Effects of Nb sub(2)O sub(5), TiO sub(2), SiO sub(2), and CaO additions on the loss characteristics of Mn-Zn Ferrite

• Published in: Journal of electroceramics 2014-12, Vol.33 (3-4), p.172-179
• Main Authors: Wang, Sea-Fue, Hsu, Yung-Fu, Chen, Chi-Huei
• Format: Article
• Language: English
• Subjects: Additives; Ferrite; Permeability; Power loss; Silicon dioxide; Sintering; Sintering (powder metallurgy); Titanium dioxide
• ISSN: 1385-3449; 1573-8663
• DOI: 10.1007/s10832-014-9943-z

The effects of SiO sub(2), CaO, TiO sub(2), and Nb sub(2)O sub(5) additives on the high-frequency magnetic properties of the Mn sub(0.3)Zn sub(0.7)Fe sub(2)O sub(4) (MZFT) ferrites were examined in this study. The content of SiO sub(2) and CaO was kept at 50 ppm and 500 ppm, while that of TiO sub(2) and Nb sub(2)O sub(5) varied respectively from 0 to 3000 ppm and from 0 to 300 ppm. All samples surpassed 95 % theoretical density after sintering at 1300 degree C with N3T30 composition (50 ppm SiO sub(2), 5000 ppm CaO, 3000 ppm TiO sub(2), and 300 ppm Nb sub(2)O sub(5)) reporting the highest sintered density. The calculated lattice constants of the ferrites evaluated appeared to be nearly the same ( approximately 0.849 Aa) and no second phase was present. It was apparent that the additions of SiO sub(2), CaO, TiO sub(2), and Nb sub(2)O sub(5) exerted no notable impact on the microstructures of the ferrites. The average grain size of the samples sintered at 1300 degree C ranged from 7.78 mu m to 9.76 mu m with both intergranular and intragranular pores. Incorporation of partial Ti super(4+) and Nb super(5+) ions into the lattices shifted the secondary maximum peak of the mu sub(i)-T curves from 90 degree C to lower temperatures (60 to 70 degree 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 degree C and 1300 degree 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 TiO sub(2) and Nb sub(2)O sub(5), SiO sub(2) 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 degree C showed the lowest total power losses of 272 mW/cm super(3) at 50 degree C.