Open AccessX‐ray absorption spectroscopy of transition aluminas
Author(s) -
Chester A. W.,
Absil R. P. A.,
Kennedy G. J.,
Lagarde P.,
Flank A.M.
Publication year - 1999
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049598016549
Subject(s) - absorption (acoustics) , x ray absorption spectroscopy , spectroscopy , materials science , extended x ray absorption fine structure , absorption spectroscopy , x ray absorption fine structure , atomic physics , chemistry , optics , physics , composite material , quantum mechanics
The X-ray absorption spectroscopy of a series of transition aluminas derived from pseudoboehmite (a-alumina monohydrate) by calcination at 350, 400, 538, 750, 1000 and 1200 °C were examined at the A1 edge. The transitions from ordered to disordered structure and eventually back to the ordered corundum structure are easily observed in both the XANES spectrum and EXAFS. The near-edge spectrum consists of 5 peaks, three of which are reasonably constant in intensity throughout the transitions. The first two peaks are attributed to the white lines of tetrahedral and octahedral AI. The tetrahedral AI white line coincides with an additional pre-edge peak, which makes accurate estimation of the tetrahedral content difficult; NMR is more accurate. Other peaks are ascribable to multiple scattering among the AI metal lattice and other structures. The EXAFS show that, with increasing calcination temperature, the AI coordination number decreases and disorder increases, as expected from the known structure changes. With the formation of a-alumina at 1000 and 1200 °C, the coordination number abruptly increases, as expected. This data will be of value in examining alumina structures in supported catalysts.