Oxygen Content Change Characters and the Influence Superconductivity in the Doped YBCO Systems

The YBa2Cu3-x(doped element)xO7-δ samples were prepared by solid-state reactions and studied by means of XRD, positron annihilation technique and simulation calculation. The results show the local electron density ne saturation and variations of oxygen content, which can be explained by the cluster effect. Another important new result is that the superconductivity does not depend directly on the valence electron density with different dopant. The Tc seems to lose the association with the ne variation. The dopants can be regarded as a kind of defects is similarly an adding or a losing oxygen ion. Oxygen interstitials reflect fractal distributions of dopants. The oxygen content and distribution reflect the superconductivity of the samples.

SHIFT CHARACTERISTICS OF Ni ION DISTRIBUTION IN Y-123 SUPERCONDUCTORS

In Ni -doped YBCO systems, Ni ions have been generally thought to enter Cu (2) sites; in fact, the relevant arguments never ceased in the past decade, because various experimental results have not achieved a definite and consistent conclusion. The present paper systemically investigates YBa 2 Cu 3-x Ni x O 7-δ(x = 0~0.4) cuprates with X-ray diffraction, positron annihilation technique, and simulated calculations. The results show that Ni ions enter Cu (2) sites at the low-doped concentration, as the concentration increases, a certain proportion of Ni ions begin to enter the Cu (1) sites until the appearance of the impurity phase.

Synthesis and superconducting properties of Nd0.33Eu0.08Gd0.58Ba2Cu3Oz materials

We have studied the effect of the ratio of different rare-earth element on the superconducting properties and phase formation of (Nd0.33Eu0.08Gd0.58)Ba2Cu3Oz ceramic. Bulk NEG samples were prepared using the solid-state reaction process. The superconducting transition for Nd0.33Eu0.08Gd0.58Ba2Cu3Oz is T c ≈90 K and the value of the critical current density (J c) is 13.9 A/cm2 at 77 K under zero magnetic fields. This value is twice as high when compared with the (J c) value of YBCO systems (J c = 7.31 A/cm2). The obtained bulk sample was used for the production of superconducting Ag-sheathed tapes by OPIT method including hot rolling. The critical current density of the obtained tape (337 A/cm2) is one order higher than the one of the bulk sample.