Partial Substitution Effects onthe Structure and Electrical Properties of the High Temperature Superconducting System Bi2-xTlxBa2-ySryCa2Cu3O10+δ

Abstract

The partial substitution effects on the structure and electrical properties of the high temperature Bi_2-xTl_xBa_2-y Sr_y Ca₂ Cu₃ O_10+δ superconducting compounds have been investigated with x=0.00, 0.05, 0.10, 0.20 and y= 0.0, 0.1, 0.2, 0.3. X-ray diffraction studies showed that the structure was tetragonal witha=b=5.43Å, c=34.13Å for x=0, y=0. The structure almost remained tetragonal for all x values with y=0, and the c-parameter increased only for x=0.05 and then a decrease in the c-parameter with increasing x value was observed. On the other hand, for x=0 and y= 0.1, 0.2, 0.3 the structure was tetragonal with a slight decrease in the lattice parameters with increasing y. There was an observed change to orthorhombic phase with increasing both x and y at the same time. The critical temperature was very sensitive to the thallium content x, in the absence of strontium, as it increased to 128K for small x butdecreased noticeably with increasing x value. A similar behavior was observed for Sr content. However a large enhancement in the critical temperature was observed in the presence oflower concentrations of both thallium and strontium. Finally, the increase in the volume of the lattice or the oxygen content is associated with higher critical temperature values.

Keywords: HTSC, Partial Substitution, Crystal Structure, BSCCO, TBCCO.