Excess Conductivity Analysis of (Cu0.5Tl0.5)-1223 Substituted by Pr and La

Series of superconducting samples of type Cu_0.5Tl_0,5 Ba₂Ca_2?y R _y Cu₃O_10??? , where R=Pr and La with 0??y??0.20, were prepared in a sealed quartz tube via a single-step solid-state reaction technique. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), and electron dispersive X-ray (EDX). XRD studies indicated that the tetragonal structure of (Cu_0.5Tl_0.5)-1223 phase does not change by Pr or La-substitutions whereas the lattice parameters a and c do. The elemental compositions analysis, determined from EDX, indicated that both Pr and La were successfully introduced into the microstructure of (Cu_0.5Tl_0.5)-1223 phase. The electrical resistivity ??(T) was measured as a function of temperature using conventional dc four-probe technique. The fluctuation conductivity ????, above the superconducting transition temperature T _c, was analyzed as a function of temperature using Aslamazov and Larkin model. It exhibits four different fluctuation regions namely critical (cr), three-dimensional (3D), two-dimensional (2D), and short-wave (sw). The zero-temperature coherence length, effective layer thickness of the two-dimensional system and inter-layer coupling strength were estimated as a function of the substitution-content y. Furthermore, the thermodynamics critical field, lower critical magnetic field, upper critical magnetic field, critical current density and Fermi energy were calculated from the Ginzburg number. The data indicated that both Pr and La-substitutions have quite similar behaviors.