Research On The Properties Control Of M-type Hexaferrite Doped With Rare Earth Ions

With the rapid development of 5G mobile communication,in order to improve data transmission rate and avoid crowding in the low-frequency microwave frequency band,the research and working spectrum of mobile communication have jumped to the millimeter wave frequency band,posing higher requirements for the miniaturization and integration of devices.As an important part of the T/R module of the microwave RF front-end system,the circulator restricts the development of the miniaturization of the circulator because of the need to add permanent magnets to the traditional circulator to provide a bias magnetic field.M-type hexagonal gyromagnetic ferrite material has high Magnetocrystalline anisotropy,which can form a large"internal field"inside the ferrite,thus making the magnetic moment ferromagnetic resonance with microwave/millimeter wave without external stable magnetic field or when the stable magnetic field is very small,so as to realize the self bias of circulator.The purpose of thesis is to optimize the magnetic properties of M-type hexaferrite for self biased circulator by means of rare earth ion substitution and process optimization.Firstly,the solid-state sintering process was used to study the substitution of M-type barium ferrite with La-Ni,La-Co,and La-Co-Zn ions.The results show that La-Ni substitution can reduce the saturation magnetization and coercivity of the material.The lowest saturation magnetization is 62.924 emu/g,and the lowest coercivity is 1943.331Oe.La-Co ion substitution can greatly improve the saturation magnetization of ferrite materials,the maximum saturation magnetization is 86.606emu/g,and can effectively improve the Magnetocrystalline anisotropy and coercivity of Ba M which is helpful to expand the application frequency of M-type barium ferrite.La-Co-Zn ion substitution can effectively increase the remanence ratio and bulk density,and reduce porosity.For the formula with La-Co substitution amount of 0.325,Zn²⁺substitution can effectively control the magnetocrystalline anisotropy field.Between 11023.46-13921.42Oe.The maximum remanence ratio of the finally obtained sample is 0.846,and the maximum bulk density is 4.722g/cm³.Two groups of formulations with Zn²⁺doping amount of 0.11 in the ion substitution experiment were selected to study the sintering temperature and dispersant,and the results showed that an increase in sintering temperature helps to improve the densification degree of the sample,while also improving the residual magnetic ratio of the material.However,when the sintering temperature increases to 1300℃,it will lead to excessive grain size and a sharp decrease in coercive force.Taking into account the magnetic properties,the optimal sintering temperature for this formula system has been determined to be 1250℃.On the basis of determining the sintering temperature,two dispersants,sodium dodecylbenzenesulfonate and calcium gluconate,were added to the selected formula during the secondary ball milling process.The addition of sodium dodecylbenzenesulfonate can effectively increase the density of the sample,reaching a maximum density of 5.012g/cm³,but it will reduce the coercivity and remanence ratio of the material.When the addition amount reaches 6wt%,the remanence ratio sharply deteriorates and decreases to 0.68.The addition of calcium gluconate x≥4.5wt%will result in a sharp decrease in the bulk density of the sample,but can slightly increase the Magnetocrystalline anisotropy field of the material.