ELECTRICAL TRANSPORT IN SUPERCONDUCTING BIPBSRCACUO

Measurements of the magnetic field and temperature dependent electrical resistance and thermoelectric power of a lead-doped polycrystalline sample of BiPbSrCaCuO are reported. According to the d.c. susceptibility data, the sample shows a major Meissner effect at 110 K with an additional feature at 80 K which indicates the presence of the second phase. Magnetoresistance is muck less sensitive to the fraction of the second phase than are the thermopower measurements that clearly resolve a shoulder-like structure at 80 K. The application of a magnetic field results in a positive contribution to the thermopower, S(B, T), below the Tc of the zero-field superconducting phase transition. Based on an analysis of the S(B, T) in terms of the transport entropy of the vortex motion we find that the data for lead-free (Tc = 85K) and lead-doped (Tc = 110K) BiSrCaCuO compounds provide a reasonable estimate of the principal quantum unit h {combining short stroke overlay} 2m of the particle flux. © 1990.