Effect of small additions of Li2O on phase separation and crystallization of barium‐silicate glasses

Abstract

AbstractIt is known that the addition of Li2O to 33.3BaO‐66.7SiO2 glass, whose composition is the same as BaSi2O5, promotes crystallization of BaSi2O5. In this study, in order to clarify the effect of a smaller amount of Li2O, xLi2O‐(30‐x)BaO‐70SiO2[mol%] (x = 0, 0.2, 0.5) glasses were prepared. The main crystalline phases in the heat treatments near the maximum crystallization peak temperature, were high‐BaSi2O5 and low‐BaSi2O5 which transformed from high‐BaSi2O5. It is found that the introduction of only 0.2 mol% and 0.5 mol% Li2O significantly changes the crystallization behavior. In the composition without Li2O, only high‐BaSi2O5 was formed after heat treatment even for 24 h. For compositions containing Li2O, low‐BaSi2O5 was formed within 1 h of heat treatment. In these compositions, it is found that the addition of Li2O enhances phase separation in the early stage of heat treatment, resulting in the formation of Si‐rich droplet phases and Ba‐rich phases. The composition of the Ba rich glass phase would be close to the stoichiometric composition of BaSi2O5, suggesting a significant change in crystallization behavior.