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

Abstract

New high-temperature superconductors based on oxides of thallium and copper, but not containing barium, have been prepared. A transition temperature (T(c)) of about 85 K is found for (Tl(0.5)Pb(0.5)) Sr(2)CaCu(2)O(7) whereas (Tl(0.5)Pb(0.5))Sr(2)Ca(2)Cu(3)O(9) has a T(c) of about 120 K. Both materials possess tetragonal symmetry with a = 3.80 A, c = 12.05 A for (Tl(0.5)Pb(0.5))Sr(2)CaCu(2)O(7), and a = 3.81 A, c = 15.23 A for (Tl(0.5)Pb(0.5))Sr(2)Ca(2)Cu(3)O(9). A structure refinement of the latter phase has been carried out with single-crystal x-ray diffraction data.