Possible Existence of a Superconducting Phase in Highly Oxygen-Deficient YBa2Cu3Oy (y<6.5)

Abstract
YBa2Cu3O y with various values of y was successfully prepared by slow cooling in Ar gas. The phase identification by an X-ray diffractometer indicates that the orthorhombic phase extends down to about y=6.2. Measurements of the superconducting transition in terms of complex susceptibility have revealed that the superconducting phase exists even for yT c phase with a different vacancy-ordered structure in the Cul-O planes.