Characterisation of mixed potassium-barium mica glass-ceramics with varying fluorine content

Fifteen glasses with varying fluorine and potassium/barium contents designe d to crystallise to fluorophlogopite have been investigated. The purpose of this investigation is to understand the nucleation and crystallisation beh aviour of mica glass-ceramics. This will allow for new materials to be deve loped for engineering and dental applications. Compositions with high fluor ine and potassium contents were shown to lower the glass transition tempera ture and promote crystallisation of fluorophlogopite by a bulk nucleation m echanism. Volatilisation of SiF4 during heat treatment of the glasses was s hown to occur by a surface loss mechanism. Fluorine deficient glasses cryst allised to both fluorophlogopite and cordierite.