Relation Between Firing Conditions Grain Boundary Structure and Magnetic Properties in Polycrystalline MnZn-Ferrites

Abstract

Abstract. The influence of the firing conditions on the nanoscale structure of the grain boundaries and on the magnetic properties of polycrystalline MnZn-ferrites is investigated, on specimens of nearly identical microstructures. High oxygen partial pressures favor accumulation of impurity ions at the triple points. Under appropriate oxygen pressures homogeneous accumulation of impurities along the grain boundaries may occur, revealing therefore chemically pure grains and low hysteresis losses; simultaneously an increase of the grain boundary resistivity occurs that results to low eddy current losses. Managing the raw material impurity cations towards controlled grain boundary structures leads to the synthesis of MnZn-ferrites with power losses similar to those achieved when high purity raw materials are used together with externally introduced additives.

The effect of TiO2 on the magnetic power losses and electrical resistivity of polycrystalline MnZn-ferrites

“…The effect of the oxygen partial pressure on the grain boundary structure of MnZn-ferrites in the absence of titanium has been discussed earlier [17]. Although the partial pressure of oxygen is the only cation vacancy generating mechanism for morphologically identical microstructures, adjusting the occupancy of the peak temperature during the sintering cycle brings the results in qualitative agreement with this study.…”

Effect of Oxygen Content during Sintering on the Losses of MnZn Ferrites

“…It is observed that, increasing O 2 content, the high temperature losses is lower. The present results confirm Lebourgeois et al [12], which mention, as Zaspalis [6,7], Eq (1). According to Eq.…”

“…Existence of Fe +2 implies in free electrons inside the lattice, thus increasing the conductivity. Morineau and Paulus [5] and Zaspalis et al [6,7] point out that the amount of Fe +2 may be controlled with oxygen pressure. Increasing oxygen, the amount of Fe +2 is reduced.…”

Non-Linear Material Model of Ferrite to Calculate Core Losses With Full Frequency and Excitation Scaling

“…Desired physical properties could then be considered in the setup of the manufacturing process. Such a material development approach could make use of existing literature on the link between manufacturing conditions and material properties [14], [15], [26].…”