Study of the heterogeneous nucleation of 211-particle by the addition of CeO2 precursor with different sizes

The microstructure and superconducting properties of air-processed melt-textured grown Y-Ba-Cu-O samples with the addition of CeO₂ precursor of different sizes, e.g. micro-scale and nano-scale were studied. Samples with micro-scale CeO₂ addition exhibit an enhanced Jc, which were attributed to the refinement of 211-particles. The mechanism for refining the 211-particles was proposed to be the formation of new nuclei sites from the reaction of CeO₂ and Y2-1-1 matrix in the melt-grown process. By reducing the CeO₂ precursors to nano-scale from micro-scale, significantly more heterogeneous nucleation site will be introduced with the same amounts of CeO₂ additions. And the J_c will be enhanced with the refining of 211 particles. But in this study, it shows the opposite results. The higher J_c value is enhanced by doping micro-scale CeO₂. Pinning forces vs. magnetic field studies indicated that both the nano- and micro- CeO₂ samples have the same pinning mechanisms as compared with that of the un-doped sample.