Synthesis and thermal stability of sodium, magnesium co-substituted hydroxyapatites

Sodium and magnesium co-substituted hydroxyapatite (Hap) and β-tricalcium phosphate mixtures were prepared through an aqueous precipitation method. Characterization results from XRD, FT-IR and thermal analysis have indicated the influence of additives (Na and Mg) on the thermal stability of the apatites. The elemental analyses have also confirmed the presence of Na+ and Mg2+ ions in the apatite structure. Calculated lattice parameters for the combined substitution of elements on the apatite structure were found to have contraction of the a-axis and expansion of the c-axis as well as of the unit cell volume with respect to that of pure Hap.