Influence of oxidation temperature on microstructure and electromagnetic performance of Fe-Si/Fe2SiO4 soft magnetic composites

Abstract In this paper, Fe-6.5 wt%Si powders were oxidized with different temperatures, and Fe-Si soft magnetic composites with Fe2SiO4 coating layer were transformed successfully by high temperature solid state reaction sintering between the surface oxides and Si element in Fe-6.5 wt%Si powders. The influence of the oxidation temperature on the microstructure and electromagnetic performance of the Fe-Si soft magnetic composites has been studied systematically. The analysis results show that when the oxidation temperature increases from 40 °C to 70 °C, the formed surface oxides are mainly γ-Fe2O3 and become more, but are more likely to fall off the surface of the Fe-6.5 wt%Si powders owing to the accelerated oxidation educed by higher oxidation temperature. Hence, the uniformity of the transformed Fe2SiO4 coating layer is getting worse, resulting in a downward trend of the resistivity and the deteriorating dynamic loss. And the saturation magnetization decreases slowly, while the coercivity exhibits an opposite trend. In addition, it is worth noting that, due to the generation of ferromagnetic Fe by the reaction between Si and γ-Fe2O3, all the Fe-Si soft magnetic composites exhibit very high saturation magnetization above 188.5 emu/g, which is benefit for the miniaturization of electromagnetic devices.