Lithium and sodium aluminosilicates are important glass-forming systems for commercial glass-ceramics, as well as being important model systems for ion transport in battery studies. In addition, uncontrolled crystallization of LiAlSiO4 (eucryptite) in high-Li2O compositions, analogous to the more well-known problem of NaAlSiO4 (nepheline) crystallization, can cause concerns for long-term chemical durability in nuclear waste glasses. To study the relationships between glass structure and crystallization, nine glasses were synthesized in the LixNa1- xAlSiO4 series, from x = 0 to x = 1. Raman spectra, nuclear magnetic resonance (NMR) spectroscopy (Li-7, Na-23, Al-27, Si-29), and X-ray diffraction were used to study the quenched and heat-treated glasses. It was found that different LiAlSiO4 and NaAlSiO4 crystal phases crystallize from the glass depending on the Li/Na ratio. Raman and NMR spectra of quenched glasses suggest similar structures regardless of alkali substitution. Li-7 and Na-23 NMR spectra of the glass-ceramics near the endmember compositions show evidence of several differentiable sites distinct from known LixNa1- xAlSiO4 crystalline phases, suggesting that these measurements can reveal subtle chemical environment differences in mixed-alkali systems, similar to what has been observed for zeolites.
All Science Journal Classification (ASJC) codes
- Ceramics and Composites
- Materials Chemistry
- lithium oxide
- nuclear waste