Hydrous lithium aluminosilicate (L–A–S–H) and lithium aluminate (L–A–H) gels are candidate precursors for glass-ceramics and ceramics with potential advantages over conventional processing routes. However, their structure before calcination remained largely unknown, despite the importance of precursor structure on the properties of the resulting materials. In the present study, it is demonstrated that L–A–S–H and L–A–H gels with Li/Al ≤ 1 can be produced via an organic steric entrapment route, while higher Li/Al ratios lead to crystallization of gibbsite or nordstrandite. The composition and the structure of the gels was studied by thermogravimetric analysis, X-ray diffraction, ²⁷Al and ²⁹Si magic-angle spinning nuclear magnetic resonance, and Raman spectroscopy. Aluminium was found to be almost exclusively in six-fold coordination in both the L–A–H and the L–A–S–H gels. Silicon in the L–A–S–H gels was mainly in Q⁴ sites and to a lesser extent in Q³ sites (four-fold coordination with no Si–O–Al bonds). The results thus indicate that silica-rich and aluminium-rich domains formed in these gels.

中文翻译：

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铝酸锂 (L-A-H) 和铝硅酸锂 (L-A-S-H) 凝胶的溶胶-凝胶合成和表征

水合铝硅酸锂 (L-A-S-H) 和铝酸锂 (L-A-H) 凝胶是玻璃陶瓷和陶瓷的候选前体，与传统工艺路线相比具有潜在优势。然而，尽管前体结构对所得材料的性质很重要，但它们在煅烧前的结构仍然很大程度上未知。在本研究中，证明了 Li/Al ≤ 1 的 L-A-S-H 和 L-A-H 凝胶可以通过有机空间位阻截留途径生产，而较高的 Li/Al 比会导致三水铝石结晶或nordstrandite。通过热重分析、X 射线衍射、²⁷ Al 和^{29研究了凝胶的组成和结构。}硅魔角旋转核磁共振和拉曼光谱。发现铝在 L-A-H 和 L-A-S-H 凝胶中几乎完全是六倍配位。L-A-S-H 凝胶中的硅主要位于 Q ⁴位点，在较小程度上位于 Q ³位点（四重配位，没有 Si-O-Al 键）。因此，结果表明在这些凝胶中形成了富含二氧化硅和富含铝的区域。