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

It was found that Tl-Sr-Ca-Cu-O system gives rise to at least two superconducting phases, a high Tc phase at 100K and a low Tc phase at about 75K. The two phases are isostructural to those of Bi Sr-Ca-Cu-0 System. Comparing the Tc’s and crystal structures of the Tl and Bi systems, it was suggested that Tc is mainly determined by the combination of two alkaline earth elements, i.e., Sr/Ca vs Ba/Ca, when the repetition unit in the layered perovskites is equal.