Abstract
In this study, we examined the pinning mechanism and fluctuations induced conductivity, and we report the superconducting critical parameters variation of fine SiO2 nanoparticles added YBa2Cu3O7 d (Y123) composite thick films of similar to 100 mu m in thicknesses on Ag substrate. Composite films (Y123 + x SiO2)/Ag were produced by the solid-state reaction process. Here, x = 0.00 and 0.01 wt% content of SiO2 nanoparticles (12 nm in diameter) were considered. The X-ray powder diffraction (XRD) together with Rietveld refinement and the scanning electron microscopy (SEM) were used to survey the structure and the morphology of thick films. Both composite films reveal a dense granular structure and similar compositions in phases. A small quantity of fine SiO2 particles intensifies the critical current density versus magnetic field Jc(H) and gives more weight to the strong pinning component of the Jc. Some important critical physical parameters of the composite films were obtained from the fluctuations induced conductivity analyses. The electrical conductivity was deduced from the electrical resistivity measurements and explained through Aslamazov-Larkin model. A small quantity of fine SiO2 particles upgrade the superconducting features, particularly the lower and the upper critical magnetic field (Bc1 and Bc2) at temperature 0 K.