Characterization of calcium phosphate apatite with variable Ca/P ratios sintered at low temperature

The characterization of calcium phosphate apatite with variable Ca/P ratios synthesized by the hydrolysis method and sintered at 1073 K has been investigated. When the precipitate powders are sintered at 1073 K for 4 h, the major phase observed is hydroxyapatite (Ca10(PO4)6(OH)2, HA), and the minor phases are rhenanite (NaCaPO4) and β-tricalcium phosphate (β-TCP, β-Ca3(PO4)). The shrinkage increased from 5.15 to 21.00%, and the grain size of the pellets also increased from 31 to 348 nm along with the ratios of Ca/P. The TEM microstructure identified with SAED and EDS analyses show that an amorphous phase of NaCaPO4 is present at the grain boundaries of HA, which promotes the sintering of calcium phosphate, but reduces the mechanical properties.