Experimental and theoretical studies of oxygen ordering in quenched and slow-cooled YBa2Cu3O7-δ

Two curves for ${\mathit{T}}_{\mathit{c}}$ vs δ in ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ are found in the literature; slow-cooled samples show 60 and 90 K plateaus while quenched specimens show a nearly linear decrease of ${\mathit{T}}_{\mathit{c}}$ with increasing δ. 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.