Fluctuation conductivity of polycrystalline Hg, Tl-1223

Detailed resistivity measurements were made for polycrystalline Hg1−xTlxBa2Ca2Cu3O8+δ (x=0 and 0.2) in zero field and above the superconducting Tc. The fluctuation conductivity Δσ is analyzed. With decreasing temperature two crossover temperatures could be identified for each sample; i.e. T∗ from two to three dimensional fluctuations in the mean field region (MFR), and TG from the MFR to the critical region. All results are in agreement with the Lawrence–Doniach model. The c-axis coherence length and the interlayer coupling factor were obtained.