Research On The Performance Of Uniaxial Hexagonal Ferrite

Electronic systems operating in the microwave/millimeter wave frequency band have been applied in-depth in the following fields:aerospace,satellite communications,electronic countermeasures,and mobile communications.In circuits and systems such as microwaves radio frequency front-end T/R components,the ferrite-based microwave material such as circulators,isolators/millimeter wave device has an indispensable role.As a kind of gyromagnetic ferrite material,uniaxial hexagonal ferrite material is used in the manufacture of gyromagnetic devices such as self-biased circulators and isolators due to its high saturation magnetization,coercive force and magnetic crystal anisotropic field,etc.Because of these great advantages,it is regard as a hot material.Therefore,in the high frequency,miniaturization and integration of microwave ferrite devices,the microwave performance of the uniaxial hexagonal ferrite material plays an important role.This dissertation first explores the preparation process of Zn₂W ferrite,mainly focusing on the influence of pre-sintering temperature on the ferrite powder;the dispersion effect of different dispersants in ferrite slurry;and how the sintering temperature influenced the sample about the magnetic properties and microscopic morphology.Among them,the pre-sintering temperature is 1250°C,the heating rate is2°C/min,and the heat preservation is 6 hours.The obtained ferrite powders are all Zn2W ferrite single phases with moderate hardness,which is beneficial to ball milling and dispersion.The experimental results of the dispersant show that sodium dodecylbenzene sulfonate,with a mass fraction of 6wt%has the best dispersion effect on the ferrite slurry,and after the dispersant,the remanence ratio parameter of Zn₂W ferrite is obviously improved.With the sintering temperature increasing,the coercive force of the Zn₂W ferrite sample decreases;and when the sintering temperature is1100℃,the Zn₂W ferrite sample has a maximum remanence ratio of 82.4%.Based on the results of process exploration,Zn₂W ferrite has studied for ion substitution.The substitution of Sc³⁺ions for Fe³⁺ions can significantly change the saturation magnetization（Ms）of the sample.As the amount of Sc³⁺substitution increases,Ms a pattern of first decreasing and then increasing.The substitution of Ca²⁺ions for Ba²⁺ions can effectively increase the coercive force Hc of the Zn₂W sample.When the substitution amount of Ca²⁺ions is x=0.5,the sample has a maximum coercive force of 1585Oe.The remanence ratio parameter of Ca²⁺ion doped Zn₂W ferrite samples is between 82%and 83%,and reaches the maximum value when Ca2+substitution amount x=0.3.Finally,the experimental work of Ca²⁺-Sc³⁺ions co-doping Zn2W ferrite has carried out.When the Sc³⁺doping amount was determined to be 0.1,the coercive force and magnetocrystalline anisotropy constant of the sample were adjusted by substitution of Ca²⁺ions.The results showed the sample has a maximum saturation magnetization（Ms）of 46.96emu/g（x=0.32）,and a maximum coercive force（Hc）of 1489Oe（x=0.38）.Finally,successfully prepared Zn2W ferrite has the characteristics of coercive force,magnetocrystalline anisotropy field,remanence ratio and high saturation magnetization,etc.Finally,ion substitution study of BaM ferrite.The Y³⁺substituted M-type barium ferrite has synthesized by traditional oxidation process.Turns out,after the doping x is greater than 0.4,the second phase Y₃Fe₅O₁₂ appeared in the synthesized BaM sample.As the Y³⁺ion content increases,the saturation magnetization（Ms）of BaM samples decreasing gradually.The change of coercivity（Hc）similar to that of magnetic crystal anisotropy constant（K₁）,when x=0.5,the value of coercivity changed from decreasing to increasing.