STRUCTURE AND SUPERCONDUCTING PROPERTIES OF (TL0.8BI0.2)( SR1.6BA0.4)CA2CU3O9-DELTA

The ''1223'' structural type of high temperature superconductor, (Tl0. 8Bi0.2)(Sr1.6Ba0.4)Ca2Cu3O9-delta (referred to as Tl,Bi-1223), based o n oxides of thallium and bismuth has been prepared by reaction of prer eacted powders of (Sr1.6Ba0.4)Ca2Cu3O7 with Tl2O3 and Bi2O3. The as-sy nthesized material has a superconducting transition temperature (T-c) of 113 K, which is relatively unaffected by post-annealing either in a n oxygen or an argon atmosphere. Polycrystalline samples of Tl,Bi-1223 exhibit a high persistent current density (J(p)) of 1.62 x 10(7) A/cm (2) at 5 K and 1 tesla, and maintain significant J(p) values to temper atures over 60 K. The structure of Tl,Bi-1223 has been refined using n eutron powder diffraction data. The crystal structure is quite similar to those of Tl-1223 related compounds, P4/mmm symmetry with a = 3.821 1 Angstrom and c = 15.4235 Angstrom. The atomic sites of thallium and oxygen in the rock-salt TlO plane are slightly vacant and occupancies of the sites were determined by the neutron diffraction study.