Nano-Scale Pinning Centers in ${\rm Y}_{2}{\rm Ba}_{1}{\rm Cu}_{1}{\rm O}_{5}$ Doped Sm-Ba-Cu-O Superconductor

It has been suggested that the addition of nano-scale RE
₂
BaCuO
₅
(nmRE211, RE = Y, Sm and Nd) in melt-textured growth (MTG) Sm-Ba-Cu-O (SmBCO) materials enhances the critical current density (Jc), especially in high magnetic fields. According to the analysis of pinning properties, the field-induced pinning was attributed to a weakly superconducting phase. This phase was correlated to nano-scale compositional fluctuation regions originated from the peritectic reaction between nano-scale additives and matrix during the melt-growth process. To further elucidate the characteristics of the compositional fluctuation regions, in this study, nano-structure of nmY211 SmBCO samples were investigated using transmission electron microscopy (TEM) and electron energy loss spectra (EELS). Periodic nano-structures with width ranging from few to several tens of nanometers were observed throughout the matrix. Variations in both chemical composition and thickness of these periodic nano-structures were compared with the observations reported in the NEG ((Nd, Eu, Gd)-Ba-Cu-O) samples.