Preparation And Magnetic Properties Of MnZn Ferrite And M-type Strontium Ferrite

Spinel manganese-zinc ferrite（Mn,Zn）Fe₂O₄ and M-type strontium ferrite SrFe₁₂O₁₉（SrM）are two kinds of the most common magnetic materials,and both of them are widely used because of their high cost performance,inexpensive raw materials and good chemical stability.Presently,the different preparation methods and ion substitution are usually used to enhance the magnetic properties of manganese-zinc ferrite and SrM ferrite.In this thesis,ion-substituted SrM ferrites and MnZn ferrites were prepared via a ceramic method and a hydrothermal method,respectively,and their phase formation,micromorphology and magnetic properties were systematically studied.Some useful results were obtained.For the preparation of SrM ferrites via a ceramic method,it was found that the best conditions for preparing single-phase SrM were that the Fe/Sr atomic ratio should be 9.5:1,and the sintering temperature was 1200°C.In addition,it was also found that the saturation magnetization and the coercivity of Ce-substituted SrM were enhanced slightly compared with the specimens without substitution,while they decreased with the increasing content of Ce substitution in a certain range,which shows that the Ce substitution can enhance the magnetic properties to a certain degree.It was found that when the sintering temperature is higher than 1300°C,the lattice plane of（008）in SrM ferrites exhibits an abnormal growth.Though the saturation magnetization did not change obviously,the coercivity decreased markedly due to the abnormal growth,which affects the comprehensive magnetic properties greatly.For the synthesis of（Mn,Zn）Fe₂O₄ ferrite,It is found that the Fe-short composition and the hydrothermal temperature play crucial roles in the synthesis of single-phase MnZn ferrites.The hydrothermal temperatures also affect the topography and the magnetic properties markedly,and the best conditions for forming the single-phase structure are that the hydrothermal temperature is 180°C,the hydrothermal time is 6 hours and the Fe-short content is 7%.The best magnetic properties of obtained MnZn ferrite are that saturation magnetization M_s is 45.5 emu/g and the coercivity H_c is 0.68 kA/m.