Optimizing Soft Magnetic Performance of FeSiAl Cores by Tailoring the Al2O3/SiO2 Insulating Layer in Ethanol/Aqueous Mixed Solvents

A soft magnetic composite core with high permeability and low core loss is the key to miniaturizing high-frequency electronic components. In order to reduce core loss and maintain high permeability, the proper insulating layer is crucial. In this work, an insulating layer of Al2O3/SiO2 has been prepared in a mixture of ethanol and aqueous solvents. As the ethanol content increases, the polarity of the mixed solvent determines the thickness and composition of the insulating layer. The thickness of the insulating layer does not affect eddy current loss once the insulating layer is complete. The thin insulating layer facilitates the motion of the domain wall during the magnetization process and weakens the demagnetizing field, leading to low coercivity, hysteresis loss, and core loss. As a result, the soft magnetic properties of FeSiAl cores can be optimized by tailoring the insulating layer. A FeSiAl composite prepared in 50 mL mixed solvents with 20 mL ethanol exhibits core loss of 167 mW/cm(3) and effective permeability of 77.4 at 100 kHz and 50 mT. At 50 kHz and 100 mT, the core loss and effective permeability are 291.7 mW/cm(3) and 75.5, respectively. The soft magnetic performance is superior to that of other FeSiAl cores that have been mechanically crushed. Furthermore, the ability to tune the insulating layer also highlights an effective strategy for optimizing the soft magnetic properties of FeSiAl cores.