Investigation of the physical properties of (Cu_0.5Tl_0.5)Ba₂Ca₂Cu₃O_10-δ impregnated with mono cobalt(II)-substituted Undecatungstosilicate Nanoparticles

Abstract

A series of (Cu_0.5Tl_0.5)Ba₂Ca₂Cu₃O_10-δ superconducting samples impregnated with different percentage additions of potassium salt {CoSiW₁₁}_x nanoparticles (x = 0.00, 0.01, 0.02, 0.04, 0.06, 0.08 and 0.12 wt.%) were prepared using a single-step solid-state reaction technique at ambient pressure. These samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) to study their structures, construction of the synthesized samples and elemental composition, respectively. XRD studies indicate that the tetragonal structure of (Cu_0.5Tl_0.5)-1223 phase has not changed by the addition of {CoSiW₁₁} nanoparticles the same as for the values of lattice parameters a and c, where they show a non-remarkable change. The relative volume fraction of (CuTl)-1223 phase record a maximum value for x = 0.02 wt.%. The formation of (CuTl)-1223 phase matches the presence of rectangular-shaped plates seen in SEM images. The enhancement of these plates after the addition of {CoSiW₁₁} nanoparticles up to x = 0.02 wt.% agreed with the measurements of relative volume fraction. The mass percentage of all elements was measured using the EDX technique, which shows the distribution composition of both superconductor and nanoparticle compounds. Vibrational mode analyses of oxygen were accomplished via Fourier transform infrared (FTIR) spectroscopy in (CuTl)-1223 phase impregnated with {CoSiW₁₁} nanoparticles. The O_δ oxygen modes observed are almost unaltered while the other oxygen modes of planar CuO₂ are slightly softened and hardened. Superconducting transition temperature (T_c) and critical current density (J_c) were determined from the electrical resistivity and I–V measurements, respectively. The results indicate an increase in the T_c values from 125 K for the pure sample to 132 K for x = 0.02 wt.% impregnated samples, while a decrease in the J_c values is observed upon increasing ‘x’ value from x = 0.00 up to 0.12 wt.%. The suppression of these electrical superconducting parameters for x > 0.02 wt.% may be due to an increase of weak links' connectivity among the grain boundaries and growth of impurity phases that affect the formation of (CuTl)-1223 superconductor phase. The fluctuation-induced conductivity (FIC) analysis has been done in the light of the Aslamasov–Larkin (AL) theory to study the fluctuation conductivity Δσ above T_c as a function of reduced temperature for (CoSiW₁₁)_x/(CuTl)-1223 superconductor. The results show four non-identical fluctuation regions that are short-wave (Sw), two-dimensional (2D), three-dimensional (3D) and critical (Cr). The zero-temperature coherence length (${\xi }_{c}(0)$), the effective layer thickness of the two-dimensional system (d), inter-layer coupling (I), Fermi velocity (v_F) and Fermi energy (E_F) were evaluated as a function of ‘x’ addition from FIC analysis of the samples and then correlated to the superconductivity order parameters. The superconducting parameters were increased upon the addition of {CoSiW₁₁} nanoparticles.