Determination of Stoichiometry and Superconducting Properties of Tl-1234 and (Cu_0.25Tl_0.75)-1234 Phases Substituted by Erbium

Abstract

Superconducting samples of type TlBa₂Ca_3−y Er _y Cu₄O_11−δ and Cu_0.25Tl_0.75Ba₂Ca_3−y Er _y Cu₄O_12−δ ,y ranging from 0.0 to 0.1, have been prepared by a single step of solid-state reaction technique at normal pressure using high-purity oxide elements. The lattice parameters, for prepared samples, have been estimated from X-ray powder diffraction (XRD). The elemental stoichiometry of the prepared samples has been determined using Particle Induced X-ray Emission (PIXE), whereas the oxygen-content has been determined using elastic backscattering spectroscopy at 3 MeV proton beam. The superconducting transition temperature T _c has been determined from the electrical resistivity measurements. The data of T _c , for TlBa₂Ca_3−y Er _y Cu₄O_11−δ , show enhancement in its value from 124.5 to 128.45 K as y (Er-content) increases from 0.0 to 0.05, whereas it began to suppress with further increase in y. T _c gradually suppresses with increase of yfor Cu_0.25Tl_0.75Ba₂Ca_3−y Er _y Cu₄O_12−δ . Finally, the applied magnetic field B=0.44 T shows enlargement in the transition width. The effect of magnetic field on Tl-1234 phase is a little higher than that on (Cu_0.25Tl_0.75)-1234, indicating that the anisotropy parameter Γ for Tl-1234 is slightly higher than that for (Cu_0.25Tl_0.75)-1234.