Enhanced soft magnetic properties and high-frequency stability of FeNiMo powder cores by coating SiO 2 insulation layer.

FeNiMo/SiO 2 powder cores were prepared using the sol-gel method. Tetraethyl orthosilicate (TEOS) was added to produce an amorphous SiO 2 coating outside the FeNiMo particles to form a core-shell structure. The thickness of the SiO 2 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/SiO 2 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 μ f / μ 100 kHz could reach 98.7% at 1 MHz. In comparison with 60 μ commercial products, the comprehensive soft magnetic properties of the FeNiMo/SiO 2 cores were superior to most manufacturers, which would be potentially applied to high-performance inductance devices in high-frequency ranges.