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The nucleation and crystallization of a series of glasses based on 4.5SiO 2 ⅐3Al 2 O 3 ⅐1.5P 2 O 5 ⅐(5 ؊ z)CaO⅐zCaF 2 with a Ca:P ratio corresponding to apatite were studied. In these glasses, the objective was to investigate the influence of fluorine content and z was varied from 3 to 0. All the glasses studied crystallized to fluorapatite (FAP) and mullite with the exception of the glass containing no fluorine, which crystallized to ␤-tricalcium phosphate (Ca 3 (PO 4 ) 2 ) and anorthite (CaAl 2 Si 2 O 8 ). Glasses that contained sufficient fluorine to form FAP bulk nucleated to give FAP without a nucleation hold. Thermal gravimetric analysis demonstrated a significant weight loss corresponding to the crystallization of mullite, which increased with the fluorine content of the glass and also with decreased particle size. The loss was attributed to volatile SiF 4 . The glass transition temperature decreased with increased fluorine content of the glass.

The nucleation and crystallization behavior of a series of glasses based on 4.5SiO2-3Al2O3-YP2O5-3CaO-1.51CaF2 was studied. The parameter Y was varied to give calcium to phosphate ratios between one and two. All of the glasses studied crystallized firstly to fluorapatite (Ca5PO4)3F). The glass with a calcium to phosphate ratio of 1.67, corresponding to apatite, bulk nucleated to give fluorapatite (FAP). The glasses with calcium : phosphate ratios either less than that of apatite, or greater than that of apatite all exhibited surface nucleation of FAP. However, following a nucleation hold of one hour at approximately 50 K above the glass transition temperature these glasses exhibited bulk nucleation of FAP.

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