Evidence of Eu2+ 4f electrons in the valence band spectra of EuTiO3 and EuZrO3

We report on optical band gap and valence electronic structure of two Eu2+-based perovskites, EuTiO3 and EuZrO3 as revealed by diffuse optical scattering, electron energy loss spectroscopy, and valence-band x-ray photoelectron spectroscopy. The data show good agreement with the first-principles studies in which the top of the valence band structure is formed by the narrow Eu 4f(7) electron band. The O 2p band shows the features similar to those of the Ba(Sr)TiO3 perovskites except that it is shifted to higher binding energies. Appearance of the Eu2+ 4f(7) band is a reason for narrowing of the optical band gap in the title compounds as compared to their Sr-based analogues. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4761933]