Study On Low Temperature Sintering And Modification Of M-type Barium Ferrite Materials

In recent years,with the rapid development of various electronic products and electrical equipments,electromagnetic interference and electromagnetic pollution have had increasingly serious impact on people's daily life and production activities.Therefore,much more researchers have focused on electromagnetic wave absorbers and devices.At present,M-type barium ferrite(BaFe₁₂O₁₉)is considered as one of the promising candidate materials for microwave absorbption.However,after the emergence of low temperature co-fired ceramic?LTCC?technology,BaFe₁₂O₁₉materials are facing the problems of excessive sintering temperature and more diverse demand,which leads to its failure to meet the requirements of industrialization.Based on the above problems,the low temperature sintering of BaFe₁₂O₁₉ was studied by adding a sintering aid,aiming to reduce the sintering temperature to 961°C or below.BaFe₁₂O₁₉ was modified by ion substitution.The effects of different ions on the phase,morphology and properties of BaFe₁₂O₁₉ were studied,so as to obtain M-type barium ferrite material with single phase,regular morphology,excellent magnetic properties and absorbing properties under low temperature sintering conditions.The main research contents and conclusions are as follows:?1?BaFe₁₂O₁₉ was prepared by chemical coprecipitation method and molten salt method.The effects of precursor and molten salt ratio,calcination temperature and calcination time on the phase and morphology of BaFe₁₂O₁₉ were studied.The results show that BaFe₁₂O₁₉ with regular single phase and hexagonal flake shape and good particle homogeneity has been obtained under the conditions of 1:1 mass ratio of BaFe₁₂O₁₉ precursor to molten salt KCl,calcination temperature of 900°C and calcination time of 2 h.The low temperature sintering of BaFe₁₂O₁₉ has been successfully realized.The magnetic properties?Ms=63.06 emu/g,Hc=4772.43 Oe?of BaFe₁₂O₁₉ obtained under this synthetic condition are close to the theoretical values?Ms=72 emu/g,Hc=6900 Oe?,which proves the feasibility of this synthetic method again.At the same time,the imaginary part of the complex permittivity and the complex permeability are small,resulting in a large reflection loss value and poor absorbing performance.?2?The effect of different doping amounts on the phase,morphology,magnetic properties and microwave absorption properties of BaZr_xFe_?12-x?O₁₉ was investigated by substituting Fe³⁺with high valence cation Zr⁴⁺.The results show that the doping of Zr⁴⁺has no obvious effect on Ms,but has a strong regulation effect on Hc,which has a relatively wide range.When the doping amount increases from 0.0 to 1.2,Hc decreases from 4772.43 Oe to 797.34 Oe.In addition,the doping of Zr⁴⁺greatly improves the absorbing properties of the material,especially when the substitution of Zr⁴⁺to Fe³⁺reaches 1.2,the reflection loss value reaches-30.2 dB at the matching frequency of16.75 GHz,and the bandwidth is 2.46 GHz,which shows strong absorbing property.?3?The effect of different doping amounts on the phase,morphology,magnetic properties and microwave absorption properties of BaTi_xFe_?12-x?O₁₉ was investigated by substituting Fe³⁺with high valence cation Ti⁴⁺.The results show that the doping of Ti⁴⁺has little effect on Ms and Hc.However,the doping of Ti⁴⁺improves the absorbing property of the material greatly.When the substitution amount is 0.9,the minimum reflection loss reaches-22.0 dB.At the same time,double resonance absorption peaks appear in BaTi_xFe_?12-x?O₁₉ material,and the low frequency absorption peaks appear near6.00 GHz,which is of great significance for broadening the absorption band of material and realizing the low frequency absorption of material.?4?The effect of different doping amounts on the phase,morphology,magnetic properties and microwave absorbing properties of Ba?MnZr?_xFe_?12-2x?O₁₉ was investigated.The results show that Ba?MnZr?_xFe_?12-2x?O₁₉ samples have regular hexagonal flake morphology.For magnetic properties,the Ms value of bimetallic co-doping is larger than that of Zr ion alone doping,which may be the reason for the introduction of magnetic ions,but the regulation of Hc value by bimetallic co-doping is far less than that by Zr ion alone doping.For the microwave absorption performance,the microwave absorption performance of bimetallic co-doped materials has been significantly improved.When the doping content x is 0.9,the minimum reflection loss reaches-20.2 dB,and the matching frequency is 16.30 GHz.Compared with Zr ion doping alone,Mn ion has a greater contribution to the enhancement of microwave absorption performance at low Zr ion doping level,but has a negative effect on the enhancement of microwave absorption performance at high Zr ion doping level.