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Systematic conductivity measurements near T c in granular ͑Bi,Pb͒-Sr-Ca-Cu-O superconductors are presented, and focus is given on the interplay between thermal fluctuations and disorder at micro-and mesoscopic levels. Experiments show that the resistive transition is a two-step process. In the normal phase, Gaussian and critical fluctuation conductivity regimes were identified. Both are affected by local disorder. Particularly, the critical regime is characterized by a power law with exponent cr ϳ3, which we interpret as resulting from microscopic granularity. Below T c and in the regime describing the approach to the zero-resistance state, fluctuation conductivity diverges as expected in a paracoherent-coherent transition of a mesoscopic granular superconductor. The results show that, instead of trivially rounding the transition, disorder at micro-and mesoscopic levels preserves a true critical phenomenology in granular superconductors.

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