Structural Characterization of Ba sub 2 YCu sub 3 O sub 7 By High Resolution Transmission Electron Microscopy.

We show that high resolution transmission electron microscopy can be used directly to reveal the structure of the metal frame work and its defects in Ba sub 2 YCu sub 3 O sub 7. The use of dynamical effects under carefully selected and controlled conditions allows the detection of long-range order in the disposition of the oxygen vacancies, but inevitable misalignments make the quantification of the order parameter difficult.