Studies of substitution in RBa2Cu3Oy

Document Type

Conference Proceeding

Publication Date

12-1-1992

Abstract

0.33-33% of the Cu in superconducting YBa2Cu3Oy has been replaced by Li (i.e., x = 0.01-1 in single-phase or nominal YBa2Cu3-xLixOy, x-ray diffraction powder patterns remain the same as YBa2Cu3Oy, with identical patterns up to about 17% substitution (i.e., x = 0.5). At higher percentages an additional phase appears. Electrical conductivity measurements indicate a small elevation of Tc at low Li content. Starting at about 5% Li (x = 0.15), Tc declines progressively and its width increases at x is raised. Attempts to substitute Bi for Nd in orthorhombic NdBa2Cu3Oy prepared in air or oxygen at about 950°C led instead to formation of Ba2NdBiO6, a new cubic compound with a = 0.8703 nm. The possibility was then explored of preparing superconducting (Nd1-xBix)Ba2Cu3Oy by first forming the tetragonal phase at 880-950°C in nitrogen or argon followed by reheating in oxygen or air at 250-500°C in order to insert the additional oxygen required to yield the orthorhombic form while avoiding oxidation of Bi3+ to Bi5+. X-ray diffraction studies, electrical conductivity measurements, and thermogravimetric analysis of products indicate that Bi does not enter the NdBa2Cu3Oy lattice in either the tetragonal or the orthorhombic phase. Ba2NdBiO6 clearly forms on reheating in oxygen or air even at low temperatures, and evidence is presented that a poorly crystallized oxygen-deficient form of this compound is already present prior to the reheating.

Identifier

0026971009 (Scopus)

ISBN

[0816905673]

Publication Title

Aiche Symposium Series

ISSN

00658812

First Page

24

Last Page

34

Issue

287

Volume

88

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