Effect of oxygen desorption on electrical transport in YBa sub 2 Cu sub 3 O sub (7-delta).

The electrical resistivity of polycrystalline YBa sub 2 Cu sub 3 O sub (7-delta) between room temperature and 900C was measured as a function of oxygen partial pressure and correlated with stoichiometry delta. The observed strong increase in resistivity at T>400C can be explained by a model of homogeneous disorder, in which the density of electronic states is depressed linearly with delta as (delta sub c - delta), where delta sub c ~ 0.85, and the elastic scattering rate is proportional to delta. The orthorhombic-to-tetragonal structural transition is marked by an intrinsically-broadened discontinuity in the resistivity temperature derivative and occurs at a value of delta which increases with reduced oxygen partial pressure.