Síntese, microestrutura e método Rietveld em amostras supercondutoras de YBa2Cu3O7−δ

Abstract

This work investigated the formation of microstructures in single-crystal and polycrystalline samples of YBa2Cu3O7−δ using Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and the Rietveld method. For these analyses, two growth techniques were employed: the sintering method for fabricating the polycrystalline sample and the self-flux method for the single-crystal sample. SEM images revealed that the polycrystalline sample exhibited a porous and heterogeneous surface with varying grain sizes, while the single-crystal sample displayed a compact and non-porous structure. The chemical analysis by Energy Dispersive Spectroscopy (EDS) confirmed the elemental purity and compositional homogeneity of both samples. Through the Rietveld refinement of the polycrystalline sample, significant results were obtained, including the lattice parameters, the identification of secondary phases, and their respective proportions. For the single-crystal sample, Rietveld refinement could not be performed, as explained in the study, however, alternative methods were employed to gather information about its microstructure. Using the Scherrer equation, the crystallite size of the polycrystalline sample is 52, 34 nm, which also enabled the identification of the plane orientation most prominently present in this sample.