INFLUENCE OF THE GRANULARITY ON THE THERMOELECTRIC-POWER OF POLYCRYSTALLINE BI1.5PB0.5SR2CA2CU3OY SUPERCONDUCTORS

We first present an empirical picture of the influence of the sample s tructural inhomogeneities, at length scales much larger than the super conducting correlation length amplitude, on the thermoelectric power, S(T) in copper oxide superconductors. Then, we present experimental re sults on S(T) near the superconducting transition obtained in two poly crystalline Bi1.5Pb0.5Sr2Ca2Cu3Oy samples with different granularity. In full agreement with our empirical model, our results show that the reduced temperature (epsilon) behaviour of the thermopower excess near but above the transition, DELTAS(epsilon), is the same for the two di fferent samples. For completness we also analize the excess of the the rmopower coefficient, L=Ssigma.