Local structure and valence states in PbBaSrY_1-xCa_xCu₃O_7+δ and Pb₂Sr₂Y_1-xCa_xCu₃O_8+δ

X-ray absorption fine structure on the Cu K and the Pb L₃-edges of PbBaSrY_1-xCa_xCu₃O_7+δ and Pb₂Sr₂Y_1-xCa_xCu₃O_8+δ systems has been measured. In the oxygen-deficient phase with δ=0 of these systems, the Cu K-near-edge spectra evidence the existence of Cu¹⁺ comprised in OCuO linear chains. The Cu K-edge position shifts to higher energy retaining the Cu¹⁺ feature by substitution of Y³⁺ with Ca²⁺ in the oxygen-deficient phase, indicating that holes are supplied to the CuO₂ basal planes of the pyramids. The Pb valence is found to be mixed states of 2+ and 4+ in the oxygen-rich phases with δ>1. The average Pb valence is estimated as 3.3+ and 3.04+ in PbBaSrYCu₃O_8.4 and Pb₂Sr₂YCu₃O_9.5, respectively.