EXPERIMENTAL AND THEORETICAL-STUDIES OF OXYGEN ORDERING IN QUENCHED AND SLOW-COOLED YBA2CU3O7-DELTA

Two curves for T(c) vs delta in YBa2Cu3O7-delta are found in the literature; slow-cooled samples show 60 and 90 K plateaus while quenched specimens show a nearly linear decrease of T(c) with increasing delta. We present a comprehensive electron-diffraction study of quenched specimens and show that there are pronounced differences in the oxygen ordering between quenched and slow-cooled samples. A simple model, in which the average antiphase domain size is the only adjustable parameter, is found to match all of the experimental electron-diffraction data to within measurement error.