Effects of Nb^sub 2^O^sub 5^, TiO2, SiO2, and CaO additions on the loss characteristics of Mn-Zn Ferrite

• Published in: Journal of electroceramics 2014-12, Vol.33 (3-4), p.172
• Main Authors: Wang, Sea-fue, Hsu, Yung-fu, Chen, Chi-huei
• Format: Article
• Language: English
• ISSN: 1385-3449; 1573-8663
• DOI: 10.1007/s10832-014-9943-z

The effects of SiO2, CaO, TiO2, 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 SiO2 and CaO was kept at 50 ppm and 500 ppm, while that of TiO2 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 °C with N3T30 composition (50 ppm SiO2, 5000 ppm CaO, 3000 ppm TiO2, 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 ([asymptotically =]0.849 Å) and no second phase was present. It was apparent that the additions of SiO2, CaO, TiO2, 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 °C ranged from 7.78 [mu]m to 9.76 [mu]m with both intergranular and intragranular pores. Incorporation of partial Ti^sup 4+^ and Nb^sup 5+^ ions into the lattices shifted the secondary maximum peak of the [mu]^sub i^-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 Nb^sub 2^O^sub 5^, 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/cm^sup 3^ at 50 °C.[PUBLICATION ABSTRACT]