A typical grain boundary has been observed in the splat-quenched and a
nnealed Bi2Sr2CaCu2O8+delta phase by HRTEM and ED studies. It is close
ly related to the modulated structure and identified as a mirror-trans
lational (011) twin the angle theta=82-degrees between two [001] axes.
Frequent occurrence of this twin interface manifests its low energy a
nd may negatively affect the current-carrying capacity of the melt-pro
cessed Bi2Sr2CaCu2O8+delta material.