Enhancing the superconducting performance of melt grown bulk YBa₂Cu₃O_y via ultrasonically refined Y₂BaCuO₅ without PtO₂ and CeO₂

The electromagnetic properties of YBa₂Cu₃O_7-δ (Y-123) were improved by reducing size of the secondary phase Y₂BaCuO₅ (Y-211) via ultra-sonication and optimization of the top seeded melt growth (TSMG). Ultra-sonication a clean and low-cost technique, which excels over other techniques in producing refined Y-211 particles with sharp edges, uniform size, and contamination-free surfaces. The Y-211 powder was ultra-sonicated for various intervals ranging from 0 to 100 min, with a constant power (300 W) and frequency (20 kHz). Single grain Y-123 bulks were prepared from these powders and their electromagnetic and superconducting performance was compared. The superconducting transition temperature of all the bulk samples was around 91 K and the transition width was less than 1.5 K. At 77 K, the highest critical current density (J_c) and trapped field was found in the sample with Y-211 ultra-sonicated for 100 min. Flux pinning studies revealed a strong contribution from δT_c pinning. The present results demonstrate that the superconducting performance can be improved by ultra-sonication process producing nanometer-sized Y- 211 particles in bulk Y-123. This technique can help to produce large bulk superconductors for commercial exploitation.