Development And Magnetic Performance Improvement Of MnZn Ferrites With High Permeability In A Wide Frequency Range

With the rapid development of digital technology and information technology,electronic devices are developing towards miniaturization,high frequency,and integration.This requires MnZn ferrites prossessing high permeability,broadband and flat ?i-f curve,good temperature stability,and high Curie temperature,so that the material can work in wide frequency and temperature range.It's required to have a high impedance characteristics to improve the anti-electromagnetic interference.In this thesis,MnZn ferrite was prepared by the traditional oxide ceramic technology.Through the optimization of the main composition,additives,sintering process and annealing process,MnZn ferrite of high magnetic permeability with wide range frequency was developed.Research indicates:?1?By adjusting the main composition,when the main composition is ZnO: Fe2O3: MnO=22.8: 52.9: 24.3 mol%,the MnZn ferrite has a high permeability with good temperature stability.The secend peak temperature of permeability is around the normal temperature,Bs>420mT?25??,Tc>120?.?2?Through the study of additives,it was found that Nb₂O₅ could hinder grain growth and refine grain.And a small amount Nb₂O₅ could increase the uniformity of grain distribution,improve the magnetic properties and frequency characteristics.Bi2O3 could promote the crystal grain growth,the moderate amount of Bi2O3 is favorable to obtain a higher permeability by the improvement of the average particle size,but excess additions will make a large number of pores at grain inside to decrease the permeability.?3?The improvement of the sintering atmosphere is favorable for the growth of the grains.However high sintering atmosphere will reduce the Fe²⁺ content which can compensate the K1 of the MnZn ferrite,so that the initial permeability is reduced.The appropriate heat treatment conditions can change the Fe²⁺ content of sintered Mn Zn ferrite,which could change its electromagnetic.Through the adjustment of the main composition,additives,sintering and heat treatment atmosphere,we have successfully prepared the wide range frequency high-permeability Mn Zn ferrite material which exhibits excellent magnetic properties with ?i =10600,Bs=427mT,?i?200kHz?/ ?i?10kHz?= 98%,at 25?,Tc>120? and good impedance characteristics.