Glass-to-Crystal Transition in Li1+xAlxGe2鈥?i>x(PO4)3: Structural Aspects Studied by Solid State NMR

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• 作者：Cornelia Schr枚der ; Jinjun Ren ; Ana Candida M. Rodrigues ; Hellmut Eckert
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：May 8, 2014
• 年：2014
• 卷：118
• 期：18
• 页码：9400-9411
• 全文大小：576K
• 年卷期：v.118,no.18(May 8, 2014)
• ISSN：1932-7455

文摘

The structural aspects of the glass-to-crystal transition in the technologically important ion conducting glass ceramic system Li_1+xAl_xGe_2鈥?i>x(PO₄)₃ (0 鈮?x 鈮?0.75) have been examined by complementary multinuclear solid state nuclear magnetic single and double-resonance experiments. In the crystalline state, the materials form solid solutions in the NASICON structure, with additional nanocrystalline AlPO₄ present at x values 鈮?.5. Substitution of Al in the octahedral Ge sites results in a binomial distribution of multiple phosphate species, which differ in the number P鈥揙鈥揂l and P鈥揙鈥揋e linkages and can be differentiated by ³¹P chemical shift and ³¹P{²⁷Al} rotational echo adiabatic passage double resonance (REAPDOR) spectroscopies. The detailed quantitative analysis of these data, of complementary ²⁷Al{³¹P} rotational echo double resonance (REDOR) and of homonuclear ³¹P鈥?sup>31P double quantum NMR studies suggest that the AlO₆ coordination polyhedra are noticeably expanded compared to the GeO₆ sites in the NASICON-type LiGe₂(PO₄)₃ (LGP) structure. While the glassy state is characterized by a significantly larger degree of disorder concerning the local coordination of germanium and aluminum, dipolar solid state NMR studies clearly indicate that their medium range structure is comparable to that in NASICON, indicating the dominance of P鈥揙鈥揂l and P鈥揙鈥揋e over P鈥揙鈥揚 and Al鈥揙鈥揋e connectivities.