Stabilization of Tl-1223 Phase by Arsenic Substitution

Abstract

Systematic studies on the Tl1−xAsxBa2Ca2Cu3O9−δ system, with 0.0≤x≤0.3, were carried out to investigate the effect of arsenic on the superconductivity of Tl-1223 phase. The prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), electron dispersive X-ray (EDX) and electrical resistivity measurements. XRD studies indicated that the tetragonal structure of Tl-1223 phase does not change by arsenic substitution whereas the lattice parameters a and c do. The elemental compositions analysis, determined from EDX, indicated that the arsenic was successfully introduced into the microstructure of Tl-1223 phase. The superconducting transition temperature Tc, determined from electrical resistivity data, increased from 122 to 127 K as x increased from 0.0 to 0.025 and then it suppressed with further increase in x. This means that the lower As-content may stabilize the Tl-1223 phase. In order to study the effect of arsenic substitution on the thermodynamic fluctuations of the Cooper pairs, above Tc, the excess conductivity analysis were performed using Aslamazov–Larkin (AL) theory. The results clarified that there are four regions appeared as the temperature increases namely critical (cr), three-dimensional (3D), two-dimensional (2D), and short-wave (sw) fluctuations. The zero-temperature coherence length along c-axis, the effective layer thickness of the two dimensional system, and the interlayer coupling strength were estimated as a function of the As-content. Furthermore, the thermodynamics critical field, lower critical magnetic field, upper critical magnetic field, critical current density, and Fermi energy were calculated from the above measurements.