Abstract
We have isolated a high- phase in the Bi-Sr-Ca-Cu-O system of composition . The crystal substructure has a tetragonal unit cell Å, Å) with similarities to both the oxygen-defect perovskites and the Ni structure of Cu. The oxygen content, determined by titration and thermogravimetric analysis experiments, corresponds to a formal oxidation state Cu(2.15). Oxygen can be reversibly depleted in an argon ambient in an amount corresponding to the reduction of the Cu(III) into Cu(II). The compound has a metalliclike resistance above its near 85 K. Processing this precursor compound by heating to temperatures near its melting point (885 °C) produces a sharp resistivity drop near 110 K that we show by ac susceptibility and Meissner effect is due to a superconducting transition.
- Received 11 February 1988
DOI:https://doi.org/10.1103/PhysRevB.37.9382
©1988 American Physical Society