High-performance Fe/SiO2 soft magnetic composites for low-loss and high-power applications

High-performance Fe/SiO2 soft magnetic composites (SMCs) by coating pure iron particles with amorphous SiO2 layers have been fabricated by controlled hydrolysation of tetraethyl orthosilicate (TEOS). Microstructural studies show that the pure iron particles are uniformly and entirely coated with the SiO2 insulating layers to form Fe/SiO2 core–shell structure. The dielectric SiO2 layers lead to the electrical insulation behaviour of the SiO2-coated iron particles, which results in low core loss of the compacted Fe/SiO2 SMCs in application of alternating current. The core loss measured at a frequency of 50 Hz and an induction level of 1 T is 3.5 W kg−1, which is much lower than that of the commercial SMCs prepared by coating iron particles with phosphate layers. The Fe/SiO2 SMCs exhibit nearly the same coercivity as that of pure iron, and saturation magnetization of 18.2 kG, a little lower than that of pure iron due to the nonmagnetic SiO2 layers. The low core loss and high saturation magnetization promise the great potential of Fe/SiO2 SMCs in high-power applications. High-frequency measurements reveal that the working frequency of the Fe/SiO2 SMCs can reach up to 20 MHz.