Journal of Superconductivity

, Volume 7, Issue 6, pp 917–920 | Cite as

Substitution-induced mid-gap states in R x Ba1−xTiO3−δ whereR = Y, La, and Nd

  • S. W. Robey
  • L. T. Hudson
  • C. Eylem
  • B. Eichhorn


Changes induced in the electronic structure of BaTiO3 by substitutions of R = Y, La or Nd for Ba to form the mixed oxides R x Ba1−xTiO3−δ have been investigated using ultraviolet photoelectron spectroscopy. Substitution of formally R+3 ions for Ba+2 leads to the introduction of filled states in the band gap that are shown by resonant photoemission measurements to have significant Ti 3d character, consistent with a Mott-Hubbard insulator description for these oxides. It is suggested that the dominant factor is electron-electron correlation and this leads to the estimatesU∼Δ∼3 eV for this system, whereU is the correlation energy for the 3d and Δ is the charge transfer energy. Changes are observed in the photoelectron spectral shape for these states as a function of increasing substitution in the Nd system and discussed in the context of the opening of the Hubbard gap.

Key words

Mixed oxides doping electronic structure photoemission 


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Copyright information

© Plenum Publishing Corporation 1994

Authors and Affiliations

  • S. W. Robey
    • 1
  • L. T. Hudson
    • 1
  • C. Eylem
    • 2
  • B. Eichhorn
    • 2
  1. 1.National Institute of Standards and TechnologyGaithersburg
  2. 2.Department of Chemistry and Center for Superconductivity ResearchUniversity of MarylandCollege Park

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