Intergranular insulated Fe-6.5 wt% Si/SiO2 composite compacts with tunable insulating layer thickness for low core loss applications

Core–shell structured Fe-6.5 wt% Si/SiO2 particles and intergranular insulated Fe-6.5 wt% Si/SiO2 composite compacts with tunable insulating layer thickness were prepared by in situ chemical deposition combined with a subsequent spark plasma sintering process. Most of conductive Fe-6.5 wt% Si alloy particles were coated with a SiO2 insulating layer in the Fe-6.5 wt% Si/SiO2 composite compacts. The SiO2 insulating layer could increase the electrical resistivity and reduce the effective radius of the eddy current in Fe-6.5 wt% Si/SiO2 composite compacts. Therefore, the intergranular insulated Fe-6.5 wt% Si/SiO2 composite compacts presented lower core loss than those of Fe-6.5 wt% Si compacts without SiO2 insulating layer. Based on this, several types of Fe-6.5 wt% Si/SiO2 core–shell particles and intergranular insulated Fe-6.5 wt% Si/SiO2 composite compacts (with various SiO2 insulating layer thicknesses) were selectively prepared by simply varying the TEOS concentration (the volume of TEOS for each gram of Fe-6.5 wt% Si particles, ml g−1). The results indicated that the thickness of the SiO2 layer and electrical resistivity of Fe-6.5 wt% Si/SiO2 composite compacts increased with increasing the TEOS concentration from 0.1 to 0.4 ml g−1, while saturation magnetization, relative permeability and core loss displayed the reverse tendencies. The as-prepared intergranular insulated Fe-6.5 wt% Si/SiO2 composite compacts exhibited excellent magnetic properties, which inspire us to develop new high silicon containing soft magnetic cores which can be widely used in various electromagnetic devices.