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

Abstract
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><fv/0 ‘‘123’’+‘‘125’’, which could possibly occur by a spontaneous, short‐range diffusion reaction. Further decomposition involves gradual removal of the extra CuO chains by long‐range diffusion to produce a mixture of ‘‘123’’+CuO.