The effect of nano-SiO2 on the magnetic properties of the low power loss manganese-zinc ferrites

The effect of the addition of nano-SiO2 on the power losses in the manganese zinc ferrites has been investigated by measuring the magnetic properties and observing the grain boundary structures. The powders of Mn0.72Zn0.21Fe2.07O4 composition were prepared by using a conventional ceramic powder processing technique. Toroidal cores were sintered at 1340degreesC for 4 It using a tube furnace with atmosphere controlled by using the equation for equilibrium oxygen partial pressure. The microstructure of grain boundary was observed by AES and SEM. It has been found that the grain boundaries resistivity and magnetic loss are greatly dependent upon the content of nano-SiO2. There is an optimum content of nano-SiO2 to produce uniform grain structure and low magnetic loss. The eddy current losses were reduced by the addition of nano-SiO2,. These losses are thought to originate from the additive effect of Si atoms, which are enriched in grain boundaries to form a high resistivity layer and prevent Ca and Nb atoms being incorporated with the spinel lattice. (C) 2003 Elsevier Science B.V. All rights reserved.