Influence of the Ca/P ratio on the morphology of fluorapatite crystals in SiO2-Al2O3-CaO-P2O5-K2O-F- glass-ceramics

The formation of fluorapatite crystals with needle-like morphology was stud ied in glass-ceramics (GCs) of the System SiO2-Al2O3-CaO-P2O5-K2O-F-. X-ray diffraction (XRD), P-31 and Al-21 nuclear magnetic resonance (NMR), scanni ng electron microscopy (SEM), temperature-dependent electric conductance me asurements, and transmission electron microscopy (TEM) with energy dispersi ve X-ray analysis were used to study the influence of the Ca/P ratio of the starting glass composition on the apatite crystal morphology. The composit ion of the ambient glass hosting apatite crystals and particularly the calc ium supersaturation herein is shown to be the key to an understanding of th e apatite crystal morphology observed. (C) 2001 Elsevier Science B.V. All r ights reserved.