Synthesis, Characterization and Magnetoresistance Studies of Tl_(0.5)Pb_(0.5)Sr_(1.6)Ba_(0.4)CaCu_(2-x)Ru_xO_(7-δ) Superconductor

摘要

Bulk superconducting samples of type Tl_(0.5)Pb_(0.5)Sr_(1.6)Ba_(0.4)CaCu_(2-x)Ru_xO_(7-δ), (Tl,Pb)/Sr-1212, with 0.0 ≤ x ≤ 0.525 were synthesized by the conventional one-step solid-state reaction technique via a short time, using SrO_2 instead of SrCO_3. X-ray powder diffraction XRD, scanning electron microscope SEM and the electrical resistivity measurements at different applied dc magnetic fields (0.0-4.4 kG) were performed in order to investigate the effect of Ru~(4+) ions substitution on (Tl,Pb)/Sr-1212 phase. Enhancement of the phase formation, the superconducting transition temperature T_c and the hole carriers concentration P was observed up to x = 0.075, and they decreased for further increase in x. The magnetoresistance data of these samples were analyzed within the thermally activated flux creep TAFC model and the Ambegaokar and Halperin AH theory. The derived flux pinning energy U, the critical current density J_c(0) and the upper critical magnetic field B_(c2)(0) enhanced up to x = 0.075, beyond which they decreased for further increase in Ru-content. The coherence length at 0 K (0) decreased up to x = 0.075 and increased with x > 0.075. In addition, we reported a comparison between the effect of Ru substitution on the physical properties for Gd-123, (Bi,Pb)-2223 and (Tl,Pb)/Sr-1212 phases.