Research On The Uniaxial Hexagonal Gyromagnetic Material And Its Performance

Microwave and millimeter wave(MMW)devices are important part of civil,commercial and military wireless and radar devices.Driven by monolithic microwave integrated circuit(MMIC)technology,the demand for next-generation microwave and millimeter wave(MMW)devices(such as circulators or isolators)toward miniaturization and planarization is increasing.Traditional millimeter wave devices are developed on the basis of spinel and garnet ferrite.Thus,they require an external permanent magnet to provide a bias magnetic field.However,this design will increase the longitudinal size.The gyromagnetic hexaferrite(BaM)magnetic material with large magnetocrystalline anisotropy field(Ha)and high remanence ratio(Mr/Ms)can establish a built-in bias magnetic field,which can partially or completely eliminate permanent magnets.It is beneficial to the device Miniaturization and planarization.The gyromagnetic hexaferrite(BaM)magnetic materials should be widely used in microwave and millimeter wave devices.This thesis focuses on the study of BaM ferrites that can be applied to self-biased devices,and explores the effect of the preparation process,the main formulation of ion doping and secondary additives on the performance of BaM.The experimental results are as follows:(1)The Ba(Zn Ti)_0.2Fe_11.6O₁₉ ferrites were prepared by solid-phase method.The pre-sintering temperature is 1260?to 1290?and the sintering temperature is 1090?to 1240.The exploratory experiment of the pre-sintering temperature shows that when the firing temperature is 1310?,the microscopic appearance of the sample is the best.When the calcining temperature is greater than 1300°C,the crystal grain size is within the single domain particle size range,and the residual magnetization is greater than 0.8.Considering the optimal calcining temperature is 1310°C.The influence of the sintering temperature was explored on the basis of the optimal pre-sintering temperature.The results show that the density and the remanence ratio increase with the increase of sintering temperature increases.When the pre-sintering temperature is 1310?and the sintering temperature is1190?,the ferrite which own the best microscopic morphology and the remanence ratio of 0.88 is prepared.(2)The effects of Zn²⁺-Ti⁴⁺substitute for Fe³⁺,Zn²⁺-Hf⁴⁺substitute for Fe³⁺,and La³⁺-Zn²⁺-Ti⁴⁺substitute for Ba²⁺and Fe³⁺on the microscopic morphology and electromagnetic properties of BaM ferrite were studied.The results show that Zn²⁺-Ti⁴⁺can effectively control the coercivity,the coercivity decreases with the increase of Zn²⁺-Ti⁴⁺ion;Zn²⁺-Hf⁴⁺ion substitution can effectively control the remanence ratio,When the Zn²⁺-Hf⁴⁺substitution amount is less than 0.04,the remanence ratio is 0.9;La³⁺-Zn²⁺-Ti⁴⁺ion substitution can effectively adjust the magnetocrystalline anisotropy field,La³⁺substitute for Fe³⁺will increase the magnetocrystalline anisotropy field.(3)The effect of CaCO₃,SiO₂ and H₃BO₃additives on the microstructure,magnetic properties were investigated through the method of orthogonal trials.The CaCO₃,SiO₂and H₃BO₃are selected as three factors.Among them,the ratio of CaCO₃ additive is 0.3wt%?1.2 wt%;The ratio of SiO₂ additives is:0.1 wt%?0.6 wt%,and ratio of H₃BO₃additives is:0.1 wt%?0.4 wt%.The effect of additives on the performance of ferrite for self-biasing was systematically studied.The experimental results show that different additives have different effects on different properties and the addition of additives cannot guarantee that the material can obtain high d,M_s,M_r,M_r/M_s and H_a at the same time.Fortunately,we can adjust the target performance by selecting appropriate additives.The details are as follows:In research scope,according to the actual experimental results,the maximum density is 5.1 g.cm^-3,and the corresponding additive content is:1.2 wt%CaCO₃,0.2 wt%SiO₂and 1%H₃BO₃.When add 0.6 wt%CaCO₃,0.2 wt%SiO₂ and 3wt%H₃BO₃,the maximum residual magnetization(92 emu/g)is obtained.When add 0.6 wt%CaCO₃,0.2wt%SiO₂ and 3 wt%H₃BO₃,the maximum residual magnetization(77 emu/g)is obtained.When add 0.3 wt%CaCO₃,0.4 wt%SiO₂ and 3 wt%H₃BO₃,the maximum remanence ratio(88%)is obtained.When add 0.6 wt%CaCO₃,0.4 wt%SiO₂ and 0.3 wt%H₃BO₃.the maximum magnetocrystalline anisotropy field(13647 Oe)is obtained.According to the range analysis table,in order to acquire the best density additives should add 1.2 wt%CaCO₃,0.4 wt%SiO₂ and 0.3 wt%H₃BO₃;to obtain the optimal saturation magnetization should add 0.6 wt%CaCO₃,0.4 wt%SiO₂ and 0.3 wt%H₃BO₃;in order to gain maximum residual saturation magnetization should add 0.6 wt%CaCO₃,0.4 wt%SiO₂ and 0.3 wt%H₃BO₃,to achieve the theoretical maximum remanence ratio should add 0.6 wt%CaCO₃,0.4 wt%SiO₂ and 0.3 wt%H₃BO₃;to obtain the maximum magnetocrystalline anisotropy field should add 0.3 wt%CaCO₃,0.6 wt%SiO₂ and 0.3 wt%H₃BO₃.