EFFECTS OF LATTICE DISORDER ON THE SUPERCONDUCTING PROPERTIES OF YBA2CU3O6.9 FILMS

We report on striking sensitivity of the superconducting properties of ion-beam sputtered YBa2Cu3O6.9 films to the lattice disorder (induced by varying growth temperatures). T-c decreases with increasing disord er, while the width of the resistive transition and the normal state r esistivity increase. We give a quantitative significance to this trend by expressing the degree of the disorder in terms of the lattice cohe rence length r(c) that is extracted from the width of X-ray diffractio n rocking curves. We find that T-c saturates to the maximum of approxi mate to 92 K for r(c) > 10 nm.