High Density B_smnzn Ferrite Material

In this dissertation,high density and high B_s MnZn ferrites were prepared by oxide ceramic technics.In order to achieve the target of high density(d),high permeability and high saturation magnetic induction(B_s),the influences of the composition,the calcining technics,the additives,the second ball-milling process and the sintering technics on MnZn ferrites were deeply investigated.As the results showed:with the increase of Fe₂O₃ from 51mo1%to 54mo1%,μ_i raises initially and then declines,and B_s raises,but density has little change.With the increase of ZnO from 15mol%to 23mol%,μ_i raises initially and then declines,B_s declines and density raises.With the raise of calcining temperature from 700℃to 900℃,the powder activity declines,μ_i,B_s and density raise initially and then decline.With the increase of holding time form 1h to 6h,μ_i and B_s raise initially and then decline,but density has little change.Quencher could promote the powder activity,then improve microstructure and magnetic properties,but hardly influence density.Small addition (＜0.03wt%) of MoO₃ could promote liquid-phase sintering and grain growth,then improve magnetic properties and density,but excessive addition(0.03～0.09wt%)could restrain grain growth,then decline the magnetic properties and density.Small addition (＜0.03wt%) of V₂O₅ or SnO₂ could promote liquid-phase sintering and grain growth, then improve magnetic properties,but excessive addition(0.03～0.09wt%) could restrain grain growth and decline magnetic properties.Besides,density has a little decline.The influence mechanism of P₂O₅ is different,according to different quantity.In the case of small addition(＜0.05wt%),element P segregates on grain boundary regions,could activate sintering process,then improve magnetic properties and density,in the case of excessive addition(0.05～0.15wt%),the volatilization of P₂O₅ could cause more pores, which restrain grain growth,and element P segregates on the walls of pore,then decline magnetic properties and density.K₂CO₃(0～0.09wt%) could thin grains,μ_i declines,B_s and density has little change.Under the condition which are ball:powders:dispersant=2: 1:1.5 and rotating speed is 196 r/min,steel ball and alcohol,which as milling medium, could promote the powders more uniform,then improve grain grow more uniform and magnetic properties.In the case of milling time is 2h,the activity of powder is optimal, then improve magnetic properties.Besides,density is hardly influenced by the second ball-milling process.With the raise of the sintering temperature from 1360℃to 1420℃, magnetic properties and density raise initially and then decline.In order to obtain high density,MnZn ferrites should sinter on the twice deoxidizing atmosphere,in order to obtain highμ_i,MnZn ferrites should sinter on the equilibrium atmosphere,Bs is hardly influenced by the atmosphere.Through large quantities of experiments about the composition,calcining technics, additives,second ball-milling process and sintering technics,the MnZn ferrites which density is 5.03g/cm³,initial permeability is 7600 and saturation magnetic induction is 513mT,was prepared.