Influence of Fluorine Content on the Crystallisation of Potassium and Barium Fluorphlogopite Glass-Ceramics

Abstract The influence of fluorine content on the nucleation and crystallization behaviour of fluormica glass-ceramics based on 8SiO2-3Al2O3-(6-X)MgO-XMgF2-(K2O/BaO) were investigated. Fluoride reduced the glass transition temperature (Tg), as well as the first peak crystallisation temperature (Tp1) in both potassium and barium series. High fluoride content (X ≥ 2) promoted bulk crystal nucleation in the potassium series. The first crystallisation peak corresponded to the crystallization of potassium fluorphlogopite in glasses with X ≥ 2.0. However, in barium glasses surface crystallization was more dominant regardless of the fluorine content with kinoshitalite found to be the main mica phase. The formulations were designed to have high aluminium content to reduce volatilisation of SiF4, therefore only small weight loss was evident from the DTA/TGA analysis,