The Application And Basic Research On Low Temperature Sintered Gyromagnetic Barium Ferrite And Circulator

As communication technology continues to advance towards 5G and 6G,microwave devices are trending towards higher frequencies,integration,miniaturization,and lower loss.This development direction has created new demands for electronic materials,particularly ferrite materials,which must not only meet low-temperature sintering requirements but also exhibit high-frequency and low-loss properties.As the preferred material for typical ferrite integrated devices in the microwave and millimeter-wave bands,M-type barium ferrite is subjected to several challenges,including reducing the sintering temperature,lowering the high-frequency ferromagnetic resonance line width,and optimizing its electromagnetic properties.These issues have become hotspots and key areas of concern in this field.With the high-frequency microstrip circulator preparation requirements as the driving force,this study conducts theoretical design and performance research on low temperature sintered M-type barium ferrite materials.It proposes the hexagonal structure barium ferrite ion substitution theory and develops a new type of LTCF barium ferrite material based on ion substitution and doping methods to improve electromagnetic performance.Based on this material,this study designs and develops a Ku-band microstrip circulator,verifying the feasibility of the material on the application.First,the effect of substitution with different trivalent metal ions of Ga³⁺and Al³⁺was investigated based on Ba Fe₁₂O₁₉.The pure-phase M-type barium ferrite was achieved by adding 3 wt.%of Bi₂O₃ at 920°C.The results indicate that as Ga³⁺ions enter the lattice to substitute Fe³⁺ions,4πM_s decreases from 3241.27 to 2571.18 Gauss,and the coercivity（H_c）increases from 4341.9 to 5258.2 Oe.Owing to the basic characteristics of M-type barium ferrite,the samples exhibit a large value of ferromagnetic resonance linewidth（ΔH）.The minimum value ofΔH（?4216.336 Oe）was obtained at 31 GHz.The results of Al³⁺substitution indicate that Al³⁺ions lead to a decrease in the lattice constant.With the increase in the content of Al³⁺ions,M_sdecreases from 56.707 to 35.206 emu/g,and H_c increases from 5719.06 to 7372.49 Oe.Besides,the permeability of the sample fluctuates in the range of 1.0–1.4 and resonates in the range of about 10-12 GHz and shows a decreasing tendency.Second,multi-ions of Bi³⁺,Co²⁺,and Ti⁴⁺were used to substitute M-type barium ferrite for fabricating Ba Bi_x（Co Ti）_1.2Fe_9.6-xO₁₉ ferrite,and the experimental result shows that low substitution of Bi³⁺ions promotes the formation of pure-phase M-type barium ferrite.However,the excess Bi³⁺ions lead to the formation of a second phase,which deteriorates the magnetic and dielectric properties.The permeability（μ′）of the Ba M sample reaches 22.60,M_s=52.639 emu/g,and the permittivity（ε′）=21.24 for x=0.45.Compared to the substitution with different trivalent metal ions,Ba Bi_x（Co Ti）_1.2Fe_9.6-_xO₁₉ ferrite shows a lower value ofΔH.With the increase of Bi³⁺ion substitution content,ΔH first decreases and then increases,and a minimum value of 1122.807 Oe is obtained at 9.56 GHz.Moreover,suitable sintering temperature promotes the synthesis of a single-phase sample and aids in optimization of the magnetic and dielectric properties of the sample.The value ofΔH first decreases and then increases with increasing sintering temperature,which reaches a minimum value of 926.536 Oe at 920°C.Thus,the main objective of reducing theΔH of M-type barium ferrite was realized.Then,the properties of M-type barium ferrite were further optimized by using the oxide sintering aid.The results illustrate that the single oxide V₂O₅ could optimize the properties to a certain extent at the sintering temperature of 1000°C.For x=3,M_s=53.084 emu/g andε′=18.96.Moreover,ΔH was also optimized based on the change of sample properties and it decreased to 924.812 Oe.The experimental results of the co-doping of Bi₂O₃-Nb₂O₅ show that the addition of Bi₂O₃ could reduce the sintering temperature and promote the solid phase reaction.Next,the appropriate amount of Nb₂O₅ could promote dense crystal growth,inhibit the generation and appearance of abnormal grains,and provide a uniform and dense microstructure.For x=0.50,the M_sof Ba M sample reached 51.293 emu/g,μ′=21.09,andε′=18.30.Besides,the magnetic loss（tanδ_μ）decreased to 0.07 and the dielectric loss tangent（tanδ_ε）decreased to a minimum value of 2.67×10^-3.More importantly,ΔH of the Ba M sample obtained a minimum value of 694.236 Oe in all experimental groups,which achieved further optimization of the performance of M-type barium ferrite.Finally,the corresponding microstrip circulator was simulated and prepared based on the Ba（Co Ti）_1.2Fe_9.6O₁₉ ferrite with 3.0 wt.%Bi₂O₃-0.50 wt.%co-doping.The results indicate that the return loss|S₁₁|of the circulator was above 10 d B in the frequency range of 14.33-16 GHz,where the maximum isolation|S₁₂|was 22.57 d B,and the insertion loss|S₂₁|was below 2.14 d B.The experiments and tests verify the feasibility of Ba M ferrite ceramic materials in microwave communication.