Roles of silver doping on joins and grain boundaries of melt-textured YBCOsuperconductor

Abstract

Grain boundaries of melt-texturedYBa2Cu3Oy(YBCO) are preferentially doped with silver by a solid-state diffusion method.Microstructural and local compositional analysis reveals that the Ag exists in theYBCO as individual atoms with their distribution being highly localized within athin layer near the grain boundaries. Compared with the pristine samples, theAg-doped YBCO textured polycrystals show a significant improvement in theJc–H behaviour. Thevalue of Jc at 60 Kand 7 T reaches 4.6 × 104 A cm−2, which is almost three times the value ofJc for the undoped samples. We propose a model in which Ag could partially replace the Cu inCuO2 planes near the grain boundaries of YBCO, therefore reducing the geometric distortion ofCu–O bonds and making the effective grain boundary thinner.