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-2SiO(2)-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 beta-quartz solid solutions Li2O center dot Al2O3 center dot nSiO(2) (n = 6-8). Additive P2O5 and NiO leading to an enhanced nucleation are proposed to be present in fragile Li2O-rich regions.