Tl1Can-1Ba2CunO2n+3 (n=1,2,3): A new class of crystal structures exhibiting volume superconductivity at up to 110 K

We report the discovery of three new phases in the Tl-Ca-Ba-Cu-O system, Tl1Can-1Ba2CunO2n+3 n=1,2,3, one of which n=3 exhibits bulk superconductivity at 100 K. The crystal structures of these new materials are closely related to that of Tl2Ca2Ba2Cu3Ox, the recently discovered 125-K superconductor. All of these compounds contain Cu perovskitelike units, but whereas these are separated by bilayer Tl-O sheets in the 125-K material, they are separated by monolayer Tl-O sheets in the new structures, enabling an examination of the effect of the coupling between successive Cu perovksite units on superconducting properties. © 1988 The American Physical Society.