Electronic structures of protonic conductors SrTiO3 and SrCeO3 by O 1s X-ray absorption spectroscopy

The electronic structures of protonic conductors SrTi1−xScxO3 and SrCe1−xYbxO3 have been studied by O 1s X-ray absorption spectroscopy (XAS). In SrTi1−xScxO3, hole state and acceptor-induced level are observed in the band gap energy region. Such a structure is also observed in the O 1s XAS spectra of SrCe1−xYbxO3. The XAS structures and their temperature dependence reflect the activation energy estimated from electrical conductivity. These facts indicate that the conductivity is achieved by deep acceptor-induced level lying in the middle of the band gap.