SUPERCONDUCTIVITY IN THE INDIUM-DOPED TL-1223 PHASE - (TL0.8IN0.2)(SR0.8BA0.2)(2)CA2CU3O9-DELTA

We report the synthesis and characterization of a new Tl- and In-based '1223' type cuprate oxide, (Tl0.8In0.2)(Sr0.8Ba0.2)(2)Ca2Cu3O9-delta (Tl,In-1223). The as-synthesized Tl,In-1223 compound becomes supercond ucting at about 80 K, The T-c increased to 103 K when the sample was a nnealed under an argon atmosphere, Magnetization studies on polycrysta lline samples of Tl,In-1223 reveal that persistent current densities ( J(p)) of the indium-doped compound are about 10 times smaller than tho se of corresponding TI,Bi-1223 and Tl,Pb-1223 with the same structure type, Small substitution of In for Tl in Tl-1223 results in a large re duction of T-c and J(p), A slight change in the electronic configurati ons of the rock-salt metal sites appears to affect the delicate balanc e of the metal and oxygen energy levels, which leads to the virtual ch anges in the superconductivity in Tl,In-1223.