Synthesis of a superconducting oxide by oxidation of a metallic precursor

A Eu-Ba-Cu alloy was oxidized completely in pure oxygen gas at 1 atm pressure at 300 °C. The alloy, which was produced by conventional melting and solidification techniques, and which was in-homogeneous, yielded an inhomogeneous oxidation product upon complete oxidation. After annealing in pure oxygen at a higher temperature (800 to 900 °C) for a sufficiently long time, the oxidation product became a high-temperature superconducting oxide (EuBa₂Cu₃07_7-x ). The onset of super-conductivity occurred at 92 K. The diamagnetic screening at 10 K for a sample cooled in zero field was approximately 70 pct of the ideal value, and a substantial Meissner effect was observed.