Abstract
Bulk superconductivity is reported in with a transition to zero resistance at ≃ 125 K, the highest transition temperature () yet found. Transmission electron spectroscopy shows that the unit cell is body-centered tetragonal and contains trilayer Cu perovskitelike units separated by bilayer Tl-O units. in this material varies from 118 to 125 K depending on preparation conditions. A high density of perovskitelike bilayer intergrowths are observed in the 118-K material, which we speculate result in the decreased . A second structure containing only bilayer perovskitelike units——is a bulk superconductor with ranging from 95 to 108 K.
- Received 14 March 1988
DOI:https://doi.org/10.1103/PhysRevLett.60.2539
©1988 American Physical Society