Tailoring the Microstructure of NiZn Ferrite for Power Field Applications

The effects of grain size and magnetic domain state on the power loss (from low to high induction conditions) and permeability characteristics of NiZn ferrites are investigated. It is found that under relatively low induction conditions (B_m<50 mT), a NiZn ferrite with a dense and monodomain microstructure obtains the lowest power loss. However, a NiZn ferrite with a larger average grain size displays a lower power loss under high induction conditions, and the influence of domain state on power loss is inconspicuous. Extremely large grain size and closed pores also lead to a poor frequency stability of permeability. Thus, synthetically considering the power loss and permeability characteristics, a NiZn ferrite with an even and large average grain size also has few closed pores and is the best choice for use under high induction conditions.