Effect of anisotropic temperature factors on convergent-beam electron diffraction intensities and measurement of the local change in the oxygen concentration of YBa₂Cu₃O_y

The local oxygen concentration of the high-T c superconductor YBa2Cu3O y was measured from large-angle convergent-beam electron diffraction patterns using a transmission electron microscope equipped with a field emission gun with an in-column-type energy filter. The anisotropic effect of thermal vibrations of atoms was considered in the analysis of the oxygen concentration, based on the many-beam dynamic theory. The observed fluctuation in the oxygen concentration can explain the peak effect in the J c–H curve, the critical current density J c plotted as a function of applied magnetic field H.