Spark plasma sintering of hydroxyapatite powders.

Dense hydroxyapatite (HA) compacts have been successfully fabricated by a spark plasma sintering (SPS). The sintering behavior of HA powders at different temperatures ranging from 850 degrees C to 1100 degrees C was studied. Results showed that spark plasma sintering resulted in rapid densification to near theoretical density. The HA compact was homogeneously sintered at 950 degrees C in a short sintering duration of 5 min, while maintaining high quality and high relative density (>99.5%). The density, microhardness and Young's modulus of HA sintered compact initially increased with the sintering temperature, reached a maximum value at around 950-1000 degrees C, then decreased with further increase in the temperature due to the decomposition of HA into beta-tricalcium phosphates. Fracture toughness results showed no significant difference with increasing temperature due to the combined influences of density and grain size. Microstructure analysis showed no noticeable grain growth under different sintering temperatures due to the short time exposure at high temperatures.