| In this paper, Mn-Zn ferrites have been prepared by the mixed-oxide route. The prescribed quantities of Mn3O4 Fe2O3 and ZnO as the starting materials, were mixed in a ball mill. After being calcinated, the obtained ferrite powder was granulated and pressed into toroidal shapes, mixing with PVA. They, then, were sintered under nitrogen atmosphere. In this study, the effect of a small amount addition of many different oxides on the various properties of Mn-Zn soft ferrite was investigated. At the same time, we also examined the effect of calcination ratio, pressure, grain size, porosity, sintering atmosphere on the initial permeability and other material characteristics. The experiments are related to the optimization of microstructure, esp. the control of grain growth with a narrow distribution of the grain size and the control of defects. Therefore the use of optimized technology was necessary in order to obtain better homogeneity of raw material and good densification of green bodies and optimum sintering. To assess the effect of those factors, XRD and typical optical microscopy were used to investigate the microstructure. The results show that the average grain size of the ferries reduces due to the increase of the milling time; that the initial permeability of the manganese-zinc ferrites decreases remarkably with the increase of some oxide additions, i.e., 61263, TiOz, CaO and SiC^; that the average grain size and the porosity in ferrites increase drastically, as the higher content of MoOs addition; that a structure showing discontinuous grain growth is observed in ferrites with the addition of small amounts of 6263 up to 0.2 wt.%. Further increase in the doping level (^0.5 wt.%) , a relatively uniform microstructure with large grain size is obtained; that increasing the average grain size contributes to the initial permeability of the ferries. Those will serves as bases on the development of even better high-permeability ferrite materials. |
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