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