Reduction of the Surface Resistance of YBa₂Cu₃O_7-x Pellets and Thick Films by Adding Ag

Abstract

This letter describes the effect of Ag addition on the surface resistance of sintered YBa 2 Cu 3 O 7- x superconductors at 17 and 50 GHz. The surface resistance decreases more than 50% by adding Ag into a pellet or a thick film of YBa 2 Cu 3 O 7- x . The thick film exhibits a surface resistance of 22 mΩ at 17 GHz and at 77 K, which is almost equal to that of pure Cu. It is also revealed that the surface resistance is proportional to the square of the frequency. These phenomena are discussed in terms of the effect of Ag on the morphologies and c -axis orientation of YBa 2 Cu 3 O 7- x grains.