New 1222-Type Thallium-Indium Layered Cuprates (Tl, In)Sr₂(Nd, Ce)₂Cu₂O_z and Their Superconductivity

A new series of 1222-type thallium-indium layered cuprate compounds (Tl, In)Sr₂(Nd, Ce)₂Cu₂O_z have been successfully synthesized in the pure or nearly pure form and identified by powder x-ray diffraction analyses. The structure of the compounds is directly related to that of Nb-1222 NbSr₂(Nd, Ce)₂Cu₂O_z, with a tetragonal body-center lattice. The lattice parameters are a=3.85Å, c=29.56Å for (Tl_0.7ln_0.3)Srz(Nd_0.5Ce_0.5)₂Cu₂O_z, and a=3.85Å, c=29.28Å for lnSr₂(Nd_0.75Ce_0.25)₂Cu₂O_z. Resistance measurements showed that (T1_1-xIn_x)Sr₂(Nd_0.75Ce_0.25)₂Cu₂O_z(x ≤ 0.8) are superconducting with Tc(onset)=30-40K .