TRANSFORMATIONS OF THE LOCAL-STRUCTURE OF YBA2CU3O7-DELTA DUE TO LASER ANNEALING

Raman spectroscopy has been applied to probe the local oxygen arrangem ents before, during, and after laser irradiation. During annealing the structure can be described as the high-temperature T' phase inlaid wi th ordered domains. The phase separation reported earlier for the case delta similar to 0.5 is found to take place over the whole 0 < delta < 1 range at room and low temperatures. The main Raman phonon bands co ntain a superposition of Ortho-I, Ortho-II and T components. The varia tions of the Raman mode intensities of the Ortho-I, Ortho-II and T mod ifications with laser irradiation dose follow the expected changes of relative weight of the corresponding microphases. Additional Raman ban ds that become strongly enhanced during annealing are assigned to vibr ations of Cu(1) and O(1) atoms belonging to Cu(1)(n+1)O(1)(n) (n = 1,2 ,...) chain fragments. (C) 1997 Elsevier Science B.V.