Effect of fluoride additive on the mechanical properties of hydroxyapatite/alumina composites

The effect of fluoride additives on the mechanical properties of hydroxyapatite/alumina composites was investigated. When MgF2 (5 vol%) was added to hydroxyapatite/alumina composites, the decomposition of hydroxyapatite was suppressed due to the substitution of F− for OH− in the crystal structure. Comparing two additives, such as MgF2 and CaF2, MgF2 showed much more effective for the suppression of phase decomposition in the hydroxyapatite/alumina composites due to the enhanced substitution of F− for OH−. In the case of MgF2 addition, a relatively high-mechanical properties (flexural strength: ∼170 MPa; Vickers hardness: ∼7 GPa) was obtained compared to MgF2-free composites.