Effects of Fullerene Addition on Pinning Properties and Microstructures in Melt-Textured Y-Ba-Cu-O Superconductors

摘要

Bulk Y-Ba-Cu-O superconductors have significant potential for engineering applications due to high critical current density (J_c) and high trapped magnetic fields, which is attributed to the presence of pinning centers such as micro-sized Y₂BaCuO₅(Y211) inclusions. The introduction of nanosized particles is known to function as more effective pinning centers than micro-sized ones. It has been reported thatJ_cvalues were enhanced with the addition of nanosized particles such as ZrO₂and Y₂Ba₄CuMO_y(M = Nb, Zr, etc.) in the YBa₂Cu₃O_x(Y123) matrix. We have focused on nanocarbon as another candidate of the pinning center and reported that the addition of carbon nanotube (CNT) and nanodiamond led to the enhancement ofJ_cin Y-Ba-Cu-O superconductors. Fullerene (C₆₀) is also expected to improve the flux pinning performance. We then fabricated melt-processed Y-Ba-Cu-O bulk samples with the addition of fullerene and investigated the pinning properties and microstructures. SEM observation showed that nanosized particles were distributed in the Y123 matrix.J_cexhibited the highest values for the sample with 1.0 wt% fullerene addition. These results suggest that fullerenes act as effective pinning centers.