X-ray absorption study on PbBaSrYCu₃O_7+δ and PbBaSr(Y, Ca)Cu₃O_7+δ

Abstract

X-ray absorption fine structure on the Cu K and the Pb L₃-edges of PbBaSrY_1−xCa_xCu₃O_7+δ has been measured. The Cu K-near-edge spectra evidence the existence of Cu¹⁺ comprised in O-Cu-O linear chains in the oxygen-deficient 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 CuO₂ 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+.