【作者】 贾浩；

【导师】 孙科；

【作者基本信息】 电子科技大学 ， 材料科学与工程， 2020， 硕士

【摘要】 传统X波段环行器工作时需给铁氧体基片外加磁钢（其体积和重量约占微波器件的80%以上）以提供偏置磁场,才能实现环行功能,这必将增加器件重量和体积,很难满足微波集成电路系统小型轻量化的需求。磁铅石型六角铁氧体材料具有高的矫顽力、高的剩磁比和高的各向异性场,可在铁氧体内部形成自建“内场”,为环行器工作提供自偏置场,完全摆脱外置磁钢束缚,实现准平面化特性,这将极大地减小环行器的重量、体积,实现器件小型化、轻量化和集成化的目的。因此,基于X波段准平面化环行器用M型六角铁氧体材料制备技术研究具有十分重要的战略意义。本论文以准平面化环行器基板材料的性能需求为基础,采用传统氧化物陶瓷法制备BaM六角铁氧体,并基于第一性原理计算了BaM六角铁氧体的离子占位,深入探究了BaM六角铁氧体的离子取代、制备工艺和添加剂与性能间的作用关系。首先,采用传统氧化物陶瓷法制备Sc取代BaM六角铁氧体,研究了Sc取代对BaM六角铁氧体性能的影响。研究结果表明:（1）Sc取代的BaM六角铁氧体物相均为纯相,表明Sc离子完全进入晶格,但Sc取代会抑制晶粒的生长,导致材料微结构变差;（2）通过第一性原理和麦克斯韦-玻尔兹曼分布联合计算了Sc在0-1500 K温度范围内占据各个晶位的理论概率,并结合Raman分析可知,Sc择优占据2a和12k晶位。（3）在研究的Sc取代范围内,Sc取代可显著降低BaM六角铁氧体的各向异性场H_a、饱和磁化强度4πM_s、剩磁比M_r/M_s和密度d,适量的Sc取代可以获得最低铁磁共振线宽ΔH,当Sc取代量为0.5时,材料具有最佳综合性能:4πM_s=3.65 kGs,M_r/M_s=0.84,d=5.11 g/cm³,H_c=528 Oe,H_a=13.9 kOe,ΔH=482Oe,f_r=43.0 GHz。（4）基于Néel亚铁磁性分子场理论,通过布里渊函数拟合计算得出Sc取代会减弱2b-4f₂、12k-4f₁、2a-4f₁、12k-4f₂和2b-12k晶位之间的分子场作用,使居里温度T_c减小,从而降低材料温度稳定性。然后,在以BaFe_11.5Sc_0.5O₁₉为主配方的基础上,研究了制备工艺（预烧温度和二次球磨时间）对BaM六角铁氧体性能的影响。研究结果表明:（1）适宜的预烧温度可促进晶粒致密化和均匀性生长,进而提高烧结样品的综合性能,当预烧温度为1250°C时,材料综合性能最佳;（2）适宜的二次球磨时间可改善BaM六角铁氧体的微结构和性能,过长时间的二次球磨反而使材料微结构和性能恶化,当二磨时间为18 h时,烧结样品综合性能最好:4πM_s=3.07 kGs,M_r/M_s=0.90,H_c=510Oe,H_a=13.2 kOe,ΔH=393 Oe,f_r=40.8 GHz。最后,研究了Bi₂O₃+CuO和Bi₂O₃+CuO+SiO₂组合掺杂BaM六角铁氧体的显微结构和性能。研究结果表明:（1）在Bi₂O₃+CuO组合掺杂中,晶界处形成的铋氧化铜混合相的熔点较低,可进一步促进晶粒致密化生长,从而提高烧结样品的密度;（2）在Bi₂O₃+CuO+SiO₂组合掺杂中,SiO₂大量富集于晶界处,抑制晶粒生长,从而细化晶粒提高矫顽力。当SiO₂掺杂量为0.6 wt%时,烧结样品的矫顽力（H_c=668 Oe）最高,且材料的铁磁共振线宽（ΔH=280 Oe）优于目前关于BaM六角铁氧体块材的文献报道。更多还原

