Single-phase 60-K bulk superconductor in annealed Ba2YCu307−δ(0.3<δ<0.4) with correlated oxygen vacancies in the Cu-O chains

Abstract

Employing a gettered annealing technique, we have prepared homogeneous polycrystalline samples of oxygen-deficient ${\mathrm{Ba}}_2\mathrm{Y}{\mathrm{Cu}}_3{\mathrm{O}}_{7-\delta }$ for $0\le \delta \le 0.7$. Measurements of resistive $T_c$, resistivity, magnetization, and lattice parameter indicate that a distinct bulk superconducting phase with a $T_c$ of 60 K occurs in the range of $0.3<\mathrm{}\delta <0.4\mathrm{}$. This phase displays partial ordering of oxygen vacancies in the Cu-O chains as found by electron diffraction studies.