Thermoelectric power and resistivity of Nd1-xPrxBa2Cu3O7-delta

The structural and transport properties of Nd1-xPrxBa2Cu3O7-delta (x = 0.0, 0.05, 0.10, and 0.15), have been studied by X-ray powder diffraction, elec trical resistivity measurements, and thermoelectric power measurements. The decrease of the superconducting critical temperature with doping is descri bed by a parabolic term and a linear term. The c-axis lattice parameter and the cell volume decrease with doping up to x = 0.10. Analyses of the therm oelectric power, critical temperature, c-axis lattice parameter, and the ce ll volume suggest that the Pr ions have a valence close to +4 at low doping concentration. The room temperature resistivity indicates that hole concen tration decreases with increasing Pr doping. The room temperature thermoele ctric power is positive for all samples and increases with increasing Pr do ping due to a decrease in the carrier concentration. We analyzed the thermo electric power as a function of temperature with a two-band model with an a dditional linear T term. An excellent agreement between model and data was obtained. The band width of the narrow band increases and its peak position moves away from the Fermi energy with increasing doping concentration. (C) 2001 Elsevier Science B.V. All rights reserved.