2006 Volume 114 Issue 1326 Pages 195-198
The effect of a small amount of K2O on the crystallization behavior of the system of Li2O-SiO2 glass was investigated. Lithium disilicate (Li2O•2SiO2; L•2S) and lithium metasilicate (Li2O•SiO2; L•S) crystals precipitate simultaneously, but only L•2S crystals grow upon further heat treatment in the glass without K2O (Li glass). In the glass containing K2O (K3 glass), only L•S crystals precipitate and grow. The stable crystalline phases are L•2S and SiO2 crystals in both glasses. Phase separation was observed before crystallization; a Li2O-rich phase formed an isolated droplet phase in Li glass and the continuous phase in K3 glass. The Li+-K+ ion exchange test confirmed these structures. [SEM-EDX] analysis confirmed that K2O exists in the Li2O rich phase after phase separation in K3 glass. Thus, K3 glass separates into two phases, one of which is a continuous phase rich in Li2O and containing considerable amount of K2O. The L•S crystal precipitates and grows in this phase upon further heat treatment. Consequently, K2O suppresses the crystallization of L•2S and promotes the precipitation of L•S crystals.
