Study On Phase Relationship And Absorption Properties Of The Pr₂O₃-BaO-Fe₂O₃ System

With the rapid development of modern science and technology and the electronic information industry,all kinds of high-frequency and digital electronic equipment,wireless communication equipment and other applications were becoming more popular in our daily lives.These devices also emitted a lot of electromagnetic pollution（EMI）while satisfying people’s life.These pollution not only interfered with the normal operation of our wireless communication equipment and electronic equipment,but also caused irreversible impact on people’s life.Therefore,in order to eliminate electromagnetic radiation,absorbing materials become the focus of our attention.In this paper,high temperature solid phase sintering method was used to prepare experimental samples,and the phase relationship of isothermal section of the Pr₂O₃-BaO-Fe₂O₃ system at 1300 ^oC was established by electron probe and X-ray diffraction technology.The missing Pr₂O₃-Fe₂O₃ binary phase diagram was filled in.Based on the reference phase diagram,Pr Fe O₃ compounds doped with alkaline earth metals Ba,Sr,and Ca elements were prepared by the sol-gel method.The crystal structure,microstructure,magnetic properties and wave absorption properties of Pr_1-XM_XFe O₃ compounds were described in detail.The phase relationship of isothermal section of the Pr₂O₃-BaO-Fe₂O₃ system at 1300^oC was determined,and 8 two-phase and 8 three-phase regions were found.Only one ternary compound Ba₆Fe₄Pr₂O₁₅ was found in the ternary phase diagram.It is found that Pr Fe O₃ and Ba Fe O₃ have partial solid solubility.The maximum solid solubility of Pr in Ba Fe O₃ is about 60 at%,the maximum solid solubility of Ba in Pr Fe O₃ is about 20 at%,and it has Pr Fe O₃ and Ba Fe O₃ two-phase region when Pr Fe O₃ doped with 20-40 at%Ba.At the boundary of ternary phase diagram,there are many solid solution phenomena of compounds.The phase composition of Pr₂O₃-Fe₂O₃ binary phase diagram was determined,and the samples were analyzed by DSC at the Fe-rich end and Pr-rich end,so as to construct the Pr₂O₃-Fe₂O₃ binary phase diagram above 1100 ^oC.Only one compound Pr Fe O₃ was found in the binary phase diagram.When Pr Fe O₃ was prepared by solid phase method and sol-gel method,it was found that the magnetic properties changed from antiferromagnetism to ferromagnetism after annealing treatment.After the experimental analysis,no phase and structure changes were found,but the bond length and bond angle changed obviously.The contraction of Fe³⁺-Oc^2-and the elongation of Fe³⁺-Od^2-led to the change of Fe³⁺-Od^2--Fe³⁺.Due to the superexchange coupling of Fe³⁺-Od^2--Fe³⁺,the spin was tilted at a small angle.A small net magnetic moment was generated after heat treatment,which was the main reason for the change of magnetic properties of Pr Fe O₃.At the same time,the preparation method also affected microwave absorption property of the material.As the rare earth ferrite of perovskite structure had good electromagnetic loss,and it was found that alkaline earth metal doped in the compound played an excellent electrical conductivity.Combined with the phase diagram,it was found that Ba ion has a large solid solubility in Pr Fe O₃.In order to improve the microwave absorbing performance of Pr Fe O₃material,Pr_1-XBa _XFe O₃（X=0,0.05,0.1,0.15,0.2）materials were prepared by sol-gel method.The microstructure of Pr_1-XBa _XFe O₃ material became more compact and porous with the increase of doping amount,which provided favorable conditions for the improvement of microwave absorbing material.When the doping amount is 20 at%,Pr_1-XBa _XFe O₃ showed excellent microwave absorption performance,the minimum reflection loss can reached-32.5239 d B,and the effective bandwidth was 4.32 GHz.In order to study the relative influence of Pr Fe O₃ doped with alkali earth metal,Pr_1-XSr _XFe O₃（X=0,0.05,0.1,0.15,0.2）materials were prepared by sol-gel method.All samples were confirmed to correspond to the diffraction peaks of Pr Fe O₃ samples by X-ray diffraction technique and refinement software.It can be observed from scanning electron microscope that the particles gradually become smaller with the increase of doping amount,which was directly related to lattice distortion in the doping process.When 10 at%Sr²⁺was doped,the minimum reflection loss（RL）of Pr_0.9Sr_0.1Fe O₃ sample at 12.4 GHz was-43.978 d B,and the effective bandwidth（EAB,RL≤-10 d B）was 4.4 GHz.Pr_1-XCa _XFe O₃（X=0,0.05,0.1,0.15,0.2）orthogonal perovskite ferrite materials have been systematically studied.As the particles of doped Ca ions samples gradually became smaller,the specific surface area became larger.This will be beneficial to improve the absorption performance of the sample.With the increase of Ca ion doping,the saturation magnetization of the sample also increases,which was mainly due to the net magnetic moment of the sample caused by the doped Ca ion.When the simulated thickness was 2.4mm,the optimal reflection loss of Pr_0.85Ca_0.15Fe O₃ sample reached-42.8462 d B at 11.44GHz,and the effective bandwidth reached 3.0462 GHz.