Crystallisation mechanism of a multicomponent lithium alumino-silicate glass

A base glass of composition 3.5 Li2O∙0.15 Na2O∙0.2 K2O∙1.15 MgO∙0.8 BaO∙1.5 ZnO∙20 Al2O3∙67.2 SiO2∙2.6 TiO2∙1.7 ZrO2∙1.2 As2O3 (in wt.%), melted and provided by SCHOTT AG (Mainz), was used to study the crystallisation mechanism of lithium alumino-silicate glass employing X-ray diffraction combined with neutron diffraction and non-isothermal differential scanning calorimetry (DSC). A high-quartz solid solution of LiAlSi2O6 with nanoscaled crystals forms at 750 °C. Quantitative Rietveld refinement of samples annealed at 750 °C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, β-eucryptite-like structure (2 × 2 × 2 cell) with Li ordered in the structural channels. The Avrami parameter (n ∼ 4), calculated from DSC data using different theoretical approaches, indicates that bulk crystallisation occurs and that the number of nuclei increases during annealing. The activation energy of the crystallisation is 531 ± 20 kJ mol−1.