Defect Evolution in Y_0.5Gd_0.5Ba₂Cu₃O_7-_δ Layer by H Ion Irradiation

Abstract

In order to further improve the superconducting current carrying capacity of REBCO coated conductor under strong magnetic field, ion irradiation is used to generate the pinning center of introduced magnetic flux in the REBCO coated conductor. In this paper, the H-ion irradiation of REBCO second generation high temperature superconductor strip was carried out by using the 320kV high charge state ion synthesis research platform. DB-SPBA combined with Raman spectroscopy was used to measure the change of microstructure in YBCO samples irradiated by H+ions within the range of 5.0×10¹⁴~1.0×10¹⁶. The positron annihilation parameters in YBCO before and after irradiation were analyzed. It is found that after 100 keV H+ion irradiation, a large number of defects including vacancy, vacancy group or dislocation group are produced in the superconducting layer. The larger the irradiation dose, the more vacancy type defects are produced, the more complex the defect types are, and the annihilation mechanism of positrons in the defects changes. Raman spectroscopy results show that with the increase of H+ion irradiation dose, the oxygen atoms in the coating rearrange, the plane spacing increases, the orthogonal phase structure of the coating is destroyed, and the degree of order decreases. The defects produced by such ion irradiation lay a foundation for the introduction of flux pinning centers. Further research can be carried out in combination with X-ray diffractometer, transmission electron microscope, superconductivity and other testing methods to provide theoretical and practical reference for the optimization of material properties.