The Effect of Additives on the Properties of Bismuth Mn—Zn–ferrite

Abstract

Ferrite−ceramic materials are widely used in electronics. The most widely used is Mn—Zn−ferrite due to its high permeability. However, Mn—Zn−ferrites obtained by the standard process flow (ITS) have the texture along the pressing axis which significantly reduces their permeability and causes anisotropic properties. The difference in the magnetic permeability along and perpendicular to the pressing axis reaches 10—20 % due to the texture. The texture of the raw blanks is caused by lamellar ferrite particles [1] and the orientation of the [111] crystallographic axes along the compression axis. During sintering the degree of texture increases due to the preferential growth of pressing−oriented particles at the expense of non−oriented ones. As a result, an easy magnetization axis formed in the sintered ferrite which coincides with the compression axis. Most sizes of ferrite products are manufactured in such a way that the magnetic field lines in their operation do not coincide with the compression axis (ring, P−and R−core), which significantly reduces their operating parameters. To reduce the texture in this study we used a short process flow diagram including only one heat treatment i.e. sintering of the blanks pressed directly from the mixture of the raw ferrite oxide particles that are oriented but slightly when pressed. We show that isotropic Mn—Zn−ferrite with the desired magnetic properties at CCC can be obtained using bismuth oxide additives and a complex composition of binder during compaction instead conventionally used polyvinyl alcohol.