New 1222-Type Thallium-Indium Layered Cuprates (Tl,In)Sr2(Nd,Ce)2Cu2Oz and Their Superconductivity

A new series of 1222-type thallium-indium layered cuprate compounds (Tl,In)Sr2(Nd,Ce)2Cu2Oz 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)2Cu2Oz with a tetragonal body-center lattice. The lattice parameters are a=3.85 A, c=29.56 A for (Tl0.7In0.3)Sr2(Nd0.5Ce0.5)2Cu 2Oz, and a=3.85 A, c=29.28 A for InSr2(Nd0.75Ce0.25)2Cu2Oz. Resistance measurements showed that (Tl1-xInx)Sr2(Nd0.75Ce0.25)2Cu 2Oz (x ≤ 0.8) are superconducting with Tc(onset)=30-40 K.