The catalytic activity of hexaaluminate is closely related to the chemical state of substituted active metal ions. In this paper, the mechanism of stabilization of Fe ions in beta(1)-Al2O3 and magnetoplumbite-type Fe-substituted Ba hexaaluminates was proposed at the molecule level on the basis of X-ray diffraction, Rietveld refinement, and Mossbauer spectroscopy. Fe3+ ions originated from oxidic entities dispersed on Ba-modified gamma-Al2O3 mainly entered into the sites in the loosely packed mirror plane of the hexaaluminates. In particular, Fe3+ ions at low concentration preferentially occupied the tetrahedral Al(5) sites of the beta(1)-Al2O3 phase, while Fe3+ ions at high concentration mainly occupied the trigonal bipyramidal Al(5) and octahedral Al(3) sites in the magnetoplumbite phase. Meanwhile, tetrahedral Fe3+ ions in the intermediate spinel-type BaAl2O4 phase preferentially entered into the tetrahedral Al(2) sites in the spinel block of hexaaluminates. Fe ions in the Al(5) sites of beta(1)-Al2O3 and the Al(3) sites of magnetoplumbite phase were highly active for N2O decomposition. (C) 2011 Elsevier Inc. All rights reserved.