Dimensionality and superconducting parameters of YBa₂Cu₃O_7−d/(WO₃ NPs)_x composites deduced from excess conductivity analysis

Superconducting composite products of type YBa₂Cu₃O_7−d (noted Y-123) added with different contents (x wt.%) of tungsten oxide nanoparticles (WO₃ NPs), x = 0.0–1.0 wt%, were produced via the standard solid-state reaction technique. Samples were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrical resistivity measurements. XRD examination showed that the Y-123 orthorhombic structure is not altered by WO₃ NPs additions. SEM observations indicated a reduction in the grains size with the increase of nanoparticles content. The investigation of the excess conductivity of different prepared composites was analyzed using Aslamazov-Larkin (AL) model. The investigated samples comprised of five distinct fluctuation regimes, namely short-wave (SWF), one-dimensional (1D), two-dimensional (2D), three-dimensional (3D), and critical (CR) fluctuations regimes. The coherence length along c-axis at zero-temperature (ξ_c(0)), lower and upper critical magnetic fields (B_c1 and B_c2), critical current density (J_c) and numerous other superconducting parameters were estimated with respect to WO₃ NPs content. Compared to undoped Y-123 sample, it was found that an amount of x = 0.05 wt% of WO₃ NPs is appropriate to improve the physical performances of Y-123, whereas with further increasing x, these performances were weakened.