Extremely low core-loss and enhanced permeability stability in hot press sintered FeSi soft magnetic composites by TiO₂ and Fe nanopowders air gap filling

Soft magnetic materials are essential components in applications of motors, generators, transformers, and many electronic devices. Here we present the improved soft magnetic properties in Fe-6.5 wt%Si/(TiO₂:Fe)(nano powder; NP) soft magnetic composite (SMC) cores with varying concentrations of Fe nanopowders (0–4 wt%) synthesized by hot-press sintering. Increasing Fe nanopowder concentration significantly increases the density and electrical resistivity by filling the airgap and grain boundary scattering of carriers, respectively. Furthermore, adding Fe nanopowders leads to remarkably low coercivity (<15 Oe) and high saturation magnetization (189.5 emu/g). Notably, the FeSi/(TiO₂:Fe)(NP) SMCs exhibited excellent soft magnetic characteristics, including high permeability with good frequency stability ranging from 0 to 1 MHz and ultra-low eddy current loss (8.16 kW/m³ decreased by 83.47 %) at the 2 wt% doping concentration of Fe nanopowder. The composite with 3 wt% Fe nanopowder showed a significant decrease in hysteresis loss P_h with a minimum value of around 0.677 kW/m³. Therefore, the appropriate incorporation of Fe nanopowders, combined with the hot-press sintering technique, effectively reduces core loss, particularly eddy current loss, indicating that the Fe NP composites with FeSi matrix are highly promising for high-power and high-frequency electronic applications.