Lattice dynamics

Structure and superconducting properties of nonstoichiometric YBa$_2$Cu$_3$O$_y$ annealed at 300$^\circ$C in a dry argon atmosphere

S. G. Titova^a, Yu. V. Blinova^b, S. V. Sudareva^b, I. B. Bobylev^b, N. A. Zyuzeva^b, E. P. Romanov<sup>b

a</sup> Institute of Metallurgy, Ural Division of the Russian Academy of Sciences, Yekaterinburg
^b Institute of Metal Physics, Ural Branch of the Russian Academy of Sciences, Ekaterinburg

Abstract: Using the full-profile X-ray analysis of diffraction lines, the behavior of YBa$_2$Cu$_3$O$_y$ nonstoichiometric ceramics upon annealing at 300$^\circ$C in a dry inert atmosphere has been investigated. It has been established that, in the YBa$_2$Cu$_3$O$_{6.3}$ sample with the initial tetragonal structure, this treatment leads to nucleation of an orthophase with a low degree of rhombicity, which becomes prevailing after annealing for 56 h. In this case, superconductivity with an initial temperature of the transition of $\sim$50 K occurs in the sample. In the YBa$_2$Cu$_3$O$_{6.7}$ sample with the initial orthorhombic structure, the orthophase with a somewhat enhanced rhombicity arises during annealing and becomes prevailing after annealing for 56 h; in this case, $T_c$ of the system grows from 57 to 63 K. Data of the magnetic measurements for both cases can be interpreted as the presence of two orthorhombic phases with different temperatures of transition to the superconducting state in the samples after annealing.

Received: 27.10.2010
Accepted: 22.12.2010

 English version: Physics of the Solid State, 2011, 53:7, 1448–1451

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