Fluctuation conductivity in NdBa2Cu3Oy superconductors with the different amounts of 422 phase

Fluctuation conductivity analysis was carried out to characterize NdBa₂Cu₃O_y superconductors with the different amounts of Nd₄Ba₂Cu₂O_y (Nd422) phase. Samples were prepared by melt-textured process from the mixtures in molar ratios of Nd123: Nd422 = 1:x (x = 0.2, 0.25, 0.3). The conduction dimensionality and the fluctuation amplitude were obtained by analyzing the fluctuation conductivity. The dimension of conduction on excess conductivity showed little variation by the addition of 422 phase. The coherence length and the correlation length obtained by this analysis became larger with increasing amount of 422 phase. The clear evidence was found that the pinning force in the sample was well correlated with the characteristic length of superconductivity.