Study On Gd₂O₃-Fe₂O₃-Bi₂O₃ Phase Relationship And Its Compound Structure And Properties

In this paper,the ternary system of Gd₂O₃-Fe₂O₃-Bi₂O₃ and related compounds are used as the research object by the solid phase method to synthesize the experimental sample of the ternary system at 973 K to determine the phase equilibrium relationship and crystal structure.Based on the phase diagram,the samples were prepared by the sol-gel method.The effects of the addition of Gd element on the phase structure,microstructure,element valence,magnetic properties,and microwave absorption properties of BiFeO₃ also with the AB position regulates Gd Fe O3 compounds were studied.The phase equilibrium relationship of the Gd₂O₃-Fe₂O₃-Bi₂O₃ ternary system at 973 K was measured by X-ray diffraction.There are 11 single-phase regions,22 two-phase regions,and 10 three-phase regions in the ternary system.However,no new ternary compounds were found.The Gd element can be solid dissolved into the lattice of the BiFeO₃ compound,and the rhomboid structure(R3c)is formed when the content of Gd x?0.1.When the content of Gd was0.15?x?0.2,it changed into an oblique cubic structure(Pm21a).When the Gd content is0.25?x?1,Bi_1-xGd_xFe O₃ is an orthogonal structure(Pbnm).In Gd₂O₃-Bi₂O₃ exist in the binary system Bi_0.775Gd_0.225O_1.5-type solid solution phase,and its structure for R-3m space structure type,includingqsolid solution(Bi₂O₃)_1-x(Gd₂O₃)_x the scope of its solid solubility for x(0.05?x?0.071);gsolid solution of(Bi₂O₃)_1-y(Gd₂O₃)_y the solid solubility scope for y(0.22?y?0.35).Bi_1-xGd_xFe O₃(x=0.0,0.05,0.1,0.15)samples were successfully prepared by sol-gel method at 1073K.X-ray diffraction analysis showed that when x=0.00,the sample had a rhombohedral perovskite structure and belonged to the R3c space group.When 0.05<x<0.15,there is a two-phase structure.When x=0.15,its spatial structure is transformed into an oblique cubic structure.Small size Gd³⁺ion can effectively inhibit grain growth by replacing large size Bi³⁺ion at the position of A.Meanwhile,the contents of Fe³⁺and oxygen vacancy in Bi_1-xGd_xFe O₃(x=0.0,0.05,0.1,0.15)compounds gradually decrease with the increase of the content of Gd element replacing Bi element.When the simulated thickness is 2 mm and the content of Gd x=0.05,BiFeO₃ has the best microwave absorption performance of-37.3 d B at the frequency of 14.8 GHz,and its effective band width(R<-10 d B)reaches 4.3 GHz,showing a relatively excellent band width effect.The small size of the Ni³⁺ion(0.60(?))successfully entered the crystal structure and replaced the large radius of Fe³⁺ion(0.645(?)),which could effectively inhibit the growth of grain.Meanwhile,the contents of Fe³⁺and oxygen vacancy in Gd Fe_1-xNi_xO₃(x=0.0,0.05,0.1,0.15)decreased gradually with the increase of the substitution of Ni element for Fe.The substitution of Ni element for Fe can significantly improve the magnetic properties of Gd Fe O₃,which with the doping of Ni element and the reduction of bond angle will lead to a certain degree of change in the bond length at the octahedral position.The doping of Ni can effectively improve the wave absorption performance of Gd Fe O₃.When the simulated thickness is 2 mm and the content of Ni x=0.10,the best microwave absorption performance is-36 d B at the frequency of 6.2 GHz,and its effective bandwidth(R<-10 d B)reaches 2.3 GHz,showing a relatively excellent band width effect.Gd_1-xEr_xFe O₃(x=0.0,0.05,0.1,0.15)samples were successfully prepared by sol-gel method.X-ray diffraction analysis showed that the crystal structure did not change after doping,and the samples were all Pbnm space groups.Small size Er³⁺ion(0.89(?))has replaced large size Gd³⁺ion(0.938(?)),which can effectively inhibit grain growth.The substitution of Er element for Gd can significantly improve the magnetic properties of Gd Fe O₃,which,together with Er element doping and the hybridization of Fe 3d and O 2p orbital,leads to the enhancement of magnetic intensity.The doping of rare earth Er can effectively improve the wave absorption performance of Gd Fe O₃.When the simulated thickness is 2 mm and the content of Er is x=0.05,the best microwave absorption performance is-40.95 d B at the frequency of 14.8 GHz,and its effective bandwidth(R<-10 d B)reaches 3.6 GHz,showing a relatively excellent bandwidth effect.