Preparation and electromagnetic performances of Finemet nanocrystalline soft magnetic composites with flake and spherical powders

Nanocrystalline soft magnetic composites (n-SMCs) with excellent soft magnetic properties are widely used in medium and high frequency electronic devices. However, the production of n-SMCs with high frequency stability and low core losses (Pc) remains a challenge. In this work, we balanced electromagnetic performances and frequency properties of Finemet n-SMCs by tuning the mass ratio of flake and spherical powders. The morphology, phase structures, electromagnetic performances or frequency characteristics of powders and n-SMCs were systematically investigated. Scanning electron microscope was employed to prove that the addition of spherical powders (SPs) can improve the matching degree of powders and density of n-SMCs. As the mass ratio of SPs increased, the Pc and the hysteresis losses (Ph) of magnetic powder cores first decreased and then increased, while the eddy current losses (Pe) showed the monotonic downward trend. What’s more, owing to the excellent insulation coating performances of SPs, quality factor (Q), DC-bias characteristics and frequency stability were significantly improved after mixing SPs with FPs. The n-SMCs with the mass ratio of 2:3 between SPs and FPs exhibited the best comprehensive performances with the effective permeability of μe = 43 (f = 100 kHz), the quality factor of Q = 78, the core losses of Pc = 294 mW/cm3 (Bm = 50 mT, f = 100 kHz), and the DC-bias characteristics of 56%. This work endows Finemet n-SMCs with a potential application for inductance components at high frequency.