Electronic structure of protonic conductor SrZr0.90M0.10O3 (M = Y3+, Sc3+) probed by soft-X-ray spectroscopy

The electronic structure of protonic conductor SrZr1–xMxO3–δ (M = Y3+, Sc3+) has been studied by soft-X-ray spectroscopy. The valence band is mainly composed of O 2p state. The conduction band is composed of Zr 4d state. The holes and the acceptor level are observed at the top of valence band and just above the Fermi level (EF), respectively. In H2-annealed SrZr1–xMxO3–δ (M = Y3+, Sc3+), their intensities decrease and the hydrogen-induced level is created at just below EF. The energy separation between the bottom of the hydrogen-induced level and the top of valence band agrees with the activation energy estimated from the electrical conductivity.