Abstract:
In the Tl1-yPbyCaSr2Cu2O7 system, monophasic superconducting compositions are form in t, range 0.25 < y < 0.60 and the minimum Pb content required to stabilize the tetragonal 1122 phase is about 25%. Maximum T(c) is found when y = 0.5, at which composition the hole concentration is optimal. Metallic compositions of Tl1-yPbyCaSr2Cu2O7 (y = 0.25) and Tl0.75Pb0.25Y1-XCaXSr2Cu2O7 (0.80 ≤ x ≤ 1.0) become superconducting on decreasing the oxygen content by vacuum annealing.
