Investigation of weak links and the role of silver addition on YBCOsuperconductors

Abstract

The effect of silver doping on the microstructure and transportproperties of the YBCO bulk system have been investigated through scanningelectron microscopy observation, resistivity and susceptibility measurements,including the critical current density. We have used the additive method forthe YBCO system (0.01-60 wt% of Ag). The results of the structural andsuperconductivity properties show that silver doping has no noticeable effecton the Tc of samples, but influences the samples' Jc, which increaseswith increasing silver doping content up to 20 wt% for the YBCO system.The intergranular Tc (detected by the imaginary parts of thesusceptibility) improved in the doped samples up to the 20 wt% Ag. It wasfound that excess metallic Ag filled the pores of the bulks and encouraged theformation of larger stacks of flat rectangular platelets, resulting in ac-axis preferred orientation.