Mis-substitution effect in Gd1-xPrxBa2Cu3O7-δ system

On polycrystalline Gd1-xPrxBa2Cu3O7-delta, samples with x=0.00, 0.05, 0.10, and 0.15, SEM, XRD, and electrical transport experiments have been carried out. Although the samples are homogenous, granular, and show a superconducting transition, the T-c decreases and the transition temperature width increases with increasing doping concentration x. Using Rietveld analysis of the XRD patterns, we have examined the real substitution positions of Gd, Pr, and Ba atoms in these samples. Our results show that the mentioned atoms occupy their own sites, and there is no Gd or Pr at the Ba site and vice versa (i.e., no mis-substitution). Thus, in our samples, Pr atom at rare earth sites suppress the superconductivity, favoring theories based on Pr at the rare earth site for describing the Pr anomaly. (C) 2002 Elsevier Science B.V. All rights reserved.