Effect Of Dopants On Sintering Properties Of Manganese Zinc Ferrite

MnZn ferrites as one of the most important soft magnetic materials are widely used in electronics due to their high permeability,high saturated magnetization,low coercivity and low power losses.Miniaturization and increase in frequency of use for the electronic devices make high demands on the MnZn ferrites.In this study,the nano MnZn ferrite powders prepared by chemical co-precipitation and boiling refluxing process were used as raw materials.Effect of chemical compositions,sintering process and dopants on magnetic properties of the sintered MnZn ferrite was studied by means of XRD analysis,VSM and LCR technique and so on..Our results show that:1.The density,initial permeability,and saturation magnetization of the Mn_1-x-x Zn_x Fe₂O₄sintered at 1250?initially increased and then decreased with an increase in the Zn²⁺content,and the sample with x=0.3 presented the maximum value??=5.01 g/cm³,?_i=1100,Ms=87.8 emu/g?.Its power loss was 814 KW/m³ at the condition of Bs=20 mT,T=80?and f=100 KHz.2.Increases in sintering temperature resulted in that the density,initial permeability and saturation magnetization varied in a parabolic form for the Mn_0.7Zn_0.3Fe₂O₄ sample.The sample sintered at 1230?showed the maximum??=5.01 g/cm³,?_i=1150,Ms=119.2emu/g,?,its power loss was 615 KW/m³ under the condition of Bs=20 mT,T=80?and f=100 KHz.In comparison with those of the samples sintered at 1250?,Ms increased about 36%and P_cv decreased nearly 24%when keeping almost same density and initial permeability.3.Introduction of B₂O₃ in the MnZn ferrite led to a parabolic variation for its density,initial permeability and saturation magnetization.The sample with B₂O₃ content of 0.15 wt.%exhibited the maximum properties??=5.04 g/cm³,?_i=905,Ms=99.1 emu/g?.The?_i and Ms reduced approximately 21%and 17%,respectively,than those of the undoped one at slightly increase for density.Simultaneouely,its Curie point T_c?118??and cut-off frequency f_r?2.1 MHz?reduced about 9%and 34%in comparison to the undoped one.Its power losses was 180 KW/m³ at a condition of Bs=20 mT,T=80?,f=100 KHz,which were decreased about 71%and 36%than that of the undoped sample.4.Similarly,addition of TiO₂ during the moulding of the nano MnZn ferrite resulted in an apparent variation in its density,initial permeability and saturation magnetization.The sample with TiO₂ content of 1.2 wt.%presented optimum properties.Its initial permeability and saturation magnetization was about 870 and 92.1 emu/g,respectively.Those values decreased about 4%and 7%,respectively,than those of the B₂O₃-doped one under almost same density.Its Curie point T_c?148??and cut-off frequency f_r?3.6 MHz?were increased about 25%and 71%,respectively,than the sample with B₂O₃ content of 0.15 wt.%.Its power losses was 164 KW/m³ at a condition of Bs=20 mT,T=80?and f=100 KHz,this value was about 9%lower than the the sample with B₂O₃ content of 0.15 wt.%.5.When the MnZn ferrite was doped with both B₂O₃ and TiO₂,its properties like density initial permeability and saturation magnetization also showed a parabolic change.The sample with B₂O₃ content of 0.2 wt.%and TiO₂ of 1.2 wt.%presented,the maximum initial permeability of 964 and saturation magnetization of Ms=105.1 emu/g,together with the density of?=5.01 g/cm³.Its Curie point T_c?135??was increased about 14%than that with B₂O₃ content of 0.15 wt.%,and about 9%lower than that with TiO₂ content with 1.2wt.%.The cut-off frequency f_r?2.1 MHz?was the same as that with B₂O₃ content of 0.15wt.%,but was reduced 42%than that with TiO₂ content of 1.2 wt.%.Moreover,its power losses was 130 KW/m³ at the condition of Bs=20 mT,T=80?and f=100 KHz.This value decreased about 28%and 21%,respectively,compared with the B₂O₃ ciontent of 0.15 wt.%and the TiO₂ of 1.2 wt.%.6.Doping of B₂O₃ and TiO₂ was favorable to decrease the power losses in the sintered MnZn ferrites with nano powder as starting materials.