Electronic Structure of SrBi2Ta2O9 Powders

X-ray diffraction, Raman scattering, and X-ray photoemission of SrBi2Ta2O9 powder sample (the Curie temperature of 310 °C) synthesized from a precursor solution showed that the crystal structure of the SrBi2Ta2O9 unit cell was preserved from bulk to surface, and the surface had never been covered with metallic Bi and/or Bi2O3. The theoretical valence band spectrum, derived from the density of states by full-potential linearized augmented plane-wave computation and the photoionization cross section, reproduced well the experimental valence band spectrum. The computation revealed that the valence band maximum is dominated by the O p states and that the low-energy part of the conduction band is formed from the Bi p and Ta d states hybridizing with the O p states. In the vicinity of the conduction band minimum, the hybridization between Bi p states and Ta d states is weak and the Bi p states have slightly lower energy than the Ta d states.