The preparation of a high-temperature superconductor based on the Y-Ba-Cu-based system without the use of any extraneous oxygen is reported. Using starting materials with a maximum possible oxygen content of 3.5 oxygen atoms per formula unit of the end product and ambient nitrogen during synthesis, we observe ∼90-K superconductivity. This challenges the traditional understanding of the essential link between oxygen and superconductivity in these materials.

• Received 3 November 1990

DOI:https://doi.org/10.1103/PhysRevB.43.13622