The Effects of Sintering Temperature and Pressure on the Sintering Behavior of Hydroxyapatite Powder Prepared by Spark Plasma Sintering

Abstract

The sintering behaviors and resulting properties of hydroxyapatite (HA) were studied by employing Spark plasma sintering (SPS) process. An As-received HA powder was sintered and the sintering pressure was set as 22.3MPa, 44.6MPa and 66.9MPa respectively. At each pressure, the HA powder was sintered at different temperatures ranging from 800°C to 1000°C with a duration time of 8 minutes. The results showed that HA compact was rapidly densified to near theoretical density with the relative density of 99.1%. The samples sintered at 44.6MPa possess higher flexural strength and Young's modulus than those at 22.3MPa. The flexural strength and Young's modulus achieved a maximum value of 123.2MPa and 75.2GPa respectively when the samples were sintered at 950°C and at pressure of 44.6MPa. The external pressure accelerates the densification behaviors and overlade external pressure at 66.9MPa resulted in high residual stresses and thus deteriorated the mechanical properties. The XRD results indicated there was no decomposition of HA sintered at elevated temperature up to 1000°C. The drop of mechanical properties was considered as the result of grain growth and hence residual stress induced microcracks.