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.