Study On BaO-Fe₂O₃-Nd₂O₃ Ternary Phase Diagram And The Properties Of Its Related Compounds

With the development of science and technology,electronic products have penetrated into all aspects of human life,but the electromagnetic waves radiated by them will cause great harm to human health.In order to reduce this electromagnetic pollution,it is urgent to study materials that can absorb electromagnetic waves to prevent electromagnetic pollution.This paper studies the wave-absorbing properties of related compounds based on the ternary phase diagram,mainly through the mutual substitution of alkaline-earth metals and rare-earth metals to study their effects on the crystal structure,magnetic properties and wave-absorbing properties.Variation in properties of composite materials.In this paper,the phase equilibrium relationship of Ba O-Fe₂O₃-Nd₂O₃system at1200℃was studied by high-temperature solid-phase sintering method,and the Ba O-Fe₂O₃-Nd₂O₃phase diagram system was analyzed to obtain 10 single-phase regions,12 two-phase regions and 10 single-phase regions.three-phase zone.There are three solid solution regions:Nd_1-xBa_xFe O₃（0≤x≤0.15）,Ba_1-xNd_xFe₁₂O₁₉（0≤x≤0.15）,and Nd Ba₂Fe₃O_8+δ.According to the phase relationship shown in the phase diagram,Nd_1-xBa_xFe O₃and Ba_1-xNd_xFe₁₂O₁₉in the solid solution region were selected as the research objects,and the samples were prepared by sol-gel method to study the influence of their crystal structure,magnetic properties and wave absorbing properties.Ba_1-xNd_xFe₁₂O₁₉（x=0,0.05,0.10,0.15）is doped at the A site of Nd element,and no impurity phase is generated.With the increase of Nd³⁺content,Ba M transforms from hexagonal to spherical,and the particle size gradually decreases,and presents a grid.Substituting small size Nd³⁺for large size Ba²⁺reduces the particle size and increases the Fe²⁺/Fe³⁺value of Fe ions.When x=0.10,there is the maximum saturation magnetization（57.8 emu/g）and coercivity（3906 Oe）,the dielectric constant（r）and permeability（r）fluctuations are also the most obvious,and the reflection loss is the largest（-34.4 d B）,the widest reflection bandwidth（4.69 GHz）,its application range can be selected according to different thicknesses,and it has a better application.For Nd_1-xBa_xFe O₃（x=0,0.05,0.10,0.15）,the introduction of Ba²⁺greatly changes the Fe-O bond length and Fe-O-Fe bond angle,but it still belongs to the Pbnm space group and does not produce the second phase.The entry of Ba²⁺breaks the electroneutrality and generates Fe²⁺and oxygen vacancies.With the increase of Ba²⁺,the Fe-O-Fe bond angle along the B axis increases,the spin direction of Fe ions is close to parallel,the net magnetic moment decreases,and the superexchange effect of Fe-O-Fe weakens.The entry of Ba element distorts the lattice,increases the space charge captured at the grain boundary,and produces relaxation polarization,thereby increasing the dielectric constant,and the microwave absorption performance moves to the low frequency direction,and the bandwidth increases.The maximum reflection loss of Nd_0.90Ba_0.10Fe O₃is-17.2 d B with a bandwidth of 3.38 GHz;the maximum reflection loss of Nd_0.85Ba_0.15Fe O₃is-36.4 d B with a bandwidth of 2.97 GHz.Since Ba M has high resistance and high magnetocrystalline anisotropy,it can provide magnetic loss for the material,while RFe O₃has excellent dielectric loss,so it is explored whether the composite material combined with the two has better absorbing performance.The composites of Sm Fe O₃and Ba Fe₁₂O₁₉were successfully prepared by sol-gel method.The composite of Sm Fe O₃and Ba Fe₁₂O₁₉did not produce impurity phase,and the Sm Fe O₃in the composite material was uniformly attached to the surface of Ba Fe₁₂O₁₉,which provided the basis for the generation of interface polarization and dipole polarization and multiple reflection losses.Through magnetic analysis,it is found that Sm Fe O₃and Ba Fe₁₂O₁₉have good exchange coupling.Ba M/10%Sm Fe O₃has the largest magnetic energy product.The addition of Sm Fe O₃increases the resonance peaks of the magnetic permeability and dielectric constant of the composite,improves its microwave absorption performance,and its absorption frequency also shifts to low frequency.Ba M/15%Sm Fe O₃has a maximum return loss of-48.5 d B at 13.7 GHz and a maximum bandwidth of 3.4 GHz.