Comparative study of structural and superconducting properties of (Cu0.5Tl0.5)Ba2Ca2Cu3O10-δ phase substituted by copper fluoride and thallium fluoride

A series of (Cu 0.5− x Tl 0.5− y )-1223 superconductor samples, doped with varying amounts of (CuF 2 ) x and (TlF) y compounds with x = y = 0.0, 0.1, 0.2, 0.3 and 0.4, were synthesized via a single-step solid-state reaction. X-ray diffraction (XRD) revealed that all the samples have a tetragonal symmetry of (Cu 0.5 Tl 0.5 )-1223 phase. Additionally, with increasing fluorine content up to x = 0.2 CuF 2 and y = 0.1 TlF, the phase fraction and the superconducting transition T c were enhanced. The scanning electron microscopy (SEM) images exhibited mainly plate-like rectangular shape grains confirming the formation of (Cu 0.5 Tl 0.5 )-1223 phase. The Fourier transform infrared (FTIR) spectra of CuF 2 - and TlF-substituted (Cu 0.5− x Tl 0.5− y )-1223 show a slight softening and hardening in few peaks related to the apical oxygen atoms and CuO 2 planar modes. The stoichiometry of elemental composition for all prepared samples has been confirmed using ion beam analysis (IBA) methods. The excess conductivity Δ σ above T c was analyzed through the Aslamasov–Larkin (AL) approach. Using the Ginzburg–Landau (GL) number (N G ) and equations, the coherence length, the effective layer thickness, the lower critical field B c1 (0), the upper critical field B c2 (0) and the critical current density J c (0) were estimated. It was found that the addition of an optimum concentration of CuF 2 and TlF, controlled the microstructure, the grains coupling and hence enhanced the physical properties of (Cu 0.5 Tl 0.5 )-1223 phase.