Superconductivity of Tl-Sr-Ca-Cu-O System in Relation to Tl-Ba-Ca-Cu-O and Bi-Sr-Ca-Cu-O Systems

Abstract

It was found that Tl-Sr-Ca-Cu-O system gives rise to at least two superconducting phases, a high- T c phase at 100 K and a low- T c phase at about 75 K. The two phases are isostructural to those of Bi-Sr-Ca-Cu-O system. Comparing the T c 's and crystal structures of the Tl and Bi systems, it was suggested that T c is mainly determined by the combination of two alkaline earth elements, i.e., Sr/Ca or Ba/Ca, when the repetition unit in the layered perovskites is equal.