Synthesize Of C-axis Oriented Hexaferrite And Study On Self-biased Gyomagnetic Devices

With the development of broadband high speed,small size and integration in the performance of electronic communication systems,higher requirements are placed on the miniaturization and high frequency of passive electronic components.On the one hand,passive electronic components,especially RF soft magnetic devices such as inductive components are required to achieve GHz frequency applications and meet the requirements of chip and passive integration,another aspect is the miniaturization of microwave magnetron devices such as circulators/isolators for T/R mould.The basis for achieving this goal is the study of low temperature sintering of hexagonal ferrite with high magnetocrystalline anisotropy and low microwave loss of uniaxial hexagonal ferrite materials.Hexagonal barium ferrite possess high magnetocrystalline anisotropy,high saturation magnetization,and can be manipulated by ion doping to determine the size and type of magnetocrystalline anisotropy?unaxial,planar?,which is a key material to meet the above requirements.The research work of this dissertation is based on the low temperature sintering,ion doping substitution and uniaxially oriented M-type and W-type hexagonal ferrite preparation.Firstly,in order to realize the miniaturization of the RF soft magnetic device and the compatibility with the LTCC process,a low-temperature sintering study of M-type barium ferrite was carried out.When the amount of BBSZ added is 4%,the comprehensive performance of the material is optimal.At this time,the density of the material is 4.62 g/cm³,the shrinkage is 13.8%,which is close to the requirement of 15%of the LTCC process,and the saturation magnetization is up to 24.5 emu/g.The high-energy ball milling process is used to refine the low-temperature sintering Ba?CoTi?_1.5Fe₉O₁₉ calcined powder.The magnetic properties are significantly improved compared with the conventional ball-milling materials.When the BBSZ content is 2%,the sample shrinkage rate reaches 14%,and the saturation magnetization reaches53emu/g.The coercive force is 113 Oe,and the cutoff frequency reaches 2.5 GHz.The key to miniaturization of microwave gyromagnetic devices,especially spacer/ring devices,is to use the magnetocrystalline anisotropy equivalent magnetic field of the material as a bias magnetic field to achieve self-biasing of the device,removing the external biasing magnet.Therefore,the preparation process,orientation degree and ion substitution modification of the spindle type hexagonal barium ferrite were carried out.Based on the preparation process of oriented M-type barium ferrite,oriented Zn₂W barium ferrite BaZn₂Fe₁₆O₂₇ was prepared.Through comparative experiments,it is found that the Zn₂W barium ferrite after sintering at 1020°C has the best performance.The squareness ratio of the hysteresis loop in the easy magnetization direction is 0.8,the ferromagnetic resonance line width is 996 Oe,the anisotropy field intensity is 7532 Oe,and saturation.The magnetization is 3115G,the coercive force is 1011Oe,and the dielectric constant is 14.Based on the fabrication of materials,the design,optimization and Simulation of self-biased triangular junction microstrip circulator are carried out by using HFSS software.According to the final simulation results,the 0.65 mm thickness substrate was used to fabricate and test the circulator.The test results show that the device does not achieve circular function in the design target frequency range of 26.5GHz.Therefore,the causes of device failure are analyzed in detail,and feasible improvement schemes are proposed for the next work.