Oxygen Stoichiometry, superconductivity and normal state properties of Ba sub 2 YCu sub 3 O sub (7-delta).

Work presented thus far on the oxygen stoichiometry dependence of both superconducting and normal state properties of Ba sub 2 YCu sub 3 O sub (7-delta) has considered the problem to be one-dimensional in nature, that is, only dependent on the value of delta. We present here data which indicate the issue to be considerably more interesting and complex, with the properties dependent on the microscopic nature in which the oxygen is accommodated. The microscopic variables involve the actual distribution of oxygen over the available sets of oxygen sites, with that distribution strongly dependent on synthetic conditions, even at fixed delta.