and MgMn ferrites.