Effect of sodium addition on the preparation of hydroxyapatites and biphasic ceramics

HAP and biphasic ceramics of two different HAP and β-TCP proportions with substituted sodium were prepared through an aqueous precipitation method. The prepared powders were characterized by XRD, thermal analysis, FT-IR and elemental analysis. Sodium was found to incorporate into the apatite structure without showing any significant change in the phase behaviour of the resultant apatites. The substitution of sodium in the calcium deficient apatites tends to form a biphasic mixture of HAP and β-TCP, while the effect of calcination beyond 700 °C and the resultant mixtures were dependent on the initial Ca/P ratios of the precursors. The calculated lattice parameter values for sodium substituted apatites have shown a marginal increase in c-axis values thereby leading to the enlargement of the hexagonal cell volume with respect to the pure HAP prepared under the same experimental conditions. Powders obtained from the present results were stable up to 1200 °C.