Soft Ferrite Materials for Multilayer Inductors
Various families of soft ferrites (Ni–Cu–Zn; Mg–Cu–Zn; Co2–Z; Mn–Zn) with a sintering temperature of T≤950°C are used for multilayer inductors. It is shown for Ni–Cu–Zn and Mg–Cu–Zn ferrites that composition, powder particle size, and sintering additive concentration strongly affect the shrinkage, sintering behavior, microstructure, and magnetic properties. A maximum permeability of i=700–900 is observed with a Bi2O3 addition of about 0.5 wt%. The maximum shrinkage can be shifted down to 700°C using nanosize powders. Z-type hexaferrites with a permeability of 10 are used for high-frequency applications up to 2 GHz.
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