Infinite Layer?IL? Of Ca_1-xSr_xCuO₂:Single Crystal Growth And Structure Characterization

Superconductivity has attracted wide attention and interest since its discovery.Superconductivity has become a hot project for scientists to study its peculiar physical properties or the promising prospects in application.Superconductivity means that when the temperature drops below a threshold temperature,the superconductor resistance becomes zero suddenly,and of perfect diamagnetism at the same time.In the field of superconductor,people want to solve two problems,one is to find room temperature superconductors,and the other is to solve the problem of superconducting mechanism.Since the discovery of cuprate superconductors,cuprate superconductors have been the hot material for physicists to study the superconducting mechanism.The copper-oxygen superconductor is a layered perovskite structure mainly composed of a copper oxide surface and a carrier reservoir layer.Cuprate superconductors are usually naturally cleavage along the carrier reservoir layer,while the copper oxide surface is considered to be the conductive layer of the cuprate superconductor.Superconductivity usually occurs in the copper oxide surface.When we detect the nature of the intrinsic copper oxide surface,we disturb the single crystal by the carrier reservoir layer.Therefore,it is very meaningful to grow the crystal in which the cleavage plane is along the copper oxide surface and the surface is separated only by the copper oxide surface,and the crystal of the copper oxide surface can be directly observed.The main research content of this paper is the single crystal growth of infinite layer Ca_1-xSr_xCuO₂.This paper first introduces the discovery history and properties of superconductors,then introduces the discovery process of copper-oxygen superconductors,the structure and physical properties of cuprate high-temperature superconductors,and reviews the research status of infinite-layer Ca_1-xSr_xCuO₂single crystals.The second part describes the angular resolution photoelectron spectroscopy technique and its principle.TheCa_1-xSr_xCuO₂ growth method and crystal structure test are introduced in the third part.The growth of polycrystalline Ca_0.84Sr_0.16CuO₂ is described in the third part,which describes the equipment and growth process required to grow polycrystalline Ca_0.84Sr_0.16CuO₂.At the same time,it is determined whether the pure phase polycrystalline Ca_0.84Sr_0.16CuO₂ is obtained by comparing the XRD test result with the standard pdf card.The infinite layer single crystal reported in the literature is grown under high temperature and high pressure.However,this paper mainly studies the reduction of sintering temperature by cosolvent method under normal pressure to obtain large-size high-quality single crystal.In the growth experiment,the single crystal growth was first attempted by the floating zone method,but it was difficult to obtain an infinite layer single crystal due to the non-integral eutectic property of the infinite layer single crystal.Then,KOH was used as a flux to grow the single crystal.After many experiments,a high quality and large size Ca_1-xSr_xCuO₂ single crystal was successfully obtained under normal pressure,and the obtained single crystal was tested by single crystal XRD,powder XRD test,four-wheel diffraction experiment,Laurier experiment and determination of lattice constant.The obtained results are compared with the existing standard pdf cards,and compared with the results reported in the previous literature.The Ca_1-xSr_xCuO₂ single crystals of the orthogonal phase are obtained.It is speculated that a tetragonal phase occurs during the growth of the crystal.In the phase transition to the orthogonal phase,the single crystal sample will be quenched or annealed in the future to improve the characteristics of the crystal and perform ARPES measurement.The Ca_1-xSr_xCuO₂ single crystal grown in this paper is the degenerate phase of the infinite Ca_1-xSr_xCuO₂ single crystal,but it may change from the orthogonal phase to the tetragonal phase after annealing or quenching treatment.Therefore,the single crystal grown in this paper is infinite layer.The study of copper oxide compounds and the study of superconducting mechanism have certain significance.