Loss-Separation Study on Silica-insulated Gas-atomized Fe-Si-Al Soft Magnetic Composites

Fe-Si-Al soft magnetic composites were composed of gas-atomized Fe-9.6wt.%Si-5.4wt.%Al alloy powders insulated with silica nanoparticles. The influence of silica insulation content on the core's magnetic properties was studied. It was found that increasing the silica mass ratio deteriorated the effective permeability and core loss in the frequency range of 40-120 kHz, while improved the quality factor at 100 kHz and DC-bias performance. The effective demagnetizing field reflected by density and the core's volume resistivity may cause the variations of these magnetic parameters. Loss separation fitting was performed using the Bertotti formula, indicating that silica insulation increased the hysteresis loss and reduced the eddy-current loss. The hysteresis loss took over at the frequency lower than 120 kHz in this work. With increasing the frequency, the eddy-current loss grew more quickly than the hysteresis loss. Therefore, different methods should be adopted to reduce the core loss according to the core's application frequency.