Composition and orientation dependence of the O K and Fe L_2,3 EELS fine structures in Ca₂(Al_xFe_1-x)₂O₅

A. Gloter (1) , J. Ingrin (2) , D. Bouchet (1) , C. Colliex (1)

1 LPS - Laboratoire de Physique des Solides
2 UMR 5563 - Laboratoire des Mécanismes et Transferts en Géologie, UMR 5563 CNRS,

Oxygen K edge and iron L_2,3 edges electron-energy-loss spectra have been collected on brownmillerites [Ca₂(Al_x,Fe_1-x)₂O₅] synthesized with different Al/Fe compositions (02,3 edges in these compounds has been evaluated together with its possible influence on the determination of the Fe 3d-band occupation. These results have been used as a reference for the study of the Fe 2p spectra in Si and Ti substituted brownmillerites, which are present on a nanometer scale in cements. They demonstrate that substitution by tetravalent cations into brownmillerite is not accompanied by a significant reduction of the valence of the iron atoms. This suggests that charge compensations operate through the increase of oxygen content in the structure.

Keywords: 61.72.Ww; 71.28.+d; 61.50.Nw; Doping and impurity implantation in other materials; Narrow-band systems; intermediate-valence solids; Crystal stoichiometry

Domains: Sciences of the Universe [physics]

A. Gloter, J. Ingrin, D. Bouchet, C. Colliex. Composition and orientation dependence of the O K and Fe L_2,3 EELS fine structures in Ca₂(Al_xFe_1-x)₂O₅. Physical Review B, 2000, 61, pp.2587-2594. ⟨10.1103/PhysRevB.61.2587⟩. ⟨insu-03642936⟩