Lezhong, Li, Zhongwen, Lan, Zhong, Yu, Ke, Sun, Zhiyong, Xu, and Haining, Ji
We investigated the influence of Zr[O.sub.2] on the microstructure and electromagnetic properties of MnZn ferrites by characterizing fracture surface micrographs, magnetic properties, and dc resistivity. Powders of [Mn.sub.o.68][Zn.sub.o.25][Fe.sub.2.07][O.sub.4] composition were prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350 [degrees]C for 4 h in [N.sub.2]/[O.sub.2] atmosphere with 4% oxygen. The results show that the lattice constant and average grain size increase with Zr[O.sub.2] concentration, but excessive Zr[O.sub.2] concentration will result in exaggerated grain growth and porosity increase. The dc resistivity, activation energy, saturation magnetic flux density, and initial magnetic permeability increase monotonically when the Zr[O.sub.2] concentration is not more than 0.04 wt% and then decrease with further increase of Zr[O.sub.2] concentration. On the other hand, the porosity, drift mobility, resonance frequency, and core loss decrease initially and then increase with the increase of Zr[O.sub.2] concentration. Index Terms--Electromagnetic properties, microstructure, MnZn ferrites, Zr[O.sub.2] addition.