Valence States of Lead and Bismuth Atoms in the High-Temperature Superconductor BaPb1-xBixO3

X-ray photoelectron spectra of valence bands and core levels of BaPb_0.8Bi_0.2O₃, PbO, PbO₂, BaPbO₃, BaBiO₃, NaBiO₃, and Bi₂O₃ were studied. Comparison of the electron binding energies of the Pb 4f7/2 or Bi 4f7/2 core levels for all the oxides studied showed that the high-temperature oxide superconductor BaPb_0.8Bi_0.2O₃ contains simultaneously two different valence forms of lead atoms (Pb^IV and Pb^II) and two different valence forms of bismuth atoms (Bi^V and BiIII). Parameters of the X-ray photoelectron spectra of the valence bands do not contradict the conclusion on heterovalent states of lead and bismuth atoms in BaPb_0.8Bi_0.2O₃.