Structural dependence of crystallization in glasses along the nepheline (NaAlSiO ₄ ) ‐ eucryptite (LiAlSiO ₄ ) join

Abstract

Abstract 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 LiAlSiO 4 (eucryptite) in high‐Li 2 O compositions, analogous to the more well‐known problem of NaAlSiO 4 (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 Li x Na 1‐ x AlSiO 4 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 LiAlSiO 4 and NaAlSiO 4 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 Li x Na 1‐ x AlSiO 4 crystalline phases, suggesting that these measurements can reveal subtle chemical environment differences in mixed‐alkali systems, similar to what has been observed for zeolites.