Heterogeneous fluoridated hydroxyapatites partially substituted with fluoride ions

The partially substituted fluoridated apatites H-FHAp_0.5 and FH-HAp_0.5 were synthesized heterogeneously by supplying fluoride at a concentration equivalent to half of the maximum value of fluorapatite during the initial or final half of the experimental period. Although X-ray diffraction patterns and SEM photos of H-FHAp_0.5 and FH-HAp_0.5 apatites were not significantly different, high-resolution transmission electron microscopy showed quite different features; H-FHAp_0.5 type apatite was an elongated hexagon with electron beam damage in the core, and FH-HAp_0.5 type apatite was a rather wide hexagon analogous to fluorapatite. Energy dispersive spectroscopy attached to the SEM showed H-FHAp_0.5 apatite to have a higher fluoride peak intensity than FH-HAp_0.5. These results supported the previ6us speculations on the two different types of heterogeneous fluoridated hydroxyapatites: hydroxyapatite covered with fluorapatite and fluorapatite coverted with hydroxyapatite.