RBa2-xLRxCu3O7-δ HTSC-A comparative study

Full text: The Tc suppression phenomena in high temperature superconductors have been a long standing subject of extensive studies and there still remain several problems unsolved. The origin of the anomalous behavior of Pr in the superconductor insulator transition with Pr doping in RBa2Cu3O7+61540; (R123) might give important clues in the study of the superconducting mechanism for high-Tc copper oxide superconductors. So, rare-earth substitutions in high temperature superconductor Y123 have long been studied. For comparing the effect of light rare earth (LR) substitution in 123 system we have fabricated the Gd(Ba2-xLax)Cu3O7+ 61540; 61472;[Gd(BaLa)123], Gd(Ba2-xNdx)Cu3O7+ 61540; [Gd(BaNd)123] and Nd(Ba2-xPrx)Cu3O7+ 61540; [Nd(BaPr)123] by the solid-state reaction method, characterized by XRD and iodometric titration, and compared their resistivity, magnetoresistivity, and structural properties with each other and with Gd(BaPr)123 and other similar compounds. The XRD patterns indicate that all Gd(BaLa)123 compounds are single phase 123, while for the Gd(BaNd)123 and Nd(BaPr)123 samples with x>0.5, several impurity peaks appear in the range of 29 8804; 952; 8804;31, which indicates that the amounts of doping exceed the solubility limit. It is due to difference radius of substituted rare earth. The resistivity measurements show that the increase of Nd doping at Ba site is more effective than La in increasing the resistivity and decreasing Tc in Gd123. The comparison of these results with Gd(BaPr)123 shows that effect of Pr at Ba site is similar to the effect of Nd at Ba site in suppression of superconductivity. In addition, the increase of resistivity and decrease of Tc with increase of Pr in Nd(BaPr)123 is more than in Gd(BaPr)123. It seems that Pr at Ba site in Nd123 is more effective than in Gd123 in the suppression of superconductivity. (authors)