Synthesis And Properties Of FeSe-based Intercalated Superconductors

In recent years,in the fields of physical chemistry such as energy,electrochemistry,and strong magnetic fields,layered materials have become more and more important because of their special structure and performance.A variety of layered compounds have good applications in electrocatalysis,electrode materials of lithium ion battery,electrode materials of sodium ion battery,high temperature superconducting materials,and supercapacitors.Therefore,it has received extensive attention from various research groups around the world.Since these layered compounds can be doped,co-intercalated,or compounded with other materials to form various materials,and these materials are also well applied in many fields such as electrochemistry and energy.Among these many layered materials,tetragonal FeSe is one of them,and it has a good application especially in high temperature superconducting properties.On this basis,tetragonal FeSe derivatizes many new compounds by doping and intercalation,and can even form composite materials with other compounds.These new materials are even more excellent than the tetragonal FeSe.The tetragonal FeSe single-layer material can also be obtained by the chemical growth method,and its superconducting property is also significantly increased relative to the bulk tetragonal FeSe.The main content of this paper includes the following three parts:1.Introduce the research history and current status of iron-based superconducting materials;and the structure and energy band of different iron-based superconducting materials;introduce the process,reaction conditions,physical and chemical properties of intercalation reaction of iron-based superconducting materials,and the application in different fields of iron-based superconducting materials,which leads to the research significance of this paper.2.Several new iron-based superconductors Ax(C3H10N2)yFe2Se2(A=Li,Na,K,C3H10N2 refers to 1,3-propanediamine)was synthesized by a two-step method.In the first step,the alkali metal lithium,sodium and potassium are separately dissolved in the 1,3-propanediamine with the precursor tetragonal FeSe for ultrasonic reaction,so that the alkali metal lithium,sodium,potassium and tetragonal FeSe are sufficiently dispersed in 1,3-propanediamine;in the second step,the reaction liquid obtained in the first step is poured into a polytetrafluoroethylene reactor,and the reaction is carried out under appropriate temperature conditions,so that the alkali metal and the 1,3-propylenediamine enter the adjacent layers of tetragonal FeSe and the intercalation compound is formed.It was found by characterization that the newly synthesized intercialation compounds have a similar lamellar structure with the precursor tetragonal FeSe;the newly synthesized intercalation compounds Ax(C3HioN2)yFe2Se2(A=Li,Na,K)superconductivity were found by magnetic susceptibility test.The transition temperature are significantly increased relative to the precursor tetragonal FeSe.3.The newly synthesized intercalation compound Lix(C3H10N2)yFe2Se2 after annealing,we found that the structure of Li,(C3H10N2)yFe2Se2 remained and did not change under certain temperature conditions.Through the magnetic susceptibility test,we found that the superconducting transition temperature of Lix(C3H10N2)yFe2Se2 is slightly higher than that of the newly synthesized sample.This is more consistent with the resistance measurement transition temperature,which indicates that the synthesized Lix(C3H10N2)yFe2Se2 of the internal structure is more uniform after annealing.