Synthesis and characterization of machinable calcium phosphate/lanthanum phosphate composites

Hydroxylapatite (HA) and tricalcium phosphate (TCP) composites with lanthanum phosphate were prepared with pressureless air sintering at 500, 700, 900, 1100 and 1300 °C for 2 h. The composites were characterized in terms of phase stability during sintering, microstructural evaluation with XRD, SEM and machinability with simple drilling operation. At sintering temperatures higher than 700 °C, hydroxylapatite and lanthanum phosphate phases reacted and formed Ca8La2(PO4)6O2. On the other hand, tricalcium phosphate and lanthanum phosphate composites were stable up to 1100 °C. However, partial reaction was observed during sintering at 1300 °C. As a result, tricalcium phosphate and lanthanum phosphate composites sintered at 1100 °C showed phase stability insuring weak interface. Thus, these composites fulfilled the requirement for machinability.