Selective oxidation of rare metal oxide insulation layers on particle substrates for optimizing the performance of FeSiCr-based soft magnetic composites

This study introduces an approach to fabricating soft magnetic composites (SMCs) that effectively address core loss while maintaining high magnetic conductivity. During the sintering process in a water vapor environment, the CeO2 insulation layer facilitates the selective oxidation of Si while simultaneously impeding the outward diffusion of Fe and Cr. Consequently, a CeO2·SiO2 composite insulation layer forms within the FeSiCr-based SMCs. The FeSiCr-based SMCs with the CeO2·SiO2 composite insulation layer achieve a saturation magnetization of 153.1 emu/g, which is 10.9% lower than that of FeSi3.7Cr4.5 compacts, and exhibits a deterioration rate lower than previously reported values. Moreover, the permeability of the FeSiCr-based SMCs remains highly stable, demonstrating outstanding insulation characteristics. The total core loss and core loss separation results further corroborate that incorporating a CeO2·SiO2 composite insulation layer leads to a more pronounced reduction in interparticle eddy current loss than using a CeO2 insulating layer alone. This performance enhancement can be attributed to the selective oxidation of a rare metal oxide insulation layer on a ferromagnetic metal particle substrate, a technique applied to SMCs for the first time. These findings hold significant implications for the design of high-performance SMCs in miniaturized and lightweight electromagnetic devices.