Magnetic properties and microstructures of SnO_2 doped Mn-Zn ferrites

摘要

The effects of additive SnO_2 (0. 4wt. %), with and without SiO_2 (0. 02wt. %) and/or CaO (0.04wt. % ), on the microstructure and magnetic properties of Mn-Zn ferrites were reported. The results reveal that SnO_2 on its own increases the initial permeability (μ_i) slightly, but SnO_2 with SiO_2 and/or CaO decreases the values of μ_i. However, ferrites with SnO_2 additions have reduced power losses. The separate contributions of hysteresis loss and eddy current loss to the total power loss show that SnO_2 (with or without SiO_2 and/or CaO) doping increases the hysteresis loss slightly, but SnO_2 doping alone reduces the eddy current loss significantly ( ～ 14%) . The additions of SiO_2 or CaO further decrease the eddy current loss, and by interaction of SnO_2-CaO-SiO_2, the eddy current loss is reduced by more than 20% . These magnetic and microstructural effects were discussed in terms of the additive-impurity interaction, the existence of grain boundary phases, and the effective bulk and grain boundary resistivities of the ferrites.