Enhanced soft magnetic properties and high-frequency stability of FeNiMo powder cores by coating SiO₂ insulation layer

FeNiMo/SiO2 powder cores were prepared using the sol-gel method. Tetraethyl orthosilicate (TEOS) was added to produce an amorphous SiO2 coating outside the FeNiMo particles to form a core-shell structure. The thickness of the SiO2 layer was designed by varying the concentration of TEOS, and the optimized permeability and magnetic loss of the powder core could achieve 78.15 and 633.44 kW m(-3) at 100 kHz and 100 mT, respectively. Compared with other soft magnetic composites, these FeNiMo/SiO2 powder cores have a significantly higher effective permeability and a lower core loss. Surprisingly, the high-frequency stability of permeability could be substantially enhanced through the insulation coating process in which mu(f)/mu(100 kHz) could reach 98.7% at 1 MHz. In comparison with 60 mu commercial products, the comprehensive soft magnetic properties of the FeNiMo/SiO2 cores were superior to most manufacturers, which would be potentially applied to high-performance inductance devices in high-frequency ranges.