Record critical current densities in IG processed bulk YBa₂Cu₃O_y fabricated using ball-milled Y₂Ba₁Cu₁O₅ phase

The infiltration-growth (IG) technique enables the uniform and controllable Y₂BaCuO₅ (Y211) secondary phase particles formation within the YBa₂Cu₃O_y (Y123) matrix. Recent results clarified that the flux pinning performance of the Y123 material was dramatically improved by optimizing the processing conditions during the IG process. In this paper, we adapted the IG technique and produced several samples with addition of nanometer-sized Y211 secondary phase particles, which were produced by a ball milling technique. We found that the performance of the IG processed Y123 material dramatically improved in the low field region for a ball milling time of 12 h as compared to the samples without a ball milling step. Magnetization measurements showed a sharp superconducting transition with an onset T_c at around 92 K. The critical current density (J_c) at 77 K and zero field was determined to be 224 022 Acm^-2, which is higher than the not ball-milled sample. Furthermore, microstructural observations exhibited a uniform microstructure with homogenous distribution of nanosized Y-211 inclusions within the Y-123 matrix. The improved performance of the Y-123 material can be understood in terms of fine distribution of the secondary phases. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)