Tl2Ba2−xSrxCuO6: A system exhibiting a compositionally controlled superconductor-metal transition

Strontium-substituted thallium cuprates of the type Tl₂Ba_2−xSr_xCuO₆ have been synthesized for various values of x. Single phases were obtained for x ≤ 1.2. The compounds crystallize in the tetragonal structure with space group I4/mmm as the parent Tl₂Ba₂CuO₆ oxide. Both a and c lattice parameter decrease with increase in x. T_c decreases gradually from 92 to 77 K (x = 0.8). Beyond x = 1.0 superconductivity is lost. The x = 1.2 comparison is metallic down to 4.2 K.