Nucleation and early stage crystallization in barium disilicate glass

Barium disilicate is one of the glass-ceramic systems where internal nucleation and crystallization can occur from quenched glass upon heat treatment without requiring nucleating agents. The structural origin of the nano-clusters formed during low temperature heat treatment is of great interest in gaining a fundamental understanding of nucleation kinetics in silicate glasses. Here, we present experimental investigations on the low temperature heat treatment of barium disilicate (BaO·2SiO₂) glass. Several experimental techniques were used to characterize the structural nature of barium disilicate glasses that were heat treated between the glass transition temperature, T_g, and the peak temperature of crystal growth, T_cr. The data show that small amounts of crystallites including BaSi₂O₅ as well as other higher Ba/Si ratio phases are formed. Moreover, unlike that reported for lower BaO content (BaO<33mol%) barium silicate glass or the analogous Li₂O-SiO₂ glasses, no clear evidence is observed for liquid/liquid phase separation in barium disilicate glass.