Excess conductivity analysis in YBa2Cu3O7-d added with SiO2 nanoparticles and nanowires: Comparative study

摘要

The effect of nanosized silicon oxide nanoparticles (denoted NP-SiO2) and nanowires (denoted NW-SiO2) additions during the final processing stage on electrical fluctuation conductivity of polycrystalline YBa2Cu3Oy (Y-123 for brevity) in the mean field region has been reported. Series of samples were synthesized in air using a standard solid-state reaction technique by adding nanosized entities up to 0.5 wt.%. Phases, microstructure and superconductivity properties have been systematically investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrical measurements. TEM investigations show the presence of inhomogeneities embedded in the superconducting matrix along with the presence of columnar defects in the case of SiO2 nanoparticles added samples, however nanowires tend to agglomerate by entangling with each other in the intergrain regions. The fluctuation conductivity was analyzed as a function of reduced temperature using the Aslamazov Larkin model. Using the Lawrence Doniach equations, the Ginzburg Landau (GL) number (NG) 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 SiO2 nanomaterials, that depends on the shape, effectively controlled the microstructure, the grains coupling and hence improved the physical properties of Y-123 compound.