Anisotropy And Magnetic Transmission Characteristics Of High-Temperature Superconducting Coated Conductors

The second-generation(2G)superconducting wire technology has high application value and wide application prospect.YBa2Cu3O7-?(YBCO)is one of the most promising high temperature superconducting(HTS)materials,due to its high superconducting critical temperature Tc,upper critical field Hc2,irreversible field Hirr and large current-carrying capability.Among various approaches making YBCO layer,Chemical Solution Deposition(CSD)method,which is low-cost and easy to scale up,is a promising technique for the industrial production of YBCO coated conductors.This works focuses on application requirements of high-temperature superconducting coated conductors.Firstly,rapid pyrolysis is achieved by reducing fluorine content in the precursor solution.Secondly,several processing parameters of preparing REBCO films have been compared and studied,and optimal process window and growth mechanism are determined.Then an effective new pinning center has been introduced,and the pinning type and mechanism are explored by studying its magnetic flux pinning properties.Finally,in order to understanding the anisotropy of REBCO superconducting materials,the electromagnetic transmission of the superconducting tape have been studied.Those explorationes pave a way for realizing industrialization and commercializes of REBCO cable.The main contents and results are as follows:(1)Various precursor solutions with different fluorine content have been developed,The DTA analysis shows that the precursor solution with lower fluorine content endures a faster pyrolysis rate.And,high-performance YBCO films can be obtained at 5 °C/min using CLF solution or 20 °C/min using ELF solution.In order to obtaining the optimized growth window,the influence of various gas flow conditions has been investigated.The growth rate and the orientation nucleation of YBCO films can be controlled by the gas flow conditions in the heat-treatment stage.So rapid and stable preparation of high-performance YBCO films has been achieved.(2)The rapid pyrolysis suitability of REBCO(RE,other rare earth)films using ELF solution has been investigated,and it was determined that smooth and homogeneous Sm BCO/Yb BCO surface can be achieved using ELF solutions at a rapid pyrolysis rate of 20 oC/min.And The Jc of the Sm BCO films reaches 1.5 MA/cm2(77 K,self-field)when crystallization temperature is 800 oC and PO2 is 20 ppm.(3)Effective pinning center have been introduced into the REBCO film by changing the proportion of cations or adding other element in the precursor solutions.Firstly,Yx Ba2Cu3O7-?(x = 0.9,1.0,1.1,1.2,1.33,1.66)films are deposited on metal substrates by CLF-MOD,and epitaxial Y2O3 nanoparticles are detected in Y-rich samples by X-ray diffraction.The Jc value of Yx BCO exhibits the highest when x=1.2.Secondly,10%,20%,and 40% Cl ion have been added in Y0.6Gd0.6Ba2Cu3 solutions respectively.The smoother and denser surface have been obtained in the Cl-doping films,especially for Cl-10%.In addition,by analyzing Tc and Jc-H of all films,the best magnetic flux pinning effect have been achieved when the molar doping amount of Cl was 10%.(4)Ion irradiation is an easier route for such microstructure engineering,since it can control the properties of irradiation defect(size,shape,density,and alignment)by external parameter(ion mass,energy,fluence,and incident angle)without altering the growth conditions of a target material.Using a tandem electrostatic accelerator in the Institute of Heavy Ion Physics in Peking University,a series of superconducting tapes with Ag layer were irradiated by Au ions with energy of 1,3,5,7 Me V and fluence of 1010-1015 ion/cm2 respectively.In addition,the superconducting coated conductor without Ag layer was irradiated by 7 Me V Xe ion using an ion accelerator of the Institute of Modern Physics in Lanzhou.Through two experimental explorations,the experimental conditions for effective pinning by ion irradiation were determined,which provided a good impetus for the development of high-temperature superconducting coated conductors.(5)The superconducting properties and anisotropy of superconducting tape YBCO/YDy0.5BCO were studied.From the dependence of the resistance on the temperature,the Tc of SC170517,SC170503,SCSC-Cu,and SCSC-Ag samples have been determined to 92.9 K,92.5 K,93.9 K and 94 K respectively.Meanwhile the relations of Hirr(T)and Hc2(T)of each sample have been obtained.In addition,the magnetic transmission anisotropy of the HTS-coated conductors was measured in the low magnetic field and high field regions,respectively.When the applied magnetic field is low,weak isotropic pinnings works as strong as the intrinsic pinning;but when the applied magnetic field becomes higher,the weak pinning center cannot continue to play the role of binding the vortex line.