Apatite crystallization from glasses in the Ca5(PO4)3F–CaAl2Si2O8–CaMgSi2O6–NaAlSi3O8 system

The aim of the present study is to investigate the apatite formation process from glasses in the fluorapatite–diopside–anorthite–albite system. The effects of partial and total replacement of anorthite fraction by albite in the ternary composition 26 Ca5(PO4)3F−44 CaAl2Si2O8− 30 CaMgSi2O6 (wt.%) on the properties of glasses and glass-ceramics were evaluated. The scanning electron microscopy (SEM) examination of glasses revealed the precipitation of a nanosize droplet phase in the glassy matrices suggesting the occurrence of amorphous phase separation in all annealed glasses. An overall trend towards polymerization of the glass network with increasing albite content was demonstrated by employing MAS-NMR and FTIR spectroscopy. X-ray diffraction (XRD) and differential thermal analysis (DTA) were used to assess the effect of albite content on the devitrification process and formation of fluorapatite crystalline phase (Ca5(PO4)3F).