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Superconductivity
Effect of structural water on the critical characteristics of highly textured YBa$_2$Cu$_3$O$_{6.9}$
I. B. Bobylev,
E. G. Gerasimov,
N. A. Zyuzeva Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg
Abstract:
The effect of low-temperature treatment (200
$^\circ$C) in a humid argon atmosphere and subsequent annealing (930
$^\circ$C) on the critical parameters of a highly textured YBa
$_2$Cu
$_3$O
$_{6.9}$ has been studied. During annealing at
$T$ = 200
$^\circ$C, the absorbed water is incorporated into the structure of the compound, which is accompanied by the deterioration of its superconducting properties. However, after the recovery annealing at
$T$ = 930
$^\circ$C and subsequent oxidation, the superconducting characteristics (
$j_c$,
$B_{1c}$, and
$F_p$) are improved. This is explained by the formation of 124-type planar defects, which are effective pinning centers, especially in high fields applied perpendicular to the
$\mathbf{c}$ axis
$(\perp\mathbf{c})$. The optimum conditions of double annealing substantially increasing the critical current density (
$j_c\ge10^4$ A/cm
$^2$) in an external magnetic field up to 10 T and also the first critical fields have been found. In fields up to
$\sim$3 T, the critical current density
$j_c$ is isotropic despite the conservation of high texture in the samples.
Received: 26.03.2014
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