Structural Characterization of Rare-Earth Doped Yttrium Aluminoborate Laser Glasses Using Solid State NMR

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• 作者：Heinz Deters ; Andrea S. S. de Camargo ; Cristiane N. Santos ; Cynthia R. Ferrari ; Antonio C. Hernandes ; Alain Ibanez ; Matthias T. Rinke ; Hellmut Eckert
• 刊名：Journal of Physical Chemistry C
• 出版年：2009
• 出版时间：September 10, 2009
• 年：2009
• 卷：113
• 期：36
• 页码：16216-16225
• 全文大小：421K
• 年卷期：v.113,no.36(September 10, 2009)
• ISSN：1932-7455

文摘

The structure of laser glasses in the system (B₂O₃)_0.6{(Al₂O₃)_0.4−x(Y₂O₃)_x} (0.1 ≤ x ≤ 0.25) has been investigated by means of ¹¹B, ²⁷Al, and ⁸⁹Y solid state NMR as well as Y-3d core-level X-ray photoelectron spectroscopy. ¹¹B magic-angle spinning (MAS) NMR spectra reveal that the majority of the boron atoms are three-coordinated, and a slight increase of four-coordinated boron content with increasing x can be noticed. ²⁷Al MAS NMR spectra show that the alumina species are present in the coordination states four, five and six. All of them are in intimate contact with both the three- and the four-coordinate boron species and vice versa, as indicated by ¹¹B/²⁷Al rotational echo double resonance (REDOR) data. These results are consistent with the formation of a homogeneous, nonsegregated glass structure. For the first time, ⁸⁹Y solid state NMR has been used to probe the local environment of Y³⁺ ions in a glass-forming system. The intrinsic sensitivity problem associated with ⁸⁹Y NMR has been overcome by combining the benefits of paramagnetic doping with those of signal accumulation via Carr-Purcell spin echo trains. Both the ⁸⁹Y chemical shifts and the Y-3d core level binding energies are found to be rather sensitive to the yttrium bonding state and reveal that the bonding properties of the yttrium atoms in these glasses are similar to those found in the model compounds YBO₃ and YAl₃(BO₃)₄. Based on charge balance considerations as well as ¹¹B NMR line shape analyses, the dominant borate species are concluded to be meta- and pyroborate anions.