Microstructure, critical current density and trapped field experiments in IG-processed Y-123

In this paper, we adapted the top-seeded infiltration growth 'IG' technique and produced several YBa₂Cu₃O_y 'Y-123' samples with an addition of Y₂BaCuO₅ 'Y-211' secondary phase particles with varying sizes by the sintering process and the ball milling technique. For the first set of samples, Y-211 disks were sintered at temperatures ranging between 900 °C and 1100 °C and were used for the production of Y-123 material by the IG process. Magnetization measurements showed a sharp superconducting transition with an onset T_c at around 92 K, irrespective of the sintering temperature. However, the trapped field and critical current density (J_c) values were dependent on the sintering temperature and it was found that the best temperature is around 925 °C. Further, the trapped field distribution measurements at 77 K indicated that all samples are of single grain nature. The highest trapped field was recorded around 0.31 T at 77 K for the Y-123 sample with 20 mm in diameter and 5 mm thickness produced by Y-211 pre-from around 925 °C. On the other hand, a second set of samples Y-211 were controlled by ball milling technique combined with an optimized slow cooling process. As a result, the critical current density (J_c) at 77 K and zero field was determined to be 225 kA cm^-2. The improved performance of the Y-123 material can be understood in terms of homogeneous distribution of fine secondary phase particles which is demonstrated by AFM micrographs.