Effect of Ultra-sonicated Y2BaCuO5 on Top-Seeded Melt Growth YBa2Cu3Oy Bulk Superconductor

In this work, we tried to improve the superconducting performance of bulk YBa2Cu3Oy (Y123) superconductors via Y2Ba1Cu1O5 (Y211) secondary phase refinement. A novel method of ultra-sonication was used to refine the Y211 secondary phase particles. The Y211 powder was treated by ultra-sonication for 0 to 80 min with steps of 20 min, keeping the power (300 W) and frequency (20 kHz) constant. For synthesis of the YBCO bulk, we employed top-seeded melt growth (TSMG) with Pt addition. Magnetization measurements showed a superconducting transition temperature at around 91 K, irrespective of ultra-sonication parameters. Interestingly, critical current density and trapped field were found to be proportional to the ultra-sonication duration. YBCO bulk sample (20 mm diameter, 7 mm in thickness) fabricated for 80 min ultra-sonicated Y211 showed a maximum trapped field of 0.42 T at 77 K, 0.3 mm above the top surface. The improved trapped field values are explained on the basis of improvements in the microstructure.