X-RAY-ABSORPTION SPECTROSCOPY OF A ND3+-EXCHANGED BETA''-ALUMINA CRYSTAL

We present an x-ray-absorption spectroscopy study of the electronic and crystallographic structure around the Nd3+ ions in 60% Nd-exchanged sodium beta''-alumina crystal. Using a multishell best-fit analysis procedure, we reconstructed the Nd3+ local environment and compared it with existing structural models. We found that neodymium ions are mainly located near the mO(9d) sites of the conduction region; they are strongly bonded to two O(5) oxygens which are located in the same plane and shifted from their ideal crystallographic positions in sodium beta''-alumina crystal. In particular, with respect to crystallographic parameters of sodium beta''-alumina, the Nd-O(5) distance is shortened by 0.36 angstrom, while the Nd-Al(6c) is slightly increased by 0.13 angstrom. Comparative analysis of Debye-Waller factors obtained for different coordination shells shows evidence of correlation in the vibrational motion of neodymium with the O(5) oxygens and with the Al(6c) aluminums