Calcium phosphate powders for manufacturing bioceramics were synthesized via precipitation from stock solutions of (NH 4 ) 2 HPO 4 and Ca(NO 3 ) 2 , or CaCl 2 or Ca(CH 3 COO) 2 with [Ca 2+ ]/[PO 43-] = 1, without pH regulation. Properties of powdered samples, including density and microstructure of ceramics sintered at 900, 1000, 1100°C, were studied. The following pairs of precursors such as Ca(NO 3 ) 2 /(NH 4 ) 2 HPO 4 , CaCl 2 /(NH 4 ) 2 HPO 4 , Ca(CH 3 COO) 2 /(NH 4 ) 2 HPO 4 gave both insoluble calcium phosphates and the corresponding by-products of synthesis -NH 4 NO 3 , NH 4 Cl, NH 4 CH 3 COO. These by-products were released from the calcium phosphate precipitates in the course of heating to the temperature of sintering. Owing to specific buffer properties of the solutions being formed during synthesis, the pH value varied in a wide range during the precipitation process leading to different final values of pH and, thus, to different target phase(s) after annealing at 900 -1100°C. After sintering, the samples based on the powders synthesized from Ca(NO 3 ) 2 /(NH 4 ) 2 HPO 4 consisted of β-Ca 2 P 2 O 7 , whereas the samples based on the powders derived from CaCl 2 /(NH 4 ) 2 HPO 4 were composed of β-Ca 2 P 2 O 7 and β-Ca 3 (PO 4 ) 2 , and the samples based on the powders synthesized from Ca(CH 3 COO) 2 /(NH 4 ) 2 HPO 4 contained only β-Ca 3 (PO 4 ) 2 . All the powders can be considered as the precursors for fabrication of bioceramics with enhanced resorption. Warsaw and Springer-Verlag Berlin Heidelberg.
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