Reactive sintering of MnZn ferrites

Reaction-formed MnZn ferrite was prepared and the decrease in shrinkage aft er sintering due to the volume expansion accompanying iron oxidation was st udied. Green compacts consisting of the milled raw oxides Fe2O3, Mn3O4, ZnO and me tallic iron powder were sintered at 1350 degreesC in air. During the first hold at 800 degreesC, Fe was oxidized to alpha -Fe2O3 and Zn ferrite was fo rmed. Above 1300 degreesC the reaction bonding was completed and MnZn ferri te, exhibiting a relatively low shrinkage, was formed. The chemical reactio ns involved during reaction bonding were associated with a volume expansion and porosity formation, compensating for the shrinkage on sintering. Inten sive milling decreases the porosity alter sintering but induces the oxidati on of iron, and partially removes the shrinkage compensation caused by the presence of metallic iron.