Mechanism of core loss and the grain-boundary structure of niobium-doped manganese-zinc ferrite

The mechanism of iron loss was investigated for Mn-Zn ferrites with and without Nb2O5 addition by observing the grain-boundary structure and measuring the various properties. Without Nb2O5 addition Ca and Si atoms concentrate near the grain boundary and are incorporated in the spinel lattice, With Nb2O5 addition Nb atoms concentrate in the grain boundary and keep Ca atoms from being incorporated in the spinel lattice. Hysteresis loss was reduced in spite of smaller magnetic permeability by the addition of Nb2O5. Eddy current loss and residual loss were reduced by the addition of Nb2O5, especially at high frequencies, The origin of the decrease in these losses was discussed on the basis of the data of the grain-boundary structure, permeability, electrical conductivity, and disaccomodation. (C) 1996 Academic Press, Inc.