Bulk Superconductivity up to 122 K in the Tl-Pb-Sr-Ca-Cu-O System

Science  14 Oct 1988:
Vol. 242, Issue 4876, pp. 249-252
DOI: 10.1126/science.242.4876.249


New high-temperature superconductors based on oxides of thallium and copper, but not containing barium, have been prepared. A transition temperature (Tc) of about 85 K is found for (Tl0.5Pb0.5) Sr2CaCu2O7 whereas (Tl0.5Pb0.5)Sr2Ca2Cu3O9 has a Tc of about 120 K. Both materials possess tetragonal symmetry with a = 3.80 Å, c = 12.05 Å for (Tl0.5Pb0.5)Sr2CaCu2O7, and a = 3.81 Å, c = 15.23 Å for (Tl0.5Pb0.5)Sr2Ca2Cu3O9. A structure refinement of the latter phase has been carried out with single-crystal x-ray diffraction data.