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

Abstract

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 μ_f/μ_{100 kHz} could reach 98.7% at 1 MHz. In comparison with 60μ 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.