| With the development of electronic device to miniaturization, lightweight, MnZnpower ferrites–the core components of electronics are required for betterperformance: higher working frequency, high saturated magnetic induction (Bs) athigh temperature, low power loss (Pcv). And advocacy of energy conservation andenvironmental protection promoted the development of high performance MnZnpower ferrite possessing the characteristics of keeping low power loss in widetemperature, the study of high performance MnZn power ferrite has become the keydirection in domestic and foreign research. In this paper, the way of ion substitutionwas used to prepare MnZn power ferrite with excellent properties.Firstly, some basic magnetic theories and magnetic parameters of MnZn powerferrite were briefly introduced, and the preparation process and the principle of oxideceramic process were also analyzed. Then the effects of main compositions anddifferent additives on the material performance were researched. On the selection ofmain formula, the influences of different Co-substitution content on the crystal phase,structural and magnetic properties were discussed, then the best main formula couldbe chose. The results showed that: Substituting with different Co content can havesome effect on the crystal phase, structural and magnetic properties. With the increaseof Co content, the magnetocrystalline anisotropy constant (K1) decreased first andthen increased, while the saturated magnetic induction increases initially and thendeclines. At room temperature, the initial permeability (μi) increased with theincreasing Co substitution content and the corresponding temperature of the minimumpower loss shifted to a lower temperature; Adding SnO2could promote grain growth,that was because liquid phase will be formed during the sintering process, the initialpermeability increased. The eddy current loss declined with increasing SnO2content,because high valence Sn4+ions could bind some Fe2+ions and the resistivity increased.With the increase of Ta2O5doping, the average grain size increased, the initialpermeability increases first and then decreases, while the power loss shows theopposite trend. When the content of Ta2O5is0.04wt%, the MnZn power ferrite showsthe highest initial permeability and the minimum power loss; As Nb2O5mainlyappears in grain boundary, adding appreciate Nb2O5in MnZn power ferrite can increase the thickness of the grain boundary, promote the initial permeability andreduce eddy current loss. In addition, the amount of Fe2+ions rises with Nb2O5dopingand the magnetocrystalline anisotropy constant of MnZn power loss can becompensated, then the initial permeability increases, the power loss decreases and thesecond peak ofμi~T curve shifts from high to low temperature. The appropriateNb2O5content is0.02wt%; Co-doping0.03wt%TiO2and0.02wt%Nb2O5can reducethe porosity, increase the material density and the initial permeability(ui), anddecreases power loss, at the same time, μi~T and Pcv~T show the good temperaturestability. Finally, the effects of precalcining temperature on the microstructure andmagnetic properties of MnZn power ferrite were studied. When precalcined at900℃,MnZn power loss shows the best performance under sintering at1320℃condition. |
