Research On MnZnNi Ferrite With High Saturation Flux Density

Soft magnetic ferrite is a kind of high-frequency soft magnetic material with wide application.With its excellent functions of electric energy conversion,signal transmission and electromagnetic compatibility,it is widely used in all kinds of high-frequency and high-power electrical and electronic equipment.With the development of industrial technology,in order to adapt to the development trend of miniaturization and high efficiency of power electronic equipment,higher performance requirements are put forward for soft magnetic ferrite.Compared with metal soft magnetic materials,the low saturation flux density of soft magnetic ferrite restricts its application in high current environment.Therefore,soft magnetic ferrite materials with high saturation flux density,high permeability and low loss have become one of the research and development hotspots.Based on the traditional Mn Zn soft magnetic ferrite,this paper introduces the Ni element to increase the Curie temperature of the material so as to improve the high-temperature saturation flux density,and improve the magnetic saturation characteristics of ferrite.Through the research on the main composition and additives,it is expected to develop a Mn Zn Ni quaternary system soft magnetic ferrite material with high saturation flux density,make it have excellent magnetic properties in a wide temperature range,and realize the miniaturization and high efficiency of magnetic components.Based on the Fe-rich Mn Zn ferrite,the magnetic properties were studied respectively by substituting Ni O for Fe₂O₃,Zn O and Mn O in the main formula of Mn Zn ferrite.The experimental results show that the comprehensive properties of ferrite are better when Ni O is used to replace Fe₂O₃ and the substitution amount is1mol%.When the Ni O content is fixed at 1mol%,the Fe₂O₃ content is optimized.It is found that when the main formula composition is Fe₂O₃=62.8mol%,Zn O=17mol%,Ni O=1mol%,Mn O=19.2mol%,the ferrite has the best comprehensive properties.At this time,the saturation flux density is 579m T（25℃）and 481m T（100℃）,and the initial permeability is 1210.The lowest power loss is 1015k W/m³ at 60℃.Three additives,In₂O₃,Co₂O₃ and Sb₂O₃,were selected for doping experiment and theoretical analysis respectively,and the influence mechanism and optimal dosage of additives were determined.In₂O₃ can be used as grain boundary additive.It is usually enriched at the grain boundary to inhibit grain growth and control grain size,but excessive addition will deteriorate the electromagnetic properties of ferrite.When the doping amount is 0.16wt%,ferrite has better properties.Co₂O₃ can optimize the loss temperature curve of the material and reduce its loss temperature coefficient.When the doping amount is 0.1wt%,the loss temperature coefficient is the lowest.At this time,the change of ferrite loss with temperature is the smallest in the temperature range of25-120℃.Sb₂O₃ has a low melting point,which can promote the formation of liquid phase sintering,make the grain grow rapidly,reduce the porosity and improve the material density.It is found that the Mn Zn Ni ferrite has higher saturation flux density and lower power loss when the doping amount of Sb₂O₃ is 0.16wt%.At this time,the saturation flux density is 603m T（25℃）and 493m T（100℃）,the power loss is829kw/m³（60℃）and 952kw/m³（100℃）,and the initial permeability is 1192.