MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass–ceramics having different Li₂O/Al₂O₃ ratio

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• 作者：A. Ananthanarayanan ; G.P. Kothiyal ; L. Montagne ; B. Revel
• 关键词：Glass ; Glass– ; ceramics ; Silicates ; Crystallization ; MAS-NMR ; XRD
• 刊名：Journal of Solid State Chemistry
• 出版年：2010
• 出版时间：January 2010
• 年：2010
• 卷：183
• 期：1
• 页码：120-127
• 全文大小：536 K

文摘

Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt % ) xLi₂O–71.7SiO₂–(17.7−x)Al₂O₃–4.9K₂O–3.2B₂O₃–2.5P₂O₅ (5.1≤x≤12.6) upon heat treatment were studied. ²⁹Si, ²⁷Al, ³¹P and ¹¹B MAS-NMR were employed for structural characterization of both LAS glasses and glass–ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO₃ and BO₄ units. ²⁷Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, ¹¹B (high field 18.8 T) and ²⁹Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi₂O₆, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li₂Si₂O₅), lithium metasilicate (Li₂SiO₃) and quartz (SiO₂) were identified in the ²⁹Si NMR spectra of the glass–ceramics. ³¹P NMR spectra of the glass–ceramics revealed the presence of Li₃PO₄ and a mixed phase (Li,K)₃PO₄ at low alkali concentrations.