The results of x-ray-absorption spectroscopy investigations of Nd31 ions in a nearly fully exchanged ~93%! sodium b-alumina crystal are reported. The Nd31 local environment is reconstructed using a multishell best fit procedure and is compared with existing structural models. The experimental extended x-ray-absorption finestructure ~EXAFS! spectra are also compared with model ab initio FEFF6 calculations based on the x-raydiffraction data for the Nd31 ions located at the BR~2d) and interstitial A(6h) sites of b-alumina. Neodymium ions are mainly found near the BR~2d) sites of the conduction plane, where they are strongly bonded to three O~5! oxygens located in the same plane and shifted by ;0.6 Å from the crystallographic positions occupied in sodium b-alumina. The atoms located at the spinel blocks below and above the conduction plane produce negligible contribution to the total Nd L3 edge EXAFS signal due to the polarization effect and, mainly, to thermal and/or static disorder. The similarity of the local structure around the Nd31 ions in the b- and b9-alumina crystals is also discussed.
X-ray-absorption spectroscopy of Nd3+-exchanged beta-alumina crystal
MARIOTTO, Gino
1996-01-01
Abstract
The results of x-ray-absorption spectroscopy investigations of Nd31 ions in a nearly fully exchanged ~93%! sodium b-alumina crystal are reported. The Nd31 local environment is reconstructed using a multishell best fit procedure and is compared with existing structural models. The experimental extended x-ray-absorption finestructure ~EXAFS! spectra are also compared with model ab initio FEFF6 calculations based on the x-raydiffraction data for the Nd31 ions located at the BR~2d) and interstitial A(6h) sites of b-alumina. Neodymium ions are mainly found near the BR~2d) sites of the conduction plane, where they are strongly bonded to three O~5! oxygens located in the same plane and shifted by ;0.6 Å from the crystallographic positions occupied in sodium b-alumina. The atoms located at the spinel blocks below and above the conduction plane produce negligible contribution to the total Nd L3 edge EXAFS signal due to the polarization effect and, mainly, to thermal and/or static disorder. The similarity of the local structure around the Nd31 ions in the b- and b9-alumina crystals is also discussed.
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