Subsitution Of Boron For Silicon In K-Fluor-Richterite Glass Ceramics

Substitution of B3+ for Si4+ in the K-fluor-richterite KNaCaMg5Si8O22F2 structure is presented through study of the crystallisation behaviour of glasses containing up to 36.55 wt% B203 upon different heat treatment regimes. Gradual additions of boron lower the melting temperatures and strongly affect nucleation and crystallisation temperatures. The effect of boron replacement on the type of crystallising phases was manifested by DTA, XRD and EDAX. A single K-fluor-richterite phase resulted in crystallisation of glasses with 17.34 wt%B203. For greater boron contents, borate mineral phase crystallised, namely suanite Mg2B2O5 in addition to fluorite CaF2 and fluorphlogopite.