Grain-boundary studies by the coincident-site lattice model and electron-energy-loss spectroscopy of the oxygen K edge in YBa₂Cu₃O₇-δ

Abstract

Electron-energy-loss spectroscopy for the oxygen K edge was performed at and near grain boundaries of YBa₂Cu₃O₇ using an electron beam of 20 Å diameter in a transmission electron microscope. The analysis of the pre-peak at the absorption edge revealed that there exist both oxygen-deficient (100 Å or less wide) and fully oxygenated grain boundaries. These differences depend on the structural misorientations between grains separated by boundaries. The results were consistent with earlier predictions of variable oxygen contents at YBa₂Cu₃O₇ grain boundaries, depending on the misorientations, based on the constrained coincident-site lattice model for the boundary structures.