Haining Ji

Microstructure, Electrical, and Magnetic Properties of ZrO

We investigated the influence of ZrO₂ on the microstructure and electromagnetic properties of MnZn ferrites by characterizing fracture surface micrographs, magnetic properties, and dc resistivity. Powders of Mn _0.68Zn _0.25Fe _2.07O ₄ composition were prepared by the conventional ceramic technique. Toroidal cores were sintered at 1350degC for 4 h in N₂/O₂ atmosphere with 4% oxygen. The results show that the lattice constant and average grain size increase with ZrO₂ concentration, but excessive ZrO ₂ concentration will result in exaggerated grain growth and porosity increase. The dc resistivity, activation energy, saturation magnetic flux density, and initial magnetic permeability increase monotonically when the ZrO₂ concentration is not more than 0.04 wt% and then decrease with further increase of ZrO₂ concentration. On the other hand, the porosity, drift mobility, resonance frequency, and core loss decrease initially and then increase with the increase of ZrO₂ concentration.

_{2}

MnZnTiSn ferrties, prepared via the conventional ceramic process, by sintering at 1360°C in N2-O2 atmosphere with 4% oxygen, were characterized in terms of microstructures, magnetic properties and dc resistivity. Experimental results showed that TiSn-substitution remarkably improved magnetic properties and temperature stabilities of the MnZn ferrite ceramics. The effects of Ti4+ and Sn4+ substitution had certain synergistic effect. The sample, substituted with 0.2 mol% Ti4+and 0.1 mol% Sn4+, possessed maximum density and initial permeability, together with minimum core loss, residual magnetic flux density and coercive force.

Added MnZn Ferrites

Ti-Substituted MnZn ferrites were prepared by the conventional ceramic process. The effects of Ti-Substitution on temperature dependence and magnetic disaccommodation of MnZn ferrites were investigated. The experimental results show that the valley between peak I and Peak II of the μi-T curve initially becomes flatter with higher Titanium content. However, if increasing Titanium content continually, the valley becomes steep eventually. Furthermore, at the same temperature section of the valley, an initial decrease followed by a subsequent increase in the intensity of peak II of disaccommodation spectra is observed with the increase in Titanium content. The valley becomes flatter when the peak II of disaccommodation spectra goes down. MnZn ferrite with low peak II of disaccommodation spectra and high thermal stability is achieved when the substitution of Ti4+ is 0.1 mol%.

Microstructure and Temperature Dependence of Magnetic Properties of MnZnTiSn Ferrites for Power Applications

MnZn ferrites substituted with titanium having the compositional formula of Mn0.679-xZn0.258TixFe2.066O4 (x = 0, 0.010, 0.020, 0.030) were prepared via a conventional ceramic process. The effect of titanium concentration on magnetic properties such as permeability, power loss, and Curie temperature were investigated. Moreover, Mossbauer spectra was recorded at room temperature. The cation distribution obtained from analysis of Mossbauer spectra revealed that the substitution of MnZn ferrites by titanium can move part of Fe3+ from octahedral (B) site to tetrahedral (A) site. Remarkably, this resulted in an increase in the amount of Fe2+A-Fe3+B ion pairs and the Curie temperature. The results obtained and mechanisms involved are discussed.