Tl 1−x Pb x CaSr 2 Cu 2 O 7 : another 1122 high-T c superconductor

The 1122 member of the Tl(Ca, Sr) n+1 Cu n O 2n+3 system is stabilized by partial substitution of Tl by Pb. Tl 1−x Pb x CaSr 2 Cu 2 O 7 with x=0.25 and 0.5 have both primitive tetragonal structures (c 12.1 A) showing onset of superconductivity around 70 K and 90 K, respectively.