TiO2 addition effect on flux pinning properties of bulk GdBa2Cu3O7−δ superconductors

Abstract TiO 2 dilute doping in melt-processed GdBa 2 Cu 3 O 7− δ bulk superconductors was studied. TiO 2 fine particles are effective additive for the enhancement of flux pinning. TiO 2 doping results in the enhanced δl pinning and the improved T c . Nevertheless, the pinning force characterizations show that δT c pinning still acts as the main role, which can be attributed to the clustered strong superconducting phases and the high B irr values. The trapped field profiles clearly show that the enhanced flux pinning is realized in the doping range from 0.0 mol.% to 0.3 mol.%. Possible reasons behind them are discussed. The main reason is that Ti occupies the Cu site in the CuO chain and thus Ti substituted region forms the high T c superconducting phase. On the other hand, owing to the enhanced strains or dislocations caused by ion substitution, this region also contributes to the enhanced δl pinning.