The Effect of Synthesis Conditions on the Phase Composition and Structure of Eu[Ba.sub.2][Cu.sub.3][O.sub.6 + [delta]] Samples

The composition and the structure of ceramic Eu[Ba.sub.2][Cu.sub.3][O.sub.6 + [delta]] (Eu-123) oxide samples annealed in steps with varying processing conditions (in air or oxygen and argon atmosphere at a temperature of 940-960[degrees]C for 1-70 h with or without homogenization) were studied by t...

Full description

Saved in:
Bibliographic Details
Published in:Physics of metals and metallography 2018-03, Vol.119 (3), p.216
Main Authors: Klinkova, L.A, Nikolaichik, V.I, Barkovskii, N.V, Fedotov, V.K, Shevchun, A.F
Format: Article
Language:English
Subjects:
Analysis
Annealing
High temperature superconductors
Oxides
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:The composition and the structure of ceramic Eu[Ba.sub.2][Cu.sub.3][O.sub.6 + [delta]] (Eu-123) oxide samples annealed in steps with varying processing conditions (in air or oxygen and argon atmosphere at a temperature of 940-960[degrees]C for 1-70 h with or without homogenization) were studied by the X-ray phase and chemical analysis, electron diffraction pattern analysis, elemental analysis, and high-resolution transmission electron microscopy. Regardless of the processing conditions, Eu-123 nanostructured oxide with a tetragonal or orthorhombic structure and domains 1-20 nm in size was obtained as a result of annealing. Nanostructuring of the samples, which was revealed by high-resolution electron microscopy, is attributed to their chemical nature: the presence of identical structural elements in members of the homologous [Eu.sub.n][Ba.sub.m][Cu.sub.m + n][O.sub.y] series of oxides allows them to intergrow coherently and create an illusion of a single crystal. Just like any other member of the [Eu.sub.n][Ba.sub.m][Cu.sub.m + n][O.sub.y] series, oxide Eu-123 is disproportionate depending on the annealing conditions to form other members of this series located on either side of the dominant oxide. Temperature [T.sub.c] of the superconducting transition of each member of the series depends on the average oxidation state of copper Cu. At [bar.Cu] < 2, all members of the series have a tetragonal structure and do not exhibit superconducting properties. At [bar.Cu] = 2.28, five members of the [Eu.sub.n][Ba.sub.m][Cu.sub.m + n][O.sub.y] series with matrices (Ba : Cu) 5 : 8, 3 : 5, 2 : 3, 5 : 7, and 3 : 4 exhibit superconducting properties with [T.sub.c] = 82-90 K. Keywords: Eu[Ba.sub.2][Cu.sub.3][O.sub.6 + [delta]] oxide, [Eu.sub.n][Ba.sub.m][Cu.sub.m + n][O.sub.y] homologous series, nanostructuring, high-temperature superconductivity DOI: 10.1134/S0031918X18030067
ISSN:0031-918X
1555-6190
DOI:10.1134/S0031918X18030067