The Effects of Additives on the Transparency of Mica Glass-Ceramics

The change in the transparency of mica glass-ceramic in the system of MgO- SiO2-Al2O3-K2O-B2O3-F with and without additions has been investigated. The applied additives were LiF, NaF and CaF2. Crystallization of glass-sample was done by controlled thermal heat-treatment, at nucleation and crystallization temperatures. The results showed that the glass-ceramic can remain transparent if fine grains with nano size are precipitated, but will turn opaque when large grains appear because of the difference in the refractive index between glass and precipitated crystals.The comparison of the additives indicated that LiF had a pronounced effects than CaF2 on the crystallization temperature as well as precipitated phase.