XPS and XANES study on Pb_2Sr_2Cu_3O_8+δ ans PbBaSr(YCa)Cu_3O_7+δ

摘要

The charge distribution in Pb_2Sr_2YCu_3O_8+δ and PbBaSrY_1-χCa_χCu_3O_7+δ has been studied by X-ray photoelectron spectro- scopy (XPS) and X-ray absorption near-edge structure (XANES), The Cu 2p core-level and the Pb M_3 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 O_2 gas. On the other hand, the substitution of Ca for Y(=0.2) hardly changes the valences of Cu and Pb.