Abstract
We report electrical conductivity fluctuation measurements on different Bismuth-based granular samples synthesized under same processing conditions. Using the fluctuation conductivity Delta sigma as a function of the reduced temperature E; in the range -7 < ln epsilon < 1, we identified Gaussian and critical fluctuation conductivity in (Bi,Pb)-2223 and Bi-2212 samples. Within the mean field region, samples show predominately two dimensional (2D) behaviour with exponent lambda = -1. Closer to critical temperature T-C, we have observed a crossover of lambda from -2/3 to -1/3 in the critical region. The obtained exponents are consistent with 3D-XY model predictions. The regime with the critical exponent -2/3 is dominate in the case of (Bi,Pb)2223 sample. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.