WET SYNTHESIS AND CHARACTERIZATION OF MODIFIED HYDROXYAPATITE POWDERS

Hydroxyapatite powders with reproducibly different Ca/P ratios and pow ders with varying amounts of co-precipitated magnesium, sodium and pot assium were synthesized by a wet method. Solids composition, particle size and morphology, crystalline structure, sintering behaviour and mi crostructure were investigated in order to understand the effect of co mposition in the properties of the powders. Under the present conditio ns of synthesis, it was concluded that magnesium, sodium and potassium will enter the hydroxyapatite lattice in vestigial amounts. Magnesium gives rise to a co-precipitated amorphous phase which crystallizes as beta-whitlockite on calcining. A relationship was found between the C a/P ratio in hydroxyapatite and its sinterability. The sintering proce ss of pure and alkali-containing hydroxyapatites is completed at 1300 degrees C and leads to dense ceramics in the case of pure and sodium-c ontaining hydroxyapatites but not in potassium-containing material.