Mechanism of Core Loss and the Grain-Boundary Structure of Niobium-Doped Manganese–Zinc Ferrite

Abstract The mechanism of iron loss was investigated for Mn–Zn ferrites with and without Nb 2 O 5 addition by observing the grain-boundary structure and measuring the various properties. Without Nb 2 O 5 addition Ca and Si atoms concentrate near the grain boundary and are incorporated in the spinel lattice. With Nb 2 O 5 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 Nb 2 O 5 . Eddy current loss and residual loss were reduced by the addition of Nb 2 O 5 , 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.