Structure and Superconductivity in YBa2Cu3O7-δ with Additives of Nano-Sm2O3

The effects of small concentration of nanometer (<= 25 nm) Sm2O3 particle addition on the structure, microstructure and superconductivity of YBCO have been studied. Polycrystalline samples were synthesized through solid state reaction by adding Sm2O3 in x wt. % (x = 0.0 - 0.6). The phase formation of all samples has been characterized by X-ray diffraction (XRD) and detailed crystal structure analysis was carried out using a Rietveld refinement technique. The results revealed that only YBCO single phase reflection is observed for samples with x <= 0.3 wt. % and 211 secondary phases is observed for samples with x >= 0.4 wt. % and no orthorhombic-to-tetragonal transition occurred. Sm3+ was found to incorporate into the crystal structure and could occupy both in Y- and Ba-sites. As the Sm2O3 concentration increased, Tc-zero value determined by four point probe technique decreases linearly from 89 K (x = 0.0) to 81 K (x = 0.6). It seems that the suppression of T may relate to the decrease of the hole concentrations.