Valence states of BaBi1-xPbxO3-δ (0≤x≤1) studied by photoelectron spectroscopy

Valence bands and core levels of BaBi1-xPbxO3-δ have been investigated over a full compositional range between x=0 and 1 using x-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS). With the substitution of Pb for Bi, the valence band centered at about 4 eV shifts toward the Fermi level (EF). A clear Fermi edge is observed in both XPS and UPS valence-band spectra for 0.7≤x≤0.9 and change of the density of states at EF is found to correspond to the Tc of this system. Pb 4f and Bi 4f core lines are broadened with x, which is analyzed by means of the peak-decomposition method. The valence states of BaBi1-xPbxO3-δ are discussed and compared with previous calculations.