Phase separation and structural differences between alkali silicate glasses prepared by the sol-gel and melt-quench methods

Glasses of composition xM₂O:(1-x)SiO₂ [M = Na, Li] with x = 0.15 and 0.2 have been prepared both by the meltquench and the sol-gel methods. X-ray photoelectron spectroscopy shows that with increasing sintering temperature the structure of gels approaches that of the melt-quench glass but does not become identical even on heating above the glass transition temperature (T_g). Phase separation occurs in gel much below T_g, and before it evolves into the structure of melt-quench glass. Thus phase separation is achieved more readily in sintered gels than in the corresponding melt-quench glass.