Defect evolution in Y_0.5Gd_0.5Ba₂Cu₃O_{7–<i>δ</i>} superconducting layer irradiated by H⁺ ions

Abstract

<sec>In order to further improve the superconducting current carrying capacity of RE-Ba-Cu-O coated conductor under the action of strong magnetic field, ion irradiation is used to generate the pinning centers of introduced magnetic flux in the RE-Ba-Cu-O coated conductor. In this work, the H⁺-ion irradiation of second-generation high-temperature superconductor RE-Ba-Cu-O strip is carried out by using the 320 kV high charge state ion synthesis research platform. Doppler broadened slow positron beam analysis combined with Raman spectroscopy is used to measure the change of microstructure in Y_0.5Gd_0.5Ba₂Cu₃O_{7–<i>δ</i>}(YBCO) sample irradiated by H⁺ ions in a range of 5.0 × 10¹⁴–1.0 × 10¹⁶ ions/cm². The positron annihilation parameters in YBCO before and after irradiation are analyzed. It is found that after 100 keV H⁺ ion irradiation, a large number of defects including vacancies, vacancy groups or dislocation groups are produced in the superconducting layer.</sec><sec>The larger the irradiation dose, the more the produced vacancy type defects are and the more complex the defect types, 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 an 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.</sec>