6533b81ffe1ef96bd1276f2d

RESEARCH PRODUCT

X-ray-absorption spectroscopy ofNd3+-exchanged β-alumina crystal

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The results of x-ray-absorption spectroscopy investigations of ${\mathrm{Nd}}^{3+}$ ions in a nearly fully exchanged (93%) sodium \ensuremath{\beta}-alumina crystal are reported. The ${\mathrm{Nd}}^{3+}$ local environment is reconstructed using a multishell best fit procedure and is compared with existing structural models. The experimental extended x-ray-absorption fine-structure (EXAFS) spectra are also compared with model ab initio FEFF6 calculations based on the x-ray-diffraction data for the ${\mathrm{Nd}}^{3+}$ ions located at the BR(2d) and interstitial A(6h) sites of \ensuremath{\beta}-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 \ensuremath{\sim}0.6 \AA{} from the crystallographic positions occupied in sodium \ensuremath{\beta}-alumina. The atoms located at the spinel blocks below and above the conduction plane produce negligible contribution to the total Nd ${\mathit{L}}_{3}$ edge EXAFS signal due to the polarization effect and, mainly, to thermal and/or static disorder. The similarity of the local structure around the ${\mathrm{Nd}}^{3+}$ ions in the \ensuremath{\beta}- and ${\mathrm{\ensuremath{\beta}}}^{\mathrm{\ensuremath{''}}}$-alumina crystals is also discussed. \textcopyright{} 1996 The American Physical Society.