Effects of Re substitution on the structure and superconductivity of Cu1-xRexBa2YCu2Ow

F. Licci et al., Effects of Re substitution on the structure and superconductivity of Cu1-xRexBa2YCu2Ow, PHYSICA C, 355(3-4), 2001, pp. 267-277
Citations number
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science
Journal title
ISSN journal
0921-4534 → ACNP
Year of publication
267 - 277
SICI code
Samples of Cu1-xRexBa2YCu2Ow, with nominal x = 0, 0.05, 0.1 and 0.15, and 6 .91 less than or equal to w less than or equal to 7.17 were prepared and ch aracterized. The aim was to evaluate the possibility of improving the trans port and magnetic properties of CuBa2YCu2Ow. (YBCO) by substituting Cu in t he reservoir blocks (Cu1) with a high-valent element such as Re. X-ray powd er diffraction and energy dispersive spectroscopy (EDS) studies indicated t hat Re substitutes for Cu1 up to x approximate to 0.1, beyond which it segr egates, mostly by forming a cubic phase with a approximate to 8.275 Angstro m. Such an impurity was identified as YBa2ReO6 on the basis of the powder x -ray and neutron diffraction data and EDS microanalysis. The crystal struct ure of Cu1-xRexBa2YCu2Ou was refined by the Rietveld analysis based on powd er neutron diffraction data. It is orthorhombic (Pmmm space group), with a, b and c (approximate to3.84, 3.88 and 11.70 Angstrom) depending on v and u . The Re cations were found to occupy the (0 0 0) position and to be surrou nded by 6 oxygen atoms at the vertices of an octahedron (201, 204 and 205). Such units do not significantly perturb the YBCO structure. No ordering be tween Cu and Re was observed by electron diffraction. The resistive and mag netic measurements indicated that the optimum oxygen doping of the Re-doped YBCO occurs at w > 7. The corresponding Cu average valence is approximate to2.27 +/- 1%, T-c of the optimally doped samples is not very sensitive to the Re content and remains as high as approximate to 91 K when I = 0.1. The residual resistivity extrapolated at T = 0 K scales linearly with. x, acco rding to the Mathiessen's rule. SQUID measurements for the x = 0.05 and x = 0.1 samples indicated that H-irr and j(c) are lower than those of the undo ped phase at any temperature. (C) 2001 Published by Elsevier Science B.V.