Direct observation and analysis of nanoscale precipitates in (Sm,Eu,Gd)Ba2Cu3Oy

We employed atomic-resolution high-angle annular dark-field scanning transmission electron microscope to characterize the chemical composition and nature of the nanoparticles dispersed in melt-processed (Sm0.33Eu0.33Gd0.33)Ba2Cu3Oy superconductor. We found two types of stable nanometer-scale particles, small LRE-Ba2CuZrOy and (LRE,Zr)BaCuOy(LRE=Sm,Eu,Gd) ones, in the 10–60nm range, and larger particles of Gd2BaCuO5 “Gd-211,” around 100nm in size. A substantial increase of critical current density was observed up to 90K. Experimental data were interpreted in terms of additive pinning by “large” defects and a point-like disorder. The nanosized particles open a new horizon for production of bulk high-Tc superconducting magnets.