Study On Electromagnetic Wave Absorption Properties Of Ru-Zn Co-Doped SrFe₁₂O₁₉ And Ca,Sr Doped La₂NiMnO₆

With the development of electronic information industry and the progress of communication technology,the problem of electromagnetic radiation is becoming more and more serious.The demand for microwave absorbing materials with low cost and high performance is becoming more and more urgent.Aiming at the problem of improving the microwave absorption performance of materials,this paper prepared microwave absorbing materials with magnetic loss dominated by the co-doping of Ru and Zn ions on Sr Fe₁₂O₁₉,and microwave absorbing materials with dielectric loss dominated by A-site replacement doping of La₂Ni Mn O₆ by Ca and Sr ions respectively.The main research contents are divided into the following three parts:Sr Fe_12-2xZn_xRu_xO₁₉ was prepared by solid state reaction method.The results of phase structure and microstructure confirmed that the doped elements successfully entered the hexagonal ferrite structure.The magnetic measurement results show that the introduction of non-magnetic Zn ions and Ru ions reduces the magnetic anisotropy and the magnetic resonance frequency of strontium hexagonal ferrite.The calculated reflection loss results show that for samples with doping concentration higher than 0.5,when the thickness range is 1.6-4 mm,the effective absorption bandwidth can range from less than 5 GHz to higher than 18 GHz,and the coverage width exceeds 13 GHz.When x=1.1 and the thickness is 2.9 mm,the minimum reflection loss is-51.6 d B.La_2-xCa_xNi Mn O₆ was prepared by solid state reaction.XRD results showed that Ca ions successfully entered the double perovskite structure of La₂Ni Mn O₆.The introduction of Ca ion increases the number of defects in the material and strengthens the dipole polarization,so the complex dielectric constant and dielectric loss of the material increase with the increase of Ca concentration.The reflection loss curve shows that the doping of Ca element increases the dielectric loss of the material.When the Ca concentration is 0.6 and 0.8,the minimum reflection loss exceeds-20 d B,and the effective absorption bandwidth can reach 14.7 GHz in the thickness range of 1.5-5 mm.It is confirmed that the introduction of Ca ion can enhance the attenuation factor of La₂Ni Mn O₆ and optimize the impedance matching,so as to improve the microwave absorption performance.La_2-xSr_xNi Mn O₆ was prepared by solid state reaction method.X-ray diffraction patterns showed that Sr element successfully entered the double perovskite lattice structure of La₂Ni Mn O₆,and the introduction of Sr element did not cause large lattice distortion.The dielectric of almost all samples often decreases with the increase of frequency,showing a typical dispersion phenomenon.The samples with doping concentrations of 0.2,0.6 and 0.8 show excellent microwave absorption performance.Among them,the sample with x=0.8 has the best microwave absorption performance,and its minimum reflection loss is-46.8 d B at the thickness of 4.4 mm;The effective absorption bandwidth is 15.38 GHz in the thickness range of 1.5-5.0 mm.In conclusion,in order to improve the magnetic loss of Sr Fe₁₂O₁₉ hexagonal ferrite and the dielectric loss of La₂Ni Mn O₆ double-layer perovskite material,a variety of element doped powder samples were prepared.The electromagnetic properties and microwave absorption properties of hexagonal ferrite and double perovskite materials were systematically studied.It paves the way for the design and preparation of electromagnetic wave absorbing materials.