Sol-gel synthesis of amorphous calcium phosphate and sintering into microporous hydroxyapatite bioceramics

A new route for preparing hydroxyapatite (Ca-10(PO4)(6)(OH)(2)) bioceramic has been described. An amorphous, nanosized, and carbonate-containing calcium phosphate powder that had a Ca:P ratio of 1.67 was synthesized from calcium diethoxide and phosphoric acid in ethanol via a sol-gel method. The ponder was pressed at 98 MPa into green specimens and then heated to a temperature range of 500 degrees-1300 degrees C. At 600 degrees C, the ponder crystallized to a carbonated hydroxyapatite and a trace of beta-tricalcium phosphate before converting to hydroxyapatite at 900 degrees C. The thermal crystallization was associated with grain growth, shrinkage, and active surface diffusion. The activation energy of grain growth was 37 +/- 2 kJ/mol, After sintering at 1100 degrees C, the decomposition of carbonated hydroxyapatite generated a microporous ceramic with an average pore size of 0.2 mu m and an open porosity of 15.5%. This microporous bioceramic can be used as a bone filler.