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

Abstract

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.