Mg–Cu–Zn Ferrites for Multilayer Inductors

Mg–Cu–Zn ferrites can be sintered at T ≤950°C to sufficient density and display adequate permeability profiles for application in multilayer ferrite inductors. The permeability and Curie temperature have to be optimized by proper selection of composition. Ferrites with <50 mol% Fe ₂ O ₃ reveal enhanced densification behavior. Submicrometer powders prepared by fine milling show good sintering activity and density after firing at 900°C. Nano‐size ferrite powders prepared by coprecipitation or flame synthesis lead to high density; maximum shrinkage already occurs at T <800°C. The use of Bi ₂ O ₃ as a sintering additive further improves the densification, but also affects the microstructure and, hence, the permeability. A maximum permeability of μ _i =450–500 is obtained.