Effects of Nb2O5, TiO2, SiO2, and CaO additions on the loss characteristics of Mn-Zn Ferrite

Abstract

The effects of SiO2, CaO, TiO2, and Nb2O5 additives on the high-frequency magnetic properties of the Mn0.3Zn0.7Fe2O4 (MZFT) ferrites were examined in this study. The content of SiO2 and CaO was kept at 50 ppm and 500 ppm, while that of TiO2 and Nb2O5 varied respectively from 0 to 3000 ppm and from 0 to 300 ppm. All samples surpassed 95 % theoretical density after sintering at 1300 °C with N3T30 composition (50 ppm SiO2, 5000 ppm CaO, 3000 ppm TiO2, and 300 ppm Nb2O5) reporting the highest sintered density. The calculated lattice constants of the ferrites evaluated appeared to be nearly the same (≈0.849 A) and no second phase was present. It was apparent that the additions of SiO2, CaO, TiO2, and Nb2O5 exerted no notable impact on the microstructures of the ferrites. The average grain size of the samples sintered at 1300 °C ranged from 7.78 μm to 9.76 μm with both intergranular and intragranular pores. Incorporation of partial Ti4+ and Nb5+ ions into the lattices shifted the secondary maximum peak of the μi-T curves from 90 °C to lower temperatures (60 to 70 °C). The initial permeability of the ferrites was strongly dependent on the additives and the sintering temperature. The initial permeability of the MZFT sample sintered at 1275 °C and 1300 °C read respectively 5056 and 5222, and that of the N3T30 sample emerged to be 2917 and 3389. Compared to that of pure MZFT ferrite, the TiO2 and Nb2O5, SiO2 and CaO added compositions displayed a nearly 45 % reduction in total power loss, mainly caused by the electrical insulating layers at the grain boundaries, which lowered the eddy current loss. The N3T30 ferrite sintered at 1275 °C showed the lowest total power losses of 272 mW/cm3 at 50 °C.