Preparation And Absorbing Properties Of Doped Barium Ferrite

In recent years,with the wide application of wireless communication technology and high-frequency electronic devices in modern life,The problem of radio electromagnetic wave pollution and interference were becoming more and more serious.In order to solve electromagnetic wave pollution and other problems,electromagnetic wave absorbing materials have received widespread attention especially in the GHz band.M-type barium ferrite(BaFe₁₂O₁₉)had a typical microwave absorbing material with high magnetocrystalline anisotropy,large electrical resistivity and high magnetic permeability,BaFe₁₂O₁₉9 became one of the choices for absorbing materials in the GHz band.However,the BaFe₁₂O₁₉9 was a hard magnetic material with a series of problems.The BaFe₁₂O₁₉9 absorbing material had a narrow absorbing band,the material thickness was thick at low frequencies.In order to reduced the thickness of the absorbing material.According to the formula t=nc/?28?4fme we have found that the thickness of the absorbing material was not only related to the magnetic permeability of the material itself,but also to the dielectric constant of the material itself.This paper mainly studied the effect of Mn-Co-Zr three-element doping on the magnetic properties of BaFe₁₂O₁₉.The magnetic properties,dielectric properties and absorbing properties of ZrO₂ doped BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 and ZrO₂doped BaFe₁₂O₁₉9 were investigated.The magnetic properties,dielectric properties and absorbing properties of CNTs doped BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 and CNTs doped BaFe₁₂O₁₉9 were investigated.First of all,in order to achieve the soft magnetization of BaFe₁₂O₁₉,Preparation of Mn-Co-Zr doped BaFe₁₂O₁₉(BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉)and BaFe₁₂O₁₉9 by solid phase method.It was found by SEM test that a sheet-like hexagonal structure appeared in both materials prepared and particle size distribution between 300 nm and1.8?m.The VSM results of BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 indicate a significant decrease in coercivity.Coercivity was as low as 50.4 Oe,Material changed from permanent magnet to soft magnetic and the saturation magnetization increased as the sintering temperature increases.The VNA test was performed on the sample,when the sintering temperature was 1250?,the maximum reflection loss peak of BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 appeared at a frequency of 2.0 mm at 14.3 GHz,and the maximum reflection loss value was-57.6 dB.The effective absorbing bandwidth below-10 dB was 2.5 GHz.As the thickness of the material increases,its maximum reflection loss peak shifted toward the low frequency.Secondly,in order to reduced the thickness of the absorbing material.BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 was doped with ZrO₂ and BaFe₁₂O₁₉9 was doped with ZrO₂.In order to increased the dielectric constant of the material,ZrO₂ was doped with the experimental sample of the first part at a ratio of 5%to 20%,and was prepared into a ceramic piece of a fixed thickness.The particle size distribution inside the material was found to be between 750 nm and 1.3?m.When the doping amount of ZrO₂ in the absorbing material was gradually increased,the dielectric constant was gradually increased.Using MATLAB calculated absorbing performance.When the sintering temperature was 1250?,the maximum reflection loss peak of the material appeared at a frequency of 6.98 GHz.The maximum reflection loss value was-38.14 dB.The effective absorbing bandwidth below-10 dB was 2 GHz.Since the doping of ZrO₂maked the dielectric constant of the material small,it had little effect on reducing the thickness of the absorbing material.So we turned our attention to the composite of CNTs and barium ferrite.Finally,in order to further reduced the thickness of the material in useing and increased its dielectric constant,we used CNTs to recombine in proportion with BaFe₁₂O₁₉9 or BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉.The material was tested by SEM,and the internal grain size increased with the increase of sintering temperature,and the grain size was distributed between 1.21⁷.33?m.The results of VNA showed that the content of CNTs increased the dielectric constant of the material significantly.When the sintering temperature was 1250?,BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 and 5%CNTs composites had a dielectric constant distribution of 19.82⁹6.24.When the sintering temperature was 1250?,BaFe₁₂O₁₉9 was combined with 3%CNTs,the maximum reflection loss peak appeared at the frequency of 9.43 GHz,and the maximum reflection loss value was-45.97 dB.When BaFe_9.6Mn_0.6Co_0.6Zr_1.2O₁₉9 was combined with 3%CNTs,the maximum reflection loss peak appeared at a frequency of 8.55GHz and the reflection loss value was-15.02 dB when the thickness was 2.0 mm.Compared with the first part of the experiment,the reflection loss peak shifted to the low frequency,the required thickness decreases at the same frequency.We found that the reflection loss peak of the material decreased with the increase of the CNTs content.When a certain value was reached,the absorbing properties of the material decreased significantly.In this paper,Mn-Co-Zr doped BaFe₁₂O₁₉9 was successfully prepared by solid phase method.High dielectric constan ZrO₂ or higher dielectric constant CNTs were combined with BaFe₁₂O₁₉,and the sample test results showed that the required thickness of the absorbing material was thin at the same frequency.