Nanoscale composition fluctuations and crystallization process: Case study in Li2O–SiO2-based glasses

Nanoscale composition fluctuations in Li₂O–SiO₂-based glasses were analyzed and discussed from the data on the structure and crystallization process reported so far to enter deeply into the medium-range ordered structure of multicomponent oxide glasses. Li₂O is proposed to have a strong tendency for dynamical heterogeneous structure, that is, the formation of fragile Li₂O-rich regions with small SiO₂ contents, resulting in the initial crystallization of metastable Li₂SiO₃ prior to the formation of stable Li₂Si₂O₅ in Li₂O–2SiO₂-based glasses. Li₂O–Ga₂O₃/Nb₂O₅–SiO₂ glasses are proposed to have nanoscale composition fluctuations of Li₂O–Ga₂O₃/Nb₂O₅-rich regions, resulting in the initial formation of LiGa₅O₈ and LiNbO₃ nanocrystals. In Li₂O–Al₂O₃–SiO₂ glasses, the distribution width of composition fluctuations is proposed to be narrow, resulting in the initial crystallization of metastable β-quartz solid solutions Li₂O·Al₂O₃·nSiO₂ (n = 6–8). Additive P₂O₅ and NiO leading to an enhanced nucleation are proposed to be present in fragile Li₂O-rich regions.