Energy shift and hole localization in Y_1-xPr_xBa₂Cu₃O_7-δ from the O 1s X-ray near-edge-absorption spectroscopy

High-resolution O Is x-ray near-edge-absorption spectra of Y_1-xPr_xBa₂Cu₃O_7-δ (abbreviated as Pr_x-123) have been measured. The spectra indicate that the Pr ions not only affect the spectral energies but also the spectral profiles. The binding energy of the Is state of the oxygen in the CuO₂ planes is suggested to become smaller when Y is substituted by Pr. The number of holes derived from the spectral intensity designated the transition of O Is to the valence band suggests that the fraction of Pr⁴⁺ is about 0.3. The holes residing in Pr_x-123 are demonstrated to be localized and completed when Pr concentration is increased beyond x ≅ = 0.5. The result of hole localization is consistent with a model based on the Pr 4f - O 2p hybridization.