Interfacial Reaction Enhanced Liquid-Phase Sintering of Metal/Oxide Soft Magnetic Composite

Soft magnetic composites (SMCs) are ungently demanded in high-frequency power electronics for their large magnetization and high electrical resistivity. However, traditional cold-pressed SMCs are faced with low mechanical strength and insulation instability, which severely restricts their applications. In this study, liquid-phase sintering techniques to prepare FeSiAl/MoO₃ SMCs are orginally employed, where consolidation and insulation of metallic magnetic particles are achieved in one step. The redox reaction between FeSiAl and MoO₃ melt greatly reduces the interfacial energy, facilitates fully wetting of FeSiAl particles by MoO₃ melt, and promotes the densification process during sintering. In the final FeSiAl/MoO₃ SMC, FeSiAl particles are bonded covalently and insulated electrically/magnetically by the resultant Al₂O₃ transition layer, endowing the SMC with high crushing strength of 250 MPa, cut-off frequency of 110 MHz, permeability of 35 (@1 MHz), and low power loss of 962 kW m⁻³ (5 MHz, 5 mT). This study provides alternative concept for designing new SMCs, and broadens the connotation and extension of liquid-phase sintering.