Lithium aluminosilicate (LAS) glass and glass ceramics derived from spodumene mineral have been studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), positron annihilation lifetime spectroscopy (PALS) and solid state nuclear magnetic resonance (NMR) as as-cast glass, as partially crystallized glasses, and as fully crystalline glass ceramics. The nucleation and growth of the crystalline phases at 725 degrees C up to 1000 degrees C have been studied as functions of varying time and temperature. Both TEM and PALS are effective tools for studying the development of the nanophase structure in the partially crystallized glass. TEM observation established the size and number of crystallites present in the glassy matrix, whilst the PALS component attributed to orthopositronium (oPs) pickoff annihilation was remarkably sensitive to the nucleation and growth of the crystalline phases in the glass ceramic. This oPs component was associated either with the nuclei/glass interface or with the nuclei structure. XRD and NMR were used to study the evolution of the two crystalline phases which form from the glass in the temperature range 725 degrees C to 1000 degrees C, the beta -quartz solid solution (ss) phase below 900 degrees C and the beta -spodumene ss phase above 900 degrees C. The 29Si NMR spectra of both beta -quartz ss and beta -spodumene ss phases show structures associated with the next nearest neighbour configurations of the central SiO4 units. The 29Si and 27Al NMR spectra of alpha -spodumene mineral and beta -spodumene ss phase formed by annealing alpha -spodumene are compared to the spectra for the glass and crystalline phases formed from the melt.

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Crystallization of nitrogen-containing glasses based on the Li 2 O-Al 2 O 3 -SiO 2 system produces materials comprised of β-quartz ss and β-spodumene ss , with minor amounts of X-phase (Si 3 Al 6 O 12 N 2 ) and silicon oxynitride (Si 2 N 2 O). X-ray diffraction and 29 Si and 27 Al magic-angle spinning NMR spectroscopy have been used to study the effect of nitrogen on the thermal stability and atomic distribution of β-quartz ss , to monitor the evolution of secondary phases in the Li-Si-Al-O-N system, and to compare the differences between using Si 3 N 4 and AlN as the nitrogen source. Samples containing e4wt % nitrogen and heattreated at temperatures up to 1300 °C were analyzed by XRD to determine their crystallinity and phase content, whereas NMR was able to more clearly elucidate the atomic coordination and Si, Al distribution in the crystal structure.