Synthesis and Stability of Potassium/Carbonate Co-Substituted Hydroxyapatites
A systematic study of the stability of potassium/carbonate co-substituted hydroxyapatite has been carried out, with samples synthesized by aqueous precipitation according to the chargebalanced mechanism: Ca10-xKx(PO4)6-x(CO3)x(OH)2 Samples up to x=1.0 were prepared and their stability determined by heating at a range of temperatures in both air and CO2 environments. Results showed that whilst samples up to x=1.0 can be prepared phase-pure, the stability of these materials is strongly dependent on sintering temperature with the full range of compositions only being stable at 600°C in CO2. The c unit cell parameter increases linearly with x, and, for a fixed composition, decreases linearly with temperature indicating loss of carbonate from the A-site. FTIR showed that samples contained carbonate at both A- and B-sites, and that carbonate content increased with x.
Guy Daculsi and Pierre Layrolle
J. Whyte et al., "Synthesis and Stability of Potassium/Carbonate Co-Substituted Hydroxyapatites", Key Engineering Materials, Vols. 361-363, pp. 207-210, 2008