Excess Conductivity Analysis of PbO Nanoparticle Added YBa2Cu3O7-δ Superconductor

The effects of nano-sized PbO (10-30 nm) addition on the excess conductivity of YBa2Cu3O7-delta have been studied. Excess conductivity is the fluctuations in conductivity due to the interaction of normal electrons with the Cooper pairs near the critical temperature, T-c. Samples with starting composition YBa2Cu3O7-delta (PbO)(x) for x = 0.00-0.45 weight percent (wt. %) were prepared using the solid state reaction method. Superconducting fluctuations and excess conductivity were analyzed using the Aslamazov-Larkin (AL) theory to determine the conductivity dimensions lambda. The Lawrence-Donaich (LD) theory was used to determine the coherence length xi c(0), Josephson coupling J, and the anisotropy gamma = (xi(ab)(0)/xi(c)(0)). The onset transition temperature, T-c onset was highest (T-c onset = 94 K) for the sample with x = 0.35. Conductivity analysis showed that nano-sized PbO induced transition from 2 dimensional to 3 dimensional conductivity with the highest transition temperature T2D-3D in the x = 0.20 sample. The Lawrence-Donaich model showed the longest coherence length xi(c)(0) and lowest anisotropy for the x = 0.25 sample. This sample also showed the highest Josephson coupling, J = 0.296. The two possible effects of nanosized PbO addition in YBa2Cu3O7-delta is the formation of non-superconducting regions and the improved inter-grains connectivity enhanced the superconducting properties.