Abstract
One challenge for high Tc superconductor research is to overcome the low intergranular transport currents which hinder practical applications. Evidence shows that lattice mismatch at the boundaries contributes to the depletion in charge carriers (holes), while the strain fields surrounding the cores of boundary dislocations suppress the superconducting order parameter. Using high-spatialresolution EDX, EELS and CBED techniques with a 20 Å field emission probe, we studied cation segregation, variations in oxygen/hole content, and lattice parameters at and across grain boundaries for various Σ and near-Σ boundaries in bulk YBa2Cu3O7-δ. The geometry of those arbitrary grain boundaries was modeled using the constrained Coincidence Site Lattice (cCSL) theory, which requires c2/a2 being rational for coincidence boundaries in non-cubic crystals.In this presentation, we report our quantitative and simultaneous measurements of lattice parameters, and of oxygen/hole content at the boundary regions. The oxygen/hole density was quantified by guassian fitting to the observed oxygen K-edge spectra and comparing them with those from the same batch which had undergone oxygen reduction process (Fig.1).
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