EFFECTS OF STARTING MATERIALS ON PROPERTI ES OF HYDROXYAPATITE POWDERS PREPARED BY SPRAY-PYROLYSIS TECHNIQUE

Nine kinds of spraying solutions with a Ca/P ratio of 1.67 were prepar ed by mixing calcium sources (Ca(NO3)(2), CaCl2 and Ca(CH3COO)(2)) and phosphorus sources ((NH4)(2)HPO4, H3PO4 and PO(OCH3)(3)). Apatites po wders were obtained by spray-pyrolysing the resulting solutions at 600 degrees C; some properties of the obtained powders were examined, The stoichiometric hydroxyapatite (HAp) was obtained by spraying the solu tions containing Ca(NO3)(2)-(NH4)(2)HPO4 and Ca(NO3)(2)-H3PO4 systems, As the solutions containing CaCl2 were sprayed, chloroapatite (CAp) a nd Ca2PO4Cl were formed; Ca2PO4Cl was changed into CAP during heating at 600 degrees C. The carbonate-containing HAp was formed when the sol utions containing Ca(CH3COO)(2)-(NH4)(2)HPO4 and Ca(CH3COO)(2)-H3PO4 s ystems were sprayed, When PO(OCH3)(3) was used as a phosphorus source, the Ca/P ratio of the apatites was below 1.67, The powder derived fro m Ca(CH3COO)(2)-(NH4)(2)HPO4 system showed the best sinterability amon g the powders examined; the relative density of the sintered body fire d at 1150 degrees C for 5h reached similar to 96%.