Effects of some additional elements on the reaction diffusion in high-Tcoxide composites

The reaction diffusion between a substrate of high melting point and a coating layer of low melting point produces a thick superconducting layer with a uniform composition. The addition of Ag to the coating layer enhances the diffusion in both Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O systems. The Ag is pushed out from the superconducting layer to the surface of the specimen, forming a laminated structure composed of a superconducting layer and an Ag layer. This movement of Ag improves the grain orientation in the superconducting layer. Meanwhile, the substitution of Li for Cu in the coating layer of the Bi-Sr-Ca-Cu-O system significantly promotes the diffusion, and a T c of 85 K is obtained after the reaction at 780 degrees C for 30 min.