X-RAY PHOTOELECTRON STUDY OF THE NON-EQUIVALENT OXYGEN LATTICE SITES IN Y-BA-CU OXIDES

X-ray photoelectron spectroscopy was applied to the perovskite-type material YBa2Cu3O7-δ to distinguish among the four structurally non-equivalent oxygen sites in the orthorhombic phase and three structurally non-equivalent oxygen sites in the tetragonal phase. In each case though, two of the sites are chemically identical and hence indistinguishable. The binding energies of the O ls electrons involved were determined. The individual contributions of the non-equivalent oxygens to the total O ls emission are proportional to the number of the particular oxygen sites in the unit cell.