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% Y
₂
Ba
₄
CuAgO
_y
(Y24Ag1) nanoparticles, the J
_c
at 77 K of YBCO bulk is ~ 5.8 × 10
⁴
A cm
^-2
, while that of the sample without the addition is ~ 1.5 × 10
⁴
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 YBa
₂
Cu
₃
O
_7-δ
(Y123) matrix. On the other hand, the Y
₂
BaCuO
₅
(Y211) remained micro-sized, which was not changed by the addition of Y24Ag1 nano particles.