Synthesis, microstructure and magnetic properties of Fe3Si0.7Al0.3@SiO2 core–shell particles and Fe3Si/Al2O3 soft magnetic composite core

• Fe3Si0.7Al0.3@SiO2 core–shell particles and Fe3Si/Al2O3 cores were prepared.
• Fe3Si0.7Al0.3 particles could be uniformly coated by nano-sized SiO2 clusters.
• Fe3Si0.7Al0.3@SiO2 particles and Fe3Si/Al2O3 cores showed good soft magnetic properties.
• Fe3Si/Al2O3 had lower core loss and better frequency stability than Fe3Si0.7Al0.3 cores.

Fe3Si0.7Al0.3@SiO2 core–shell particles and Fe3Si/Al2O3 soft magnetic composite core have been synthesized via a modified stöber method combined with following high temperature sintering process. Most of conductive Fe3Si0.7Al0.3 particles could be uniformly coated by insulating SiO2 using the modified stöber method. The Fe3Si0.7Al0.3@SiO2 core–shell particles exhibited good soft magnetic properties with low coercivity and high saturation magnetization. The reaction 4Al+3SiO2=2α-Al2O3+3Si took place during the sintering process. As a result the new Fe3Si/Al2O3 composite was formed. The Fe3Si/Al2O3 composite core displayed more excellent soft magnetic properties, better frequency stability at high frequencies, much higher electrical resistivity and lower core loss than the pure Fe3Si0.7Al0.3 core. The method of introducing insulating layers surrounding magnetic particles provides a promising route to develop new and high compact soft magnetic materials with good magnetic and electric properties.

In Fe3Si/Al2O3 composite, Fe3Si phases are separated by Al2O3 layers and the eddy currents are confined in Fe3Si phases, thus increasing resistivity and reducing core loss.Figure optionsDownload as PowerPoint slide