Superconductivity in the Tl-Bi-Ca-Ba-Cu-O and Tl-Bi-Ca-Sr-Cu-O Systems

Abstract

The influence of the substitution of Bi for Tl in forming the superconducting phases in Tl-Bi-Ca-Ba-Cu-O and Tl-Bi-Ca-Sr-Cu-O systems was investigated. In the Tl-Bi-Ca-Ba-Cu-O system, the Tl Ca 2 Ba 2 Cu 3 O 9 phase forms from a 10% to 40% substitution of Bi for Tl in the nominal composition. With a further increaseing Bi, the superconducting phase disappears because of the formation of BaBiO 3 . On the other hand, the superconducting phase of (Tl, Bi)CaSr 2 Cu 2 O 7 forms from a 10% to 90% substitution of Bi for Tl in the Tl-Bi-Ca-Sr-Cu-O system. It is recognized that the substitution of Bi for Tl stabilizes and accelerates the formation of the (Tl, Bi)CaSr 2 Cu 2 O x phase.