Effect of Simultaneous Doping of Rhenium and Tellurium on T<SUB>c</SUB> and Phase formation of Tl- Based Cuprate Superconducting Materials

Abstract

Preparation of new High Temperature Superconductor (HTS) materials is the important factors for development of efficient and lossless energy systems. Here the effect of tellurium (Te) and Rhenium on the critical temperature (Tc(0)) of Tl- based Cuprate Superconductors is presented. Tl_1.85Re_0.12Te_0.03Ba₂Ca₂Cu₃O_x and Tl_1.88Re_0.12Ba₂Ca₂Cu₃O_x have been prepared with nominal starting composition by solid-solid reaction method. Ba-Ca-Cu-O precursor was made for this purpose by mixing and grinding of stoichiometric amounts of BaCO₃, CaCO₃ and CuO followed by sintering at 850°C. Finally, appropriate amounts of Re₂O₇, and (Re₂O₇-TeO₂ ) with Tl₂O₃ were added to the precursor and the whole mixture was annealed at 950°C under oxygen flow. Doping of Re produced a chemical stabilization of the precursor against barium carbonation under ambient air. The critical temperatures Tc(0) of Re-doped compounds were found 86K. Simultaneous doping of Te and Re increases the value of Tc(0) (123K) of the superconductor. X-ray diffraction revealed the presence of some additional phases in ((Te-Re) - doped compound including the high Tc Tl-1223 and Tl-2223 phases. The gain homogeneity of the prepared specimens were excellent as obtained through SEM analysis. Simultaneous doping of tellurium and rhenium in Tl-cuprates induced pairing mechanisms to occur outside the CuO₂ layers, thus enhancing the high Tc phase formation and hence the Tc(0) value.