Study On Sintering Phase Transition And Electromagnetic Properties Modulation Of Cu/Ni Doped Ordered Sr₃YCo₄O_10.5+δ Syste

Sr3YCo4O10.5+δhas A-site ordered/oxygen vacancy ordered tetragonal superstructure and a high Curie temperature（T_c≈335 K）,which has potential applications in microwave absorbing materials,spintronic devices,solid oxide fuel cells,and other fields.In order to study the complex phase structure evolution of Sr3YCo4O10.5+δand the effect of Cu doping on the electrical transport properties and magnetic properties of the samples.A series of Cu-doped Sr3YCo4-x Cux O10.5+δ（x=0,0.2,0.4,0.6,0.8）polycrystalline samples were prepared by solid-state reaction method at 1100℃for 24 h in air.When x=0～0.4,the（103）and（215）crystal planes were observed by transmission electron diffraction.Combined with the Rietveld refinement results of X-ray diffraction data,it was confirmed that the ordered tetragonal Sr3YCo4-x Cux O10.5+δwas formed.When the phase is formed,the mass increases by about 0.8%and is accompanied by heat release at 1042℃.With the increase in copper content,the sintering quality of the sample is significantly improved,the porosity is reduced,and the density is increased.When x=0.6,a low melting point impurity phase appears.The solid solubility of Cu is between 0.4 and 0.6.In the solid solution range（x=0～0.4）,the hole carrier concentration increases,the resistivity decreases significantly,and the resistivity decreases by92～99%at room temperature.As the temperature increases（80～300 K）,the polycrystalline material has a semiconductor electrical transport behavior with a three-dimensional Mott variable-range hopping mechanism.The spin states of some Co³⁺ions decrease,and the spin entropy increases.In order to study the effect of Ni doping on the electrical transport properties and magnetic properties of the samples,Ni-doped Sr3YCo4-x Nix O10.5+δ（x=0,0.1,0.2,0.3,0.4,0.5）polycrystalline samples were prepared by solid-state reaction method at 1200℃/24 h+1200℃/24 h in air.When x=0～0.3,（103）and（215）crystal planes were observed.Combined with the Rietveld refinement results of X-ray diffraction data,it was confirmed that the sample was an ordered tetragonal phase.The results of TG-DSC show that Ni doping reduces the crystallization temperature and increases the melting point of the sample.When x=0.4,the impurity phase appears.Microscopic morphology observations showed that nickel doping had little effect on the crystal quality of the sample.In the pure phase range（x=0～0.3）,the hole carrier concentration increases and the resistivity decreases significantly.The resistivity decreases by 98.3～98.6%at room temperature.As the temperature increases（80～300 K）,the polycrystalline material has a semiconductor electrical transport behavior with a three-dimensional Mott variable-range hopping mechanism.In terms of magnetic properties,Hopkinson peaks were observed in all samples,and T_c≈324～332 K.With the increase of Ni content,the magnetization,and Tc of the samples decrease,which is due to the decrease of Co³⁺ions caused by Ni²⁺doping,which inhibits the magnetic ordered structure.Because Ni²⁺is in a stable high spin state,the magnetic ground state of the sample has a certain ferromagnetism,and Tc is maintained above 320 K.