EFFECT OF OXYGEN DEPLETION ON THE TRANSPORT-PROPERTIES OF YBA2CU3O7-DELTA

We report measurements of the resistivity (rho), thermoelectric power (TEP), and Hall coefficient (R(H)) of sintered YBa2Cu3O7-delta for a range of delta-values and for temperatures up to 300 K. As delta is increased, T(c) increases slightly, reaching a maximum for delta-close to 0.1, and the TEP changes sign from negative to positive, while R(H) is positive for all values of delta. At low values of delta there is a marked increase in the fluctuation conductivity, which we have analyzed in terms of Aslamazov-Larkin fluctuations to determine the out-of-plane correlation length xi(perpendicular-to) (0). A corresponding analysis of specific-heat data enables us to deduce the in-plane correlation length as well. We discuss the strong dependence of the Hall number on temperature and delta.