Enhanced soft magnetic properties of SiO₂-coated FeSiCr magnetic powder cores by particle size effect

It has been known that metal FeSiCr powders with large average particle sizes have been typically employed to prepare magnetic powder cores (SMCs), with few studies reported on the influence of magnetic properties for original powders with various average particle sizes less than 10 μm. In this work, SiO₂-coated FeSiCr SMCs with different small particle sizes were synthesized using the sol–gel process. The contribution of SiO₂ coating amount and voids to the soft magnetic properties was elaborated. The mechanism was revealed such that smaller particle sizes with less voids could be beneficial for reducing core loss in the SMCs. By optimizing the core structure, permeability and magnetic loss of 26 and 262 kW/cm³ at 100 kHz and 50 mT were achieved at a particle size of 4.8 μm and ethyl orthosilicate addition of 0.1 mL/g. The best DC stacking performance, reaching 87%, was observed at an ethyl orthosilicate addition rate of 0.25 mL/g under 100 Oe. Compared to other soft magnetic composites (SMCs), the FeSiCr/SiO₂ SMCs exhibit significantly reduced magnetic loss. It further reduces the magnetic loss of the powder core, providing a new strategy for applications of SMCs at high frequencies.