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

Previous investigations have typically employed metal FeSiCr powders with large average particle sizes to prepare the magnetic powder cores (SMCs), with few studies reporting on the influence of magnetic properties for original powders with various average particle sizes less than 10 μm. In this work, the 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 by 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, respectively. 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 exhibited significantly reduced magnetic loss. It further reduces the magnetic loss of the powder core, providing a new strategy for the application of SMCs at high frequencies.