Excess conductivity analysis for Y3−xNdxBa5−xCaxCu8O18−δ superconducting phase

Abstract

Superconducting samples of type [Formula: see text] substituted by both [Formula: see text] and [Formula: see text] ions were prepared by a solid-state reaction technique. These substitutions affect the phase formation, lattice parameters, grains formations and superconducting transition temperature [Formula: see text]. The change in these parameters is mainly due to the partial substitution of [Formula: see text] by [Formula: see text] ions rather than the partial substitution of [Formula: see text] by [Formula: see text] ions. The analysis of the electrical resistivity [Formula: see text] versus temperature above [Formula: see text] was carried out using Aslamazov–Larkin (AL) and Lawrence–Doniach (LD) models. Different fluctuation regions starting from high temperature up to [Formula: see text] were estimated, and denoted by short-wave (sw), two-dimensional (2D), three-dimensional (3D) and critical (cr) fluctuations. A distinct crossover temperature [Formula: see text] from 2D to 3D, in the mean field region (MFR), is shifted to lower temperature by increasing substitutions content. The superconducting parameters such as zero temperature coherence length along the [Formula: see text]-axis [Formula: see text], inter-layer coupling strength [Formula: see text], Fermi velocity [Formula: see text] of the carriers and Fermi energy [Formula: see text] were calculated as a function of substitution content.