Microstructure and magnetic properties of Sn-substituted MnZn ferrites

Sn-substituted MnZn ferrites were prepared by conventional oxide ceramic process. The influences of Sn substitution on microstructure and magnetic properties of MnZn ferrites were investigated. The results indicated that with increase of Sn substitute concentration, the diffraction peaks shifted slightly towards the lower angles and the lattice parameter (a) increased. And at room temperature, the bulk density (dm), initial permeability (μi), saturation magnetic induction (Bs) and electrical resistivity (ρ) of Sn-substituted MnZn ferrites all increased initially and then decreased with the further increase of Sn substitute concentration, while the power losses decreased first and then increased subsequently. Meanwhile, the temperature of secondary maximum peak of μi–T curve and the minimum losses moved to lower temperature while the Sn substitute concentration increased. When the content of Sn substitution was 0.3 mol%, at room temperature, the initial permeability, saturation magnetic induction, density and electrical resistivity reached their maxima, while the hysteresis loss (Ph), eddy current loss (Pe) and total losses (Pcv) achieved their minima. The Ph∼T and μi–T curves varied contrarily, and due to the contribution of extra eddy current loss (Pe,exc) that was proportional to Ph, the Pe–T curve did not agree with its classical expression. Finally, MnZn ferrite substituted with 0.3 mol% SnO2 shows the highest initial permeability (3894) and lowest losses (303 kW/m3) at room temperature.