The electromagnetic properties of YGdBCO coated conductors with periodic micro-holes arrays

Abstract

Improvement of in-field critical current (Ic) remains a significant issue for the power applications of REBa2Cu3O7−x (REBCO, RE = Rare earth) coated conductors (CCs). It is extremely difficult to produce cost-effectively batched CCs with strong flux pinning behaviors due to the special processing requirements of nano defects, although the batch production of pure CCs has been realized for many years. In this work, a prospective and convenient approach was proposed to enhance the current carrying capability of REBCO CCs by producing mesoscopic holes in CCs via laser drilling. The effect of micro-hole structure such as diameter (d) and spacings (l) between two neighboring holes along longitudinal and transverse directions on Ic, superconducting transition temperature (Tc) and diamagnetism of YGdBCO CCs was comprehensively investigated. With d ≤20 µm and l ≥0.6 × 0.6 mm, the Ic values of drilled samples are nearly identical with those of original one. However, a considerable decrease of Ic was found in the drilled samples with d>20 µm and l<0.6 × 0.6 mm, displaying a nonlinear Ic change. The Tc values of samples with various micro-hole structures remain the same as that of the virgin one, but the maximum diamagnetic signals reduce gradually with decreasing l. Based on the optimal micro-hole structure (20 µm diameter, 0.6 × 0.6 mm spacing), the Ic anisotropy at low magnetic fields was studied. Compared to the original sample, the optimally drilled sample has not only obviously higher Ic values at different angles and magnetic fields as a whole, but also maximumly improved Ic about 24% at 160 mT, showing strong flux pinning properties. The possible reasons were discussed in the article.