Fluctuation conductivity of polycrystalline Y1-xPr xBa2Cu3O7-delta superconductors

Abstract

We studied the effect of superconducting fluctuations on the electrical conductivity of granular samples of Y 1−x Pr x Ba 2 Cu 3 O 7−δ superconductors, with x =0.01, 0.03, 0.05, 0.07 and 0.10. Samples were prepared by the standard solid-state reaction technique, with two different types of calcination process, in air at 900˚C ( x ≤ 0.07 ) and in vacuum at 850˚C ( 0.05 ≤ x ≤ 0.10 ). For the samples prepared in air, our results revealed a splitting of the bulk transition, denoted by T C1 and T C2 , besides the coherence transition. It was observed fluctuation regimes above the highest transition ( T C1 ) and the lowest transition ( T C2 ). For the samples calcinated in vacuum and high concentrations of Pr, changes were observed in the critical region with chemical substitution of the Pr ion for the Y ion. In the regime of approach to the zero resistance state it was observed an occurrence of a coherence transition for all concentrations of praseodymium.