Ag doping effects on the superconduction of YBa 2Cu 3O y ceramics

Abstract

We have studied the Ag doping effects on the superconduction of YBa 2Cu 3O y ceramics. Three type systems of the nominal composition, i.e., YBa 2−xAg xCu 3O y, YBa 2Cu 3−xAg xO y, and YBa 2Cu 3O y·Ag x (x=0.1, 0.3, 0.7), were used as the Ag substituted and doped samples, and were compared each other in the structural, morphological, and superconducting properties. Ag is substituted for Cu in preference to Ba, although Ag is not completely substituted for these cations in the range of x>0.1. Ag promotes the crystallization and c-axis orientation in Y-Ba-Cu systems, especially in the case of the presence of Ba vacancy. Ag will catalyze the intergranular coupling of the superconductor grains in the ceramics, even if relatively large amount of the impurity phases are present. The Tc slightly shifts to higher temperature and the Jc increases by the nominal Ag substitution for Cu. This result suggests that the Ag substituted superconductor phase for Cu has the higher Tc and larger Jc than those of the non-doped phase.