Spatial Distribution and Local Coordination Regulation of Nano-Oxide-Modified Si–O Interfaces in FeSiAl Soft Magnetic Composites

Existing strategies for modifying soft magnetic composites (SMCs) with nano-oxides primarily rely on their high electrical resistivity, with limited attention paid to interfacial coupling between the nano-oxides and the insulating matrix. This study proposes a high-temperature annealing strategy to regulate the spatial distribution and local coordination of nano-oxide-modified Si–O interfaces by incorporating Al₂O₃ and CeO₂ into a silicone resin coating system, thereby harnessing their potential for interfacial modification at elevated temperatures. After annealing at 800 °C, the silicone resin forms an inorganic insulating interface characterized by an amorphous Si–O-rich network. The incorporation of Al₂O₃ and CeO₂ alters the spatial distribution of the insulating interface and generates Si–O–Al/Al–O- and Si–O–Ce/Ce–O-related oxygen environments, respectively, thereby regulating the local coordination of the Si–O network. Al₂O₃ modification facilitates core-loss reduction, with the sample containing 0.5 wt.% Al₂O₃ achieving a core loss of 144.31 mW/cm³ at 100 kHz and 50 mT. In contrast, CeO₂ incorporation is more favorable for maintaining high effective permeability, with the sample containing 1 wt.% CeO₂ achieving a value of 97.88 at 100 kHz. These findings provide insights into the relationships among interfacial spatial distribution, local coordination, and high-frequency magnetic properties, offering guidance for the design of high-temperature composite insulating interfaces for FeSiAl SMCs.