Direct Observation of Atomic Arrangement of High-Tc Superconductor YBa₂Cu₃O6.74 by High-Resolution Electron Microscopy

The crystal structure of YBa 2 Cu 3 O 6.74 superconducting oxide with a transition temperature higher than liquid nitrogen temperature has been studied by high-resolution electron microscopy. The observed high-resolution micrograph is consistent with the oxygen-deficient perovskite structure model proposed in previous work with neutron and X-ray diffraction. In the image, Y, Ba and Cu atoms are represented as dark spots with different contrast depending on their atomic numbers. Unoccupied oxygen atom positions are distinguished from occupied oxygen atom positions as brighter regions.