【Abstract】 When traditional X-band circulators operate,it is required to provide the external permanent magnets（its volume and weight account for more than 80%of the microwave device）for ferrite substrates as indispensable biasing fields to achieve the circular function which will increase the weight and volume of the device,and it is difficult to meet the miniaturization and lightweight demand of the microwave integrated circuit system.Magnetite-type hexagonal ferrite materials have high coercive force,high remanence ratio,and high anisotropic field,which can form a self-built"internal field"inside the ferrite to provide self-biased field,completely get rid of the constraints of external magnetic steel,and achieve quasi-planarization characteristics,which will greatly reduce the weight and volume of the circulator,and achieve the purpose of device miniaturization,light weight and integration.Therefore,it is of great strategic significance to study the preparation technology of M-type hexagonal ferrite materials for X-band quasi-planarized circulators.This paper is based on the performance requirements of quasi-planarized circulator substrate materials,and uses traditional oxide ceramics to prepare BaM hexagonal ferrite.The ion occupancy of BaM hexagonal ferrite was calculated based on the first-principles,and the relationship between the ion substitution of BaM hexagonal ferrite,the preparation process,and the relationship between additives and properties were thoroughly explored.Firstly,the traditional oxide ceramics method was used to prepare Sc substituted BaM hexagonal ferrite,and the effect of Sc substitution on the properties of BaM hexagonal ferrite was studied.The results show that:（1）The phases of BaM hexagonal ferrite substituted by Sc are pure phases,indicating that Sc ions completely enter the crystal lattice,but Sc substitution inhibits the growth of crystal grains,resulting in deterioration of the microstructure of the material;（2）Through the first-principles and Maxwell-The Boltzmann distribution jointly calculates the theoretical probability that Sc occupies each crystal position in the temperature range of 0-1500 K,and combined with Raman analysis,we know that Sc preferentially occupies 2a and 12k crystal positions.（3）Within the range of Sc substitutions studied,Sc substitution can significantly reduce the anisotropy field H_a,saturation magnetization 4πM_s,residual magnetism ratio M_r/M_s,and density d of BaM hexagonal ferrite.The proper amount of Sc substitution can get the lowest ferromagnetic resonance linewidthΔH.When the amount of Sc substitution is 0.5,the material has the best synthesis performance:4πM_s=3.65 kGs,M_r/M_s=0.84,d=5.11 g/cm³,H_c=528 Oe,H_a=13.9 kOe,ΔH=482 Oe,f_r=43.0 GHz.（4）Based on Néel’s ferrimagnetic molecular field theory,calculations by Brillouin function fitting show that Sc substitution will weaken the molecular field interactions between 2b-4f₂、12k-4f₁、2a-4f₁、12k-4f₂and 2b-12k crystal positions,so that the Curie temperature T_c is reduced,thereby reducing the material temperature stability.Then,based on BaFe_11.5Sc_0.5O₁₉9 as the main formula,the influence of the preparation process（pre-calcination temperature and secondary ball milling time）on the properties of BaM hexagonal ferrite was studied.The results show that:（1）The appropriate pre-firing temperature can promote the densification and uniform growth of the crystal grains,thereby improving the comprehensive properties of the sintered sample.When the pre-firing temperature is 1250°C,the comprehensive properties of the material are the best;（2）The secondary ball milling time can improve the microstructure and properties of BaM hexagonal ferrite.If the secondary ball milling is too long,the microstructure and performance of the material will be deteriorated.When the secondary milling time is 18 h,the sintered samples have the best overall performance:4πM_s=3.07 kGs,M_r/M_s=0.90,H_c=510 Oe,H_a=13.2 kOe,ΔH=393 Oe,f_r=40.8 GHz.Finally,the microstructure and properties of the BaM hexagonal ferrite doped with Bi₂O₃+CuO and Bi₂O₃+CuO+SiO₂ were studied.The results show that:（1）In the combined doping of Bi₂O₃+CuO,the melting point of the mixed phase of bismuth copper oxide formed at the grain boundary is lower,which can further promote the growth of grain densification,thereby increasing the density of the sintered sample;（2）In the combined doping of Bi₂O₃+CuO+SiO₂,a large amount of SiO₂ is concentrated at the grain boundaries,which suppresses the growth of the grains,thereby refining the grains and increasing the coercive force.When the doped amount of SiO₂ is 0.6 wt%,the coercive force（H_c=668 Oe）of the sintered sample is the highest,and the ferromagnetic resonance line width（ΔH=280 Oe）of the material is better than the current literature report on BaM hexagonal ferrite bulk materials.更多还原