Photoelectron spectroscopic study ofSrxNbO3

X-ray and ultraviolet photoelectron spectroscopic (XPS and UPS) data were obtained for ${\mathrm{Sr}}_{\mathit{x}}$${\mathrm{NbO}}_{3}$ (x=0.8,0.85,0.9). The valency of the Nb ion was found to be between pentavalent and tetravalent. No shifts of the XPS core-level spectra, such as O 1s, Sr 3p, and Sr 3d, were observed in this system even when x was varied. For all samples, sharp Fermi edges were observed with He I (21.2 eV) photon excitation. The results indicate that this valence band was mainly caused by the hybridization between the O 2p and Nb 4d orbitals, as had been proposed for the tungsten bronze by Goodenough. Eu substituted samples, (Sr,Eu${)}_{0.9}$${\mathrm{NbO}}_{3}$, were also studied. An additional sharp peak, due to Eu 4f state, was clearly observed in the valence-band region close to the Fermi level.