| Due to large resistance,high saturation flux density,and good DC-bias performance,soft magnetic powder corewith distributed air gaps,as the hot topic of the research of soft magnetic material,meets the requirements of miniaturization,higher frequency,lower loss,and higher powerdensity of electronic devices.An improved bluing technique was developed to coat a uniform and continuous bluing film/silica insulating layer on the surface of Fe-6.5wt.%Si soft magnetic powder particles.The Fe-6.5wt.%Si powder cores were prepared by using these insulated particles.The influences of the bluing solution concentration,the silica content,the compaction pressure,and the annealing temperature on the core's microstructure and magnetic properties were studied and loss separation was performed.It is found that with the bluing solution concentration increasing,the effective permeability decreases after the initial increase,while the DC-bias performance and the core loss exhibit an opposite variation tendency.With the increase of the silica content,the effective permeability decreases and the DC-bias performance and the core loss increase.As the compaction pressure increases,all the magnetic parameters are improved.With the annealing temperature increasing,the effective permeability increasesafter the initial decrease,while the DC-bias performance and the core loss display an opposite variation tendency.The demagnetization field determined by the air gap within the core is believed to have a great influence on the core's magnetic properties.The study on the loss separation indicates that the core loss is mainly determined by the hysteresis loss at the frequency lower than 100 kHz,while the eddy-current loss dominates at the frequency higher than 220 kHz.The relatively best performance for Fe-Si powder corewith a nominal effective permeability of 60?was achieved as follows:the percent permeability at 100Oe is 72.82%and the core loss at 50 kHz/1000Gs 547.66mW/cm~3. |
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