Successive phase transformation in stoichiometric glassy Li ₂Ge₄O₉: Isothermal and nonisothermal study

Stoichiometric glassy germanate is an important material in geophysics and materials science. Despite the binary Li₂O-GeO₂ system being primitive, its crystallization mechanism remains undetermined. In this study, we investigated crystallization and structural ordering in glassy ferroelectric Li₂Ge₄O₉. Using isothermally and nonisothermally prepared samples, we demonstrated that the glassy Li ₂Ge₄O₉ shows no direct structural change to the stoichiometric phase; it rather forms α-GeO₂ nanocrystals, i.e., it undergoes successive phase transformation. The results suggest that the metastable immiscibility is related to the ordering that occurs prior to crystallization of the stoichiometric phase.