Effect of Sol-Gel Derived Nano-Scale ${\hbox {Y}}_{2}{\hbox {Ba}}_{4}{\hbox {CuAgO}}_{\rm y}$ Addition in Bulk Y-Ba-Cu-O Superconductors

This study reports a new method to prepare Y-Ba-Cu-O (YBCO) bulk superconductors with high critical current density (J_c). With the addition of 1 mol% Y₂Ba₄CuAgO_y (Y24Ag1) nanoparticles, the J_c at 77 K of YBCO bulk is ~ 5.8 × 10⁴ A cm^-2, while that of the sample without the addition is ~ 1.5 × 10⁴ A cm^-2, which reflects about 4 times the enhancement. The above Y24Ag1 nano-particles were prepared by a sol-gel process of mixing metal nitrate with a polyacrylic acid (PAA) solution as precursors, followed by heating at 1000°C for 3 h. X-ray diffraction (XRD) analysis indicated that the Y24Ag1 precursor particles are well crystallized with an average cluster size of 0.67 μm . In the as-grown single grain melt-textured sample, Y24Ag1 nano particles with the size of 10-20 nm were found to be homogeneously distributed in the YBa₂Cu₃O_7-δ (Y123) matrix. On the other hand, the Y₂BaCuO₅ (Y211) remained micro-sized, which was not changed by the addition of Y24Ag1 nano particles.