X-ray absorption study on PbBaSrYCu3O7+Δ and PbBaSr(Y,Ca)Cu3Cu3O7+Δ

X-ray absorption fine structure on the Cu K and the Pb L3-edges of PbBaSrY1-xCaxCu3O7+Δ has been measured. The Cu K-near-edge spectra evidence the existence of Cu1+ comprised in O-CuO linear chains in the oxygendeficient phase with Δ=0. The Cu K-edge position shifts to higher energy retaining the Cu1+ feature by substitution of Y3+ with Ca2+ for in the oxygen-deficient phase, indicating that holes are supplied to the CuC>2 basal planes of the pyramids. The Pb valence is found to be mixed states of 2+ and 4+ in the oxygen-rich phase with Δ>1 and the average Pb valence is estimated as 3.3+.