The Research Of Composite Doping On MnZn Ferrite

In the21st century, the electronic information technology develops rapidly. We have increasingly demand of electronic information equipment. In order to adapt to the green energy of the time’s demand, we have to develop low loss ferrites. And we have to prepare ferrites which have good temperature stability in order that power supply could get a low loss at room temperature or working temperature. The ferrites should get lower power loss in each temperature points. We can reduce the volume of switch power supply with high initial permeability of ferrites.This paper prepares MnZn ferrites with solid state methods. The main formula used in the paper is Fe2O3:MnO:ZnO=52.3:35.93:11.77(mol%). After ball milling, presintering, molding, sintering with oxygen partial pressure and other processes related, the MnZn magnetic rings are prepared successfully. The experiment sintering temperature is1350℃for4hours. During this period, oxygen partial pressure is adjusted at4%. At beginning of cooling process, cooling rate is slowed down for improving the performance of ferrite. The heating program is turned off until1050℃. The minimum of oxygen partial is103ppm.SEM is used for observing the rings microstructure of section. XRD is used for analysis of grain structure. The ferrite rings’density is measured by Archimedes drainage method. The inductances of ferrite rings are measured by digital bridge, and the initial permeability of MnZn ferrite is calculated. The power loss and saturation magnetic induction is measured by BH analyzer at point of temperature of25℃、60℃\80℃、and100℃.The paper focuses on the research on the influence of Ca2+、Si4+、Co2+、Sn4+Ti4+doping of MnZn ferrite. The impact of ZnO content and molding pressure on MnZn ferrite is also studied in this paper. Ti4+、Co2+doping before and after resintering is studied as well. CaCCO3and SiO2are added with the ratio of1:1. The optimal proportion is0.04wt%CaCO3and0.024wt%SiO2through observation of ferrite section microstructure. After the optimum of CaCO3and SiO2is determined, study of Co2+doped is expanded to the range from0.2mol%to0.5mol%. We get the conclusion. With the increasing of Co2O3, the second peak of μi～T and Pcv-T gradually move to the lower temperature. And the Pcv-T curve becomes flatter gradually. So Co2+has great contribution to the temperature stability of MnZn ferrite. Sn4+could affect the power loss of MnZn ferrite. The optimum of SnO2is considered to be0.2mol%according to the results of these contrast experiments. The grain grows even, and porosity gets reduced. The initial permeability at room temperature is2720. The lowest power loss is531kW/m3.This paper optimizes the content of ZnO in main formula after ion doping is confirmed. ZnO content is changed from11mol%to14mol%. And12mol%ZnO makes the MnZn ferrite get the best performance. With0.04wt%CaCO3,0.15wt%Co2O3,0.2wt%SnO2added, the initial permeability of MnZn ferrite at the room temperature gets2209, and power loss gets the lowest of509.2kW/m3, the saturation magnetic induction gets the highest of481mT.The paper concludes the best molding pressure is150Mpa. Doping of Ti4+before presintering reaches a better performance of MnZn ferrite than doping after presintering. The doping of Co2+before presintering is beneficial to wide temperature stability. And after presintering, it could reduce power loss and improve initial permeability at the room temperature.