Preparation of Thin and Thick Film Superconductors in the Tl-Ca-Ba-Cu-O System

Abstract

The advent of high temperature superconductivity in Cu-O based materials has catalyzed a tremendous amount of activity in the synthesis, characterization and application of these materials [1]. The recent discovery of superconductivity above liquid nitrogen temperature in the Bi-Ca-Sr-Cu-O system [2] and Tl-Ca-Ba-Cu-O system [3] has led to hopes that these materials could overcome some of the problems experienced to date in the first system to superconduct above liquid nitrogen temperature, the rare earth (Re)Ba₂Cu₃O₇ [4] The (Re)Ba₂Cu₃O₇ materials suffer from many problems including: weak links between the grains in polycrystalline aggregates [5], a complex equilibrium with oxygen, a phase change in the region where the material is processed and limited chemical stability. Further, the T_c of these materials near 90K is probably too close to 77K for many applications. These limitations mean substantial hurdles to the practical utilization of the (Re)Ba₂Cu₃O₇ materials.