Phase decomposition and structural defects in a Y-Ba-Cu-O superconductor

Phase decomposition of a bulk Y2Ba4Cu8O16 superconductor has been studied. The microstructure of the sample is heavily faulted and contains many stacking defects, including a new ‘‘125’’ structure. It is likely that these fine-scale (10–30 Å thick) stacking defects are responsible for the significantly improved flux pinning in the phase-decomposed sample. It is proposed that the decomposition process begins with the reaction ‘‘248’’ 0>