XPS and XANES study on Pb₂Sr₂YCu₃O_8+δ and PbBaSr(YCa)Cu₃O_7+δ

The charge distribution in Pb₂Sr₂YCu₃O_8+δ and PbBaSrY_1-xCa_xCu₃O_7+δ has been studied by X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge structure (XANES). The Cu 2p core-level and the Pb M₃ XANES show that the valences of Cu and Pb in the blocking layers are + 1 and + 2, respectively, for the oxides synthesized in a reducing atmosphere (δ = 0). The valences of Cu and Pb increase after oxidation by annealing in O₂ gas. On the other hand, the substitution of Ca for Y (x = 0.2) hardly changes the valences of Cu and Pb. The core-levels of Ba, Sr and Y are not changed in the binding energy by the oxidation, but are shifted to the lower-binding-energy side by the substitution. These results will be discussed in terms of charge distributions in the crystal structures before and after the oxidation and substitution.