Bulk superconductivity at 91 K in single-phase oxygen-deficient perovskite Ba2YCu3O9−δ

Abstract

We have prepared and identified as a single phase the high-temperature superconducting compound in the chemical system Y-Ba-Cu-O, an orthorhombic, distorted oxygen-deficient perovskite of stoichiometry ${\mathrm{Ba}}_2$ ${\mathrm{YCu}}_3$ ${\mathrm{O}}_{9\mathrm{-}\mathrm{\delta }}$ (δ≃2.1). Samples exhibit zero resistance at 91 K, with a transition width of 1.5 K. The Meissner effect attains a value of 76% of the independently measured diamagnetic susceptibility. We estimate parameters that characterize this superconductor, e.g., γ≃3–5 mJ (mole Cu${)}^{\mathrm{-}1}$ ${\mathrm{K}}^{\mathrm{-}2}$. The critical current density at 77 K and H=0 exceeds 1100 A/${\mathrm{cm}}^2$.